Page 1 : PLASTICS, DESIGN, , HANDBOOK

Page 3 : Library of Congress Cataloging-in-Publication Data, Rosato, Dominick V., Plastics design handbook 1 by Dominick V. Rosato, Donald V. Rosato, Marlene G. Rosato., p. cm., ISBN 978-0-7923-7980-5, ISBN 978-1-4615-1399-5 (eBook), DOI 10.1007/978-1-4615-1399-5, 1. Plastics-Handbook, manuals, etc., 2. Engineering design-Handbook, manuals, etc., 1. Rosato, M.G. Il. Rosato, Donald V. III. Title., TA455.P5 R66 2000, 620.1'923-dc21, 00-61054, , Copyright © 2001 by Springer Science+Business Media New York, Originally published by Kluwer Academic Publishers in 2001, Softcover reprint of the hardcover 1st edition 2001, , Ali rights reserved. No part of this publication may be reproduced,, stored in a retrieval system or transmitted in any form or by any means,, mechanical, photocopying, recording or otherwise, without the prior, written permission of the publisher, Springer Science+Business Media,, LLC., , Printed on acid-free paper.

Page 4 : Contents, , xvii, , Preface, Chapter 1, , Introduction, Overview, Generalization Justifiable, Design Definition, Design Technology 16; Industrial Designer 16, Human engineering 17, Engineering Designer 17; Graphic Designer 17; Innovative, Designer 17; Material Optimization Designer 18; Maximum Diametrical Interference Designer 18; Medical Device Designer 18, Design Features That Influence Performance, Interrelating Product-Plastic-Process Performance 20;, Advantage and Disadvantage of Plastic 21, Basics in Designing, Design Approach, , 1, 1, 14, 15, , 18, 22, 23, , ~~~~re, , ~, , Computer Use, Computer-Aided Design 28; Computer-Aided Design Drafting 29; Computer-Aided Manufacturing 29;, Computer-Integrated Manufacturing 29; ComputerAided Testing 29; Computer Software Program 30, Software and database 31; RAPRA free Internet, search engine 31, Short and Long Term Performance, Predicting Performance, A Changing World, Recreation 33; Electronic 33; Packaging 33, Building and Construction 33; Health Care 33; Transportation 34; Aerospace 34; Appliance 34, Success by Design, Responsibility, Responsibility Commensurate with Ability 36, Ethic, Terminology, , 25, , 31, 32, 33, , 35, 35, 36, 36

Page 5 : vi, , Chapter 2, , Contents, , Design Influencing Factor, , 37, , Introduction, Material Behavior, Rheology and Viscoelasticity 38; Viscoelasticity Behavior, 39, Pseudo-elastic design 40; Effect of strain rate 40, Correlating Rheological Parameter, Mechanical Load, Damping 44; Dynamic Mechanical Behavior 44, Short-Term Load Behavior, Tensile Stress-Strain 45, Tensile strength 46; Area under the curve 47;, Elongation 47; Yield 47; Proportional limit 47;, Elastic limit 47; Modulus of elasticity 47; Secant, modulus 50; Hysteresis effect 50; Poison's ratio 50;, Ductility 52; Brittleness 52; Crazing 52; Test rate, and property 53; Viscoelasticity 55, Flexural Stress-Strain 55; Compressive Stress-Strain 59;, Shear Stress-Strain 60, Torsion property 62, Applying Stress-Strain Data 62, Long-Term Load Behavior, Viscoelastic Creep 63; Stress Relaxation 64; Long-term, Viscoelastic Behavior 65; Creep Property 65, Basics 65; Creep modeling 66; Product performance data 67, Creep rupture 68; Overall behavior 69;, Crazing 70; Stress whitening 70; Rupture, 70; Apparent creep modulus 71; Stress relaxation 72; Intermittent loading 73; Material and processing 74; Designing with, creep data 77; Allowable working stress, 79; Isometric and isochronous graph, 80; Deformation or fracture 81; Creep, guideline 81, Fatigue Property 82, Introduction 82; Testing mode 84; Endurance limit, 85; Heat generation 85; Fracture mechanic 85; Reinforced plastic 86; Designing with fatigue data 87, High Speed Property, Impact loading 90, Design feature 91, Impulse Loading 92; Puncture Loading 93; Frictional, Loading 94; Hydrostatic Loading 96; Erosion Loading 97, Cavitation erosion 97; Rain erosion 98, Thermal Expansion and Contraction, Hysteresis Effect 99; Energy and Motion Control 100, Viscoelastic damping 101, Weathering/Environment, Temperature Review 102; Stress Cracking and Crazing, 104; Weather Resistance 106; Sterilization-Irradiation 106;, , 37, 38, , 41, 43, 45, , 63, , 88, , 98, 101

Page 6 : Contents, , Harmful Weather Component 107; Assessing Weathering, Effect 107; Outer Space 108; Ocean 109; Time-Dependent, Data 113, Viscoelastic and rate theory 113; Time dependence 113; Creep behavior 113; Linear viscoelasticity 113; Creep and stress relation 114; Rate theory 114; Designing plastic 115, Molecular Weight and Aging 115; Arrhenius Plot Theory, 115, Why material age 115; Rate of aging process 116;, Using the Arrhenius equation to predict performance 116, Test temperature 117; Normal oxidative, degradation 117; Cross-linking 117; Catalytic degradation 117; Arrhenius plot 117, Usefulness of thermal evaluation technique 118, High Temperature, Hypersonic Atmospheric Flight 119, Hyperenvironment 120; Thermal protection 120;, Ablation 121, Chemical Propulsion Exhaust 122, Cooling technique 122, Flammability 123, Smoke 124; Intumescence coating 124, Instability Behavior, Shrinkageffolerance 125; Heat Generation 126; Annealing 126; Plastic Material and Equipment Variable 127, Finite Element Analysis, Introduction 127; Fundamental 128; Operational Approach 128, Safety Factors, Uncertainty 130, , Chapter 3, , Product Design Feature, Introduction, Design Analysis, Overview 132; Pseudo-Elastic Design Method 132; Analysis Method 133; Analysis Requirement 137; Material Characteristic 137, Reinforced plastic 137, Design Concept, Loading Mode 138; Load 138; Loading Type 139; LoadBearing Product 139; Multiaxial Stresses and Mohr's Circle 140; Design Criteria 140; Geometrical Shape 141, EI theory 141, Rib 142, Rib design 143, Beam 144; Beam Bending and Spring Stress 145; Torsional, Beam Spring 147; Folded Plate 147; Sandwich Construction 150, Stiffness 151, , vii, , 118, , 125, 127, 129, , 131, , 131, 132, , 138

Page 7 : viii, , Contents, Reinforced Plastic Directional Property 152, Isotropic material 152; Anisotropic material, 153, Monocoque Structure 153; Integral Hinge 153; Snap Joint, 155; Product Size and Shape 155, Basic Feature, Tolerance 158; Shrinkage 165; Processing and Tolerance/, Shrinkage 170, Cost advantage with tight tolerance 173; Blowing, agent and tolerance 174, Impact Load 174; Thermal Stress 174; Film 174; Weld Line, 175; Meld Line 176; External Thread 176; Coating 176;, Functional Surface and Lettering 177; Fiber Reinforcement 177; Process 177, Prototype, Rapid Prototyping and Tooling 178, Features Influencing Performance, Residual Stress 179; Cold Working 180; Stress Concentration 180; Injection Molding 181, Design concept 181; Sharp corner 183; Uniform, wall thickness 184; Wall thickness tolerance 184;, Flow pattern 185; Parting line 185; Gate size and, location 185; Taper of draft angle 185; Weld line, 185; Undercut 187; Blind hole 187; Boss 187; Coring 187; Press fit 188; Internal plastic thread 189;, Molded-in insert 190; Screw 191; Rib 192, Extrusion 192, Tolerance 193, Blow Molding 195, Hinge 195; Consolidation 198, Thermoforming 198, Tolerance 199, Rotational Molding 200, Mold 200; Cost 201; Wall thickness/surface 201;, Processing technique 201, Design Failure Analysis, , Chapter 4, , Designing Plastic Product, , Introduction, Book Shelve, Material 205; Prototype 206; Testing 206; Summary 207, Pipe, RPPipe, Load Testing 209; Directional Property 210; Filament, Wound Structure 210; Stiffness and Strength 211; Deflection Load 211; Stiffness and Buckling 212; Anisotropic Behavior 213; Stress-Strain Curve 213; Weep Point 214; Poisson's Effect 214; Conservative Approach 215; Pipe Joint, 217, Bearing, PV Factor 218, , 158, , 177, 179, , 203, , 204, 204, 204, 208, 208, , 217

Page 8 : Contents, , Gear, Load Requirement 219; Hysteresis Effect 219; Processing, 220, Gasket and Seal, Grommet and Noise, ElectricallElectronic Product, Property 223, Insulation 224; Leakage resistance 224; Dielectric, constant/loss 224; Dielectric loss 224, Connector 225; Insulation 227, Dielectric break down and mechanical creep 227;, Dielectric break down and S-N analysis 227, Environment 227; Different Behavior 228, Capacitor 228; Electret 228; Structural binder 228;, Electro-optic 229, Summary 229, Toy and Game, Toys-Electronic 229, Transparent and Optical Product, Overview 229; Property, Performance, and Product 230;, Lens 231; Fresnel Lens 231; Lenticular 232; Piping Light, 232; Fiber Optic 233; Polarized Lighting 233, Application 234, Laser Lighting 235; Color Filter 235; Processing 235;, Designing 236, Packaging, Aseptic 237; Bag-in-Box 237; Beverage Can 237; Biological Substance 237; Blister 237; Bubble Pack 237; Clasp, 237; Contour 238; Dual-Ovenable Tray 238; Electronic, 238; Film Breathable 238; Food 238; Food, Oxygen Scavenger 239; Grocery Bag 239; Hot Fill 239; Loose Fill, 239; Modified-Atmosphere 239; Peelable Film 239; Pouch, Heat-Sealed, Wrap, and Reusable Container 239; Retortable Pouch 240; Shrink Wrap Tunnel 240; Container, Content Misrepresentation 240; Permeability 240, Basics 241; Permeability and barrier resistance 241, Product 242, Building, Overview 242; Application and the Environment 244; The, Architect Approach 246; House of the Future 246; Designing a Structure 248, Chair, Load Requirement 250; Form and Dimension 251; Stiffness 251; Environment 252; Prototype 253, Automobile, World's First All-Plastic Car Body 254, Aircraft, Medical Product, Bioplastic 259; Bioscience 259; Surgical Product 260; Complex Environment 261; Dental Product 261; Medical Packaging 262, , ix, 219, 221, 221, 222, , 229, 229, , 237, , 242, , 250, 253, 255, 259

Page 9 : x, , Contents, Biological and Microbial Degradation, Other Form of Degradation 262, Dynamic Load Isolator, Filter, Water 264, Plastic membrane 265, Gas 266, Liner, Paper and Plastic, Save the Tree Myth 268, Developing Idea, Joining and Assembling, Molded-In Insert 269; Holding with Formed Head 270;, Snap Fit 270; Welding 273; Summary 274, Predicting Performance, Design Verification 274, Design and Safety, Risk, Acceptable Risk 276; Perfection 277, Plastic/Process Interaction, Molding 278; Injection Molding 278, Freezing action 278; Thin to large wall 278; Melt, flow restriction 279; Residual stress 279; Gate area, 280; Jetting 280; Weld line 281; Venting 281, Extrusion 281, Melt flow 282; Memory 282; Distortion 282; Dimension 282, Thermoforming 283, Stress 283; Memory 283; Orientation 284, Blow Molding 284, Complex design 284, Casting 284, Law and Regulation, Designing and Legal Matter, Accident Report 286; Acknowledgment 287; Chapter 11, Act 287; Conflict of Interest 287; Consumer Product Safety, Act 287; Copyright 287; Defendant 287; Employee Assignment Invention 287; Expert Witness 287; Insurance, Risk Retention Act 288; Invention 288; Mold Contractional Obligation 288; Patent 288; Patentability 288; Patent, Information 288; Patent Infringement 288; Patent Pooling with Competitor 289; Patent Search 289; Patent Term, Extension 289; Patent Terminology 289; Plaintiff 289; Processor Collaborative Venture 289; Processor Contract 290;, Product Liability Law 290; Protect Design 290; Protection, Strategy 290; Quotation 290; Right-to-Know 290; ShopRight 290; Software and Patent 291; Tariff 291; Term 291;, Tort Liability 291; Trademark 291; Trade Name 291; Warranty 291, Design Detractor and Constrain, Troubleshooting Design ProblemlFailure, , 262, 263, 264, , 266, 267, 268, 269, 274, 275, 276, 277, , 285, 286, , 291, 292

Page 10 : Contents, , xi, , Troubleshooting Guide 292; Troubleshooting by Remote, Control 292; Defining the Trouble 293; Design Failure Theory 293; Product Failure 293; Managing Failure 294, Business and change 294; Bureaucratic dry rot 295, Business Failure 295, , Chapter 5, , Testing and Meaning of Test Data, , 296, , Introduction, Overall Responsibility 296, Destructive and Nondestructive Testing, Testing and Classification 299; Testing and Quality Control, 299; Testing and People 300; Basic vs. Complex Test 300;, Specification and Standard 300, Stress Analysis, Flaw Detection, Limitation of Test, Meaning of Data, Physical Property, Specific GravitylDensity 305; Water Absorption 306; Water Vapor Transmission 306; Water Vapor Permeability, 307; Shrinkage 308, Tolerance 308, Mechanical Property, Tensile Property 309; Flexural Property 311; Compressive, Property 311; Shear Strength 312; Izod Impact 312; Tensile, Impact 312; Impact Strength 313; Hardness 313, Durometer hardness 315; Barcol hardness 315;, Brinell hardness 315; Knoop hardness 315; Mohs, hardness 315; Rockwell hardness 315; Scleroscope, hardness 316; Shore hardness 316; Vicat hardness, 316, Deformation Under Load 316; Fatigue Strength 316; LongTerm Stress Relaxation/Creep 316; Summation 318, Stiffness 318; Strength 318; Toughness 318, Thermal Property, Deflection Temperature Under Load 319; Coefficient of, Linear Thermal Expansion 321; Brittleness Temperature, 322; Thermal Aging 323; Other Heat Test 324, Electrical Property, Electrical Resistance 327; Arc Resistance 327; Dielectric, Strength 327; Dielectric Constant and Dissipation Factor, 328, Optical Property, Haze and Huminous Transmittance 328; Luminous Reflectance 329; Opacity and Transparency 330; Abrasion, and Mar Resistance 330, Weathering, Outdoor Weathering 331; Accelerated Weathering 331;, Accelerated Exposure to Sunlight 331; Conditioning Procedure 332; Harmful Component 332; Environmental, Stress Cracking 332, , 296, 297, , 302, 303, 304, 305, 305, , 309, , 319, , 327, , 328, , 331

Page 11 : Contents, , xii, , Chapter 6, , Chapter 7, , Fire, , 332, , Flammability 332; Oxygen Index 332, Analyzing Testing and Quality Control, Statistical Process Control and Quality Control, , 333, 333, , Plastic Material Formation and Variation, Introduction, Definition 337; Thermoplastic and Thermoset Plastic, 338, Structure and Morphology, Crystalline and Amorphous Plastic 342; Liquid Crystalline, Polymer 343; Copolymer 345, Compounded/Alloyed Plastic, Alloy and Blend 345; Interpenetrating Network 347; Reactive Polymer 348; Grafting 348; Additive, Filler, and Reinforcement 348, Reinforced Plastic, Basic Design Theory 357, Theory of combined action 358, Property Range 359, Elastomer, Commodity and Engineering Plastic, Neat Plastic, Structural Foam, Plastics with a Memory, Orientation, Material Variable, Recycling, Recycling Energy Consumption 370; Design Source Reduction 372; Recycling Method 372, Recycling limitation 372; Reactive extrusion recycling 372, Web Site Connect Buyer and Seller of Recycled Plastic, 373, Plastic Future and Biotechnology, , Material Property, Introduction, Mechanical Property, Toughness 376; Deformation and Toughness 377; Stiffness, 380; Strength 380; Temperature Effect 380; Other 381, Electrical Property, Electromagnetic Compatibility 382; Design Concept 389, Thermal Property, Residence Time and Recycling 395; Melt Temperature 395;, Glass-Transition Temperature 395; Mechanical Property, and Tg 396; Dimensional Stability 397; Thermal Conductivity and Thermal Insulation 397; Heat Capacity 397; Thermal Diffusivity 398; Coefficient of Linear Thermal Expansion 398; Thermal Stress 399; Decomposition Temperature, 399; Aging at Elevated Temperature 399; Temperature Index 400; Intumescent Coating 400; Other 400, , 335, 335, 340, 345, , 353, , 359, 361, 363, 363, 367, 368, 368, 369, , 373, , 374, 374, 375, 381, 391

Page 12 : Contents, Other Behaviour, Drying Plastic 400; Moisture Influence 401; Plastic Memory 401; Corrosion Resistance 401; Chemical Resistance, 406; Friction, Wear, and Hardness Property 410; Plasticto-Metal Wear 411; Plastic-to-Plastic Wear 411, Selecting Plastic, Computerized Database 412, Electronic marketplace/E-Commerce 415;, RAPRA free internet search engine 416, Selection Worksheet 416; Other Guide 417; Preliminary, Consideration 417; Thermoplastic 425, Acetal 426; Acrylic 426; Acrylonitrile-butadienestyrene 427; Cellulosic 427; Chlorinated polyether, 427; Chlorinated polyethylene 427; Ethylenevinyl acetate 427; Expandable polystyrene 427;, Fluoroplastic 427; Ionomer 427; Nylon (Polyamide) 427; Parylene 427; Phenylene oxide 428;, Polyarylate 428; Polybutylene 428; Polycarbonate, 428; Polyester, thermoplastic 428; Polyetheretherketone 428; Polyetherimide 428; Polyethylene, 428; Polyimide 429; Polyphenylene sulfide 429;, Polypropylene 429 ; Polystyrene 429; Polysulfone, 429; Polyurethane, thermoplastic 429; Polyvinyl, chloride 429; Styrene-acrylonitrile 429; Styrene, maleic anhydride 430, Thermoset Plastic 430, Alkyd 430; Allyl 430; Amino (Melamine & Urea), 430; Diallyl phthlate 430; Epoxy 430; Phenolic, phenol formaldehydes 430; Polyester, thermoset, 430; Polyurethane, thermoset 430; Silicone 431, Property Category 431, Elasticity 431; Odor and taste 431; Temperature, 431; Flame resistance 431; Impact 431; Electric, arc resistance 432; Radiation 432; Transparency, 432; Applied stress 432; Color 432; Moisture 432;, Chemical 433; Surface wear 433; Permeability 433;, Electrical 433; Dimensional stability 433; Weathering 434, , Chapter 8, , Plastic Processing, Overview, Influence on Performance, Processing and Material Behavior 442; Tolerance and Dimensional Control 442, Shrinkage 442; Inspection and tolerance 443, Viscoelasticity 446, Shear rate 447, Model/Prototype Building, Processing Behavior, Rheology and Melt Flow 448; Molecular Weight Distribution and Melt Flow 448; Melt Flow and Viscosity 449, Newtonian flow 449; Non-Newtonian flow 449, , xiii, 400, , 412, , 435, 435, 435, , 447, 447

Page 13 : xiv, , Contents, , Melt Flow Rate 449, Melt index test 449, Melt Flow and Elasticity 450; Flow Performance 451; Flow, Defect 452, Nonlaminar flow 452; Sharkskin 453; Nonplastication 453; Volatile 453; Shrinkage 453; Melt structure 453, Thermodynamic 453; Residence Time 453; Chemical, Change 453; Trend 454, Processing And Property, Problem/Solution 454; Plastic with a Memory 454; Orientation 454; Directional Property 457, FALLO Approach, Tooling, Mold 457; Die 460; Basics of Flow 463, Injection Molding, Thickness of Section and Rib 468, Designing bucket 468, Productivity 469; Modified 1M Technique 469, Coinjection molding 470; Gas-assist injection, molding 471; Injection-compression molding 472;, Soluble core molding 472; Over-molding 473, Extrusion, Modified Extrusion Technique 477, Coextrusion 477; Special shape 481; In-line postforming 481, Coating 481; Orientation 481, Blow Molding, Complex Irregular Shape 489; Coextrusion or Coinjection, 491; Collapsibility Container 492; EBM and IBM Comparison 492; Blow Molding-Compression-Stretched 492, Thermoforming, Temperature Control 495; Thermoforming Thermoset, Plastic 496; Thermoforming vs. Injection Molding 496, Foaming, Blowing Agent 499; Formation and Curing of Rigid, Polyurethane Foam 499; Expandable Polystyrene 500; Syntactic Foam 500, Static and dynamic property 501, Cushioning Design 502, Density effect 502; Creep resistance 502, Foam Reservoir Molding 503, Reinforced Plastic, RP Characterization 504; RP Directional Property 504, Orientation of reinforcement 504; Hetergeneous/homogeneous/anisotropic 508, Advanced Reinforced Plastic 509; Micromechanic 509;, Material 509, Flexible RP 510; Preimpregnation 510; Bulk, molding compound 510; Sheet molding compound 510; Surfacing reinforced mat 511; Gel coat, 511; RP Cost 511, , 454, 457, 457, 463, , 474, , 485, , 493, 496, , 503

Page 14 : Contents, , Process 512, Autoclave molding 512; Bag molding 512; Bag, molding Hinterspritzen 512; Contact molding 512;, Hand lay-up 514, Boat 514; Untraditional hull design, 514, Filament winding 515; Injection molding 517;, Lost-wax 517; Marco process 517; Pressure bag, molding 517; Pultrusion 517; Resin transfer molding 517; SCRIMP process 522; Spray-up 522;, Stamping 522; Vacuum bag molding 523, RP Future 523, Calendering, Compounding Material 526; Coating 526; Calendering or, Extrusion 526, Compression and Transfer Molding, Reaction Injection Molding, Liquid Injection Molding, Rotational Molding, Encapsulation, Casting, Powder Coating, Vinyl Dispersion, Process Control, Processing Window 533, Auxiliary Equipment, Secondary Equipment, Machining and Prototyping 535; Drilling and Reaming, 535; Thread Tapping 537; Sawing, Milling, Turning, Grinding, and Routing 537, Finishing and Decorating, In-Mold Decoration 538; Painting 538; Vacuum Metallizing and Sputter Plating 545; Electroplating 545; Flame, Spray/Arc Spray 545; Hot Stamping 545; Sublimation, Printing 545; Printing 546; Decal and Label 546; Surface, Treatment 546, Joining And Assembly, Troubleshooting, Safety And Processing, Equipment/Processing Variable, Combining Variable 552, Selecting Process, Shape 553; Size 555, Thickness tolerance 555, Surface Finish 558; Cost 560; Summary: Matching Process, and Plastic 563, , Chapter 9, , xv, , 523, 527, 528, 528, 528, 529, 529, 530, 530, 530, 533, 534, , 537, , 546, 546, 547, 551, 552, , Cost Estimating, , 567, , Introduction, Effective Control, Technical Cost Modeling, MoldlDie Cost, , 567, 571, 571, 573

Page 15 : xvi, , Contents, Cost Analysis Method, Cost-Benefit Analysis 573; Direct and Indirect Cost 573;, Cost Effectiveness 574; Cost-Effectiveness Analysis 574;, Cost Estimating 574; Cost Estimating Factor 574; Cost Reduction 574; Cost Target 575; Variable Cost 575; Energy, Cost 575; Product Cost 575, Designing Product, Energy, Solid Waste 577, Competition, Quotation, Market, , Chapter 10, , Appendix, , Summary, , Overview, Design Success, Challenge 586; Challenge Requires Creativity 587; Value, Added/Analysis 587, Plastic Industry Size, Fabricating Employment 589, Future, Research and Development 589; Theoretical vs. Actual, Value 589; Design Demand 591, , A. Plastics Design Toolbox, , 1. Plastics Databases, Electronic, 2. Hard-Copy Data Sources, 3. Process Simulation Software, 4. Plastics Design Books, 5. Design Education, 6. Trade Publications, 7. Trade Associations, 8. Industry Conferences, 9. Key Related Websites, 10. Key Corporate Websites, , B. Terminology, C. Abbreviation, D. Conversion, E. Mathematical Symbol and Abbreviation, References, Index, , 573, , 575, 576, 577, 579, 579, , 580, 580, 580, 588, 589, , 593, 593, 599, 602, 610, 616, 619, 621, 622, 623, 624, , 630, 648, 656, 662, 663, 671

Page 16 : Preface, , This book provides a simplified and practical approach to designing with plastics that fundamentally relates to the load, temperature, time, and environment subjected to a product. It, will provide the basic behaviors in what to consider when designing plastic products to meet, performance and cost requirements. Important aspects are presented such as understanding, the advantages of different shapes and how they influence designs. Information is concise,, comprehensive, and practical., Review includes designing with plastics based on material and process behaviors. As designing with any materials (plastic, steel, aluminum, wood, etc.) it is important to know their, behaviors in order to maximize product performance-to-cost efficiency. Examples of many, different designed products are reviewed. They range from toys to medical devices to cars to, boats to underwater devices to containers to springs to pipes to buildings to aircraft to spacecraft. The reader's product to be designed can directly or indirectly be related to product, design reviews in the book., Important are behaviors associated and interrelated with plastic materials (thermoplastics,, thermosets, elastomers, reinforced plastics, etc.) and fabricating processes (extrusion, injection molding, blow molding, forming, foaming, rotational molding, etc.). They are presented, so that the technical or non-technical reader can readily understand the interrelationships., This type of basic information has been reviewed for many centuries with different types, of materials and more recently (in just over a century) with plastics. Recognize the design basics and/or fundamentals remain the same. Their interpretation and applicability, improves with time. It is like saying 2 + 2 = 4 for the many past centuries. Now we can, say it with a computer where in the recent past we used an abacus, adding machine, slide, rule, etc., It has been prepared with the awareness that its usefulness will depend on its simplicity, and its ability to provide essential information. Examples are provided of designing different, plastic products and relating them to critical factors that range from meeting performance, requirements in different environments to reducing costs and targeting for zero defects., Reviews range from small to large and simple to complex products., As explained in the book many designs do not require the use of engineering equations, since a practical approach can be used. The engineering equations needed for designs are, plentiful and readily available. When using these equations in designs all that is required is, to incorporate basically the load, temperature, time, and environment behavior of plastics. A, limited amount of equations as well as plastics material properties and processing information, presented are provided as comparative guides that relate to the many behavior patterns, available to meet your design requirements. As reviewed and referenced in this book there are, extensive resources available to obtain detailed worldwide engineering equations, material

Page 17 : xviii, , Preface, , data, and processing techniques such as those reviewed in Appendix A: PLASTICS DESIGN, TOOLBOX and references., There is an endless amount of available data for many plastic materials worldwide. Unfortunately, as with other materials, there does not exist only one plastic material that will, meet all performance requirements. However it can be stated that for practically any product, requirement(s), particularly when not including cost, more so than with other materials, there, is a plastic that can be used., The data included provides examples of what are available. As an example static properties, (tensile, flexural, etc.) and dynamic properties (creep, fatigue, impact, etc.) can range from, near zero to extremely high values. They can be applied in different environments from, below the surface of the earth, to over the earth, and into space., Designing depends on being able to analyze many diverse, already existing products, such, as those reviewed in this book. One important reason for studying these products and design, approaches is that they provide a means to enhance the designers' skills. Design is interdisciplinary. It calls for the ability to recognize situations in which certain techniques may be used, and to develop problem-solving methods to fit specific design situations., The many problems that are reviewed in this book should not occur. They can be eliminated, so that they do not effect the product performances when qualified people understand that, the problems can exist. They are presented to reduce or eliminate costly pitfalls resulting, in poor product performances or failures. With the potential problems or failures reviewed, there are solutions presented. These failure/solution reviews will enhance the intuitive skills, of those people who are already working in plastics., This book provides the reader with useful reference of pertinent information readily available as summarized in the table of Contents and particularly the Index. From a pragmatic, standpoint, any theoretical aspect that is presented has been prepared so that the practical, person will understood it and put it to use. The theorist, for example, will gain an insight, into the limitations that exist and relate to those that exist with other materials such as steel,, wood, and so on., Based on over a century of worldwide production of billions of plastic products, they, can be designed and processed successfully, meeting high quality, consistency, long life, and, profitability. All that is needed is understanding the behavior of plastics and properly applying, these behaviors., The information contained in this book is of value to even the most experienced designers, and engineers, and provides a firm basis for the beginner. The intent is to provide a review, of the many aspects of designing that goes from the practical elementary to the advanced or, theoretical approach. In addition to the plastic designer, this book will be useful to different, people where they can interrelate their interests that interface with designing. Included are the, tool maker (mold, die, etc.), designer of other materials (metals, aluminum, glass, wood, etc.),, fabricator, plant manager, material supplier, equipment supplier, testing and quality control, personnel, cost estimator, accountant, sales and marketing personnel, new venture type,, buyer, vendor, educator/trainer, workshop leader, librarian, industry information provider,, lawyer, and consultant. People with different interests can focus on and interrelate across, subjects that they have limited or no familiarity in the World of Plastics., Patents or trademarks may cover information presented. No authorization to utilize these, patents or trademarks is given or implied; they are discussed for information purposes only., The use of general descriptive names, proprietary names, trade names, commercial designations, or the like does not in any way imply that they may be used freely. While information, presented represents useful information that can be studied or analyzed and is believed to be, true and accurate, neither the authors nor the publisher can accept any legal responsibility, for any errors, omissions, inaccuracies, or other factors.

Page 18 : xix, , Preface, , In preparing this book and ensuring its completeness and the correctness of the subjects, reviewed, use was made of the authors worldwide personal, industrial, and teaching experiences that total over a century, as well as worldwide information from industry and trade, associations., THE ROSATOS, YEAR, , 2001

Page 19 : 1, Introduction, , Overview, , This book was written to serve as a useful reference source for the product designer, new to plastics as well as providing an update for those with experience. It should also, be of interest to non-designers and management personnel involved in plastic products, that need a general overview of the concepts, and critical issues related to plastic products, in this World of Plastics. It highlights designing with plastics based on material & process behaviors. As with designing any materials (plastic, steel, aluminum, wood, ceramic,, etc.) it is important to know their behaviors, in order to maximize product performanceto-cost efficiency., The mature plastics industry is a worldwide, multibillion-dollar industry in which a, steady flow of new or improved plastic materials, new or improved production processes,, and new or improved market demands has, caused rapid and tremendous growth in the, use of plastics. For over a century the World, of Plastics product production, with over a, billion products, continues to expand enormously with the passing of time. Manufacturers are introducing new products in record, time. The ability to shrink time-to-market, schedules continues to evolve through the, more knowledgeable application and behavior or familiarity of the different plastic ma-, , terials, processing techniques, and design approaches (Fig. 1-1)., During this time very successful and long, lasting designed products have been in service that range from primary and secondary, structures in toys to packages to computer, hardware to electrical/electronic communication hardware to boats to aircraft to, space craft and so on. There are those exposed to extreme environmental conditions, that range from in the ocean, underground,, earth's surface, and to outer space. Temperature exposures have been from below freezing to elevated conditions that extended to, 2500°F (1370°C) for very short time periods., Products have performed meeting static and, dynamic loads (creep and fatigue stresses, impact loads, and so on). An inherent characteristic that makes most plastics performanceto-cost efficient is the different available low, to high production methods that results in relatively low processing cost (Fig. 1-2)., So the answer to the question of what, is new in designing with plastics actually is, that we continue to do it easier and quicker, because new, improved, and more uniform, behaviors of plastics and their processing, capabilities are always developing. Designwise little is new conceptually. What changes, with the passing of time is the level of sophistication that is applied to designing any, products.

Page 20 : 2, , 1 Introduction, Dimensions, strucluralloads, gov'tlindustry standards, service environments, etc., PROJECT, TEAM, FEASIBILITY, STUDY, , Set up processing specifications, , Plant layout, , Manufacturing processing specifications, , Plant personnel capability evaluation, , Ensure product quality, , Product output schedule, Accounting schedule, Purchasing schedule, Inventory schedule, Documentation for management to ensure meeting delivery schedules and profitability, , Ensure meeting all product functions, , [~~~;~~~~~::~, Set up value analysis (VA), , After start of production, analyze complete design (again), , to change design/production/safety factors in order to, reduce costs, , Fig.l-l, , Design flow diagram for product design.

Page 21 : 3, , 1 Introduction, , MARKETABLE, PRODUCTS, , l, , ", , LEADS, , }, , ~, , l, , GOOD, BUSINESS, , &, MANUFACTURING, PRACTICES, , l, , ", , ~, Performance, , Rcqulrements, Engineering, Evaluation, , Molding, Molecular, Structures, , Setectlng, Material Precess, , R&D, , Evaluate, DetractcrsConstraints, , E><Iruslon, , Rheology, Properties, , Cost Analys is, , Compounding, A lloys, , Injection, Blow, Compression, Reinforced PI.stlc., , Blends, , Others, , l, , GOOD, ENGINEERING, , Film, Sheet, Prolile, Pipe, Coating, Etc., , Etc., , Fig.1-2 Plastics product growth related to a tree growth., , Unfortunately there is no one plastic or, process (as with other materials such as steel,, wood, glass, etc.) that provide all types of, performance requirements. However it can, be stated that for practically any product requirement(s), particularly when not including cost, more so than with other materials, there is a plastic that can be used. The, many different plastics meet different property and processing requirements that the de-, , signer uses in selecting the most appropriate, plastic that can be fabricated by the required, process., What has made these plastic products successful was that there were those that knew, the behavior of plastics and how to properly apply this knowledge. Recognize they, did not have the "tools" that make it easier, for us to now design products. Now we are, more knowledgeable and in the future it will

Page 22 : 1 Introduction, , 4, , THE COMPLETE PROCESSING OPERATION ... THE FALLO APPROACH, , PRODUCT, PERFORMANCE, REQUIREMENTS, based on, market, requirements, , ORGANDESIGN, , INE, , PRODUCT, , PLANT, , MATERIAL, HAND·, LING, , LAYOUT, , Use the FALLO approach by, reexamining the parameters, going from the product design, through production. Examples of, potential cost reductions include:, (1) redesign product with thinner, walls to reduce production, etc.: (2) reduce cost by using I, plastic, change to a more, expensive plastic that reduces, processing cost, etc.; (3) modify, process control to reduce, production cost, etc.; and (4), other parameters reviewed in this, publication., , Storage,, , Use VALUE, , dryer,, blender,, , ANALYSIS, approach, , andlor, , to meet, , others., , performance, to cost, requirements, , 1--1...__se_t...;uP_P_R_E_VE_N_1:_AT_tV_E_M_A_IN_T_EN_A_N_C_E_ _---I, FALLO, Follow ALL Opportunities, , I, I, I, I, I, I, , IF YOU DO NOT TAKE THIS, ACTION - someone else, , Set up TESTING I QUALITY CONTROL -, , WILL TAKE THE ACTION ..., , Characterize properties: mechanical, physical,, chemical, thermal, etc., , Set up practical I useful TROUBLESHOOTING, , GUIDE based on "causes & remedies", of potential "faults.", , I, I, I, , ~------------------------1:======~~~~~~~~~======]---------------D~.V~.R~1, Fig.1-3 The FALLO approach: !,:ollow ALL Qpportunities., , continue to be easier with new or improved, materials and processing techniques ever, present on the horizon. What is still needed,, as usual, is to have a design plan conceived in, the human mind and intended for subsequent, fabricating execution by the proper method, (Fig. 1-3)., Designers and processors to produce products at the lowest cost have unconsciously, used the basic concept of the FALLO approach. This approach makes one aware that, many steps are involved to be successful,, all of which must be coordinated and interrelated. It starts with the design that involves specifying the plastic, and specifying, the manufacturing process. The specific proCeSS (injection, extrusion, blow molding, thermoforming, and so forth) is an important part, of the overall scheme and should not be problematic., Following the product design is producing a tool (mold, die, and so forth) around, , the product. Next is putting the proper fabricating process around the tool. This action, requires setting up the necessary auxiliary, and/or secondary equipment to interface in, the complete fabricating line. Next is setting, up completely integrated inline equipment, controls to target for the goal of zero defects., Also in the FALLO process is that of purchasing equipment as well as materials, then, properly warehousing the material and maintaining equipment. If processing is to be subcontracted ensure that the proper equipment, is available and used efficiently. This interrelationship is different from that of most other, materials, where the designer is usually limited to using specific prefabricated forms that, are bonded, welded, bent, and so on., The designer matches the end Use requirements with the properties of the selected material using a practical or engineering technique (Fig. 1-4). Target is to achieve the basic, three general requirements of design SUCCess:

Page 23 : 1 Introduction, , Fig.1-4 Practical and engineering approaches to, designing., , (1) economical, (2) functional, and (3) attractive in appearance. In turn the functional aspect relates to the product's three basic environment conditions of load, temperature,, and time. The production method to be used, will often set limitations on designs and vise, versa. The way in which a product is manufactured has a profound influence on its design., There is a number of processing techniques, from which to choose, each of which usually, produces a different type of product., Consider that the first step is a general, product description with requirements such, as what is it to do, how it is to be used, where, it is to fit, etc. An example of a design program approach is reviewed in Table 1-1. Overall design or product conception can be initiated from many sources. The most obvious is, the completely new product. Although such, products are not in abundance compared to, modifications, they offer designers the opportunity to utilize their abilities fully. Depending on its complexity, a new product requires, several months to several years before commercial introduction. More commonly, overall design is using a practical approach such, as a modification of an existing product. This, may be initiated by a company's need to make, the product more attractive or easier for consumers to use. Manufacturing may request a, new design to simplify assembly or minimize, breakage; or management may demand that, costs be reduced., In some cases, achieving these goals requires only a material substitution or a minor design change. But it could mandate that, , 5, , the product be redesigned, different material used, and/or the components made and, assembled using a different approach. After, the product is defined, the functional requirements and the cost value are established,, which is then followed by a preliminary design. After a preliminary design is completed, and approved, different departments such as, the manufacturer's engineering, marketing,, manufacturing, and quality assurance departments should review it; or perhaps one person may have all these responsibilities. Inevitably, some changes will be required. If, they are found to be practical (capable of, achievement without compromising product, cost or functionality in the intended use environment), the design project can proceed to, its next stage., The next step is to prepare a detailed design, with drawings, Once the drawings are available, prototyping and testing can be initiated., Methods of prototyping vary greatly. In some, cases, a painted model cut from polystyrene, foam blocks will suffice. In other cases, a prototype must be made using the specified material and manufacturing process. Prototyping is essential in many designs, regardless of, how it is done, in order to ensure that a product will perform properly prior to production, (Chapter 3)., The aim of product design or redesign is to, achieve the best possible product at the least, practical cost. It is a dynamic procedure, with, the key being communication. As the design, project progresses and as more is learned,, modifications may need to be made. Compromise may also be essential. For example,, a superior design may cost more to produce, than was originally estimated, but after an objective evaluation it may be determined that, it is worth more and market acceptance will, occur. Thus, product cost can be increased, without jeopardizing its chances for success., Similarly, prototypes usually show where additional strength is required, where a product, is over designed resulting in unnecessary cost,, and so on., A final note regarding overall product design procedure is that any design, no matter, how good, can be improved. However, there, comes a time when the design must be frozen, and prototyping or production must begin. If

Page 24 : 6, , 1 Introduction, , Table 1·1 Example of a design program approach, , Design Category, Establish functional, and performance, requirements, , Subcategories, , Detailed Requirements, , Product basic functions, Aesthetics and marketing, Shipping, Available space, Weight, Standardization, Strength and stiffness criteria, Flexibility, Process limitations, Loads:, Establish structural, Gravity, requirements, Dead-Own weight superimposed, Live-Occupancy, Snow, Misc., Pressure, Fluid, Earth, Wind, Dynamic, Impact, Seismic, Handling and shipping, Cyclic, Temperature:, . range- {Interior, Service, E, ., xtenor, Gradient across component thickness, No. of cycles-high to low, No. of cycles-freeze-thaw, Solar gain, surface air flow, Liquid, moisture, and/or vapor tightness, Strength-weight ratios-relative significance, Establish nonstructural Service environment:, requirements, Corrison resistance { Interior, Chemical, Exterior { Soil, Moisture, Organic, Weathering Moisture, wet-dry cycles, {, Freeze-thaw cycles, UVexposure, Rain abrasion, Aging, Moisture, Temperature, Fire safety Incombustibility, Flame spread rate, Toxic gases, Fuel content, (Continues), Estimate allowable, size and shape

Page 25 : 1 Introduction, Table 1-1, , 7, , (Continued), , Design Category, , Subcategories, , Detailed Requirements, Light, Transparency, transmission Translucency, Opaque, Surface texture, Surface coatings, , Preliminary, design of, component, , Control of sunlight, and solar heat, Color, {Aesthetics, {Abrasion resistance, Barrier, {, Thermal insulation, Gradient, Moisture and vapor penetration {Condensation, Electrical insulation, {Dielectric properties, Establish cost targets Examine economics for successful competition with, similar products in conventional materials, Consider total effect of new design on end product, costs: materials, tooling, finishing, assembly,, warehousing and inventory, quality control,, packaging and shipping, and installation, Consider effect on operating costs. Light weight is, important in some applications, Number of identical pieces, Establish production, Minimum and maximum probable production rates, and marketing, requirements, Available plant, Market locations, Shipping costs, Method of marketing, Installation criteria, if applicable, Cost restrictions imposed by competing products or, technology. Prices can shift with short- and, long-term changes in market conditions, Select size and general Consider end use and limitations of suitable plastics,, configuration, efficient manufacturing processes, requirements, for sufficient strength and stiffness with, efficient use of materials, and cost, Select feasible, Satisfy structural requirements with favorable, plastics material or, cost ratios, Satisfy nonstructural criteria with acceptable, materials, compromises and trade-offs where necessary, Is efficient fabrication process available?, Provide required size and configuration, Select feasible, Tooling and plant capital costs to be appropriate for, manufacturing, process or, number of pieces and rate of production, Compatible with available plant and marketing plan, processes, Provides required structural properties and quality, control, Determine structural Develop suitably simplified concept of structural, response based, behavior to permit approximate determination, of structural response-reactions, stress resultants,, on approximate, analysis, stability and stiffness requirements. Make, appropriate assumptions within confines of laws of, statics, ( Continues), {

Page 26 : 8, , 1 Introduction, , Table 1-1, , (Continued), , Design Category, , Subcategories, Establish design, criteria for, trial materials, selected, Proportion, component, for specific, configuration, and thickness, Develop significant, details, , Detailed Requirements, Determine suitable allowable design strengths, and stiffness, taking into account type and, duration of load, service environments, process, effects, quality expectations, etc., Determine trial shape of plates, shells, and ribs, depth, of ribs and sandwiches, and wall thicknesses to meet, strength, deflection, and stability criteria, Review economics and suitability, , Determine concept and principal details for shop, and field connections, penetrations, and other, subparts (if required), Determine materials for connections, coatings,, subparts, etc., Evaluate preliminary Review economics and suitability of materials, Revise preliminary, design, and process based on preliminary proportions., design of component, Consider overall compatibility and practicality of all, materials and parts in component as a system, Does it meet functional and performance, requirements?, Is it compatible with other components that may, interact with it, relative to effects of expansion, and contraction, structural support or movement,, fire safety, etc.?, Review performance Determine if all original performance requirements, and functional, are feasible within economic objectives,, requirements, or whether compromises and tradeoffs should, be considered, Optimize design, General configuration, Configuration proportions such as rib depths,, to reduce cost or, shell radii, fillet radii, etc., satisfy, Material thickness, functional and, Material alternatives-consider additives to, performance, requirements, tailor properties, Process alternatives, Perform structural, Determine structural response-stresses, support, Develop final, analysis of, design of, reactions, deflections, and stability-based on a, acceptable, structural analysis of acceptable accuracy., component, Determine acceptable accuracy based on, accuracy, economic value of component, consequences of, failure, state-of-the-art capability in stress and, stability analysis, margin of safety, knowledge, about loads and materials properties,, conservatism of loads, provisions for further, evaluation by prototype testing, Allowable stresses, strains, deflections, Establish final, Margins of safety against local and overall, design criteria, instability, vibrations, etc., Take into account type and duration of load,, service environments, process effects, equality, expectations, (Continues)

Page 27 : 1 Introduction, Table 1-1, , 9, , (Continued), , Design Category, , Subcategories, Evaluate, proportions, and design, details; revise, if necessary, , Prepare engineering, drawings, Prepare specifications, for technical, requirements, of product, and materials, , Evaluate design, by prototype, and materials, tests, , Prepare manuals or, instructions for, maintenance and, repair, Develop practical, full-scale prototype, for structural tests, , Test materials for, structural, properties and, effect of service, environment, Revise design, if, required, , Develop production Pattern design, and distribution, and drawings, system, Mold design and, drawings, , Detailed Requirements, Shape of plates, shells, ribs, Depth of ribs and sandwiches, Thickness of shells, flanges, and stiffeners, Connections: Shop, Field, Edge conditions, • Penetrations, Subparts, Inserts, Drawings are sometimes prepared in two stages:, Design drawings, Detail or fabrication drawings, Materials requirements including composition,, quality standards, and minimum structural properties, Fabrication requirements and standards, including, dimensional tolerances, allowable defects,, and minimum structural properties, Requirements for prototype and quality control tests, and procedures, Shipping and handling, Requirements for field assembly, installation, or, erection, Periodic maintenance, recoating, Service conditions: temperature limits, chemical, exposure limits, Repair procedures, Develop practical test program to demonstrate, components ability to meet structural and, performance criteria. Extent of such test program, if, any, depends on economic value of component,, number of units to be produced, consequences of, failure, accuracy of structural analysis and, design, margins of safety used in design, knowledge, about service loads and environments, and difficulty, of duplicating service loads and conditions, in test, Determine that materials produced in actual fabrication, process will have the minimum structural properties, and resistance to service environment assumed in, the design. Extent of testing, if any, depends, on available information about specific materials, and processes to be used, Correct design and detail problems, if any, revealed, in tests, Modify materials, or process, if production materials', properties not adequate, Protect or modify materials if service environment, causes excessive degradation of properties, , Take into account shape limitations and design, rules that facilitate molding, , ( Continues)

Page 28 : 1 Introduction, , 10, Table 1-1, , (Continued), , Design Category, , Subcategories, Production process, design and, layouts, Develop any special, equipment, Distribution and, marketing plan, Procedures for, packaging, storing,, handling, and, shipping, Installation requirements, , this is not done, the new design will remain, on the board until competition beats you to, the marketplace., The fabricator places no limits on the design. There is a way to make the product if, the price is justified. Any job can be done, at a price. The truly limitations are factors, such as usable tool size (mold, die, etc.), material shrinkage, substance finishing operation (that usually is not required), dimensional tolerance allowance, undercut, insert, inclusion, parting line, fragile section, production rate, and the essential selling price., Note that there are companies with in-house, fabricating capabilities that will replace existing equipment to produce a new product at a, lower cost., Table 1-2 provides estimates of the major, types of plastics consumed yearly worldwide, that now total 339,990 million Ib (154 million, tons). About 90% are thermoplastics (TPs), and 10% thermoset (TS) plastics. USA and, Europe consumption's are each about onethird of the world total. There are well over, 35,000 different type plastic materials worldwide. However, most of them are not used, in large quantities; they have specific performance and/or cost capabilities generally for, specific products by specific processes that, principally include many thousands of products (Chapters 6 & 7)., , Detailed Requirements, Take into account materials and configuration, characteristics that simplify processes, Automated processes are needed for high-volume, production, Production for inventory, or by special order, Replacement part inventory, Locate production facilities to optimize, distribution, Identify special requirements for protection in, handling and shipment, Specify special requirements for assembly or, installation, , The plastics industry is characterized by a, wide variety of many different plastic materials and distinct processing methods that fabricate many different plastic materials into, many different products. The following Fig., 1-5 provides a summary of the interrelations, of plastics-to-processing-to-products. By following this type of a practical sequence of, events permits fabricating products that meet, performance and cost requirements used substantially in all industries. This is a "back to, basic" approach that helps one to understand, that there is a logical approach in producing, products that range from the initial concept, to the customer receiving the product., Plastics are now among the nations and, world's most widely used materials, having, surpassed steel on a volume basis in 1983 (Fig., 1-6). By the beginning of this century, plastics, surpassed steel even on a weight basis (Fig. 17). These figures do not include the two major, and important materials consumed, namely, wood and nonmetallic earthen (stone, clay,, concrete, glass, etc.). Volumewise wood and, construction materials each are possibly about 70 billion ft 3 (2 billion m 3 ). Each represents about 45 % of the total consumption, of all materials. The remaining 10% include, those shown in Figs. 1-6 & 1-7. Plastic materials and products cover the entire spectrum, of the world's economy, so that its fortunes

Page 29 : ">, , 90, 192, 70, 30, 30, 121, 412, 6,018, , 110, 410, 90, 45, , 40, 166, 763, 8,441, , 1267, 4330, 857, 346, , 389, 1800, 8150, 91,414, , 70, 195, 875, 9,892, , 170, 482, 155, 65, , 610, 1590, 1388, 410, 1456, 280, 1366, 365, 165, 250, , Brazil, , 4093, 10,254, 9178, 5481, 12388, 6180, 13566, 1410, 576, 1036, 1210, 2464, 607, 243, 317, 1625, 7250, 77,878, , 145, 386, 140, 50, 45, 162, 74, 7,607, , Western, Europe 2, , 900, 619, 417, 390, 1837, 495, 1307, 290, 140, 210, , Other, Latin, America l, , 63, 220, 1750, 17,655, , 242, 493, 121, 48, , 1023, 2563, 2294, 1808, 2477, 1236, 2713, 282, 115, 207, , Eastern, Europe 3, , 212, 502, 255, 23,478, , 339, 1178, 443, 164, , 1439, 1804, 2158, 1512, 3761, 2175, 5001, 948, 302, 1285, , Japan, , 106, 453, 198, 21,148, , 170, 715, 215, 85, , 2661, 1938, 1218, 1825, 5338, 2299, 2667, 460, 155, 645, , China, , 235, 1254, 5310, 63,325, , 425, 5441, 475, 322, , 6121, 3391, 4967, 4850, 11,633, 5275, 11,176, 950, 325, 1175, , Other, AsiaPacific4, , 63, 165, 740, 8,580, , 155, 390, 145, 42, , 580, 1210, 1325, 390, 1250, 190, 1275, 305, 140, 215, , Africa &, Middle, East, , 21, 88, 344, 4,554, , 59, 224, 45, 20, , 367, 457, 532, 310, 773, 352, 738, 92, 37, 95, , Rest of, World, , 1,591, 6,751, 26,121, 339,990, , 4,382, 16,705, 3,363, 1,460, , 27,352, 34,031, 39,630, 23,096, 57,610, 26,201, 55,039, 6,831, 2,723, 7,104, , Grand, Total, , 1 Argentina, Chile, Columbia, Venezuela and all other., 2European Union plus Norway and Switzerland., 3Includes Russia and the Balkans., 4 Australia, India, Indonesia, Malaysia, North Korea, Pakistan, South Korea, Taiwan, Thailand, Philippines, Singapore, Vietnam., 5High Performance, other thermosets, specialty elastomers, tailored blends and alloys., Source: Concise Encyclopedia of Plastics: Fabrication & Industry, by Rosatos, Kluwer Publ., 2000; Injection Molding Handbook, 3ed Edition, by Rosatos, Kluwer Publ., 2000., , 480, 1176, 952, 380, 605, 405, 695, 175, 80, 125, , 610, 1281, 1136, 475, 1394, 725, 796, 145, 75, 180, , 8468, 7748, 14,065, 5265, 14,698, 6589, 13,739, 1409, 613, 1681, , Mexico, , Canada, , United, States, , World plastic consumption (million 1b), , LLDPE, LDPE, HDPE, Urethane, PVC, Polystyrene, Polypropylene, ABS, Acrylic, Unsaturated, Polyester, Nylon, PET, Poly-carbonate, Thermoplastic, Polyester, Acetal, Recycle Plastics, Other Plastics5, Total, , Table 1-2, , ......., ......., , ~, , 0, , :::t., , ("), , l:::, , $:).., , ~, ...., ...., 0, , .......

Page 31 : I, , 13, , Introduction, Steel, , Plastics, , 1,000,000 1----+---+---+---+---+-:::.II""""---::;;orV--+--ri, , Aluminum, , 100,000, Rubber, , .., c, , ..., 0, , Copper, , 8, 0., , Zinc, , 10,000, , 1940, , 1950, , 1960, , 1970, , 1980, , 1990, , 2000, , Year, , Fig.1.' World consumption of plastics by weight., , What this book provides is information on, the extensive different properties (Figs. 1-8, & 1-9) and processing capabilities the many, different plastics offer. It also provides facts, such that most of the plastic products produced only have to meet the usual requirements we humans have to endure such as, the environment (temperature, etc,). Thus, there is no need for someone to identify that, most plastics can not take heat like steels,, For certain plastic products there are definite, properties (temperature, chemical resistance,, load, etc.) that have far better performance, than steel and other materials, Recognize that, most plastics in use also do not have a high, modulus of elasticity or long creep and fatigue behaviors because they are not required, in their respective product designs, However, there are plastics with extremely high modulus and very long creep and fatigue behaviors, (Chapter 2)., , What this discussion identifies is that each, material (specific plastic, specific steel, specific wood, etc.) behaves certain ways. If a, product can be made from a specific steel, rather than a specific plastic, that is the material to use. However, unfortunately for steel, and other materials, plastics continue to expand its use where these other materials are, not competitive propertywise and/or costwise., This book will not provide extensive engineering equations since they are readily, available from industry that are reviewed in, Appendix A: PLASTICS DESIGN TOOL·, BOX and references (3, 6, 10, 14,20,29,31,, 36, 37, 39, 43 to 125). Equations will be reviewed throughout this book where they are, required to understand the behavior of plastics in order to meet different load requirements (static to dynamic), What this book, provides is information on the behavior of

Page 32 : 14, , 1 Introduction, Thennal Expansion, Plastics, , ~~~~gssites I ReinfOr~L-Ood-lr:::=!:"I, Steel and Iron, Aluminum, Concrete and Glass, , Strength, , 25, , Plastics~iL=ili~~~~~3', ~:~~r-, , 50, , 75, , 100, , 125, , -li, 150,10 in./in.oF, , Composites I Reinforced Plastics, , 0, , Aluminum, , concrel';v', , 50, , s60, , Thennal Conductivity, , 150 2OO'10 3p'i, , 100, , W/moK, 0.0, , 1000 MPa, , Modulus of Elasticity, , Plaslics.~00~~~~~~==~, Sleel, [), , Plastics, , Composites / Reinforced Plastics, Wood, , IReinforCedP,asticsf~~~~i~b:::], Wood, Brick, Glass, Concrete, , 10, , Aluminum~, , Btu I SQ.ft./ OF I in. /hr, , concrel'iLT=-::t1110;';=;22=0:;;t.30=:;?i40:;;:1V50' 106psi, 100, , 200, , Specific Gravity, Plastics ~, Composites / Reinforced Plastics, , Wood, SleeI, Aluminum, Glass~, Concrete - Stan, , ,, , 300 GPa, , Maximum Continuous Service Temperature, o, , -'-~ [!ffJ;~;m~~, o, , /, , Fig.l-S, , 1.0, , 0.5, , 100, , 200, , 300, , 400, , ·c, , 500, , 600, , 700, , 600, , 900, , General comparison of different materials., , plastics that permits the designer to properly, design with plastics usually not requiring any, engineering equations., When one becomes familiar with plastics, such as their viscoelastic behavior [that is, a combination of viscous and elastic properties in a plastic with the relative contribution of each being dependent on time,, temperature, stress, and strain rate (Chapter 2)], plastics can be properly applied to the, equations, etc. This book is targeted to have, you become both familiar and how to apply the behavior of plastics in any equations., Your book authors as well as many of the, referenced authors have extensive experience in adapting the behavior of plastics to, products with or without equations that have, different shapes, decorations, etc. They include toys, packages, building panels, medical, devices, electronic devices, lighting devices,, chemical operations, building to bridge structures, small to very large pipe lines, boats,, underwater devices, aircraft primary and sec-, , ondary structures, missile components, reentry spacecraft protective shields, etc. These, examples of a few of the products designed, basically range from just requiring the proper, aesthetics (practical approach) to those being subjected to extensive high dynamic, creep and fatigue stress loads (engineering, approach)., Generalization Jnstifiable, A short dissertation upon almost any extensive subject such as this subject is usually, blessed by the reader's understanding that, generalizations are not only justifiable but, also mandatory in order to cover the scope, of the subject. However, a learned treatise, of ponderous bulk can be readily exempted, from criticism for tedious passages devoted, to details in that the authors are attempting, to present a full and uncompromised assay of, the subject. Somewhere in between lies this

Page 33 : 15, , 1 Introduction, , Composition, Microstructure, Metals, , {, , Ph...., Grein size, Corrosion resistance, Inclusions, , ;;::~oSition, Plastics, , {, , Crystallinity, Molecular waight, Flammability, Spatial configuration, Chemical rasistanca, , Melting point, Thermel, Magnetic, Electrical, Optical, Acoustic, Gravimetric, , Composition, PorositY, Grain size, Binder, Corrosion resistance, Composition, (matrix/reinforcamentl, Matrix/reinforcement, bond, Volume fraction, reinforcement, Reinforcement nature, Corrosion resistance, , Tensile properties, Toughness, Ductility, Fatigue, Hardness, Creep resistance, , Available shapes, Available sizes, Available surface texture, Manufacturing tolerances, , Tensile properties, Heat distortion, Compression strength, PV Limit, Toughness, , Manufacturing tolerances, Stabilitv, Available siles, , Tensile properties, Compression strength, Fracture toughness, Hardness, , Available shapes, Avaiiable sizes, Manufacturing tolerances, Available surface tex lure, , Tensile properties, Compression strength, Fracture toughness, Creep resistanca, , Available shapel, Available sizes, Manufacturing tolerances, Stability, , Fig.1-9 Guide to various material properties., , book. For those desiring more details, appropriate references are provided., Often the authors set their own ground, rules in a probably futile attempt to satisfy, the inquisitiveness of those from another, technical discipline in an expeditious manner, and yet not to incur the criticism of those, highly knowledgeable in the subject area., The writers have followed this important but, perilous course., Design Definition, , The term "design" has many connotations., They can range from industrial designers to, high structural load engineering designers., A few of these will be summarized in order to highlight that different designer skills, are used to meet different product requirements. Essentially it is the process of devising, a product that fulfills as completely as possible the total requirements of the user, and, at the same time satisfies needs in terms of, , c9st-effectiveness or ROI (return on investment). It encompasses the important interrelationship practical factors such as shape, material selection (including unreinforced and, reinforced, elastomers, foams, etc.), consolidation of subparts, fabricating selection, and, others that provide low cost-to-performance, products., Product design is as much an art as a, science. Recognize that a successful design, is usually a compromise between the requirements of product function, productibility, and cost. Basically design is the mechanism whereby a requirement is converted to, a meaningful plan. Design guidelines for plastics have existed for over a century., With plastics to a greater extent than other, materials, an opportunity exists to optimize, product design by focusing on material composition and orientation to structural member geometry when required. The type of designer to produce a product depends on the, product requirements. As an example in most, cases an engineering designer is not needed

Page 34 : i6, , i, , introduction, , because the product has no major load requirement. All that is needed is experience, and/or a logical evaluation approach based, on available material and processing data., This practical approach is the least consumer, of time and least expensive (Fig. 1-4)., , Design Technology, It is the prediction of performance in its, broadest sense, including all the characteristics and properties of materials that are essential and relate to the processing of the plastic., To the designer, an example of a strict definition of a design property could be one that, permits calculating product dimensions from, a stress analysis. Such properties obviously, are the most desirable upon which to base, material selections., However, like with metals, there are many, stresses that cannot be accurately analyzed., Hence one is forced to rely on properties that, correlate with performance requirements., Where the product has critical performance, requirements, such as ensuring safety to, people, production prototypes will have to, be exposed to the requirements it is to meet, in service., In plastics, these correlative properties, together with those that can be used in design, equations, generally are called engineering, properties. They encompass a variety of situations over and above the basic static strength, and rigidity requirements, such as impact, fatigue, flammability, chemical resistance, and, temperature., , industrial Designer, IDs are essential to all industries that relate to research, engineering, production, and, marketing activities. They must exercise the, creativity imagination that sets them apart, from being a mere modifier of what the competition offers. There is a difference between, IDs and other professions whose functions, are sometimes confused with those of IDs., The true artist, for instance, produces a personal interpretation of what one feels and creates the final object alone. The IDs do not;, , they help to provide directions by which others create the final product. They differ in, their approach as an engineering designer., The ID profession has embraced plastics, with enthusiasm for several reasons. First,, plastics provide enormous freedom of shape, compared with traditional materials of design. They also permit product production, that is faster and more consistent, and they, can do it all at a fraction of the cost for making nonplastic products. This low product cost, does not stem from the fact that plastics are, low in cost. On a per-pound basis, they are actually more costly than many competing materials. But the process ability and relatively, low density of plastics (which translates into, lower costs per volume) gives them a big economic advantage. The net result is that the ID, can now achieve quality products at disposable price levels (216)., Colorability is another reason IDs select, plastics for many products. Molding color, into a product eliminates finishing and painting operations, thus reducing costs. Beyond, cost, integral color also masks the nicks, chips, and scratches that impair appearance during the life of the product. Color effects, are almost limitless. Transparent, translucent,, pearlescent, fluorescent, or marbleized colors, are readily available for use in plastics., Another design appeal of plastics is, their ability to accept topical decoration. A, permanently affixed multicolor label can be, provided by means of heat transfer or hot, stamping. When a more secure surface is, required (for computer keycaps, containers,, etc.) the markings, decorations, or labels can, be placed directly in the mold cavities and, subsequently molded into the product as it, is formed. Two-color injection molding is, another option. This is a process in which a, product is first molded in line color and then, (without demolding) a second cavity is placed, over the part permitting a second color to, be molded over a predetermined portion of, it. Other in-mold decoration processes are, available, including a selection of patterns, that can be etched into the mold surface ranging from a very high polish usually reserved, for lenses to a medium matte finish adequate, to mask minor sink marks (Chapter 8).

Page 35 : I, , Introduction, , Appearance means something different to, each discipline involved in the development, of a new product. Industrial designers, engineering designers, tool builders, and processors are each affected in a different way., Yet the cooperation of all is necessary in order to achieve the best possible appearance., Concern for appearance generally translates, to more work for the designer. It would, certainly be far easier to construct a rectangular box or a drafted cylinder with a few appropriately placed screws. But a world full of, rectangular boxes and drafted cylinders usually would not be eye appealing. The principal, problems associated with appearance factors, are the development of contoured housings,, space limitations, and assembly devices. Contoured housings are far more difficult to calculate than those with regular dimensions. In, some cases, initially it is practically impossible to achieve complex molded shapes without creating wall thickness variations that can, cause sink marks and warpage., The ID function involves a great deal more, than appearance design. The designer is often called on to create the very concept of the, product. In doing so, they will consider the, utility, cost, innovation and human engineering aspects of the proposed product that relates to its basic appeal to the end-user., , 17, , ments to bear on the appearance and performance of the product., Engineering Designer, It is the area of engineering that involves, the application of graphic principles and, practices to the solution of engineering loading equation problems. It is the systematic, process by which a solution to a problem, is created. A definition that contains the, necessary ideas and speaks broadly is that, engineering design is a decision-making activity whereby scientific and technological information is used to produce a product or system. It is different in some degree from what, the designer knows to have been done before, and that is meant to meet new needs., , Graphic Designer, It covers the principles of engineering, drawings, computer graphics, descriptive geometry, and problem solving. The overall, study of graphics involves the three basic aspects of terminology, skills, and theory., , Innovative Designer, Human engineering. While the designer, usually regards the problems of space limitations as being appearance related, they are, most often the outcome of the ID's concern, for human engineering, or the proper relationship of the product to the human body., For example, personal computers should be, small enough to be carried by many people,, coffee-cup handles should be comfortable to, the hand, eyeglass frames should be easy on, the ears, etc., Human engineering requirements often, dictate the size, weight, and form of a product., This translates to smaller, lighter and contoured products as the ID works from the, outside to its interior. Often this results in, conflict with the company's engineering designer, who works basically from the interior, to its outside. Compromise becomes an important factor as they all bring their require-, , A skilled designer blends a knowledge of, materials, an understanding of manufacturing processes, and imagination of new or innovative designs. Recognizing the limits of, design with traditional materials is the first, step in exploring the possibilities for innovative design with plastics. Some designers operate by creating only the stylish outer appearance, allowing basic designer to work, within that outside envelope. This approach, is used very successfully such as in certain, products or parts for furniture, etc. There, are also the combination of designing appearance with engineering so that the stylish product incorporates the best combination with, ease of processing when using a specific plastic, simplify assembly, provide capability of, repair, streamlining quality control, and/or, other conditions. The stylish envelope that

Page 36 : 18, , 1 Introduction, , eventually emerges will be a logical and aesthetic answer to the design challenge., Material Optimization Designer, Designers can turn to materials as a means, of dramatically improving their products', performancewise and costwise. Over 70%, of product designs are geometric. With over, 80,000 materials worldwide (including over, 35,000 plastics) to choose from, the material, software tools have become an asset to designers and engineers with or without experience in material familiarity. There is software that provides information on specific, performance requirements so that only one, or a few will be listed as the best material to, meet the product performance requirements., These tools let designers consider materials, as a variable in design to meet their specific, product requirements. (Appendix A: PLASTICS TOOLBOX), Maximum Diametrical Interference Designer, An example of an interference fit design, is the maximum allowable interference for a, particular hub and shaft. It depends on the, types of materials used in the hub and shaft,, and on the ratio of the shaft diameter to the, hub outside diameter. It is determined to ensure that hoop stress in the interference fit, does not exceed the allowable stress of materials used (Chapter 7)., Medical Device Designer, Designing medical devices is one of many, others (buildings, chairs, jewelry, aircraft,, toys, etc.) with each having their specific requirements. As an example in USA designing, medical devices with developing controlled, manufacturing environments are required to, be submitted to FDA for approval. They are, (necessary) time-consuming, costly activities, for medical device manufacturers. Such activities generally have a target time line with a, set completion date and budget. In the mean, time, the daily operations of manufacturing in, , a controlled environment present continual, challenge that vary as the regulations change, and the cost of materials and manufacturer, increases., Different systems are used to aid people,, including designers. An example is a system, designed to ensure efficient contamination, control operations. It is called PACT (prevention, assessment, corrective action, and training). PACT is designed to assist supervisor,, managers, and engineers with contamination, control management. It involves the continuous improvement principles of total quality management. Also involved is the quality, system regulation (Appendix: TERMINOLOGY, Quality system regulation)., , Design Features That Influence Performance, One of the earliest steps in product design is to establish the configuration of the, product that will form the basis on which a, suitable material is selected to meet performance requirements. During this phase certain design features have to be kept in mind, to avoid problems such as reduction of properties. Such features are called detractors or, constraints. Most of them are responsible for, the unwanted internal stresses that can reduce the available stress level for load bearing, purposes. Other features may be classified as, precautionary measures that may influence, the favorable performance of a product if, they are properly incorporated., For example, something as simple as a stiffening rib is different in size for a solid or, foamed product even when both products, use the same plastic. Familiarization of design constrains is a critical first step in design, to eliminate product problems. A designer, might have an expensive tool (mold or die), prepared based on a plastic's shrinkage value., It is discovered belatedly that the plastic did, not meet some overlooked design constrain, and the plastic required a much lower shrinkage value. The tool has too large a mold cavity, or die opening requiring expensive modification or replacement of the tool., This book contains information that can, be used to setup a checklist on plastic

Page 37 : 1 Introduction, capabilities and constrains based on performance requirements. A general guide of the, design process anatomy can use the overlapping approach of chronological order, clarifying the task, conceptual design, embodiment, of design, and detailed design. To do full justice to plastics, one should become familiar, with the meaning of the data furnished by, the material supplier, the long-term effect on, properties when subjected to a load, the influence of surrounding environment, and other, material requirements that, as a rule, may be, insignificant with metals or some of the other, materials (Chapter 5)., With this type of action, it will become, rather routine to follow through with a design, to build a prototype, to test performance, capability, and so forth. Design examples, reviewed were selected for the purpose of, demonstrating that the standard technical or, engineering handbooks are in general of the, same importance in conjunction with plastics, as they are with steels, aluminum, wood, etc., Product reviews have been modified to eliminate strength detractors and to incorporating, needed features in such a manner that overall, product characteristics will be protected., Before investigating anyone or a group, of any materials, product performance and, environmental conditions are to be determined. This is a major area of product failure because, in most cases, a complete set, of requirements is not properly determined., A few or many requirements may exist. Examples of a few of these requirements are, reviewed., 1. Determine requirements under which, the product will be used. Examples include, color, temperature, moisture, ultraviolet exposure, exposure to fungus, flammability,, chemical, electrical resistance, arc resistance,, light transmission, stability or permanency,, physical property, mechanical property, optical property, heat and/or electrical insulation,, resistance to scratching (mar resistance), and, special requirements such as self-lubrication,, lightness, hinging property, spring property,, time of exposure, etc. Also important will be, meeting existing government and/or industry, regulation., , 19, , 2. Determine tolerance requirements that, are expected in the performance of the product. Shrinkage characteristics of the selected, plastic should be as small as possible so that, tolerances can be anticipated with a reasonable degree of accuracy., 3. If required, determine the nature of the, load to which the product will be exposed,, such as impact, creep, deflection, stresses,, bending, gliding, etc., 4. Color matching may be a factor., 5. Cost of plastic by volume and cost to, fabricate., Once the performance and environmental conditions have been defined, the selection of a suitable material can be made, and, this in turn can be followed, if necessary,, with the necessary engineering calculations, to establish strength requirements. The basic data needed for calculations have to be, collected and have to pertain to the specific, grade of the selected material. The pertinent, information required for making determinations for longevity of the product and obtaining a general concept of the character and, behavior of the selected material should be, supplied by the manufacturer of the raw material and/or obtained in-house or via a contractor., Examples of information that could be required follows:, 1. Data sheets of the specific grade of material containing the properties required,, 2. Stress-strain curves at the conditions of, product application. If applicable, this would, usually indicate the toughness of material by, sizing up the area under the curve (Chapter 2). It would also show the proportional, limit, yield point, corresponding elongations,, and other relevant data., 3. Curves showing change of tensile, strength, flexural strength, and modulus with, increasing temperatures or other environments., 4. Creep data for periods at 100 and 1000, hours (or more, if available) covering stress, and temperature conditions closely comparable to those of product application.

Page 38 : 20, , i, , introduction, , 5. The allowable working stress, based on, successful performance at conditions of product usage., 6. Chemical and/or heat resistance at conditions in service., 7. Others (fatigue, etc.) (Chapter 2)., Not all product components are subjected, to a load; in fact most are not subjected to, loads requiring an engineering analysis via, engineering equations, etc. Experience in the, material behavior on similar products and/or, similar performance requirements are all that, is needed. In these products designers become involved in their processing features, that will prevent or reduce internal stresses,, with elements that will lead to consistent and, economical production, with appearance and, dimensional control, etc., Products that are subjected to a load have, to be analyzed carefully with respect to the, type and duration of the load, the temperature conditions under which the load will be, active, and the stress created by the load. A, load can be defined as continuous when it remains constant for a period of 2 to 6 hours,, whereas an intermittent load could be considered of up to two hours duration and is, followed by an equal time for stress recovery., The temperature factor requires greater attention than would be the case with metals., The useful range of temperatures for plastic applications is relatively low and is of a, magnitude that in metals is viewed as negligible., Most design books continually report that, plastics cannot take the heat of metal (steel,, etc.) indicating that plastics cannot take heat., As reviewed, by far practically most plastic, products do not have to take any more heat, then the human body. Practically all plastics, easily meet this heat requirement for these, type products and in fact many types of these, plastics meet the higher heat requirements, of plastic products that exist under the engine hood of an automobile, in the trunk of, an automobile (excellent user-environmental, test), electrical/electronic devices, etc., An important subject to introduce concerns the allowable working stress for a spe-, , /, , fmlIlIm, , Properties, Appearance, Cost, , IIu!n, , Density, Mellindex, MoL Wt. Distribution, Additives, , ,, lrum, , •, , .., , Temperature, Pressure, Cycle, Mold And Process Design, , Fig. 1-10 Interrelating product-plastic-process, performance., , cific plastic that relates to their viscoelasticity., Other important subjects include their static, and dynamic loading capabilities as well as, their creep to fatigue behaviors. Details on, these subjects are presented in Chapter 2., , Interrelating Product-Plastic-Process, Performance, , In order to understand potential problems, and solutions of design, it is helpful to consider the relationships of machine capabilities, plastics processing variables, and product performance (Fig. 1-10). A distinction, has to be made here between machine conditions and processing variables. For example,, machine conditions include the operating, temperature and pressure, mold and die, temperature, machine output rate, and so, on. Processing variables are more specific,, such as the melt condition in the mold or, die, the flow rate vs. temperature, and so on, (Chapter 8)., A distinction between machine conditions, and processing variables must be made in order to avoid mistakes in using cause-effect, relationships to advantage. It is the processing variables, properly defined and measured, not necessarily the machine setting,, that can be correlated with product performance. There was a time when designers took, little interest in the processing of the products they had designed. They simply sent the, drawings to the processor in another department or company and expected perfect products to emerge, but design and processing, are now so interrelated that this separation

Page 39 : 21, , 1 1ntroduction, should not exist if products are to be consistently successful., Those familiar with processing can detect, and correct visible problems or readily measure factors such as color, surface condition, and dimension. However, less-apparent, property changes are another matter. These, may not show up until the products are in, service, unless extensive testing and quality, control are used., As there are many different plastics, a number of techniques for defining and quantifying, their characteristics exist. As an example, molecular weight distribution (MWD) is an, indication of the relative proportions of, molecules of different weights and lengths., In turn MWD relates to processing characteristics that directly relate to product performances (Chapter 8)., , Advantage and Disadvantage of Plastic, As a construction material, plastics provide practically unlimited benefits to the design of products, but unfortunately no one, specific plastic exhibits all these positive, characteristics. The successful application of, their strengths and an understanding of their, weaknesses (limitations) will allow designers, to produce useful products. With any material (plastic, steel, etc.) products fail not because of its disadvantage(s). They failed because someone did not perform in the proper, manner. It could be the designer even though, the processor goofed and the designer was, not aware that a goof could occur. When a, situation exists that one person does not have, the total responsibility, goofs can easily occur., If the designer does not have the overall responsibility, then his boss or someone else up, the management line has the responsibility, and is accountable for the goof., There is a wide variation in properties, among the over 35,0000 commercially available materials classified as plastics. They, now represent an important, highly versatile, group of commodity and engineering plastics., Like steel, wood, and other materials, specific, groups of plastics can be characterized as having certain properties. As with other materi-, , Become aware that for any gain there could be a loss, not originally included in the design performance., , c- ...L-• - .., , -.-, , --.,:: ..., , When you gain ·something·there will be a loss ..... does, that loss influence product performance (for any material:, plastic, wood, steel, glass, etc.)., Fig.1-11 For any gain, there could be a loss not, originally included in design performance using, plastic or any other material., , als, for every advantage cited, a corresponding disadvantage can probably be found, (Fig. 1-11)., In general, most plastics can easily be fabricated into all shapes and sizes. As reviewed, throughout this book, if desired they can, have highly intricate shapes held to tight tolerances by using certain plastics and processes suitable for either limited or mass production. Many plastics can be worked using, common shop techniques. Other generalizations include, as reviewed, the fact that many, consider plastics to be of low cost. In fact, some are so expensive that their use is limited to the most sophisticated technology and, applications. Regardless, if the cost of materials appears to be too high for an application,, a look at the processing method to be used, usually shows that it could be less expensive,, based on the material-to-processing costs., There are designers who overlook this aspect. Many plastic products are very successful costwise because their fabricating costs, are low., Many plastics are typically not as strong, or as stiff as metals, and they are prone to, dimensional changes, especially under load, and/or heat. Successful designs take these, conditions into account when they influence, design requirements. As will be seen, there, are plastics that meet dimensional tight requirements, dimensional stabilities, and are

Page 40 : 22, , 1 Introduction, , stronger or stiffer based on product shapes, than other materials., Highly favorable conditions such as less, density, strength through shape, good thermal insulation, high degree of mechanical, dampening, high resistance to corrosion and, chemical attack, and exceptional electric resistance exist for certain plastics. There are, also those that will deteriorate when exposed, to sunlight, weather, or ultraviolet light, but, then there are those that resist such deterioration., No matter what the material may be, there, is always room for improvement, whether it, is in plastics, metals, wood, design parameters, testing procedures, or any other category. To date designers are generally most familiar with metals and wood as well as their, behavior under load and varying conditions, of temperature and environment. For those, designing in metals and the other materials, that have been used for centuries there is extensive literature available (and much more, continually being developed because they are, needed). One can easily enter the field of, designing with these materials and refer to, the handbooks that tell one what to do similar to what this book provides when using, plastics., As an example, for room-temperature applications most metals can be considered to, be truly elastic. When stresses beyond the, yield point are permitted in the design, permanent deformation is considered to be a, function only of applied load and can be determined directly from the stress-strain diagram. The behavior of most plastics is much, more dependent on the time of application, of the load, the past history of loading, the, current and past temperature cycles, and, the environmental conditions. Ignorance of, these conditions has resulted in the appearance on the market of plastic products that, were improperly designed. Fortunately, product performance has been greatly improved, as the amount of technical information on, the mechanical properties of plastics has increased in the past half century. More importantly, designers have become more familiar with the behavior of plastics rather than, , just explaining that one cannot design with, plastics., Basics in Designing, , Plastic materials are predominantly synthetic materials. Since their inception over, a century ago they have enjoyed a growth, that has been unequaled by any other group, of materials. This demand continues to increase, and the facilities for meeting the new, requirements are being expanded continuously. There have been good reasons for the, phenomenal application of plastics in order, to justify the large investments needed to produce the raw materials and to convert them, into finished products., Overall, it can be stated that plastic products meet the following criteria: their functional performance meets use requirements;, they lend themselves to esthetic treatment, at comparatively low cost; and, finally, the, finished product is cost competitive. Examples of their desirable behaviors can start, with providing high volume production. Plastic conversion into finished products for large, volume needs has proven to be one of, the most cost-effective methods. Combining, bosses, ribs, and retaining means for assembly are easily attained in plastic products, resulting in manufacturing economies that are, frequently used for cost reduction. It is a case, where the art and technology of plastics has, outperformed any other material in growth, and prosperity., Their average weight is roughly one-eighth, that of steel. In the automotive industry,, where lower weight means more miles per, gallon of gasoline, the utilization of plastics is increasing with every model-year. For, portable appliances and portable tools lower, weight helps people to reduce their fatigue, factor. Lower weight is beneficial in shipping, and handling costwise, and as a safety factor, to humans (no broken glass bottles, etc.)., The value of heat insulation is fully appreciated in the use of plastic drinking cups, plastic handles on cooking utensils, electric irons,, and others where heat can cause discomfort

Page 41 : 1 Introduction, or burning. As insulation in the walls of buildings, homes, etc. energy and cost advantages, are obvious. In electrical devices the plastic, material's application is extended to provide, not only voltage insulation where needed, but, also the housing that would protect the user, against accidental electrical grounding. In industry the thermal and electrical uses of plastics are many, and these uses usually combine, additional features that prove to be of overall, benefit., Corrosion resistance and color are extremely important in many products. Protective coatings for most plastics are not, required owing to their inherent corrosionresistant characteristics. The eroding effects, of rust are well known with certain materials. Whereas certain plastics do not deteriorate offering distinct advantages. Colors for, esthetic appearance are incorporated in the, material compound and become an integral, part of the plastic for the life of the product., Those with transparency capabilities provide many different products that include, toys, protective shields (high heat resistance,, gunfire, etc.), transportation vehicle lighting,, camera lenses, eyeglasses, contact lenses, etc., When transparency is needed in conjunction, with toughness, plastic materials are the preferred candidates. Add to the capability of, providing simple to very complex shapes., Include plastics with coefficient of friction,, chemical resistance, and others. Many plastic materials inherently have a low coefficient, of friction. Other plastic materials can incorporate this property by compounding a suitable ingredient such as graphite powder into, the base material. It is an important feature, for moving products, which provides for selflubrication. Chemical resistance is another, characteristic that is inherent in most plastic, materials; the range of this resistance varies, among materials., Materials that have all these favorable, properties also have their limitations. As, with other materials, every designer of plastic, products has to be familiar with their advantages and limitations. It requires being cautious and providing attention to all details., Nothing new since this is what designers have, , 23, , been doing for centuries with all kinds of materials if they want to be successful., As reviewed throughout this book one, must determine what measures were taken, to evaluate the materials. Carefully study, the test results and test methods that are, employed in obtaining these properties and, their interpretation for application purposes, (Chapter 5), and finally determine the fine, details of use conditions to establish the suitability of a plastic material for the intended, product. It is easily accomplished to determine the plastic to be used but requires familiarity with the test results being evaluated, and behavior of plastics to meet your performance requirements., Design Approach, , The highest skill a designer can possess, consists of making full use of the properties of, materials to create truly distinctive products., In the process the designer needs to know, and explore the limits of design that can start, with a feasibility study (Fig. 1-12). For example, limits are imposed by such factors as the, manufacturing process limits on the material, that will determine the shapes to which the, material can economically be converted, the, physical properties of the materials that will, limit their applications and useful environments, and the designer's imagination in combining form and function. In theory, the imagination is limitless, but in practice the first, two limitations affect a designer's ability to, exercise it., Design ideas in the industry using plastics, continue to be extensive. New ideas and applications for meeting performance-to-cost, requirements are seemingly end-less. They, include the capability of being innovative, to applying practical concepts. There are all, sorts of novel approaches to design ideas with, plastics. An innovative design exercise to produce automotive products that includes consolidations is reviewed in Fig. 1-13., This design exercise relates to different, products and their consolidation such as, front-end parts (valance panel can be joined

Page 42 : 24, , 1 Introduction, , PROJECT TEAM, FEASIBILITY STUDY, , I, , Identify, Specific, Functions, , I, , I, Conceptual, Product Layout, , Apply available, experience, , 1, , Dimension.., dructural, loads,, gov'tllndustrY, standards,, s.rvlce, environment-,, etc., , I, , I, , quantity,, cost and, , I, , production, schedule, , I, Computer, Approach, , Manual, Approach, , Target, , I, , I, , I, I, Apply Design, Creativity, , PALLO, , FOLLOW ALL OPPORTUNITIES, , Fig.I-12, , Project team feasibility study., , to make a one-piece front end) and rear-end, parts consolidation. The materials used include unreinforced and reinforced plastics., Products include fender extension, headlamp, housing, taillamp housing, rear finish panel,, front and upper grille panel, hoods, scoops,, rear deck-lid, and spoilers. The future will, probably include the mass production of onepiece plastic molded mono co que chassis and, even incorporate other parts., Most successful designers have the ability to develop products that will be instantly, acceptable to a buyer. Their designs have a, recognizable, functional improvement along, with some visual appeal to set their products apart from conventional ones. Too many, new product designs or redesigns are nothing more than slight improvements that anybody could make with a minimum of thought., Many companies inch there way to progress, with just such a slight change every now and, then. This is the easy way to give the appearance of improving a product line with, , the least disruption of the manufacturing process and requires little adjustment by the sales, staff, with the exception of printing new sales, brochures., , Design Feature, , As reviewed throughout this book and, particularly in Chapter 3, Design Concept,, there are many design features that keep expanding the use of plastics in different products. These features include shapes, sandwich, constructions, shrinkages, tolerances, and, processes., One factor that has done a great deal to, harm the reputation of plastics is that in many, cases designers and engineers have, after deciding tentatively to try to introduce plastics, then lavishly copied the metal product, it was to replace. Too much emphasis cannot, be given to the general principle that plastics are to be used based on their behavior

Page 43 : 25, , 1 Introduction, An upper grille panel, and a valance panel could join to make a, one-piece front end., , SECTION A-A, , ..---------, , -----------------~------, , A, , Fig.l-B An innovative design exercise to produce automotive products., , characteristics in order to eliminate failures., It is essential to cast aside all preconceived, notions of design in metals and treat plastics, on their own merit as one would with any, other material., A hard-and-fast rule to be followed by all, intending to use plastics is to design for plastics. As an example, for the same-size crosssection the strength of conventional plastics, (not the high-performance reinforced types), is considerably less than that of most metals. The designer will thus find it necessary to, increase thickness, introduce stiffening webs,, and/or possibly use design inserts of various, types ofthreads to secure the proposed product. The process will in some instances also require modification to the shape of the equipment used to produce the product., It will become obvious that what is considered good design practice insofar as metals, are concerned will not necessarily be good, practice for processing plastics. It is advisable, , when in doubt to review this book, the referenced literature on the subject, and/or consult processing experts who know the behavior of plastics. Almost all current methods of, design analysis are based on models of material behavior that are relevant to traditional, metallic materials, as for example elasticity, and plastic yield. These principles are embodied in design formulas' design sheets or, charts and in more modem techniques, such, as computer-aided design (CAD) using finite, element analysis. The design analyst is merely, required to supply appropriate elastic or plastic constants for the material as reviewed in, Chapter 2., , Computer Use, The computer supports rather routine, tasks of embodiment and detailed operation, rather than the human creative activities of

Page 44 : 1 Introduction, , 26, , The two-piece hood with outer panel and inner, support panel may give way in the future to a, one-piece. self-reinforced molded hood., , I~, , ;Q, SECTION A-A, , ~, , +1, , \(=====V4), SECTION A-A, , Fenders and adjoining parts in the future can be, molded in one piece., A, , t, , Fig.I-13 (Continued), , conceptual human operation. Recognize that, if the computer can do the job of a designer,, there is no need for a designer. The computer is another tool for the designer to use., It makes it easier if one is knowledgeable on, the computer's software capability in specific, areas of interest such as designing simple to, complex shapes, product design of combining, , parts, material data, mold design, die design,, finite element analysis, etc. By using the computer tools properly, the results are a much, higher level of product designing and processing that will result in no myths., Successful designed products require the, combination of various factors that includes sound judgment and knowledge of

Page 45 : 27, , 1 Introduction, Another step would join the hood-fender to the one-piece front end, --a single joint-free automobile front end assembly--as a, single molded component., , A, , ,, , MOLDING, ANGLE, , SECTION A-A, , Fig.l-13, , processing. Until the designer becomes familiar with processing, a fabricator must be, taken into the designer's confidence early, in development and consulted frequently., There are software programs that can provide some assistance in this area. It is particularly important during the early design, phase when working with conditions such as, shapes and sizes. There are certain features, that have to be kept in mind to avoid degradation of plastic properties. Most of these detractors or constrains are responsible for the, unwanted internal stresses that can reduce, the available stress for load bearing purposes, (Chapter 5)., Computers permeate all areas of the plastics industry from the concept of a product, design, tb raw material, to processing, to marketing, to sales, to recycling, to government, and industry regulations, and so on. Computers have their place, but most important is, , (Continued), , the person involved with proper knowledge, in using its software in order to operate and, use them efficiently., The industrial production process as practiced in today's business is based on a smooth, interaction between regulation technology,, industrial handling applications, and computer science. Particularly important is computer science because of the integrating functions it performs that includes the primary, processing equipment, auxiliary equipment,, material handling, and so forth up to business management itself. This means that ClM, (computer-integrated manufacturing) is very, realistic to maximize reproducibility that results in producing successful products., The use of computers in design and related fields is widespread and will continue, to expand. It is increasingly important for designers to keep up to date continually with, the nature and prospects of new computer

Page 46 : 28, , 1 Introduction, Deck lids can take the same parts consolidation path as hoods., The deck lid, inner, with spoiler and the deck lid, outer, could, be combined into a one-piece self-reinforced deck lid., A, , SECTIONA·A, , Rear finishing panels, rear valance panels and rear fender, extensions are realities. Tail lamp housings, both hidden and, with exterior finish are in common usage. A relatively simple, flight of imagination joins all these elements into a one-piece, rear end panel., , SECTIONC-C, SECTION, A-A, , iV??3, , SECTIONA·A, , Fig. 1-13, , hardware and software technologies. For example, plastic databases, accessible through, computers, provide product designers with, property data and information on materials and processes. To keep material selection, accessible via computer terminal and a modem, there are design database that maintain, graphic data on thermal expansion, specific, heat, tensile stress and strain, creep, fatigue,, programs for doing fast approximation of the, stiffening effect of rib geometry, educational, , (Continued), , information and design assistance, and more, (Appendix A: PLASTICS DESIGN TOOLBOX)., , Computer-Aided Design, CAD is the process of solving design problems with the aid of computers. This function, includes the computer generation and modification of graphic images on a video display,

Page 47 : 1 Introduction, The one-piece deck lid. and the one-piece rear end panel., with the addition of a quarter panel section. could become, a fully integrated rear end assembly in a single. joint-free, molded component., , 29, , the fundamental role of the designer's innovation capability., , Computer-Aided Design Drafting, CADD, a part of CAD, is the computerassisted generation of working drawings and, other documents. The CADD user generates, graphics by interactive communication with, the computer. The graphics are displayed on, a video terminal and can be converted into, hard copy by a printer or plotter., , Computer-Aided Manufacturing, CAM describes a system that can take a, CAD product, devise its essential production, steps, and electronically communicate this information to manufacturing equipment such, as robots. The CAD/CAM system has offered, many advantages over past traditional manufacturing systems, including the need for less, design effort through the use of CAD and, CAD databases, more efficient material use,, reduced lead time, greater accuracy, and improved inventory functions., Fig. 1·13, , (Continued), , printing these images as hard copy using a, printer or plotter, analyzing the design data,, and electronic storage and retrieval of design information. Many CAD systems perform these functions in an integrated fashion, that can increase the designer's productivity., It is important to recognize that the computer does not change the nature of the design process; it is simply a tool to improve, efficiency and productivity. It is appropriate, to view the designer and the CAD system together as a design team, with the designer, providing knowledge, creativity, and control, and the computer accurate, easily modifiable, graphics and the capacity to perform complex, design analysis at great speeds and store and, recall design information. Occasionally, the, computer can augment or replace many of, the designer's other tools, but it is important, to remember that this ability does not change, , Computer-Integrated Manufacturing, CIM is the coordination of all stages of, manufacturing, which enables the manufacturers to custom design products efficiently, and economically, by a computer or a system, of computers., , Computer-Aided Testing, In addition to computer-aided activities,, CAT involves the testing that takes place, in all stages of product development (Chapter 5). The advantage of CAT is that the, output of sensors measuring the characteristics of the prototype or finished product, can manipulate the product model to improve its accuracy or identify design modifications needed. In this way testing integrates, design and fabrication into an ongoing, selfcorrecting development process.

Page 48 : 30, , I, , Introduction, , It seems appropriate to close this design, guide, which featured tiny details of design,, with one designer's idea of how the first, all - plastic - automobile may, be assembled., , Fig.l-B, , Computer Software Program, Available are many software programs that, provide guides in simulating the different design and processing operations. These guides, provide a logical approach in training and, conducting research. There are programs that, allow fabricating of different designs using, different types of plastics. There are also simulated process controls that permit processing operators to make changes and see the effects that occur on a fabricated product such, as thickness or tolerance., , (Continued), , Basically a computer software is a set of, instruction guidelines that "tells and documents" what is to be done and how to, do it. There are many off-the-shelf software, instruction programs, with many more always on the horizon, in addition to some, operations developing there own. They include product design, mold design, die design, processing techniques, management,, storage, testing, quality control, cost analysis, and so on. The software tasks vary so, that if you need a particular program, one, should be available or close to it. Recognize

Page 49 : 1 Introduction, that if you are not successful in your selection, you probably did not set up the complete requirements. Also if your software can, not easily accommodate change, then you, have the wrong program. A few introductory examples of design software follow with, more in Appendix A: PLASTICS DESIGN, TOOLBOX:, 1. MOLDEST: Provides product design,, mold design, and injection molding process, control by Fujitsu Ltd., Tokyo, Japan., 2. CAD Plus SOLID EDGE: Advanced mechanical simulation via finite element analysis, by Algor, Inc. Pittsburgh, PA www.algor.com, 3. DFMA: Design for Manufacture & Assembly provides determinants of costs associated with processes by Boothroyd Dewhurst, Inc., Wakefield, RI www.dfma.com, 4. Prospector: Examines and provides tabular, single-point (for preliminary material, evaluation) and multi- point data (predict, structural performance of a material under, actual load conditions) for its 35,000 plastics, by IDES Inc., Laramie, WY., Remember we do not need people if the, software does all the jobs of product design,, mold or die design, material selection, processing setup, making financial profits, and so, on. Software programs are useful tools and, can perform certain functions. The key to success is the designer's capability in using what, is available that includes understanding and, putting to practical use software programs, and recognizing their limitations., As an example since the development of, the first injection molding (1M) simulation, program modules in the 1970s, they (rheology, thermal, mechanical, process control,, quality control, statistical analysis, cost modeling, and so on) have become more and more, powerful as well as compact. The predictive, value of their computations much greater, [but not perfect (Chapter 4, RISKS, Perfection)]. The software program systems also include areas of product applications to their, performance characteristics. Simulation programs can be clearly differentiated partly, by their user-friendliness and computational, precision, and partly on theoretical grounds., , 31, , Thus a design can be evolved as a planar 2-D, model or 3-D model., , Software and database. Many thousands, of software and database programs expand, design capabilities, simplifies design analysis,, material processing properties, processing capability startups, training, and so on. As an example a worldwide software program that has, been extremely useful, based on how it was, organized, is the CAMPUS Database software. This Computer-Aided Material Selection by Uniform Standards of Testing Methods (CAMPUS) compares different plastics, available from different material suppliers., Special CAMPUS pages are on their web, sites, updated each time they finish further, testing of present and new materials., Its data can be directly merged into CAE, programs. CAMPUS provides comparable, property database on a uniform set of testing, standards on materials along with processing, information. The database contains singlepoint data for mechanical, thermal, rheological, electrical, flammability, and other properties. Multipoint data is also provided such as, secant modulus vs. strain, tensile stress-strain, over a wide range of temperatures, and viscosity vs. shear rate at multiple temperatures., RAPRA free Internet search engine. The, number of plastic-related web sites is increasing exponentially, yet searching for relevant information is often laborious and costly., During 1999 RAPRA Technology Ltd., the, UK-based plastics and rubber consultancy,, launched what is believed to be the first free, Internet search engine focused exclusively, in the plastics industry. It is called Polymer, Search on the Internet (PSI). It is accessible at www.polymersearch.com. Companies, involved in any plastic-related activity are, invited to submit their web-site address for, free inclusion on PSI. RAPRA Technology's, USA office is in Charlotte, NC (tel. 704-5714005)., Short and Long Term Performance, , Product design starts by one visualizing a certain material, makes approximate

Page 50 : 32, , 1 Introduction, , calculations to see if the contemplated idea is, practical to meet requirements that includes, cost, and if the answer is favorable, proceeds to collect detailed data on a range of, materials that may be considered for the new, product. When plastics are the candidate materials, it must be recognized from the beginning that the available test data require, understanding and proper interpretation before an attempt can be made to apply them, to the product design. For this reason, an explanation of data sheets is required in order, to avoid anticipating product characteristics, that may not exist when merely applying data, sheet information without knowing how such, information was derived (Chapter 5)., The application of appropriate data to, product design can mean the difference, between the success and failure of manufactured products made from any material (plastic, steel, etc.). There are different sources, of information on plastics. There is the data, sheet compiled by a manufacturer of the material and derived from tests conducted in, accordance with standardized specifications., Another source is the description of outstanding characteristics of each plastic, along, with the listing of typical applications., It is important for the designer to become, familiar with all the information that is available for each plastic, especially that which, is pertinent to the product design requirements. Designers, who are knowledgeable of, the data derived from metal tests, could have, a tendency to apply the plastic data sheet, information in a manner similar to that used, for metals. This could be understood because, there is no warning that some of the data, supplied by the manufacturer are applicable, only when use and test conditions are nearly, the same., However, if suppliers' data were to be applied without a complete analysis of the test, data for each property, the result could prove, costly and embarrassing. The nature of plastic materials is such that an oversight of even, a small detail in its properties or the method, by which they were derived could result in, problems and product failure., Once it is recognized that there are certain reservations with some of the properties, , given on the data sheet, it becomes obvious, that it is very important for the designer to, have a good understanding of these properties. Thus the designer can interpret the test, results in order to make the proper evaluation in selecting a material for a specific, product., Predicting Performance, , Avoiding structural failure can depend in, part on the ability to predict performance, of materials. When required designers have, developed sophisticated computer methods, for calculating stresses in complex structures, using different materials. These computational methods have replaced the oversimplified models of materials behavior relied, upon previously. The result is early comprehensive analysis of the effects of temperature, loading rate, environment, and material, defects on structural reliability. This information is supported by stress-strain behavior data collected in actual materials evaluations., With computers the finite element analysis (FEA) method has greatly enhanced the, capability of the structural analyst to calculate displacement, strain, and stress values in, complicated plastic structures subjected to arbitrary loading conditions. Details on FEA, are reviewed in Chapter 2, Finite Element, Analysis., Nondestructive testing (NDT) is used to, assess a component or structure during its operational lifetime. Radiography, ultrasonics,, eddy currents, acoustic emissions, and other, methods are used to detect and monitor flaws, that develop during operation (Chapter 7)., The selection of the evaluation methodes), depends on the specific type of plastic, the, environment of the evaluation, the effectiveness of the evaluation method, the size of the, structure, the fabricating process to be used,, and the economic consequences of structural, failure. Conventional evaluation methods are, often adequate for baseline and acceptance, inspections. However, there are increasing, demands for more accurate characterization, of the size and shape of defects that may

Page 51 : 1 Introduction, , require advanced techniques and procedures, and involve the use of several methods., A Changing World, It would be difficult to imagine the modem world without plastics. Today they are, an integral part of everyone's life-style, with, products varying from commonplace domestic articles to sophisticated scientific and medical instruments. Nowadays designers readily turn to plastics. Exceptional progress has, been made in over the past century worldwide in all markets. As a matter of fact, many, of the technical wonders we take for granted, would be impossible without versatile, economical plastics. Yet some that are not mindful of the many benefits of plastics still carry, negative feelings about them. Some examples, of their creative use follow that in turn show, the actions by creative designers., , Recreation, , Because people everywhere tend to take, their fun seriously, they spend freely on sports, and recreational activities. The broad range, of properties available from plastics has made, them part of all types of sports and recreational equipment for land, water, and airborne activities. Roller-skate wheels are now, abrasion- and wear-resistant polyurethane,, tennis rackets are molded from specially reinforced plastics (using glass, aramid, graphite,, or other fibers), skis are laminated with plastics, and so on., Electronic, , Most of the electrical equipment and electronic devices we use and enjoy today would, not be practical, economical, or occasionally, even possible without plastics., Packaging, , When packaging problems are tough, plastics often are the answer and sometimes the, , 33, , only answer. They can perform tasks no other, materials can provide. As an example plastics have extended the life of vegetables after, they are packaged. Packaging represents the, largest consumer market for plastics., Building and Construction, , This market is the second-largest consumer, of plastics, after packaging. Durable and easy, to install, as well as cost effective, plastics continue to find more and more applications. This, is a market where spectacular growth will occur when their performance is understood by, the building industry (meeting their specifications, etc.) and/or the price is right. Recognize that if wood with its excellent record, of performances for many centuries, based, on present laws and regulations, could not be, used. They burn, rot, etc. It would be ridiculous not to use wood., Health Care, , Plastics have made many major contributions to the contemporary scene. Health-care, professionals depend on plastics for everything from intravenous bags to wheelchairs,, disposable labware to silicone body parts,, etc. The diversity of plastics allows them, to serve in many ways, improving and prolonging lives, such as a braided, corrugated, Dacron (Du Pont's polyester) aorta tube (24)., Another example of thousands is a biodegradable plastic developed at the Massachusetts Institute of Technology that may, be saving lives in the form of a medical, implant. This plastic is being tested nationwide to determine its effectiveness as a drugreleasing implant in brain cancer patients., These implants, roughly the size of a quarter,, are being placed in patients' brains to release, the chemotherapy drug BCNU (Carmustine). These biocompatible implants have, been found to be safer than injections, which, can cause the BCNU to enter the bone marrow or lungs, where the drug is toxic., This plastic, known as polyanhydride, was, designed shapewise so that water would

Page 52 : 34, , 1 Introduction, , trigger its degradation but would not allow, a drug to be released all at once. The implant, degrades from the outside, like a bar of soap,, releasing the drug at a controlled rate, as it, becomes smaller. The rate at which the drug is, released is determined by the surface shaped, area of the implant and the rate of plastic, degradation, which can be customized to release drugs at rates varying from one day to, many years. This design approach also holds, promise for use with different drugs for various other-medical problems., , Transportation, For today's autos, trucks, busses, vans, etc., plastics offer a wide variety of benefits that, include durability, light weight, corrosion resistance, safety, and fuel savings., , Aerospace, During the last half-century, aeronautics, technology has soared, with plastics playing a, major role. Lightweight durable plastics and, reinforced plastics (RPs) save on fuel while, standing up to forms of stress like creep and, fatigue, in different environments., , Appliance, In this market plastics have been exceptionally beneficial. For example, in the early, 1900s doing simple household tasks was a real, chore. Washing, drying, and ironing clothes, was a rigorous, two-day affair involving the, filling of metal tubs, scrubbing by hand, hanging clothes to dry, and heating cast-iron flat, irons on a stove. With new technology and, "plastics" laundry rooms and kitchens worldwide are operating in relatively minutes and, looking better than ever before., As one of thousands of examples, in the fall, of 1987, Milwaukee Electric Tool Corp. found, itself on the short end of the age-old supplyand-demand equation. That is, it was unable, to keep up with demand for its heavy-duty, electric power tools. The problem was that, their machining operations could not turn out, , enough aluminum die-cast motor housings, to keep up with market demand. The firm, briefly considered what would have been a, long-term solution; a state-of-the-art machining center. But a feasibility study showed that, capital costs for such a facility would run into, hundreds of thousands of dollars, while resulting savings would amount to a few cents, per part., Fortunately, there was the other option of, using plastic motor housings. Du Pont agreed, to produce plastic prototypes of the housing in Zytel nylon 82G plastic. The prototypes were quickly assembled; then they endured demanding drop tests and other field, tests that are standard for Milwaukee Electric, tools. When the housings of impact-resistant, Zytel passed the tests with no problem, the, firm had a new, lower-cost solution to its machining problem; a plastic housing, produced, from a production mold that required no machining., The redesign presented several additional, opportunities. Initial target was to replace, aluminum die-casting, and thereby eliminate, machining as well as deflashing, trimming,, and spadoning (a surface treatment that imparts a matte finish). But they also wanted to, eliminate as many parts as possible, simplify, the assembly, and use a product that worked, as well or better than aluminum. Achieving, these goals produced some spectacular benefits; parts costs dropped by two-thirds while, manufacturing throughput rates increased., Savings in labor, machining, and assembly, operations were augmented by lower capital, and maintenance costs. As many as one million plastic housings were injection molded, without major tool repair or replacement, vs., 100,000 parts for the die-casting operation., Six parts in the housing were eliminated., Because plastic used was not conductive, designers were able to do away with insulating parts, such as a coil shield that separated, the electric brush holder area from the aluminum, and the cardboard insulating sleeve, that went between the copper wiring of the, field core and the housing. Removing the, sleeve had the added benefit of creating better airflow inside the housing, so the motor, ran cooler under load. Press-fitting a rear, ball bearing into the housing and keeping the

Page 53 : i, , introduction, , bearing securely in place proved to be a major, obstacle. The solution was to use eight small, ribs inside the rear-bearing pocket. The ribs, increase the amount of interference that can, be overcome when press-fitting the ball bearing, and keep the bearing in its pocket with a, strong, uniform force., Another concern was achieving overall, perpendicularity of the housing face where, it fitted with a mating gear case. The molder, solved this problem by repeatedly adjusting, molded housing dimensions by a few thousands of an inch. The key to this fine-tuning, was to establish three adjustment spots; one, at each screw hole location. Thus it was much, easier to design mating parts so that they sat, on the lands, specific points, rather than trying to align a complete surface. Accurately, repeating such minute dimensions required, batch-to-batch plastic consistency and process control., , Success by Design, A skilled designer blends a knowledge of, materials, an understanding of manufacturing processes, and imagination into successful new designs. Recognizing the limits of, design with traditional materials is the first, step in exploring the possibilities for innovative design with plastics. What is important, when analyzing plastic designs is the ease to, incorporate ergonomics and empathy that results in products that truly answers the user's, needs., With designing there has always been, the need to meet engineering, styling, and, performance requirements at the lowest, cost. To some there may appear to be a, new era where ergonomics is concerned, but, this is not true. What is always new is that, there are continually easier methods on the, horizon to simplify and meet all the specific, requirements of a design. Some designers, operate by creating only the stylish outer, appearance, allowing basic engineers to work, within that outside envelope. Perhaps this is, all that is needed to be successful, but a more, in-depth approach will work better. Beginning with a thorough understanding of the, , 35, , user's needs and keeping an eye toward ease, of manufacture and repair, designers should, also work from the inside out. The envelope, that eventually emerges will then be a logical, and aesthetic answer to the design challenge, (Fig. 1-14)., With new plastics and processing techniques always becoming available, the design, challenge becomes easier, even when taking, today's solid-waste problem into account. Today's plastics and processes allow designers, to incorporate and interrelate all the aspects, of success. In products such as electronics,, medical devices, transportation controls, and, many others where user-friendly design is required, it has to be obvious to all that plastics, play an important role., , Responsibility, The responsibilities of designers encompass all aspects of design. Although functional design is of paramount importance, a, design is not complete if it is functional but, cannot easily be manufactured, or functional, but not dependable, or if it has a good appearance but poor reliability, or the product, will not fail but does not meet safety requirements. Designers have a broad responsibility to produce designs that meet all the objectives of function, durability, appearance,, safety, and low cost. They should not contend that something is now designed and it is, now the manufacturing engineer's job to figure out how to make it at a reasonable cost., The functional design and the production design are too closely interrelated to be handled, separately., Product designers must consider the conditions under which fabrication will take place,, because these conditions affect product performance and cost. Such factors as production quantity, labor, and material cost are, vital. Designers should also visualize how, each product is to be fabricated. If they do, not or cannot, their designs may not be satisfactory or even feasible from a production standpoint. One purpose of this book, is to give designers sufficient information, about manufacturing processes so that they

Page 54 : 36, , 1 Introduction, MARKETING, , /l~, , PERFORMANCE, , 1 ~AG.NCV, , COMPETITION, , STRUCTU~, , ......I---J.~, , LEGAL, , R&O, , LAB, , SUPPLIERS, , Fig.1-14 The overall design challenge., , can design intelligently from a productivity, standpoint., , Responsibility Commensurate with Ability, Designers have the responsibility of being, committed to developing experience so that, they can function properly. They design products to meet performance and other requirements such as those reviewed in Chapter 4,, DESIGNING AND LEGAL MATTER and, also RISK., Recognize that people have certain capabilities; the law says that people have equal, rights (so it reads that we were all equal since, 1776) but some interpret it to mean equal capabilities. So it has been said via Sun Tzu,, The Art of War, about 500 BC "Now the, method of employing people is to use the, avaricious and the stupid, the wise and the, brave, and to give responsibilities to each in, situations that suit the person. Do not charge, people to do what they cannot do. Select them, and give them responsibilities commensurate, with their abilities.", , Ethic, , Although there is no substitute for individual action based on a firm philosophical and, ethical foundation, designers have developed, guidelines for professional conduct based on, the experience of many of them who have, had to wrestle with troublesome ethical questions and situations previously. These guidelines can be found in the published codes of, ethics for designers and engineers of a number of industry and technical societies such as, the Industrial Designer societies., Terminology, , Different terms are used when discussing, the subject of designing with plastics. Many of, them could be repeated in this book. To eliminate repeating the same definition the Appendix B: TERMINOLOGY has been prepared. Where it is important to describe a, term in the text, its definition is only used in, the text. The INDEX includes the definitions, in the text.

Page 55 : 2, Design Influencing Factor, , Introdnction, , The basic information involved in designing with plastics concerns the load, temperature, time, and environment. As reviewed, throughout this book there are other performance requirements that may exit such as, aesthetics., Design is essentially an exercise in predicting performance. The designer must therefore be knowledgeable in such behavioral, responses of plastics as those ranging from, short time static (tensile, flexural, etc.) to long, time dynamic (creep, fatigue, impact, etc.), mechanical load performances in different, environments. This chapter presents important basic concepts that concern this type information. Along with the other chapters, it, provides the background needed to understand plastics different load performance behaviors in different environments., Many plastic products seen in everyday, life are not required to undergo sophisticated design analysis because they are not, required to withstand extreme loading conditions such as creep and fatigue loads. Examples include containers; cups; toys; boxes;, housings for computers, radios, televisions, and the like; and nonstructural or secondary, structural products of various kinds in buildings, aircraft, appliances, and electronic devices. These type products require reviewing, , the routine performance properties such as, static strength and stiffness to impact that are, primarily available in-house, material software, and/or from material suppliers., In evaluating and comparing specific plastics to meet these requirements past experience and/or the material suppliers are, sources of information. It is important to, ensure that when making comparisons the, data be available where the tests were performed using similar procedures (Chapter 5)., Where information or data may not be available some type of testing can be performed, by the designer's organization, outside laboratory (many around), and/or possible the, material supplier if it warrants their participation (technicalwise and potential costwise). If, little is known about the product or cannot be, related to similar products prototype testing, will definitely be required (Chapter 3)., Designing is, to a high degree, intuitive, and creative, but at the same time empirical and technically mechanical. An inspired, idea alone will not result in a successful, design; experience plays an important part, that can easily be developed. An understanding of one's materials and a ready acquaintance with the relevant processing technologies (Chapter 8) are essential for converting, an idea to an actual product. In addition, certain basic tools are usually needed when conducting prototype evaluation, such as those

Page 56 : 38, , 2 Design Influencing Factor, , for computation and measurement to ensure, that the loads and forces the product is to absorb can be safely withstood., When required plastics permit a greater, amount of structural design freedom than, any other material. Products can be small, or large, simple or complex, rigid or flexible,, solid or hollow, tough or brittle, transparent, or opaque, black or virtually any color, chemical resist or biodegradable, etc. Materials, can be blended to achieve any desired property or combination of properties (Chapters 6, and 7). The final product performance is affected by interrelating the plastic with its design and processing method. The designer's, knowledge of all these variables can profoundly affect the ultimate success or failure, of a consumer or industrial product., For these reasons design is spoken of as, having to be appropriate to the materials of, its construction, its methods of manufacture,, and the loads (stresses) involved in the product's environment. Where all these aspects, can be closely interwoven, plastics are able, to solve design problems efficiently in ways, that are economically advantageous., Material Behavior, , An adequate description of material behavior is basic to all designing applications., Fortunately, many problems may be treated, entirely within the framework of plastic's, elastic material response. While even these, problems may become quite complex because of geometrical and loading conditions,, the linearity, reversibility, and rate independence generally applicable to elastic material, description certainly eases the task of the analyst for static and dynamic loads that include, conditions such as creep, fatigue, and impact., However, we are increasingly confronted, with practical problems that involve material, response that is inelastic, hysteretic, and rate, dependent combined with loading which is, transient in nature. These problems include,, for instance, structural response to moving, or impUlsive loads, all the areas of ballistics (internal, external, and terminal), contact, stresses under high speed operations, high, , speed fabricating processes (injection molding, extrusion, blow molding, thermoforming, etc.), shock attenuation structures, seismic wave propagation, and many others of, equal importance., As these problems were encountered in, the past, it became evident that we did not, have at hand the physical or mathematical description of the behavior of materials necessary to produce realistic solutions., Thus, during the past half century, there has, been considerable effort expended toward, the generation of both experimental data on, the static and dynamic mechanical response, of materials (steel, plastic, etc.) as well as, the formulation of realistic constitutive theories (Appendix A: PLASTICS DESIGN, TOOLBOX)., As a plastic is subjected to a fixed stress or, strain, the deformation versus time curve will, show an initial rapid deformation followed, by a continuous action. Examples of the, standard type tests are included in Fig. 2-l., Details on using these type specimens, under static and dynamic loads will be reviewed throughout this chapter. (Review also, Fig. 8-9 that relates elasticity to strain under, different conditions.), Dynamic loading in the present context, is taken to include deformation rates above, those achieved on the standard laboratorytesting machine (commonly designated as, static or quasi-static). These slower tests, may encounter minimal time-dependent effects, such as creep and stress-relaxation, and, therefore are in a sense dynamic. Thus the, terms static and dynamic can be overlapping., Rheology and Viscoelasticity, Rheology is the science that deals with, the deformation and flow of matter under, various conditions. The rheology of plastics,, particularly of TPs, is complex but understandable and manageable. These materials, exhibit properties that combine those of an, ideal viscous liquid (with pure shear deformations) with those of an ideal elastic solid, (with pure elastic deformation). Thus, plastics are said to be viscoelastic.

Page 57 : 39, , 2 Design Influencing Factor, , Tensile load, , Resistance, to, bending, , Deflec tion,, rigidity, , ~, ----,., b-., , _, , -, , f, , Buckling, , Fig.2-1, , Schematics of different type test specimens., , The mechanical behavior of plastics is, dominated by such viscoelastic phenomena, as tensile strength, elongation at breaks, stiffness, and rupture energy, which are often the, controlling factors in a design. The viscous, attributes of plastic melt flow are also important considerations in the fabrication of plastic products. (Chapter 8, INFLUENCE ON, PERFORMANCE, Viscoelasticity)., , Viscoelasticity Behavior, The viscoelasticity is a combination of viscous and elastic properties in a plastic with, , the relative contribution of each being dependent on temperature, load, and time. It, relates to the important mechanical behavior, of plastics in which there is a temperature and, time dependent relationship between stress, and strain. A material having this property is, considered to combine the features of a perfectly elastic solid and a perfect fluid., The viscoelastic nature of the material requires not merely the use of data sheet information for calculation purposes, but also, the actual long-term performance experience, gained that can be used as a guide. The allowable working stress is important for determining dimensions of the stressed area and

Page 58 : 40, , 2 Design Influencing Factor, , also for predicting the amount of distortion, and strength deterioration that will take place, over the life-span of the product. This means, that the allowable working stress for a constantly loaded product that is expected to, perform satisfactorily over many years has to, be established using creep characteristics of, a material that has sufficient data with which, a reliable long-term prediction of short-term, test results can be made. (The book authors, includes starting from 1943 in personally conducting extensive creep, fatigue, impact, etc., test in order to design and fabricated primary, structural products such as the first all-plastic, airplane.), Pseudo-elastic design Since at least the, 1940s there have been extensive research, and developments in applying standard engineering equations for plastics based on the, behavior of plastics. Many different plastic products have been designed using these, equations, fabricated, and providing long service life of primary structures such as used in, aircraft, buildings, boats, transportation vehicles, signs, deep space antennas, and many, more., For those not familiar with this type information recognize that the viscoelastic behavior of plastics shows that their deformations, are dependent on such factors as the time, under load and temperature conditions., Therefore, when structural (load bearing), plastic products are to be designed, it must be, remembered that the standard equations that, have been historically available for designing, steel springs, beams, plates, cylinders, etc., have all been derived under the assumptions, that: (1) the strains are small, (2) the modulus, is constant, (3) the strains are independent of, the loading rate or history and are immediately reversible, (4) the material is isotropic,, and (5) the material behaves in the same way, in tension and compression., These assumptions are not justifiable when, applied to plastics unless modified. The classical equations cannot be used indiscriminately. Each case must be considered on, its own merits, with account being taken, of such factors as the mode of deformation, service temperature and environment,, , and fabrication method. (These factors can, also apply to steels, etc.) (Appendix A:, PLASTICS DESIGN TOOLBOX)., In particular, it should be noted that the, past traditional equations that have been developed for other materials, principally steel,, use the relationship that stress equals the, modulus times strain, where the modulus, is constant. Except for thermoset-reinforced, plastics and certain engineering plastics, most, plastics do not generally have a constant modulus of elasticity. Different approaches have, been used for this non-constant situation,, some are quiet accurate. The drawback is that, most of these methods are quite complex, involving numerical techniques that are not attractive to the average designers., One method that has been widely accepted, is the so-called pseudo-elastic design method., In this method appropriate values of such, time-dependent properties as the modulus, are selected and substituted into the standard equations. It has been determined that, this approach is sufficiently accurate in most, cases if the value chosen for the modulus, takes into account the projected service life, of the product and the limiting strain of the, plastic, assuming that the limiting strain for, the material is known. Unfortunately this is, not a straightforward value applicable to all, plastics or even of one plastic in all applications. This value is often arbitrarily chosen, although several methods have been suggested, for arriving at a suitable value., For the past century one successful approach is to plot a secant modulus that is, at 1 % strain or 0.85% of the initial tangent modulus and noting where they intersect, the stress-strain curve (Fig. 2-2). However, for many plastics, particularly the crystalline, thermoplastics, this method is too restrictive., So in most practical applications the limiting, strain is decided based on experience and/or, in consultation between the designer and the, plastic material manufacturer. Once the limiting strain is known, design methods based, on its creep curves become rather straightforward (additional information to follow)., Effect of strain rate Workers in the field of, continuum mechanics have had occasion to

Page 59 : 2 Design Influencing Factor, Slope reeresents tangent,, or Young s modulus ~, Slope represents secant, modulus at strain C', , A', , Strain, , 41, , some cases, they were unduly restrictive, but, nonetheless they provided a basis from which, viscoelastic behavior was better understood, and moreover they led to the later development of mathematically more elegant expositions. In 1964 a paper was presented on Thermodynamics of Materials with Memory. This, was a work of power and depth, such depth, according to some people, that it gave "no, status at all" to the other theories (144)., , C', , (a), , Strain, , (b), , Fig.2-2 (a) Example of the modulus of elasticity determined on the initial straight portion of, the stress-strain curve and secant modulus and, (b) secant modulus for two different plastics that, are 85% of the initial tangent modulus., , witness in the past, a significant evolution in, the theory of irreversible thermodynamics of, viscoelastic materials. Following work in the, early 1930's that principally involved steels,, there ensued an intense activity consisting, in attempts to give a thermodynamic basis, to the mechanical theory of small viscoelastic deformations in metals which, of course,, constitute processes that may be regarded as, small deviations from an equilibrium state., It is of historical interest that this activity, left in its wake a divided opinion. Strong objections were voiced from the mathematical, wing of "natural philosophers" who in a tours, de force attacked such assumptions which,, apparently, were arbitrary and, at most, of, debatable validity., These assumptions concerning steel were, often based on physical intuition and in, , Correlating Rheological Parameter, , Object in this section is to review how rheological knowledge combined with laboratory, data can be used to predict stresses developed in plastics undergoing strains at different rates and at different temperatures. The, procedure of using laboratory experimental, data for the prediction of mechanical behavior under a prescribed use condition involves, two principles that are familiar to rheologists;, one is Boltzmann's superposition principle, which enables one to utilize basic experimental data such as a stress relaxation modulus in, predicting stresses under any strain history;, the other is the principle of reduced variables, which by a temperature-log time shift allows, the time scale of such a prediction to be extended substantially beyond the limits of the, time scale of the original experiment., Ludwig Boltzmann (1844-1906) was born, in Vienna. His work of importance in chemistry became of interest in plastics because, of his development of the kinetic theory of, gases and rules governing their viscosity and, diffusion. They are known as the Boltzmann's, Law and Principle, still regarded as one of the, cornerstones of physical science., Mechanical properties of plastics are, invariably time-dependent. Rheology of, plastics involves plastics in all possible states, from the molten state to the glassy or crystalline state (Chapter 6). The rheology of, solid plastics within a range of small strains,, within the range of linear viscoelasticity, has, shown that mechanical behavior has often, been successfully related to molecular structure. Studies in this area can have two objectives: (1) mechanical characterization of

Page 60 : 42, , 2 Design Influencing Factor, , a plastic in order to predict its behavior in, practical applications, and (2) rheological experimentation as a means for obtaining a, greater structural understanding of the material. Much has been explored in these areas, during the past many decades with the result, that a great deal is known about the effect of, structure on the properties of plastics, particularly in the case of amorphous plastics in a, rubbery state., In this approach the reviews concerned the, rheology involving the linear viscoelastic behavior of plastics and how such behavior is, affected by temperature. Next is to extend, this knowledge to the complex behavior of, crystalline plastics, and finally illustrate how, experimental data were applied to a practical example of the long-time mechanical, stability., When a plastic material is sUbjected to an, external force, a part of the work done is elastically stored and the rest is irreversibly (or, viscously) dissipated; hence a viscoelastic material exists. The relative magnitudes of such, elastic and viscous responses depend, among, other things, on how fast the body is being, deformed. It can be seen via tensile stressstrain curves that the faster the material is, deformed, the greater will be the stress developed since less of the work done can be, dissipated in the shorter time., When the magnitude of deformation is not, too great, viscoelastic behavior of plastics is, often observed to be linear, i.e., the elastic, part of the response is Hookean and the viscous part is Newtonian. Hookean response, relates to the modulus of elasticity where, the ratio of normal stress to corresponding, strain occurs below the proportional limit of, the material where it follows Hooke's law., Newtonian response is where the stress-strain, curve is a straight line., From such curves, however, it would not, be possible to determine whether the viscoelasticity is in fact linear. An experiment is, needed where the time effect can be isolated., Typical of such experiments is stress relaxation. In this test, the specimen is strained, to a specified magnitude at the beginning of, the test and held unchanged throughout the, experiment, while the monotonically decay-, , ing stress is recorded against time. The condition of linear viscoelasticity is fulfilled here, if the relaxation modulus is independent of, the magnitude of the strain. It follows that a, relaxation modulus is a function of time only., There are several other comparable rheological experimental methods involving, linear viscoelastic behavior. Among them are, creep tests (constant stress), dynamic mechanical fatigue tests (forced periodic oscillation), and torsion pendulum tests (free oscillation). Viscoelastic data obtained from any, of these techniques must be consistent data, from the others., If a body is subjected to a number of varying deformation cycles, a complex time dependent stress would result. If the viscoelastic, behavior is linear, this complex stress-straintime relation is reduced to a simple scheme, by the superposition principle proposed by, Boltzmann. This principle states in effect that, the stress at any instant can be broken up into, many parts, each of which has a corresponding part in the strain that the body has experienced. This is illustrated in Fig. 2-3, where, the stress is shown to consist of two parts,, each of which corresponds to the time axis as, the temperature is changed. It implies that all, viscoelastic functions, such as the relaxation, modulus, can be shifted along the logarithmic, time axis in the same manner by a suitable, temperature change. Thus, it is possible to, reduce two independent variables (temperature and time) to a single variable (reduced, time at a given temperature). Through the, use of this principle of reduced variables, it is, thus possible to expand enormously the time, range of a viscoelastic function to many years, and many decades., The relaxation modulus (or any other viscoelastic function) thus obtained is a mean's, of characterizing a material. In fact relaxation spectra have been found very useful in, understanding molecular motions of plastics., Much of the relation between the molecular, structure and the overall behavior of amorphous plastics is now known., Mechanical properties of crystalline plastics are much more complex than those of, amorphous plastics (Chapter 6, STRUCTURE AND MORPHOLOGY). For

Page 61 : 2 Design Influencing Factor, , 43, , Boltzmann superposition, , c, , .~, , U5, , 1----1", , Time, , Fig. 2-3, , Time, , Boltzmann superposition principle., , example, a simple temperature-time shift is, respective strain. Viscoelastic data, at least in, theory, can be utilized to predict mechanical, performance of a material under any use, conditions. However it is seldom practical, to carry out the necessarily large number, of tests for the long time periods involved., Such limitations can be largely overcome by, utilizing the principle of reduced variables, embodying a time-temperature shift., While a plastic usually exhibits not one but, many relaxation times, each relaxation time, is affected by the temperature in exactly the, same manner as another. That is the whole relaxation spectrum shifts in unison along the, logarithmic no longer applicable in these materials, because the crystalline morphology, changes with the temperature., , of application of each load, geometry of the, structure, manner in which that structure is, supported, and time at temperature. The behavior of the material in response to these, induced stresses determines the performance, of the structure., The behavior of materials (plastics, steels,, etc.) under dynamic loads is important in, certain mechanical analyses of design problems. Unfortunately, sometimes the engineering design is based on the static loading properties of the material rather than dynamic, properties. Quite often this means overdesign at best and incorrect design resulting, , Mechanical Load, It is well known that mechanical loads on a, structure induce stresses within the material, such as those shown in Fig. 2-4. It is also well, known that the magnitudes of these static and, dynamic stresses depends on many factors, including forces, angle of loads, rate and point, , Fig. 2-4 Interaction of static and dynamic loads, on materials.

Page 62 : 44, , 2 Design Influencing Factor, , in failure of the product in the worst case., The complex nature of the dynamic behavior problem can be seen from Fig. 2-4, which, depicts a wide range of interaction of dynamic loads that occurs with various materials (metals, plastics, etc.). Ideally, it would be, desirable to know the mechanical response, to the full range of dynamic loads for each, material. However, certain load-material interactions have more relative importance for, engineering design, and significant work on, them exists already. The mechanical engineers, civil engineers, and the metallurgical, engineers have always found these materials to be most attractive to study. Even so,, there is a great deal that we do not understand, about them (includes steels, plastics, etc.) in, spite of voluminous scientific literature existing in this area. Each type of load response,, e.g., creep, fatigue/vibratory, or impact, is a, major field in itself. Regardless one has been, able to design products that are subjected to, dynamic loads even though there is always, a desire to obtain more data. The following, review describes the types of material behavior that must be examined and evaluated in, any structural design project involving plastics. They start with damping followed with, short-term stress-strain behavior, long-term, viscoelastic behavior (creep and stress relaxation), fatigue, load material interaction, and, thermal expansion and contraction. Damping, The dynamic mechanical behavior of plastics, is of great interest and importance. For one, thing, the dynamic modulus, or for that matter the modulus measured by any other technique, is one of the most basic of all mechanical properties, with its importance being well, known in any structural application. The role, of mechanical damping is, however, not as, well known. Damping is to diminish progressively vibration or oscillation., Damping is often the most sensitive indicator of all kinds of molecular motions, going on in a material, even in its solid, state. Aside from the purely scientific interest in understanding the molecular motions, that can occur, analyzing these motions is of, great practical importance in determining the, mechanical behavior of plastics. For this reason, the absolute value of a given damping, , and the temperature and frequency at which, the damping peaks occur can be of considerable interest and use., High damping is sometimes an advantage,, sometimes a disadvantage. For instance, in a, car tire high damping tends to give better friction with the road surface, but at the same, time it causes heat buildup, which makes tires, degrade more rapidly., Damping reduces mechanical and acoustical vibrations and prevents resonance, vibrations from building up to dangerous, amplitudes. However, the existence of high, damping is generally an indication of reduced, dimensional stability, which can be undesirable in structures carrying loads for long, periods of time. Many other mechanical, properties, including fatigue life, toughness, and impact, and wear and the coefficient of, friction are intimately related to damping., , Dynamic Mechanical Behavior, Dynamic mechanical tests measure the response or deformation of a material to periodic or varying forces. Generally an applied, force and its resulting deformation both vary, sinusoidally with time. From such tests it· is, possible to obtain simultaneously an elastic, modulus and mechanical damping, the latter, of which gives the amount of energy dissipated as heat during the deformation of the, material., The behavior of materials under dynamic, load is of considerable importance and interest in most mechanical analyses of design, problems where these loads exist. The complex workings of the dynamic behavior problem can best be appreciated by summarizing, the range of interactions of dynamic loads, that exist for all the different types of materials. Dynamic loads involve the interactions, of creep and relaxation loads, vibratory and, transient fatigue loads, low-velocity impacts, measurable sometimes in milliseconds, highvelocity impacts measurable in microseconds,, and hypervelocity impacts as summarized in, Fig. 2-4., Metals are unique under both static and dynamic loads that can be cited as outstanding

Page 63 : 2 Design Influencing Factor, cases. The continuum mechanical engineer, and the metallurgical engineer have both, found these materials to be most attractive to, study. At the same time, metals, as compared, to plastics, are easier to handle for analysis., Yet there is a great deal that is still not understood about metals, even in the voluminous scientific literature available. The importance of plastics and reinforced plastics, (RPs) has been growing steadily, resulting in, more dynamic mechanical behavior data becoming available. However more is required, to meet new design challenges., Material behavior have many classifications. Examples are: (1) creep, and relaxation, behavior with a primary load environment of, high or moderate temperatures; (2) fatigue,, viscoelastic, and elastic range vibration or impact; (3) fluidlike flow, as a solid to a gas,, which is a very high velocity or hypervelocity, impact; and (4) crack propagation and environmental embrittlement, as well as ductile, and brittle fractures., Short-Term Load Behavior, , The mechanical properties of plastics enable them to perform in a wide variety of, end uses and environments, often at lower, cost than other design materials such as, metal or wood. This section reviews the static, property tests. Chapter 5 provides more information on the meaning of these type, data., As reviewed thermoplastics (TPs) being, viscoelastic materials respond to induced, stress by two mechanisms: viscous flow and, elastic deformation. Viscous flow ultimately, dissipates the applied mechanical energy as, frictional heat and results in permanent material deformation. Elastic deformation stores, the applied mechanical energy as completely, recoverable material deformation. The extent to which one or the other of these mechanisms dominates the overall response of, the material is determined by the temperature and by the duration and magnitude, of the stress or strain. The higher the temperature, the most freedom of movement of the, individual plastic molecules that comprise the, , 45, , TP and the more easily viscous flow can occur, , with lower mechanical performances., Likewise, the longer the duration of material stress or strain, the more time for viscous, flow to occur. Finally, the greater the material stress or strain, the greater the likelihood, of viscous flow and significant permanent deformation. For example, when a TP product, is loaded or deformed beyond a certain point,, the material comprising it yields and immediate or eventually fails. Conversely, as the, temperature or the duration or magnitude, of material stress or strain decreases, viscous, flow becomes less likely and less significant as, a contributor to the overall response of the, material; and the essentially instantaneous, elastic deformation mechanism becomes predominant., Consequently, changing the temperature, or the strain rate of a TP may have a considerable effect on its observed stress-strain, behavior. At lower temperatures or higher, strain rates, the stress-strain curve of a TP, may exhibit a steeper initial slope and a, higher yield stress. In the extreme, the stressstrain curve may show the minor deviation, from initial linearity and the lower failure, strain characteristic of a brittle material., At higher temperatures or lower strain, rates, the stress-strain curve of the same material may exhibit a more gradual initial slope, and a lower yield stress, as well as the drastic deviation from initial linearity and the, higher failure stain characteristic of a ductile, material., There are a number of different modes, of stress-strain that can be taken into account by the designer. They include tensile, stress-strain, flexural stress-strain, compression stress-strain, and shear stress-strain., , Tensile Stress-Strain, One of the most informative properties, of any material is their mechanical behavior specifically the determination of its stressstrain curve in tension (ASTM D 638). This, is usually accomplished in a testing machine, by measuring continuously the elongation, (strain) in a test sample as it is stretched by an

Page 64 : 46, , 2 Design Influencing Factor, , increasing pull (stress). Stress is defined as the, force on a material divided by the cross sectional area over which it initially acts. If the, area over which the force acts changes significantly because the material deforms, one, can use that area to calculate its engineering, stress. The usual method used is the stress, with its prevailing initial area concept., Strain is defined as the deformation of a, material divided by a corresponding undeformed dimension. The units of strain are, meter per meter (m/m) or inch per inch, (in.lin.). Since strain is often regarded as, dimensionless, strain measurements are typically expressed either as a percentage deformation or in microstrain units. One microstrain is defined as 10-6 mlm or in.lin., , Tensile strength The maximum tensile, stress sustained by a specimen during a tension test is its tensile strength. Figure 2-5 identifies the different types of tensile strengths., When a material's maximum stress occurs at, its yield point this stress is designated its tensile strength at yield. When the maximum, stress occurs at a break, the designation is, its tensile strength at break. In practice these, differences are frequently ignored. The tensile strength of different materials is shown, in Fig. 2-6., The generalized stress-strain curve for, plastic shown in Fig. 2-7 serves to define, several useful qualities that include the tensile strength, modulus (modulus of elasticity) or stiffness (initial straight line slope of, , A, , CIl, CIl, W, , g:, , CIl, , A&E, , = TENSILE STRENGTH AT BREAK, ELONGATION AT BREAK, , B = TENSILE STRENGTH AT YIELD, ELONGATION AT YIELD, C = TENSILE STRESS AT BREAK, ELONGATION AT BREAK, D = TENSILE STRESS AT YIELD, ELONGATION AT YIELD, , STRAIN, , Fig.2-5 Tensile designations according to ASTM, D638., , the curve), yield stress, and the length of, the elongation at the break point. The ultimate tensile strength is usually measured, in megapascals (MPa) or pounds per square, inch (psi). Values of tensile strength range, from under 20 MPa (3000 psi) for low density polyethylene and some vinyls, to 76 MPa, (11,000 psi) for Nylon 6, to more than 350, MPa (50,000 psi) for reinforced thermoset, plastics (RTPs). The curves shown in Fig. 2-7, are typical for a plastic such as polyethylene., Figure 2-8 compares tensile curves for hard, and soft steels with polycarbonate (top) and, an extended scale for polycarbonates with, specific behaviors usable in a design analysis., , Ratio tensile strength (psi) to dansit, (Ibs./Cu. In.) II 106, - -- Ratio tenslla modulus of elasticity (psi) to density (Ibs./cu.ln.) 1106, , 4 -, , 3, 2, , 1, , -- -, , 1910 1920 1930 1940 1950 1960 1970 1980, , 1990 2000, , Fig. 2-6 The growth for structural properties of reinforced plastics, steel, and aluminum during the, 20th century.

Page 65 : 2 Design Influencing Factor, , These type curves can be related to the, plastic's degree of flexibility as depicted by, Fig. 2-10., , ~---Elonptlon.t break-----40, , EJonptlon, , at yield, , Yield, , Strain--, , (a), , 12,500, , Ultimate strength, , 19500psil, , Proportional limit A material's proportional limit is the greatest stress at which it, is capable of sustaining an applied load without deviating from the proportionality of a, stress-strain straight line (Fig. 2-2)., , Proportional limit, , -14oo0psil, 2.500, , 0.2, , 0.4, , Yield It is the first point on a stress-strain, curve at which an increase in strain occurs, without any increase in stress. This yield point, is also called yield strength or tensile strength, at yield. Some materials may not have a yield, point. Yield strength can in such cases be, established by picking a stress level beyond, the material's elastic limit. The yield strength, is generally established by constructing a line, to the curve where stress and strain is proportional at a specific offset strain, usually at, 0.2% (Fig. 2-11). The stress at the point of, intersection of the line with the stress-strain, curve is called its yield strength at 0.2 % offset., , T, Ullimata, , T, , 47, , 0.6, , 0.8, , 1.0, , 1.2, , Strain lin.(in.l, , (b), , Fig. 2-7 (a) Generalized tensile stress-strain, curve for plastics and (b) example of a commodity, plastic's stress-strain diagram., , Area under the curve Generally, the area, under the stress-strain curve is proportional, to the energy required to break the specimen. It is thus sometimes referred to as the, toughness of the plastic. Figure 2-9 shows tensile stress-strain curves for the usual different, plastics that relate the area under the curve to, their toughness or physical properties. However, there are types, particularly among the, many fiber-reinforced TSs, that are very hard,, strong, and tough, even though their area is, extremely small., Elongation The elongation is the stretch, that a material will exhibit before break, or deformation. It is usually identified as a, percentage. Some materials like the styrenes, and phenolics yield little before break, while, others like polypropylene can be stretched, many times their length before deformation., , Elastic limit The elastic limit of a material, is the greatest stress at which it is capable of, sustaining an applied load without any permanent strain remaining, once stress is completely released., Modulus of elasticity Most materials, including plastics and metals, have deformation proportional to their loads below the, proportional limit. Since stress is proportional to load and strain to deformation, this, implies that stress is proportional to strain., Hooke's Law, developed in 1676, follows that, this straight line (Fig. 2-2) of proportionality, is calculated as:, Stress/Strain, , = Constant, , (2-1), , The constant is called the modulus of elasticity (E) or Young's modulus (defined by, Thomas Young in 1807 although the concept, was used by others that included the Roman, Empire and Chinese-BC), the elastic modulus, or just the modulus. This modulus is the, straight line slope of the initial portion of, the stress-strain curve, normally expressed in, terms such as MPa or GPa (106 psi or Msi). A

Page 66 : 2 Design Influencing Factor, , 48, 100, 90, , ~I, j, , ,I ,I I, i-&: Hard, steal, , 80, .;;, , 0-, , I'), , 0, , ., , ~, , ....!l, ., , 70, , /', , 60, , <II, , /J), , .t::, , c, :::>, , 50, , I', , 40, , V, , -" r, , i..', , "., , B, , ~-, , -, , Ultimate stress,, , r-Soft steel, , ~, , r-...., , I", , "I, , Breaking point-, , ./, , ~, , 30 ( - Elastic limit-beginning of, yield strength,, I , 'f, I I, 20, A-Proportional limit", , -, , 10, 0, , :,; Polycarbonate, , i"""", , /, , 'rielld, 0.05, , 0.10, , 0.15, , 0.25, , 0.20, , Unit Strain e {in.lin.}, , 12,500, 10,000, .;;;, , ., , E- 7,500, .,, , Ultimate strength, {9500 psi!, _ - Yield point, (9000 psi), , /, , ...f, , (fl, , 5,000, , Break, Proportional limit, - - (4000 psi), , 2.500, , 0.2, , 0.4, , 0.6, , 0.8, , 1.0, , 1.2, , Strain (in./in.l, , Fig. 2-8, , Tensile stress-strain curves., , material not loaded past its proportional limit, will return to its original shape once the load, is removed. However, some elastic materials, do not necessarily obey Hooke's law., With certain plastics, particularly high performance RPs, there can be two or three, moduli. Their stress-strain curve starts with, a straight line that results in its highest E,, followed by another straight line with a lower, E, and so forth. To be conservative providing, , a high safety factor the lowest E is used in a, design however the highest E is used in certain designs where load requirements are not, critical (Chapter 6, REINFORCED PLASTIC, Basic Design Theory)., In many plastics, particularly the unreinforced TPs, the straight region of the, stress-strain curve is not linear or the straight, region of this curve is too difficult to locate., It then becomes necessary to construct a

Page 67 : 49, , 2 Design Influencing Factor, Higher Strength, Higher Modulus, , Lower Strength, Lower Modulus, , Strain _, , Strain_, , TOUGH MATERIALS, , t, , Higher, Strength, , r, , Lower Strength, Lower Modulus, , Higher, Modulus, , ::!, , ~, , ~, , ~, , (I), , (I), , Strain, , ., , Strain_, , BRITTLE MATERIALS, 1:, , HARD & TOUGH, , ()", , SOFT &TOUGH, , HARD & BRITTLE, , ()", , 1:, , HARD & STRONG, , Fig. 2-9, , ()", , SOFT & WEAK, , Examples of areas under the tensile stress-strain curves., , straight-line tangent to the initial part of the, curve to obtain a modulus called the initial, modulus. Designwise, an initial modulus can, be misleading, because of the nonlinear elasticity of the material. For this reason, a secant, modulus (to be reviewed) is usually used to, identify the material more accurately. Thus,, a modulus could represent Young's modulus, of elasticity, an initial modulus, or a secant, , modulus, each having its own meaning. The, Young's modulus and secant modulus are, extensively used in design equations., Standard ASTM D 638 states that it is COfrect to apply the term modulus of elasticity, to describe the stiffness Of rigidity of a plastic where its stress-strain characteristics depend on such factors as the stress or strain, rate, the temperature, and its previous history

Page 68 : 2 Design Influencing Factor, , 50, , .., , Extension (or strainl, , Fig.2-10 Examples of elongation where usually, A = hard to brittle, B = ductile, and C = rubbery., , as a specimen. However, D 638 still suggests, that the modulus of elasticity can be a useful measure of the stress-strain relationship,, if its arbitrary nature and dependence on load, duration, temperature, and other factors are, taken into account., , Secant modulus The secant modulus is, the ratio of stress to the corresponding strain, at any specific point on the stress-strain curve., As shown in Fig. 2-2(a), the secant modulus, is the slope of the line joining the origin and, a selected point C on the stress-strain curve;, this could represent a vertical line at the usual, 1 % strain. The secant modulus line is plotted, from the initial tangent modulus and where it, intersects the stress-strain curve. The plotted, line location is also based on the angle used in, relation to the initial tangent line from the ab-, , ---, , Yield point, (proportional limit), , ...., , E, , /, , .....ECl, , /, , -", , ,, , /, , ., , Tensile, strength, , Engineering, , vietd strength, , tiSt"'', , I, , A Strain, , 0.2%, , Strain, in.lin. [em/em], , Fig. 2-11 Example of determining yield point, and offset strain., , scissa (horizontal coordinate). Figure 2-2(b), shows curves for two different plastics each, at 85% of their respective angles; for design, purposes the 85% is usually used. However, the 1 % strain approach is preferred because, it provides the E required and is easier to, plot., The secant modulus measurement is used, during the designing of a product in place of a, modulus of elasticity for materials where the, stress-strain diagram does not demonstrate a, linear proportionality of stress to strain or E, is difficult to locate., , Hysteresis effect The hysteresis effect is, a retardation of the strain when a material, is subjected to a force or load. Figure 2-12, are examples of different hysteresis recovery, rates., The top view represents incomplete recovery of strain in a material subjected to a, stress during its unloading cycle due to energy consumption. This energy is converted, from mechanical to frictional energy (heat)., It can represent the difference in a measurement signal for a given process property value, when approached first from a zero load and, then from a full scale. Middle view is an example of recovery to near zero strain. It shows, that material can withstand stress beyond its, proportional limit for a short time, resulting, in different degrees of the hysteresis effect., Bottom view is a hysteresis loop applicable, to dynamic mechanical measurement. The, closed curve represents the successive stressstrain status of the material during a cycle, deformation., Poison s ratio It is the proportion of, lateral strain to longitudinal strain under, conditions of uniform longitudinal stress, within the proportional or elastic limit. When, the material's deformation is within the, elastic range it results in a lateral to, longitudinal strain that will always be constant. In mathematical terms, Poisson's ratio is the diameter of the test specimen, before and after elongation divided by the, length of the specimen before and after elongation. Poisson's ratio will have more than, one value if the material is not isotropic

Page 69 : 51, , 2 Design Influencing Factor, , 1, , Strain15, , Proportional, , ·iii, , lim~, , CI., , ~..., , 10, , rii, II), , i, .!!, , ·iii, c, ~, , 5, , ;;, , /:, , ,, , ,, I, , I, , I I ,, , ,'", , ,, o ,'", o, , ", , '", , .,. '", , ,, , ,, , /,/', ,, , ,, , ,, ,,, , ... ", , _,3%, , --2%, , " '", , ", ... ... ", 2, , I, , '" '", , ,, , ,, ,,, , ,, , I, , 3, , 4, , Strain, (%J, , 0", , E, , Fig.2-12 Hysteresis effects on material., (Chapter 8, RP Directional Property, Orientation of Reinforcement)., Poisson's ratio always falls within the range, of 0 to 0.5. A zero value indicates that the, specimen would suffer no reduction in diameter or contraction laterally during elongation, but would undergo a reduction in density. A, value of 0.5 indicates that the specimen's volume would remain constant during elongation or as the diameter decreases. For most, plastics the ratio lies between 0.10 and DAD, (Tables 2-1 and 2-2)., , Poisson's ratio is a constant in engineering design analysis for determining the stress, and deflection properties of plastic, metal,, and other structures such as beams, plates,, shells, and rotating discs. When temperature changes, the magnitude of stresses and, strains, and the direction of loading all have, their effects on Poisson's ratio. However,, these factors usually do not alter the typical, range of values enough to affect most practical calculations, where this constant is frequently of only secondary importance.

Page 70 : 52, , 2 Design Influencing Factor, , Table 2-1 General range of Poison's ratio for, different materials, Material, Aluminum, Carbon steel, Rubber, Rigid thermoplastics, Neat, Filled or reinforced, Structural foam, Rigid thermosets, Neat, Filled or reinforced, , Range of Poisson's Ratio, 0.33, 0.29, 0.50, 0.20-0.40, 0.10-0.40, 0.30-0.40, 0.20-0.40, 0.20-0.40, , The application of Poisson's ratio is frequently required in the design of structures, that are markedly 2-D or 3-D, rather than, one-dimensional like a beam. For example,, it is needed to calculate the so-called plate, constant for flat plates that will be subjected, to bending loads in use. The higher Poisson's, ratio, the greater the plate constant and the, more rigid the plate., Ductility A typical tensile stress-strain, curve of many ductile plastics is shown in, Fig. 2-13. As strain increases, stress initially increases approximately proportionately (from point 0 to point A). For this reason, point A is called the proportional limit, of the material. From point 0 to point B, the, behavior of the material is purely elastic; but, beyond point B, the material exhibits an, , o, , oL---------------St-ra-;n----------------, , Fig. 2-13 Tensile stress-strain curve typical of, many ductile plastics., , increasing degree of permanent deformation., Consequently, point B is called the elastic, limit of the material., The first point of zero slope on the curve, (point C) is identified with material yielding, and so its coordinates are called the yield, strain and stress (strength) of the material., The yield strain and stress usually decrease, as temperature increases or as strain rate decreases. The final point on the curve (point D), corresponds to specimen fracture. This represents the maximum elongation of the material specimen; its coordinates are called the, ultimate, or failure strain and stress. Ultimate, elongation usually decreases as temperature, decreases or as strain rate increases., Brittleness Brittle materials exhibit tensile stress-strain behavior different from that, illustrated in Fig. 2-13. Specimens of such materials fracture without appreciable material, yielding. Thus, the tensile stress-strain curves, of brittle materials often show relatively little deviation from the initial linearity, relatively low strain at failure, and no point of, zero slope. Different materials may exhibit, significantly different tensile stress-strain behavior when exposed to different factors such, as the same temperature and strain rate or at, different temperatures. Tensile stress-strain, data obtained per ASTM for several plastics, at room temperature are shown in Table 2-3., Crazing When tensile stress is applied, to an amorphous glassy (Chapter 6) plastic such as polystyrene, crazing may occur, before fracturing. Crazes are like cracks in, that they are wedges shaped and formed perpendicular to the applied stress. However,, they differentiate from cracks by containing, plastic that is stretched in a highly oriented, manner perpendicular to the plane of the, craze, which is to say parallel to the applied, stress's direction. Another major distinguishing feature is that unlike cracks, crazes are, able to bear stress. Under static loading, the, strain at which crazes start to form decreases, as the applied stress decreases. In constant, strain-rate testing crazes always start to form, at a well-defined stress level.

Page 71 : 53, , 2 Design Influencing Factor, Examples of specific room temperature shear stress-strain data and Poisson's ratio, for several plastics and other materials, , Table 2-2, , Generic Material, Type, ABS, , Acetal copolymer, Acetal, homopolymer, Acrylic, Nylon (DAM), (0.2% moisture), , Shear Modulus,, MPa, 960, 810, 810, 660, 1000, 1330, 1330, , Shear Stress,, MPa, , At, , 51.0, 37.9, 32.9, 30.0, 53, 65.5, 68.9, 44.6, 66.2, 57.9, 59.3, 62.7, , Ultimate, Ultimate, Ultimate, Ultimate, Ultimate, Ultimate, Ultimate, , 0.35, 0.35, 0.35, 0.36, 0.35, 0.35, 0.35, , Ultimate, Ultimate, Ultimate, Ultimate, , 55.8, , Ultimate, , 0.34-0.43, 0.34-0.43, 0.34-0.43, 0.34-0.43, 0.35-0.50, 0.35-0.50, 0.35-0.50, 0.35-0.50, , 82.7, 41.3, 68.9, 62.6, 66.2, 41.4, 62.1, , Ultimate, Yield, Ultimate, Ultimate, Ultimate, Yield, Ultimate, , Nylon (50% RH), (2.5% moisture), Phenolic, Polycarbonate, , 785, , Phenylene ether, copolymer, Polysulfone, , 917, , Steel, structural, ASTM A7-61T, Brass, naval, Aluminum,, wrought 2014-T6, Pine (southern, long-leaf) (with grain), Oak (white) (with grain), , 79200, 38000, 30000, , Test rate and property The test rate or, cross-head rate is the speed at which the, movable cross-member of a testing machine, moves in relation to the fixed cross-member., The speed of such tests is typically reported, in crn/min. (in.lmin.). An increase in strain, rate typically results in an increase yield point, and ultimate strength. Figure 2-14 provides, examples of the different test rates and temperatures on basic tensile stress-strain behaviors of plastics where: (a) is at different, testing rates per ASTM D 638 for a polycarbonate, (b) is the effects of tensile test-, , Poisson's, Ratio, , 120, 280-310, 240, 270, 10, , 0.37, , 0.37, , Yield, , 0.27, , Ultimate, Yield, Ultimate, , 0.33, , 13.0, , ing speeds on shapes of stress-strain diagrams, and (c) is a simplified version of the, effects on curves of changes in test rates and, temperatures., For most rigid plastics the modulus (the initial tangent to the stress-strain curve) does, not change significantly with the strain rate., For softer TPs, such as polyethylenes, the, theoretical elastic or initial tangent modulus is usually independent of the strain rate., The significant time-dependent effects associated with such materials, and the practical, difficulties of obtaining a true initial tangent

Page 72 : 54, , 2 Design Influencing Factor, , Table 2·3 Examples of room temperature tensile stress-strain data for several plastics, and other materials, , Generic, Material Type, ABS, , Acetal copolymer, Acetal, homopolymer, Acrylic, , Modulus,, MPa, , Yield, Stress, MPa, , Elongation, at Yield, %, , Elongation, at Break, %, , 2,600, 2,200, 2,200, 1,800, 2,800, 2,800, 3,100, 3,100, 3,100, 2,960, 2,239, 1,720, , 52, 43, 40, 34, 61, 61, 68.9, 68.9, 68.9, 72, 48, 38, 82.7, , 2.5, 2.5, 2.5, 3.3, 12, 12, 12, 12, 12, , 25-75, 25-75, 25-75, 25-75, 75, 60, 75, 40, 25, 5.4, , 5.0, 5, , 60.7, 51.0, 58.6, , 7, 20, 25, , 51.0, 40.7, 55.2, 58.6, , 40, 30, , 35, 60, 60, 150, 290, >300, 210, >300, 285, 0.29, 0.57, 0.63, 110, 90, 900, 900, 900, 500, 50-100, 50-100, , Nylon (DAM), (0.2% moisture), Nylon (50% RH), (2.5% moisture), Phenolic, Polycarbonate, , 19,310, 10,340, 7,590, 2,380, 2,240, , 2,500, 2,500, 1,400, 1,200, 830, 3,100, 2,070, 2,070, 1,930, 2,482, 2,482, 2,482, 200,000, , 62, 62, 30, 29, 24, 14, 58, 55, 35.5, 27.3, 20.0, 52, 31, 25, 25, 70.3, 70.3, 68.9, 230, , 100,000, 73,000, , 170-340, 410, , Polyethylene, , Phenylene ether, copolymer, Polypropylene, Polystyrene, , Polysulfone, Steel, structural, ASTM A7-61T, Brass, naval, Aluminum,, wrought 2014-T6, Pine (southern, long-leaf), Oak (white), , 48 h, , 13,700, 11,200, , 6-8, 6-8, , 4-6, , 4-6, 12, 13, 6.3, , 5-6, 5-6, 5-6, , <300, 2.5, 30, 60, 50, 50-100, 50-100, 50-100

Page 73 : 55, , 2 Design Influencing Factor, 11, , 'w, a., , "'~, , 0", vi, m, w, , a:, Im, , 10, , A, , 70, , 9, , B, C, , 60, , 8, , 50, , 7, 6, , 40, , A = 20 in.lmin, (8.5 mmfsec), , 5, 4, 3, 2, , B = 0.2 in.lmin, (.085 mmfsec), , 30, , C = 0.002 in.lmin, (.00085 mmfsec), , 20, , Eo - 350,000 psi, (2.41 GPa), 1, , 2, , 3, , 4, , STRAIN,, , 5, E,, , a:, Im, , 10, , 0, 0, , 8.'., , ::;:, 0", vi, m, w, , 6, , 7, , 0, , %, , (a), , ~, , en, 00, , 00, High Speed, , 0~~-4~4-~rLow Speed, , Medium Speed, , Strain, , (b), increasing strain rate or, decreasing temperature, , Viscoelasticity It is the plastics respond, to stress with elastic strain. In the material,, strain increases with longer loading times and, higher temperatures., Flexural Stress-Strain, , Like tensile testing, flexural stress-strain, testing according to ASTM D 790, determines the load necessary to generate a, given level of strain on a specimen, typically using a three-point loading (Fig. 2-15)., Testing is performed at a constant rate of, crosshead movement, typically 0.05 in.lmin., for solids and O. 1 in.lmin. for foamed, samples., Simple beam equations are used to determine the stresses on specimens at different, levels of cross-head displacement. Using traditional beam equations and section properties, the following relationships can be derived where Y is the deflection at the load, point (refer to Fig. 2-15):, Bending stress where a = 3FL/2bh2, (2-2), Bending or flexural modulus where, E = FL3 /4bh 3 y, (2-3), , ", , vi, m, w, , a:, ~, , STRAIN,, , Using these relationships, the flexural, strength, also called the modulus of rupture,, E, , (e), , Fig.2-14 Examples of using different tensile testing rates., , modulus near the origin of a nonlinear stressstrain curve, render it difficult to resolve the, true elastic modulus of the softer TPs in respect to actual data. Thus, the observed effect, of increasing strain is to increase the slope of, the early portions of the stress-strain curve, [Fig. 2-10(c)], which differs from that at the, origin. The elastic modulus and strength of, both the rigid and the softer plastics each decrease with an increase in temperature. While, in many respects the effects of a change in, temperature are similar to those resulting, from a change in the strain rate, the effects, of temperature are relatively much greater., , !, , APPLIED LOAD, , F, , Fig.2-15 Three-point flexural test schematic.

Page 74 : 56, , 2 Design Influencing Factor, , Table 2-4 Examples of flexural modulus of, elasticity for polypropylene compounds, Unreinforced, (neat), , 40% Glass, Fiber', , 40% Talc', , 180,000 psi, (1,240 MPa), , 1,100,000 psi, (7,600 MPa), , 575,000 psi, (3,970 MPa), , 'Glass fiber and talc content are by weight., , and the flexural modulus of elasticity can be, determined. Table 2-4 provides examples of, the flexural modulus of elasticity for different formulations of polypropylene. The flexural modulus reported is usually the initial, modulus from the load-deflection curve. The, flexural data can be useful in product designs that involve such factors as bending, loads., Significantly, a flexural specimen is not in a, state of uniform stress. When a simply supported specimen is loaded, the side of the, material opposite the loading undergoes the, greatest tensile loading. The side of the material being loaded experiences compressive, stress (Fig. 2-16). These stresses decrease linearly toward the center of the sample. Theoretically the center is a plane, called the neutral axis, experiences no stress., Real differences between the tensile and, the compressive yield stresses of a material, may cause the stress distribution within the, test specimen to become very asymmetric at, high strain levels. This cause the neutral axis, to move from the center of the specimen toward the surface which is in compression., This effect, along with specimen anisotropy, due to processing, may cause the shape of the, stress-strain curve obtained in flexure to dif-, , T, , _ ___, , _, , TENSILE, STRESS, , Fig. 2-16 Flexural specimen subjected to compressive and tensile stresses., , fer significantly from that of the tensile stressstrain curve. Flexural stress-strain data obtained per ASTM for several plastics at room, temperature are shown in Table 2-5., The stress-strain behavior of plastics in, flexure generally follows from the behavior, observed in tension and compression for either unreinforced or reinforced plastics. The, flexural modulus of elasticity is nominally the, average between the tension and compression moduli. The flexural yield point is generally that which is observed in tension, but, this is not easily discerned, because the strain, gradient in the flexural RP sample essentially, eliminates any abrupt change in the flexural, stress-strain relationship when the extreme, "fibers" start to yield., The flexural strength for most plastics under standard ASTM bending tests is typically somewhat higher than their ultimate, tensile strength, but flexural strength itself, may be either higher or lower than compressive strength. Since most plastics exhibit, some yielding or nonlinearity in their tensile, stress-strain curve, there is a shift from triangular stress distribution toward rectangular distribution when the product is subject, to flexure (Fig. 2-17). This behavior is similar to that assumed for plastic design in steel, and for ultimate design strength in concrete., Thus, the modulus of rupture reflects in part, nonlinearities in stress distribution caused by, plastification or viscoelastic nonlinearities in, the cross-section. Shifts in the neutral axis, resulting from differences in the yield strain, and post-yield behavior in tension and compression can also affect the correlation between the modulus of rupture and the uniaxial strength results., Even plastics with fairly linear stress-strain, curves to failure, for example short-fiber reinforced TSs (RPs), usually display moduli of, rupture values that are higher than the tensile strength obtained in uniaxial tests; wood, behaves much the same. Qualitatively, this, can be explained from statistically considering flaws and fractures and the fracture energy available in flexural samples under a, constant rate of deflection as compared to, tensile samples under the same load conditions. These differences become less as the

Page 75 : 2 Design Influencing Factor, , 57, , Room temperature flexural and compressive stress-strain data for several plastics, and other materials, , Table 2-5, , Generic, Material, Type, ABS, , Acetal copolymer, Acetal, homopolymer, Acrylic, Nylon (DAM), (0.2% moisture), Nylon (50% RH), (2.5% moisture), , Flexural, Modulus,, MPa, , Flexural, Yield Stress,, MPa, , Compressive, Modulus,, MPa, , 2800, 2300, 2300, 1900, 2590, 2590, 2620, 2830, 2960, 3170, 2239, 1720, 2827, 1689, 2034, 1034, 1207, 862, 1241, 745, , 90, 74, 69, 59, 89.6, 89.6, 98.6, 97.2, 96.5, 110, 72, 62, , 2600, 2200, 2200, 1800, , Phenolic, Polycarbonate, Polyethylene, , Phenylene ether, copolymer, Polypropylene, Polystyrene, Polysulfone, Steel, structural, ASTMA7-61T, Aluminum, wrought, 2014-T6, Pine (southern long-leaf), (with grain), Oak (white) (with grain), , 2340, 2240, 1100, 1100, 861, 410, 2500, 2500, 1750, 1295, 1065, 2689, , 96.5, 89.6, 82h, 93.0, 90.9, , 86, 94, 54.4, 48.2, 34.5, 86.2, 106.2, , 101, 95.8, , 4600, 4600, 4600, , 2380, 2240, , Compressive, Stress,, MPa, , At, , 42.4/45.1, , 10% yield, , 31/110, 31/110, 35.9/124, 35.9/124, 34.5/121, 117, 72, 41, 33.8, 13.1, 16.6, , 1%/10%, 1%/10%, 1%/10%, 1 %/10%, 1%/10%, Maximum, Maximum, Yield, 1%, 1%, 1%, , 193.1, 206.9, 193.1, 86.1, 86.1, , Ultimate, Ultimate, Ultimate, Yield, Yield, , 96/276, 230, , Yield/break, Yield, , 430, , Yield, , 2500, 2500, , 2579, , 58.2, , Ultimate, , 48.5, , Ultimate

Page 76 : 58, , 2 Design Influencing Factor, tensile, , yield, , ~, neutral, axis, , ----, , 4, , ·, , ----~~- ---, , fneutral, axis, shift, , -------------, , l·compreSSiv:-1, yield stress, , No Yield, , Lineor Stress, , Extreme Fibers Yield, , Full Plasl ificotion, , of Cross Section, , Fig.2·17 Elastic and plastic flexural behavior of unreinforced and reinforced plastics., , thickness of the bending specimen increases,, as would be expected by examining statistical, considerations., Another method of flexural testing tha t can, be used is, for example, the cantilever beam, method (Fig. 2-18), which is used to relate, different beam designs. It provides an exam-, , pIe of the effect of the modulus of elasticity on elastic deflection for different materials, using cantilever test specimens. All the, test beams have the same lengths and crosssections. It is used in creep and fatigue testing, and for conducting testing in different environments., , Steel, 6, , E = 30x 10 psi, [206 x, , lcr MPa], , Aluminum, E = 10 x 10& psi, 1, , [69 x 10 MPa], , POlystyrene, , E = .5 x 1(t psi, , cr MPa], , [3.4 x 1, , Fig. 2·18, , Cantilever tests.

Page 77 : 2 Design Influencing Factor, Compressive Stress-Strain, Data are generated by placing a test specimen between the two flat, parallel faces of a, testing machine and then moving these faces, together at a specified rate (ASTM D 695). A, displacement transducer may be used to measure the compression of the specimen, while, a load cell measures the compressive force, exerted by the specimen on the testing machine. Stress and strain are computed from, the measured compression load, and these, are plotted as a compressive stress-versusstrain curve for the material at the temperature and strain rate employed for the test., In general, the compressive strength of a, non-reinforced plastic or a mat-based RP, laminate is usually greater than its tensile, strength. The compressive strength of a unidirectional fiber-reinforced plastic is usually, slightly lower than its tensile strength. Roomtemperature compressive stress-strain data, obtained per ASTM for several plastics are, shown in Table 2-5., The majority of tests to evaluate the characteristics of plastics are performed in tension or flexure; hence, the compressive stressstrain behavior of many plastics is not well, described. Generally, the behavior in compression is different from that in tension, but, the stress-strain response in compression is, usually close enough to that of tension so, that possible differences can be neglected, (Fig. 2-19). The compression modulus is not, always reported, since defining a stress at, COMPRESSIVE, , TENSILE, , ET, , STRAIN, , = ;, , l, , I, , ~, , CI), , ~, , f.;;;, , !S!, CiS, , f3, g:, ~, C,.), , Fig.2-19 Comparison of tensile and compression, stress-strain behavior of TPs., , 59, , a strain is equivalent to reporting a tensile, secant modulus. However, if a compression, modulus is reported, it will generally be an, initial modulus., As reviewed a general rule is that the compressive strength of plastics is greater than, its tensile strength. However, this is not generally true for reinforced TSs (RTSs). Different results occur with different plastics., As an example the compression testing of, foamed plastics provides the designer with, the useful recovery rate. A compression test, result (Fig. 2-20) for rigid foamed insulating, polyurethane (3.9 Ib/ft 3) resulted in almost, one-half of its total strain recovered in one, week., Many of the procedures in compression, stress-strain testing are the same as in tensile, testing, but in compression testing particular, care must be taken to specify the specimen's, dimensions. If a sample is too long and narrow, for instance, buckling may cause premature failure. To avoid this, designers should, test a specimen with a square cross-section, and a longitudinal dimension twice as long as, a side of the cross-section., At higher stress levels, compressive strain, is usually less than tensile strain. Unlike tensile loading, which usually results in failure,, stressing in compression produces a slow,, indefinite yielding that seldom leads to failure. Where a compressive failure does occur, catastrophically, the designer should determine the material's strength in the same way, as with tensile testing by dividing the maximum load the sample supported by its initial cross-sectional area in kPa (psi). When, the material does not exhibit a distinct maximum load prior to failure, the designer should, report the strength at a given level of strain, (often 10%)., Since the ends of compression specimens, usually tend to "flower" and not remain rigid,, test results are usually very scattered requiring close examination as to what the results, mean in reference to the behavior of the, test specimens. Different clamping devices, are used to eliminate the flowering action, that could provide inaccurate readings that, in turn influence results by usually making, them stronger.

Page 78 : 2 Design Influencing Factor, , 60, 20, , Test stopped due to, buckling of specimen, 15, Rate of strain, recovery = 270 psi, , ·00, , S, , til, til, , 10, , ~, , iii, , Density: 3.9 Ib ef, Cross-section: 5.0 x 5.4", Height: 6.75", , 5, , 0.05, , 0.10, Strain (in.lin.), , Fig. 2-20, , Compression test for rigid PUR foam., , Shear Stress-Strain, The shear mode involves the application, of a load to a material specimen in such a, way that cubic volume elements of the material comprising the specimen become distorted, their volume remaining constant, but, with opposite faces sliding sideways with respect to each other. Shear deformation occurs, in structural elements subjected to torsional, loads and in short beams subjected to transverse loads., Shear stress-strain data can be generated, by twisting (applying torque) a material specimen at a specified rate while measuring the, angle of twist between the ends of the specimen and the torque load exerted by the specimen on the testing machine. Maximum shear, stress at the surface of the specimen can be, computed from the measured torque that is, the maximum shear strain from the measured, angle of twist., The shear modulus of a material can be, determined by a static torsion test or by a dynamic test employing a torsional pendulum, or an oscillatory rheometer. The maximum, short-term shear stress (strength) of a material can also be determined from a punch, shear test., Unlike the methods for tensile, flexural,, or compressive testing, the typical procedure, used for determining shear properties is intended only to determine the shear strength., It is not the shear modulus of a material, that will be sUbjected to the usual type of, , direct loading (ASTM D 732). Torsion pendulum and oscillatory rheometer techniques, are used to determine the shear modulus. The, shear strength values are obtained by such, simple tests using single or double shear actions. In these tests the specimen to be tested, is sheared between the hardened edges of, the supporting block and the block to which, the load is applied. The shearing strength, is calculated as the load at separation divided by the total cross-sectional area being, sheared., The use of the word direct in these tests, might seem to imply that this is the only stress, being placed on the specimen. However, an, inspection of the test fixtures in these test, devices indicates that bending stresses do in, fact exist and the stress cannot be considered, as being purely that of shear. Therefore, the, shearing stress calculated must be regarded, as an average stress. This type of calculation is justified in analyzing bolts, rivets, and, any other mechanical member whose bending moments are considered negligible., Because strain measurements are difficult, if not impossible to measure, few values of, yield strength can be determined by testing., It is interesting to note that tests of bolts and, rivets have shown that their strength in double shear can at times be as much as 20% below that for single shear. The values for the, shear yield point (kPa or psi) are generally, not available; however, the values that are, listed are usually obtained by the torsional, testing of round test specimens.

Page 79 : 61, , 2 Design Influencing Factor, The data obtained using the test method, above should be reported as direct shear, strength. Designers are nevertheless cautioned to use the shear strength reported, by this method only in similar direct-shear, situations, because this is not a pure shear, test. This test cannot be used to develop, shear stress-strain curves or determine a, shear modulus, because a portion of the, load is transferred by bending or compression rather than pure shear. Also, the test, results can depend on the susceptibility of, the material to the sharpness of load faces., When analyzing plastics in a pure shear situation or when the maximum shear stress, is being calculated in a complex stress environment, a shear strength equal to half the, tensile strength or that given above is generally used, whichever is less., Basically, shearing stresses are tangential, stresses that act parallel to the planes they, stress. For example, the shearing force in, a beam provides shearing stresses on both, the vertical and horizontal planes within the, beam. The two vertical stresses must be equal, in magnitude and opposite in direction to, ensure vertical equilibrium. However, under, the action of those two stresses alone the, element would rotate. Clearly, this pair of, stresses must be negated by another couple. If the small element is taken as a differential one, the magnitude of the horizontal stresses must have the value of the two, vertical stresses. This principle is sometimes, phrased as "cross-shears are equal." In other, words, a shearing stress cannot exist on an element without a like stress being located 90, degrees around the corner., The block diagram in Fig. 2-21 is subjected, to a set of equal and opposite shearing forces, (0). The top view (a) represents a material, with equal and opposite shearing forces and, (b) is a schematic of infinitesimally thin layers, subject to shear stress. If the material is imagined as an infinite number of infinitesimally, thin layers, as shown at the bottom, then, there is a tendency for one layer of the material to slide over another to produce a shear, form of deformation or failure if the force is, great enough. The shear stress will always be, tangential to the area upon which it acts. The, , 0 .....1 - - - - /, , o, , SHEARING LOAD, , (a), AREA, , o, , ~ ~, , y (RADIANS), , SHEAR STRAIN, , (b), , Fig. 2-21, , Basic analysis of shear stress., , shearing strain is the angle of deformation y, as measured in radians. For materials that behave according to Hooke's Law, shear strain, is proportional to the shear stress producing, it., The constant G, called the shear modulus,, the modulus of rigidity, or the torsion modulus, is directly comparable to the modulus, of elasticity used in direct-stress applications., Only two material constants are required to, characterize a material if one assumes the, material to be linearly elastic, homogeneous,, and isotropic. However, three material constants exist: the tensile modulus of elasticity, (E), Poisson's ratio (v), and the shear modulus (G). An equation relating these three constants, based on engineering's elasticity principles, follows:, E/G = 2(1, , + v), , (2-4), , This calculation, which holds true for most, metals, is generally applicable to TPs. However, the designer is to be familiar with the, inherently nonlinear, anisotropic nature of, most plastics, particularly the fiber-reinforced, and liquid crystal plastics (Chapter 6).

Page 80 : 62, , 2 Design Influencing Factor, , It is important to note material such as, those plastics or wood that are weak in either tension or compression will also be basically weak in shear. For example, concrete is, weak in shear because of its lack of strength, in tension. Reinforced bars in the concrete, are incorporated to prevent diagonal tension cracking and strengthen concrete beams., Similar action occurs with RPs using fiber filament structures., Although no one has ever been able to, determine accurately the resistance of concrete to pure shearing stress, the matter is not, very important, because pure shearing stress, is probably never encountered in concrete, structures. Furthermore, according to engineering mechanics, if pure shear is produced, in one member, a principal tensile stress of, an equal magnitude will be produced on another plane. Because the tensile strength of, concrete is less than its shearing strength, the, concrete will fail in tension before reaching, its shearing strength. This action also occurs, with plastics., , Torsion property As noted, the shear, modulus is usually obtained by using pendulum and oscillatory rheometer techniques., The torsional pendulum (ASTM D 2236: Dynamic Mechanical Properties of Plastics by, Means of a Torsional Pendulum Test Procedure) is a popular test, since it is applicable to, virtually all plastics and uses a simple specimen readily fabricated by all commercial processes or easily cut from fabricated products., The moduli of elasticity, G for shear and, E for tension, are ratios of stress to strain, as measured within the proportional limits, of the material. Thus the modulus is really a, measure of the rigidity for shear of a material, or its stiffness in tension and compression., For shear or torsion, the modulus analogous, to that for tension is called the shear modulus, or the modulus of rigidity, or sometimes the, transverse modulus., Applying Stress-Strain Data, The information presented is used in different load bearing equations such as those, , reviewed in the literature (3, 6, 10, 14, 20,, 29, 31, 36, 37, 39, 43 to 125). As an example stress-strain data may guide the designer, in the initial selection of a material. Such, data also permit a designer to specify design, stresses or strains either safely within the proportional/elastic limit of the material. On the, other hand, if a vessel is being designed to fail, at a specified internal pressure, the designer, may choose to use the tensile yield stress of, the material in the design calculations., Designers of most structures specify material stresses and strains well within the proportional/elastic limit. Where required (with, no or limited experience on a particular, type product materialwise and/or processwise) this practice builds in a margin of safety, to accommodate the effects of improper material processing conditions and/or unforeseen loads and environmental factors. This, practice also allows the designer to use design equations based on the assumptions of, small deformation and purely elastic material behavior. Other properties derived from, stress-strain data that are used include modulus of elasticity and tensile strength., Modulus of elasticity (E) is one of the two, factors that determine the stiffness or rigidity (EI) of structures comprised of a material. The other is the moment of inertia (I) of, the appropriate cross section, a purely geometric property of the structure. Figure 3-1, provides examples of moment of inertia (I)., In identical products, the higher the modulus of elasticity of the material, the greater, the rigidity; doubling the modulus of elasticity doubles the rigidity of the product. The, greater the rigidity of a structure, the more, force must be applied to produce a given deformation., It is appropriate to use Young's modulus to determine the short-term rigidity of, structures subjected to elongation, bending,, or compression. It may be more appropriate to use the flexural modulus to determine, the short-term rigidity of structures subjected, to bending, particularly if the material comprising the structure is non-homogeneous,, as foamed or fiber-reinforced materials, tend to be. Also, if a reliable compressive, modulus of elasticity is available, it can be

Page 81 : 63, , 2 Design Influencing Factor, , used to determine short-term compressive, rigidity, particularly if the material comprising a structure is fiber-reinforced. The room, temperature moduli of elasticity for several, plastics and some other materials are presented in Table 2-3., , I~II, , to, , tl, Time, (I), , Long-Term Load Behavior, , Long time dynamic load involves behaviors such as creep, fatigue, and impact. Two of, the most important types of long-term material behavior are more specifically viscoelastic creep and stress relaxation. Whereas, stress-strain behavior usually occurs in less, than one or two hours, creep and stress relaxation may continue over the entire life of the, structure such as 100,000 hours or more., , ~"EO~, !i, ...., "R"", c_, , JOE~~, to, , tl, Time, (b), , Viscoelastic Creep, , When a viscoelastic material is subjected, to a constant stress, it undergoes a timedependent increase in strain. This behavior is, called creep. The viscoelastic creep behavior, typical of many TPs is illustrated in Figs. 2-22, and 2-23. At time to the material is suddenly, subjected to a constant stress that is main-, , ~:II, , to, , Time, (8), , 'Rr--------------------------------,, , '0, OL-~----------------------------~tR, , Time, (b), , Fig. 2-22 Viscoelastic creep behavior typical of, many TPs under long-term stress to rupture:, (a) input stress vs. time profile and (b) output, strain vs. time profile., , Fig. 2-23 Viscoelastic creep behavior typical, of many TPs under short-term stress: (a) input, stress vs. time profile and (b) output strain vs., time profile., , tained for a long period of time as shown in, Fig. 2-22. The material responds by undergoing an immediate initial strain that increases, to time t r , when it fails. In Fig. 2-23 the constant stress is maintained for a shorter time., The material undergoes an immediate initial, strain at to which increases to t1, at time t1., When the stress is removed, the material immediately decreases in strain from 81 to lOt, followed by a gradual decrease from 81, to a, permanent residual strain., Although the creep behavior of a material, could be measured in any mode, such experiments are most often run in tension or flexure. In the first, a test specimen is subjected, to a constant tensile load and its elongation, is measured as a function of time. After a, sufficiently long period of time, the specimen, will fracture that is a phenomenon called tensile creep failure. In general, the higher the, applied tensile stress, the shorter the time, and the greater the total strain to specimen, failure. Furthermore, as the stress level decreases, the fracture mode changes from ductile to brittle. With flexural, a test specimen

Page 82 : 64, , 2 Design Influencing Factor, , is subjected to a constant bending load and, its deflection is measured as a function of, time. Tests are conducted at different constant loads., Viscoelastic creep data are usually presented in one of two ways. In the first, the total, strain experienced by the material under the, applied stress is plotted as a function of time., Families of such curves may be presented at, each temperature of interest, each curve representing the creep behavior of the material, at a different level of applied stress. Below a, critical stress, viscoelastic materials may exhibit linear viscoelasticity; that is, the total, strain at a given time is proportional to the, applied stress. Above this critical stress, the, creep rate becomes disproportionately faster., In the second, the apparent creep modulus is, plotted as a function of time., The viscoelastic creep modulus may be determined at a given temperature by dividing the constant applied stress by the total, strain prevailing at a particular time. Since, the creep strain increases with time, the viscoelastic creep modulus must decrease with, time (Fig. 2-23). Below its critical stress for, linear viscoelasticity, the viscoelastic creep, modulus versus time curve for a material is, independent of the applied stress. In other, words, the family of strain versus time curves, for a material at a given temperature and severallevels of applied stress may be collapsed, to a single viscoelastic creep-modulus-timecurve if the highest applied stress is less than, the critical value., Different viscoelastic materials may have, considerably different creep behavior at, the same temperature. A given viscoelastic material may have considerably different creep behavior at different temperatures., Viscoelastic creep data are necessary and, extremely important in designing products, that must bear long-term loads. It is inappropriate to use an instantaneous (short load), modulus of elasticity to design such structures because they do not reflect the effects, of creep. Viscoelastic creep modulus, on the, other hand, allows one to estimate the total, material strain that will result from a given, applied stress acting for a given time at the, anticipated use temperature of the structure., , The viscoelastic creep modulus is particularly useful to the designer because it may, be substituted for Young's modulus to predict the long-term rigidity of load bearing, structures. Thus, creep data allows to design, a structure so that the stress within the material comprising it will remain at or below the, desired level. This testing procedure has been, followed for almost a century in designing all, kinds of products., Stress Relaxation, When a viscoelastic material is subjected to, a constant strain, the stress initially induced, within it decays in a time-dependent manner., This behavior is called stress relaxation. The, viscoelastic stress relaxation behavior is typical of many TPs. The material specimen is a, system to which a strain-versus-time profile, is applied as input and from which a stressversus-time profile is obtained as an output., Initially the material is subjected to a constant, strain that is maintained for a long period of, time. An immediate initial stress gradually, approaches zero as time passes. The material responds with an immediate initial stress, that decreases with time. When the applied, strain is removed, the material responds with, an immediate decrease in stress that may result in a change from tensile to compressive, stress. The residual stress then gradually approaches zero., The stress-relaxation behavior of a material is normally determined in either the, tensile or the flexural mode. In these experiments, a material specimen is rapidly elongated or compressed to produce a specified, strain level and the load exerted by the specimen on the test apparatus is measured as a, function of time. Specimens of certain plastics may fail during tensile or flexural stressrelaxation experiments., Viscoelastic stress-relaxation data are usually presented in one of two ways. In the, first, the stress manifested as a function of, time. Families of such curves may be presented at each temperature of interest. Each, curve representing the stress-relaxation behavior of the material at a different level of

Page 83 : 2 Design Influencing Factor, , applied strain. Below a critical strain,, viscoelastic materials may exhibit linear viscoelasticity; that is, the stress at a given time is, proportional to the applied strain. Above this, critical strain, the stress relaxation rate becomes disproportionately faster. In the second, the apparent stress relaxation modulus, is plotted as a function of time. Apparent, or viscoelastic stress relaxation modulus is a, time- and temperature-dependent parameter, that reflects the stress relaxation behavior of, the material., Although all viscoelastic materials undergo stress relaxation, the rate at a give, temperature may differ considerably from, material to material. A given viscoelastic material may have considerably different stress, relaxation behavior at different temperatures. Such data are necessary in designing, structures that will be subjected to long-term, deformation, including gaskets, springs, and, force-fit components. The viscoelastic stress, relaxation modulus allows one to estimate, the material stress that will result from a given, applied strain after a given time at the anticipated use temperature of the structure. It is, particularly useful to the designer because it, may be substituted for Young's modulus (E), in the appropriate elastic design equations, to predict the long-term resiliency of such, structures., Stress-relaxation data enables the design, of a structure so that the strain of the material comprising it will remain at the desired, level. Too high a strain level and the material, may cease to be linearly viscoelastic, which, may lead to a significantly higher rate of stress, relaxation. Too Iowa level and the material, stress may not be high enough to generate the, required spring force., Long-term Viscoelastic Behavior, , The rate of creep and stress relaxation of, TPs increases considerably with temperature;, those of the TSs (thermoset plastics) remain, relatively unaffected up to fairly high temperatures. The rate of viscoelastic creep and, stress relaxation at a given temperature may, also vary significantly from one TP to an-, , 65, , other because of differences in the chemical, structure and shape of the constituent plastic, molecules (Chapter 6). These differences affect the way the plastic molecules interact, with each other, and hence they're relative, freedom of movement. For the sake of practicality, viscoelastic creep and stress relaxation, experiments are normally terminated at 1000, hours. Time-temperature super-positioning is, often used to extrapolate this 1,000 hours of, data to approximately 100,000 hours (~12, years)., Creep Property, Basics Creep data can be very useful to, the designer. In the interest of sound designprocedure, the necessary long-term creep, information should be obtained on the perspective specific plastic, under the conditions, of product usage (Chapter 5, MECHANICAL PROPERTY, Long-Term Stress, Relaxation/Creep). In addition to the creep, data, a stress-strain diagram under similar, conditions should be obtained. The combined information will provide the basis for, calculating the predictability of the plastic, performance., The factors that affect being able to design, with creep data include a number of considerations., , 1. The strain readings of a creep test can be, more accessible to a designer if they are presented as a creep modulus. In a viscoelastic, material, namely plastic, the strain continues, to increase with time while the stress level, remains constant. Since the creep modulus, equals stress divided by strain, we thus have, the appearance of a changing modulus., 2. The creep modulus, also known as the, apparent modulus or viscous modulus when, graphed on log-log paper, is normally a, straight line and lends itself to extrapolation, for longer periods of time., 3. Creep data applications are generally, limited to the identical plastic, temperature,, stress level, atmospheric conditions, and type, of test. Data of a relatively short duration of 1000 h can be extrapolated to long

Page 84 : 66, , 2 Design Influencing Factor, , term needs. Reinforced thermoplastics and, particularly reinforced thermosets display a, much higher resistance to creep than do the, unreinforced plastic., An introduction is provided to analyzing, creep data and determining guidelines on, how they should be used. The viscoelastic nature of plastic reacts to a constant load over, a long period of time by an ever-increasing, strain. Since the modulus formula states that, modulus = stress/strain and the stress is constant, while the strain is increasing, we see an, ever decreasing modulus. This type of modulus is called an apparent modulus, and the, data for it are collected from test observations for the purpose of predicting long-term, behavior of plastics subjected to a constant, stress at selected temperatures., , Creep modeling A stress-strain diagram, is a significant source of data for a material., In metals, for example, most of the needed, data for mechanical property considerations, are obtained from a stress-strain diagram. In, plastic, however, the viscoelasticity causes an, initial deformation at a specific load and temperature and is followed by a continuous increase in strain under identical test conditions, until the product is either dimensionally out, of tolerance or fails in rupture as a result, of excessive deformation. This type of, an occurrence can be explained with the, aid of the Maxwell model shown in Fig. 2-24., , •, , ~DaShPot, , Fig. 2-24 Maxwell model used to explain viscoelastic behavior., , The Maxwell model is also called Maxwell, fluid model. Briefly it is a mechanical model, for simple linear viscoelastic behavior that, consists of a spring of Young's modulus (E) in, series with a dashpot of coefficient of viscosity (1]). It is an isostress model (with stress 8),, the strain (e) being the sum of the individual, strains in the spring and dashpot. This leads, to a differential representation of linear visco~lasticity . as de/dt = (l/E) d8/dt + (8/1])., ThIS model IS useful for the representation of, stress relaxation and creep with Newtonian, flow analysis., When a load is applied to the system,, shown diagrammatically, the spring will deform to a certain degree. The dashpot will first, ~emain stationary under the applied load, but, If the same load continues to be applied, the, viscous fluid in the dashpot will slowly leak, past the piston, causing the dashpot to move., Its movement corresponds to the strain or deformation of the plastic material., .When the stress is removed, the dashpot, WIll not return to its original position, as the, spring will return to its original position. Thus, we can visualize a viscoelastic material as, having dual actions: one of an elastic material, like the spring, and the other like the, ~scous liquid in the dashpot. The properties of the elastic phase are independent of, time, but the properties of the viscous phase, are very much a function of time, temperature, and stress. This phenomenon is further, explained by looking at the dashpot again,, where we can visualize that a thinner fluid, resulting from increased temperature under, a higher pressure (stress) will have a higher, r~te of leakage around the piston during the, tIme that the conditions described prevail., Translated into plastic creep, this means that, at higher use temperature and higher stress, levels the strain will be higher, resulting in, greater creep., Visualizing the reaction to a load (without time) by such a dual-component interpretation is valuable to our understanding, of the creep process but is basically meaningless for design purposes. For this reason, the designer is interested in the actual def?rmation or product failure over a specific, time span. Observations of the amount of, strain at certain time intervals must be made,

Page 85 : 67, , 2 Design Influencing Factor, which will then make it possible to construct, curves that can be extrapolated to longer time, periods. The usual initial readings at 1,2,3,5,, 7, 10, and 20 hours, are followed by readings, every 24 hours up to 500 hours, then readings every 48 hours up to 1,000 hours. The, time segment for the creep test is common, to all materials. Strains are recorded until, the specimen ruptures or is no longer useful because it has yielded. In either case, a, point of failure of the test specimen has been, reached., , IS, , Time, , Fig.2-26 Typical creep and stress-rupture curves., , Product performance data Products subjected to a given load develop a corresponding predictable deformation. If it continues, to increase without any increase in load or, stress, the material is said to be experiencing, creep or cold flow. Creep in any product is, defined as increasing strain over time in the, presence of a constant stress (Figs. 2-25 and, 26). The rate of creep for any given plastic,, steel, wood, etc. material depends on the basic applied stress, time, and temperature., Creep-test specimens may be loaded in, tension or flexure (to a lesser degree in compression) in a constant temperature environment. With the load kept constant, deflection, or strain is recorded at regular intervals of, hours, days, weeks, months, or years. Generally, results are obtained at three or more, stress levels., Stress-strain-time data are usually presented as creep curves of strain versus log, time. Sets of such curves, seen in Fig. 2-27,, can be produced by smoothing and interpolating data on a computer. These data may, also be presented in other ways, to facilitate, the selection of information to meet specific, design requirements. Sections may be taken, , through creep curves at constant times to, yield isochronous stress versus strain curves, or at a constant strain, giving isometric stress, versus log-time curves as in Fig. 2-27. Standard ASTM D 2990 provides details for different creep tests., CREEP CURVES, STRAIN, VS., LOG TIME, , ISOMETRIC STRESS, VS LOG TIME, Fracture, , J~, Log time, , Fig. 2-25, , Concept for evaluating creep-test data., , ISOCHRONOUS STRESS, VS STRAIN, , ~-----=----, , Strain, , Fig. 2-27 Typical creep data vs. log time.

Page 86 : 68, , 2 Design Influencing Factor, , If a designer is faced with decisions concerning creep, the most reliable source of information is a test program run under simulated or actual conditions on the product, itself or at least on test specimens. The expected operating life of most products designed to withstand creep is usually ten to, twenty years. It is apparent that actual longtime testing is not likely to be undertaken, so, available creep test-data must be used. The, so-called long-time tests are undertaken for, at least 1,000 hours, the recommended time, specified in the ASTM standard based on extensive data accumulated since at least 1943., The tests are performed under carefully, controlled stress (load), temperature, time,, and creep (elongation) conditions. To save, time, tests for different constant loads are, performed simultaneously on different specimens of the same material. Creep tests may, be rather extensively conducted, as for example when developing creep data prior to the, design and fabrication of the first all-plastic, airplane (41). The usual procedure is to plot, the creep versus time curve, but other combinations are possible., The theoretically shaped curve in Fig. 2-25, provides the three typical stages for evaluation. An initial strain takes place almost immediately, consisting of the elastic strain plus, a plastic strain, if the deformation extends beyond the yield point. This initial action in the, first stage shows a decreasing rate of elongation because of strain hardening. The action most relevant to the designer concerns, the second stage, which begins at a minimum strain rate and remains rather constant,, , because of the balancing effects of strain, hardening and annealing. In the third stage, a rapid increase in the creep rate is accompanied by severe necking (that is, thickness, reduction) and ultimately rupture., Designers are concerned with the second, stage in the sense that their target is not to, have the product being designed enter into, the third stage. Thus, after plotting the creep, versus time data of the 1,000 h test, the second stage can be extrapolated out to the, number of hours of desired product life. This, process is then followed for each of the creep, curves. In making this extrapolation it is assumed that the 1,000-hour test has allowed, the material to enter into the second stage., The material will have behaved similarly to, that shown in the curve in Fig. 2-25., Creep rupture. Creep-rupture data are, obtained in the same way as creep data except, that higher stresses are used and the time is, measured to failure (Figs. 2-28 and 29). The, strains are sometimes recorded, but this is not, necessary for creep rupture. The results are, generally plotted as the log stress versus log, time to failure (110). In creep-rupture tests it, is the material's behavior just prior to the rupture that is of primary interest. In these tests, a number of samples are subjected to different levels of constant stress, with the time to, failure being determined for each stress level., General technical literature and product data, sheets seldom provide a complete description of a material's behavior prior to rupture., It should include the development of any, crazing and stress whitening, its strain-time, , 1000 hour Slress, ruplure sirength, allOOO"F (!i38CI, , 60, , ;, , 450, , ---------, , 20, 100, , 1000, , ..., , a.., 300 ::i:, , represents a, lest to failure, , 150, , 10.000, , 100.000, , Time to Failure. hours, , Fig.2-28 Typical stress-rupture data vs. temperature.

Page 87 : 69, , 2 Design Influencing Factor, 60, , 50, , \, , W, , ...e, , N, , z, , ::E, , ..., Vi, , J:), , 1/1, 1/1, , 20, , ,%....., , "'", , ~~ ~, I~, 2"-.. . "'... ..................., , 1"--_ _, , ~ ~...... ~, ...-. r-............., , -._-. --, , I--, , ~, , .., , ~, , \, , 10, , 0, , 10, , 10, , 1C, , 10, , 1~, , Log time to failure, , 10', , ,, , 10, , ,, 10', , (51, , Fracture, Whitening or crazing, ------ Isometric curves, , Fig.2-29 Typical creep-rupture ductile-to-brittle behavior of TPs., , behavior, the nature of the fracture process,, and describe yielding, necking, and brittleness., The Fig. 2-30 shows the curves of a family, of TPs describe as failure that is fairly typical of the behavior of certain TPs. The timedependent strains resulting from several, levels of sustained or creep stress are shown,, , together with the development of crazing, and of stress Whitening. The features that develop in the failure process follow a particular, pattern:, Overall behavior. It is the timedependent strain at which crazing, stress, whitening, and rupture decreases with a, , al is the highest stress, a 5 is the lowest stress, , TIME, t, hrs - Log Scale, Fig. 2-30, , Generalized strain vs. time in TP.

Page 88 : 70, , 2 Design Influencing Factor, , decreasing level of sustained stress. The time, to development of these defects increases, with a decreasing stress level., Crazing. This develops in such amorphous plastics as acrylics, PVCs, PS, and, PCs as creep deformation enters the rupture, phase. Crazes start sooner under high stress, levels. Crazing occurs in crystalline plastics,, but in those its onset is not readily visible., It also occurs in most fiber-reinforced plastics, at the time-dependent knee in the stressstrain curve., Stress whitening. This occurs in many, types of plastics, including the amorphous, ones like PVC and ABS, and in the crystalline, types such as PE and PP. A stress-whitening, zone may be a sign of crazing in some plastics, where individual fine crazes may be difficult, to detect. Stress whitening occurs fairly late, in the rupture stage, just prior to yielding., Rupture. Rupture strain decreases steadily with increases in the duration of stress., Alternately, the magnitude of stress needed, to cause rupture decreases as the duration, of stress increases. Figure 2-31 shows the development first of damage and then of yielding in a PVC compound as a function of its, being under sustained stress. The decay at, the onset of the first damage and of yield, , strength with the increasing duration of sustained stress is also evident. In other words,, a decrease in the magnitude of the sustained, stress lengthens the time over which crazing,, stress whitening, and yielding develop. Yielding is frequently taken as the failure criterion, for plastics. However, some common types, of standardized creep-rupture tests do not, determine yielding, only the sustained stress, and time to failure. One example of this is, the ASTM D 1598 procedure for determining, the time-dependent burst strength of plastic, pressure pipes. Plotting the failure or bursting stress against the time to failure for a, given material defines its strength regression, relationship., Comparisons have been made of the, strength-regression characteristics of plastics, with those of wood. The capacity of wood to, resist sustained stress has been determined, to decay at a rate of 8% for each decade, of time change, that is, its capacity at the, end of each decade is 92 % of what it was at, the start of the decade. The decay rates calculated from published strength-regression, information on pressure-rated plastic pipe, compounds are shown in Table 2-6. The decay rate for the specific plastics tested varies, from 7 to 32 % per decade, depending on the, generic type of plastic and the specific compound within that type. The time-dependent, strength behavior of some of these plastics is, similar to that of wood., , ~------------------------------------------~90, SO, , 70, , ,\~fQH~'''necl<iO'', , , '., , -, , ' ,~., --.--.-:~~:----------------l·_·-., ,, , ' ..... -T---- . . . ~, stress whItening, , craze initiationJ, , 60, 50, , TIME, t, hrs, , o~, , .n, 40tn, a:, 30, , 20, , 10, , o~~--~~--~----~--~~--~----~--~~~o, 0.001, 0.01, 0.1, 10, I 2, 103, 104, , Fig.2-31 Example of stress vs. time to damage and failure of PVc., , 0, , ~, , t-, , ~

Page 89 : 71, , 2 Design Influencing Factor, , Table 2-6 Rate of strength decay for wood, and TPs, , per in., then:, E = 10,000/0.015, , Range of Decay Rate:, % per Decade of Time, , Material, Wood, , Similarly, Ea can then be determined for, one year. Extrapolating from the creep-data, curve, which is in fact a straight line, gives a, deformation of 0.025 in. per in. Thus,, , 8, , PVC, , 7-19, , ABS, , 12-32, , PE, , = 5,000,000 psi (3,500 MPa) (2-8), , 8-13, , * Change in strength under sustained stress from beginning to end of decade, or unit change in log time., , Apparent creep modulus. The concept of, an apparent modulus is a convenient method, for expressing creep, because it takes into account the initial strain for an applied stress, plus the amount of deformation or strain that, occurs over time. Thus, the apparent modulus, Ea is calculated in a very simplified approach, as:, , Ea, , = Stress/Initial strain + Creep, , (2-5), , Because products tend to deform in time at, a decreasing rate, the acceptable strain based, on the desired service life of the product is determined. The shorter the duration of load,, the higher the apparent modulus and thus, the higher the allowable stress. The apparent modulus is most easily explained with an, example. As long as the stress level is below, the elastic limit of the material, its modulus, of elasticity E can be obtained from the usual, equation:, E, , = Stress/Strain, , (2-9), , When plotted against time, these calculated values for the apparent modulus provide a simplified means of predicting creep at, various stress levels (Fig. 2-32). For all practical purposes, curves of deformation versus, time eventually tend to level off. Beyond a, certain point, creep is small and may safely, be neglected for many applications., There have been continuing attempts, made to create meaningful formulas for the, apparent modulus change with respect to, time. However the factors in the formulas, that would fit all conditions are more cumbersome to use than presenting test data in, a graph form and using it as the means for, predicting the strain (elongation) at some distant point in time. The test data when plotted, on log-log paper usually form a straight line, and tend themselves to easy extrapolation., , (2-6), , For example, a compressive stress of, 10,000 psi (69 MPa) gives a strain of 0.015, in.lin. (0.038 cm/cm) for FEP plastic at 63°F, (17°C). Then:, E, , E = 10,000/0.025, = 400,000 psi (2,800 MPa), , !g, , INCREASING, STRESS OR STRAIN, , ~, , ..., , = 10,000/0.015 = 667,000 psi (4,600 MPa), (2-7), , If the same stress level prevails for 200, hours, the total strain will be the sum of the, initial strain plus the strain due to time. This, total strain can be obtained from a creep-data, curve. If, for example, the total deformation, under a tension load for 200 hours is 0.02 in., , LOG TIME, , Fig.2-32 Example of plotting the apparent creep, modulus vs. log time.

Page 90 : 2 Design Influencing Factor, , 72, , The slope of the straight line indicating a decreasing modulus depends on the nature of a, material (principally its rigidity and temperature of heat deflection), on the temperature, of the environment in which the product is, used, and on the amount of stress in relation, to tensile strength., Extensive amount of these type data has, been plotted but unfortunately most of it is, privately owned. Creep data available from, material suppliers, college and government, projects, etc. can provide guidelines. However where the product has to meet critical, requirements that usually include safety of, people and data from previous work does not, exist, creep test have to be conducted and, properly applied by the designer., Stress relaxation. In a stress-relaxation, test a plastic is deformed by a fixed amount, and the stress required to maintain this deformation is measured over a period of time, (Fig. 2-33) where: (a) recovery after creep,, (b) strain increment caused by a stress step, function, and (c) strain with stress applied, (1) continuously and (2) intermittently. The, maximum stress occurs as soon as the deformation takes place and decreases gradually, with time from this value. From a practical, standpoint, creep measurements are generally considered more important than stressrelaxation tests and are also easier to conduct., Those interested in the theory of viscoelasticity and in the relationship of materials', properties to their molecular structure tend, to concentrate more on stress-relaxation than, , TIME,, , creep measurements. One reason may be that, stress-relaxation figures are generally more, easily interpreted in terms of viscoelastic theory than are creep data. Stress-relaxation, data also provide practical information such, as determining the stress needed to hold, a metal insert in a plastic product, evaluating the additives needed such as antioxidants, choosing cantilever-type beams, and, soon., The stress-relaxation behavior of plastics, is extremely temperature dependent, especially in the region of the plastics' glass, transition temperature (Tg) (Chapter 7)., Many unreinforced amorphous types of plastics at temperatures well below the Tg have a, tensile modulus of elasticity of about 3 x lO lD, dynes/cm2 [300 Pa (0.04 psi)] at the beginning, of a stress-relaxation test. The modulus decreases gradually with time, but it may take, years for the stress to decrease to a value near, zero. Not only is the stress-relaxation behavior of an amorphous plastic most sensitive to, temperature in its transition region, but at a, given temperature in that region the stress, changes rapidly with time., With crystalline plastics, the main effect of, the crystallinity is to broaden the distribution, of the relaxation times and extend the relaxation stress too much longer periods. This pattern holds true at both the higher and low, extremes of crystallinity (Chapter 6). With, some plastics, their degree of crystallinity, can change during the course of a stressrelaxation test. This behavior tends to make, the Boltzmann superposition principle difficult to apply., , t, , TIME,, (a), , t, , TIME,, (b), , t, , (c), , Fig. 2-33 Example of strain behavior under various intermittent and cyclic loads.

Page 91 : 2 Design Influencing Factor, Many designs incorporate the phenomenon of stress-relaxation. For example,, in many products, when plastics are assembled they are placed into a permanently, deflected condition, as for instance press fits,, bolted assemblies, and some plastic springs., In time, with the strain kept constant the, stress level will decrease, from the same, internal molecular movement that produces, creep. This gradual decay in stress at a, constant strain (stress-relaxation) becomes, important in applications such as preloaded, bolts and springs where there is concern for, retaining the load. The amount of relaxation, can be measured by applying a fixed strain to, a sample and then measuring the load with, time., The resulting data can then be presented, as a series of curves much like the isometric, stress curves in Fig. 2-27. A relaxation modulus similar to the creep modulus can also be, derived from the relaxation data. It has been, shown that using the creep modulus calculated from creep curves can approximate the, decrease in load from stress relaxation., Plastic products with excessive fixed strains, imposed on them for extended periods of, time could fail. One example might be the, eventual splitting of a plastic tube press fitted over a steel shaft. Unfortunately, there is, no relaxation-rupture corollary to creep rupture. For developing initial design concepts,, a strain limit of 20% of the strain at the yield, point or of the yield strength is suggested for, high-elongation plastics. Likewise, using 20%, of the elongation at the break is suggested, for low-elongation brittle materials without, a yield point, as only a guideline for initial, design. Prototype products should then be, thoroughly tested at end-use conditions to, confirm the design, or the available data on, specific material of interest can provide more, exacting limits., Intermittent loading. The creep behavior, of plastics that has been considered so far, has assumed that the level of the applied, stress will be constant. However, in service, the material may be subjected to a complex pattern of loading and unloading cycles, (Fig. 2-33). This variability can cause design, , 73, , problems in that it would clearly not be feasible to obtain experimental data to cover, all possible loading situations, yet to design, on the basis of constant loading at maximum, stress would not make efficient use of materials or be economical. In such cases it is useful, to have methods for predicting the extent of, the accumulated strain that will be recovered, during the rest periods after a number of cycles of load changes (100)., Recovery is the strain response that occurs, upon the removal of a stress or strain. The mechanics of the recovery process are illustrated, in Fig. 2-34, using an idealized viscoelastic, model. The extent of recovery is a function, of the load's duration and time after load or, strain release. In the example of recovery behavior shown in Fig. 2-34 for a polycarbonate at 23°C (73°F), samples were held under, sustained stress for 1,000 hours, and then the, stress was removed for the same amount of, time. The creep and recovery strain measured, for the duration of the test provided several, significant points., First the sample, that was loaded to about, 20% of its short-term yield strength or 13.8, MPa (2,000 psi), recovered almost completely one hour after the release of the, load, the net strain being 0.03%. Second, the, sample loaded to 66%of its short-term yield, strength, or 41.4 MPa (6,000 psi), retained, a strain of 0.8% at 1,000 hours after the release of the load. The initial strain was 2.8 %,, the strain from the 1,000 hour creep an additional1.7%. Thus only about one-half the, creep strain was recovered. Visually extrapolating the recovery curve reveals that even, after a year (104 hr.), about one-third of the, creep strain (0.6%) will remain., The first damage developed during creep, or relaxation also affects recovery behavior., If limiting the magnitude and duration of the, stress prevents the first damage, recovery will, eventually be substantially complete for all, practical purposes., Conversely, at strains above the first damage limit recovery will be incomplete and permanent deformation should be expected and, accounted for in the evaluation. This is true, not only for plastics in general but also of, reinforced plastics. When RPs are stressed

Page 92 : 74, , 2 Design Influencing Factor, Load, Removed, , ...- --,, , Creep, , -~, , 5, , ,, , ~~\, , ~, , 3, , -~, , 2, , ..-, , 3pOOpS~, , ~, '", c:, , psi, 7 !--- 2000, ', , - ,, , ~\ \ ......... i'-., \, , -+-r, , 0i!, , Q), , --'\--, , 1'\ \., , !' ,, T"\, , 5, , Recovery, , ........, , .........., , 3, , -.Ll, \ \, , 2, , - - L 1'0.., , ,, , ....., , \, , 10-t, 7, , ", , 5, , 3, , 10-', , 100, , 10', , 10', , ---, , .........., , "", , '-...., , "'", , i'..., , ""~, , "" ..., 'I., , II, , \.., , ~, , 10', 10-' IO" 10', Time (hours), , .....It., , 10', , 103 10', , Fig. 2·34 Tensile creep and recovery during the intermittent loading., , beyond the knee in their stress-strain curve,, recovery becomes incomplete and hysteresis, is clearly evident., Material and processing. As covered particularly in Chapters 6 and 7, the various material types and compositions as well as their, processing methods, influence their properties including creep. When properly processed, in general crystalline materials have, lower creep rates than the amorphous type,, and RPs as a whole have significantly improved creep resistance., Some examples of creep data presented, in different formats are given in Figs. 2-35, 2.S, , f-:", , 2.0, , e, , .5, , S, I. 0, , '", , o. S, , S, , ", 1., , Poly_cetal, , E, ~ I., , to 2-40 and Table 2-7. The data show all, kinds of creep behavior, including the effects of time and temperature on amorphous, materials that basically have a curve spread, over a much wider time scale than that of, the crystalline types. If the temperature is, well below the T g' only the first part of the, curve will be observed, for it might require, years or even centuries to observe the complete curve. In the transition region nearly, the complete curve can be observed in a period from a few seconds to a few hours. If, , Polycarbonate, 1 - - - -_____ _, , 2, , .._----, , ........, , o~--~~~~----~--~~--~~~~., , o, , 0.01, , 2000, , 4000, , 6000, , 8000, , Time (hours), , Fig. 2·35 Tensile creep curves for TPs., , 10,000, , 0.10, , 1.0, , 10, , Tim. to rupture, hr, , 100, , 1000, , 10,000, , Fig. 2·36 Stress-rupture data for rigid 2 in. diameter PVC pipe as a function of temperature.

Page 93 : 2 Design Influencing Factor, 1~.---'---r---'---~--'---~~TI, 8, , :~~~, 4 --.-.----., , ~, , 3, , ~, , 2, , ~, , r:==i--k;;::::-··;.·---·····-·-+--···-·i==1-~, , .!!, , ~, - 10 ~, , J, lrt·:=···:=-:~-~---~-~~=t==~==~~~::, 7, , I-·-----+---·-··-···-·j---·-----f-----·-··-+---····---t_-.-.-t-, , . ·5, , 6 1--------~---+---4----+-------~···----~·--·~_r~, 5 1--····---+---·-··--·,----··1··-··-·--t-, , 4L---l...---l,---::l,---:.i::---:-=---:-=-+;;;:--', 10·', , 10-', , 10", , 10', 10', 10', Time (hOurs), , 10', , 5.10', , Fig. 2-37 Tensile stress-strain-time correlation, resulting from creep for Pc., , the temperature is well above the T g, only, the upswing in the curve (that is, an increase, in the creep) will be observed, unless measurements can be made in a fraction of a, second., Not only do the creep properties of crystalline polymers change rapidly with temperature, but in some cases at a given temperature a crystalline type will creep more with, time than will the rigid amorphous or crosslinked (TS) types. However, a crystalline type, above its T g creeps very little, compared to, the others. Thus, crystalline types tend to, 23°C (73.5°F), 8000, , 50, , 7000, ~6000, , ;;, , "~ 5000, , ii, , ~, , ~., , ~, , 30, , !!4000, 'iii, c:, , .,, , t-, , ..51~, 0, , ~, , 3000, , 20, , ~, , 2000, 10, 1000, , o, , 0.5, , 1.0, , 1.5, , 2.0, , 25, , 3.0, , 3.5, , 4.0, , Strain c (%), , Fig. 2-38 Example of isochronous stress-strain, curves for pes resulting from stress relaxation., , 75, , have an even broader distribution of retardation times than do the amorphous types, (the term crystalline refers to plastics that are, actually semicrystalline)., At small loads the compliance of most, materials at a given time is independent, of stress. For example, doubling the load, doubles the deformation. At higher loads,, especially those approaching that which is, required to break the plastic, compliance, at any given time increases with the load., This effect is generally most pronounced, with the crystalline types, the tough polyblends, and the amorphous types in the, transition region or above it. However, the, rigid types like polystyrene and the highly, cross-linked phenol-formaldehyde plastics, also show creep elongation, which increases, at a rate greater than the first power of the, stress at high loads. As a result, doubling the, stress more than doubles the amount of elongation., The load or stress has another effect on the, creep behavior of most plastics. The volume, of isotropic or amorphous plastic increases as, it is stretched unless it has a Poisson ratio of, 0.50. At least part of this increase in volume, manifests itself as an increase in free volume, and a simultaneous decrease in viscosity. This, decrease in turn shifts the retardation times, to being shorter., A creep test can be carried out with an imposed stress, then after a time have its stress, suddenly changed to a new value and have the, test continued. This type of change in loading allows the creep curve to be predicted., The simple law referred to earlier as the, Boltzmann superposition principle, hold for, most materials, so that their creep curves can, thus be predicted., The first assumption involved in using the, Boltzmann superposition principle is that, elongation is proportional to stress, that is,, compliance is independent of stress. The second assumption is that the elongation created, by a given load is independent of the elongation caused by any previous load. Therefore, deformation resulting from a complex, loading history is obtained as the sum of the, deformations that can be attributed to each, separate load.

Page 94 : 2 Design Influencing Factor, , 76, , 10 rs, , 6 min., 6, , ~", 4, , o, , 0.1, , 10, , 10 2, TIME, t, hrs, , 10 yrs, , .;, , :, , O.IC--r_____~::::::=..-J, 0.1, , 10 2, , 10, , 104, , 103, , 105, , TIME, t, hrs, , Fig.2.39, , Tensile-creep behavior of PP; top on semilog scale and bottom on log-log scale., , 1.00,.----------,---------,...,.---------,, FLEXURAL CREE?, r - -..... 73°F, , o~, , 10, , Fig. 2·40, , __________, , ~~, , 10Z, , __________, , ~----------~, , 1~, , 10, , Example where creep rate is related inversely to the reinforcements and filler content.

Page 95 : 77, , 2 Design Influencing Factor, Table 2-7, , Flexural creep data of reinforced plastics at 23°C, , Base Resin, Nylon 6/6, , Filler Type and, Content (%), , Polyester, (PBT), Nylon 6/10, , Glass fiber 15,, mineral 25, Glass fiber 15,, mineral 25, Ferrite 83, , Polypropylene, , Carbon powder, , Nylon 6/6, , Glass fiber 15,, carbon powder, Glass beads 30, , Nylon 6, , Strain (%) Hours, , Apparent Modulus, (10 3 psi)' Hours, , Stress (psi)', , 10, , 100, , 1,000, , 10, , 100, , 1,000, , 2,500, 5,000, 2,500, 5,000, 2,500, 5,000, 2,500, 5,000, 2,500, 5,000, 1,250, 5,000, , 0.555, 0.823, 0.452, 0.693, 0.463, 0.638, 1.100, 6.230, 2.160, , 0.623, 0.967, 0.470, 0.742, 0.507, 0.732, 1.140, 6.920, 2.400, , 0.709, 1.140, 0.482, 0.819, 0.568, 0.952, 1.970, 8.660, 2.510, , 450, 607, 553, 721, 540, 784, 114, 40, 116, , 401, 517, 532, 674, 493, 683, 87, 36, 104, , 353, 439, 519, 610, 440, 525, 63, 29, 100, , 0.140, 0.290, , 0.320, 0.650, , 0.368, 0.750, , 893, 862, , 391, 385, , 340, 333, , , To convert psi to pascals (Pa), multiply by 6.895 x 103 ., , Designing with creep data. The factors, that affect being able to design with creep, data include a number of considerations., First, the strain readings of a creep test can be, more accessible to a designer if they are presented as a creep modulus. In a viscoelastic, material the strain continues to increase with, time while the stress level remains constant., Since the creep modulus equals stress divided, by strain, we thus have the appearance of a, changing modulus., Second, the creep modulus, also known, as the apparent modulus or viscous modulus, when graphed on log-log paper, is normally a, straight line and lends itself to extrapolation, for longer periods of time. The apparent modulus should be differentiated from the modulus given in the data sheets, which is an instantaneous or static value derived from the, testing machine, per ASTM D 638., Third, creep data application is generally, limited to the identical material, temperature, use, stress level, atmospheric conditions, and, type of test (that is tensile, flexural, or compressive) with a tolerance of ±10%. Only, rarely do product requirement conditions coincide with those of a test or, for that matter,, are creep data available for all the grades of, materials that may be selected by a designer., In such cases a creep test of relatively short, duration, say 1,000 hours, can be instigated,, and the information be extrapolated to long-, , term needs. In evaluating plastics it should, be noted that reinforced thermoplastics and, thermosets display a much higher resistance, to creep than do unreinforced plastics., Finally, there have been numerous attempts to develop formulas that could be, used to predict creep information under varying usage conditions. In practically all cases, the suggestions have been made that the calculated data be verified by actual test performance. Furthermore, numerous factors have, been introduced to apply such data to reliable, predictions of product behavior., Creep data can be very useful to the designer. The data in Fig. 2-41 have been plotted from material available from or published, by material manufacturers. It shows the apparent modulus versus time at 23°C (73°F), for (A) MerIon polycarbonate at 13.8 MPa, (2,000 psi); (B) an extrapolation of (A) beyond 107 hrs.; (C) Noryl 731 modified PPO, at 13.8 MPa (2,000 psi); (D) Delrin 500 acetal at 6.9 MPa (1,000 psi); and (E) Zytel109, nylon at 50% relative humidity and 6.9 MPa, (1,000 psi). The broken lines represent extrapolated values, the circles are actual testreading points. The log-log graph sheets are, 9 in. x 15 in. and contain 3 x 5 cycles. The, end of the first time cycle of 103 represents, 1,000 hours., The first point is the 100 h time interval., The data for shorter intervals do not as a rule

Page 97 : 2 Design Influencing Factor, fit the straight-line configuration that exists, on log-log charts for the long-term duration, beyond the first 100 h test period. The circled points are the 100 h, 300 h, and 1,000 h, test periods, and other observed values, and a, straight line is fitted either through the circles, or tangent to them to give the line a slope for, long-term evaluation., From this line can be estimated the time at, which the strain will be such as to cause tolerance problems in product performance. Or, by using the elongation at yield as the point, at which the material has attained the limit, of its useful life, we can estimate the time at, which this limit will be reached., The equation "modulus (apparent) equal, stress/strain" enables us to locate the modulus that corresponds to the test stress and, strain (the strain being obtained by using, the dimensional change or elongation limit), where it intersects the straight line leading, to an appropriate time value. The polycarbonate creep line shows that a limit of 0.010, in elongation is reached at the end of 105, hours (apparent modulus = 200,000 psi) and, an elongation (yield) of 0.06 is arrived at after, 106 hours, or indefinitely if the 0.010 limitation does not exist., As reviewed in the interest of sound, design-procedure, the necessary creep information should be procured on the prospective material, under the conditions of product usage. In addition to the creep data,, a stress-strain diagram, also at the conditions of product usage, should be obtained. The combined information will, provide the basis for calculating the predictability of material performance in the designed product., Allowable working stress. The viscoelastic nature of the material requires not merely, the use of data sheet information for calculation purposes but also the actual longterm performance experience gained from it, which can be used as a guide. The allowable, working stress is important for determining, dimensions of the stressed area and for predicting the amount of distortion and strength, deterioration that will take place over the life, span of the product. The allowable working, , 79, , stress, for a constantly loaded product that is, expected to perform satisfactorily over many, years has to be established using creep characteristics for a material with enough data to, make reliable long-term predictions of shortterm test results., Creep test data when plotted on log-log, paper usually form a straight line and tend, themselves to extrapolation. The slope of, the straight line, which indicates a decreasing modulus, depends on the nature of the, material (principally its rigidity and temperature of heat deflection), the temperature of, the environment in which the product is used,, and the amount of stress in relation to tensile, strength., Certain conclusions can now be developed,, based on creep-data test results: First, for, practical design purposes, the data accumulated for up to 100 hours of creep are of no, real benefit. There is usually too much variation during this test period, which is of a relatively short duration., Next, the apparent modulus values, starting with a test period of 100 hours and continuing up to 1,000 hours, form a straight line, when plotted on log-log paper. This line may, be continued for longer periods on the same, slope for interpolation purposes. This action, can be taken (based on a guide) provided the, stress level is one quarter to one fifth that of, the ultimate strength and the test temperature is no greater than two thirds of the difference between room temperature and the, heat deflection temperature at 264 psi (1,800, kPa). When these limitations are exceeded,, there is a potential sharp decrease in the apparent modulus after 1,000 hours, with indications that failure from creep is approaching, (that is, the material has attained the limit of, its usefulness)., Since the designer will be expected to plot, curves to suit requirements, some examples, will be cited that can serve as a guide for potential needs (Fig. 2-42)., This example for ABS uses creep data for, 1,000 psi stress at 23°e. When the line is, extended to 105 h, the apparent modulus is, 140,000 psi. If the product is designed for, the duration of 105 h and calculations are, made for product dimensions, the modulus

Page 98 : 2 Design Influencing Factor, , 80, , --107 End 01, , ---, , loS, , usefullif., Time (hours), , Fig. 2·42, , Creep data for ABS., , of 140,000 psi should be inserted into any formula in which the modulus appears as a factor. At 105 h the total strain is:, (2-10), E = Stress/Strain, (2-11), 140,000 = 1,000/Strain, Strain = 1,000/140,000 = 0.007 or 7%, (2-12), Based on this calculation, if the product can, tolerate this type of strain without affecting, performance, then the dimensional requirements are met., The elongation at yield for this particular, ABS is 0.0275, which could be considered the, end of the useful strength of the material., The apparent modulus corresponding to this, strain at 1,000 psi and 23°C is:, E, , = 1,000/0.0275 = 36,364 psi, , (2-13), , In the lower part of the graph in Fig. 2-42,, draw at the point of 56 x 103 on the left side a, line parallel to the original creep line and find, that it intersects the apparent modulus line at, a time of 109 x 0.5 h. The product would fail, at this time, owing to its loss of strength, even, if dimensional changes permitted satisfactory, functioning of the product., Some charts show creep test data beyond, the 1,000 h duration, and in fact under most, conditions the straight line between the 100, , and 1,000 h points is continued into the 10,000, and 20,000 h range. Even in such charts a deviation from the straight line occurs occasionally, which should not be considered unreasonable, because of all the variables that enter, into the test data., Selecting an allowable continuous working stress at the required temperature must, be a procedure that allows for making an, estimation of the elongation at the end of, the product's life. For example, if a product, will be stressed to 1,700 psi at a temperature, of 66°C (150°F), and data are available for, 2,000 psi stress at 71°C (160°F), this information plotted on log-log paper should allow, to extrapolate the long-term behavior of the, material., , Isometric and isochronous graph Creep, curves are a common method of displaying the interdependence of stress-straintime. However, there are other methods that, may also be useful in particular applications, specifically isometric and isochronous, graphs. An isometric graph is obtained by, taking a constant strain section through the, creep curves and replotting this as stress versus time (Figs. 2-33 and 2-34). It is an indication of the relaxation of stress in the plastic, when strain is kept constant. These data are, often used as a good approximation of stress

Page 99 : 2 Design Influencing Factor, relaxation in a plastic. In addition, if the vertical (stress) axis is divided by the strain, one, obtains a graph of the modulus against time, (Figs. 2-28 and 2-29). These graphs provide a, good illustration of the time-dependent variation of the modulus., An isochronous graph may be obtained by, taking a constant time section through the, creep curves and then plotting stress versus, strain as shown in Fig. 2-38. It can also be obtained experimentally by performing a series, of brief creep and recovery tests on a plastic. In this procedure a stress is applied to a, plastic test piece and the strain is recorded, after a specified time, typically 100 seconds., The stress is then removed and the plastic allowed to recover, normally for a period of, 4 (4 x 100 see.). A larger stress is then applied to the same specimen, after recording, the strain at the 100 s. time period; then this, stress is removed and the material allowed, to recover. This procedure is repeated until, enough points have been obtained to let an, isochronous graph to be plotted., Isochronous data are usually presented in, log-log scales. One reason for doing so is that, on linear scales any slight, but possibly important, nonlinearity between stress and strain, may go unnoticed. Whereas the use of loglog scales will usually produce a relatively, straight-line graph the slope of which gives, an indication of the linearity of the material., If the material is perfectly linear, the slope, will be at 45 degrees, but if it is nonlinear the, slope will be less than 45 degrees., Isochronous graphs are particularly valuable when obtained experimentally, because, they are less time consuming and require, less specimen preparation than creep curves., Such graphs at several time intervals can also, be used to build up creep curves and indicate areas where the main experimental, creep program could be most profitable. They, are also popular as means of evaluating deformational behavior, because their method, of data presentation is similar to the conventional tensile test data., Deformation or fracture. The failure of a, plastic product in the performance of its normal long-time function is usually caused by, , 81, , one of two factors: excessive deformation or, fracture. For plastics it is more often than not, found that excessive creep deformation is the, limiting factor. However, if fracture occurs,, it can have more catastrophic results. Therefore, it is essential that designers recognize, the factors that are likely to initiate fracture,, so that steps can be taken to avoid them., Fractures are usually classified as either, brittle or ductile. Although any type of fracture is serious. Brittle fractures are potentially more dangerous, because there is no, observable deformation of the material prior, to or during breakage. When the failure is, ductile, however, large nonrecoverable deformations become evident, which serve as, a warning that all is not well. Plastic fractures, are ductile or brittle depending on such variables as their polymer structure, additives,, processing conditions, strain rate, and temperature with its stress system. The principal, external causes of fracture are a prolonged, steady stress (creep rupture), the continuous application of a cyclically varying stress, (fatigue), and the application of a stress, (creep rupture). In all these cases the fracture, processes can be accelerated if the plastic is, in an aggressive environment., Creep guideline. Here is a summation of, the factors to consider when reviewing creep, properties:, , 1. Predictions can be made on creep behavior based on creep and relaxation data., 2. There is generally a less-pronounced, curvature when creep and relaxation data are, plotted log-log. This facilitates extrapolation, and is commonly practiced, particularly with, creep modulus and creep-rupture data., 3. Increasing the load on a product increases its creep rate., 4. Increasing the level of reinforcement in, a composite increases its resistance to creep., 5. Particulate fillers provide better creep, resistance than unfilled plastics but are less, effective than fibrous reinforcements., 6. Glass-fiber-reinforced amorphous TP, RPs generally have greater creep resistance than glass-fiber-reinforced crystalline

Page 100 : 82, , 2 Design Influencing Factor, , TP RPs containing the same amount of glass, fiber., 7. Carbon-fiber reinforcement is more effective in resisting creep than glass-fiber reinforcement., 8. The effect of a flame-retardant additive, on the flexural modulus provides an indication of its effect on long-time creep., 9. Over the past century, many plastic, products have been successfully designed for, long-time creep performance based on the, information and test data then available,, but much more exists now and will in the, future., , Fatigue Property, Introduction Fatigue is the phenomenon, of having materials under cyclic loads at levels of stress below their static yield strength., Fatigue data are used so the designer can, predict the performance of a material under, cyclic loads. The fatigue test, analogous to, static long-term creep tests, provides information on the failure of materials under repeated stresses. This fatigue behavior is by no, means a new problem. The term was applied, to the failure of a wooden mast by hoisting, too many sails too often in the pre-Christian, era., As plastics replaced metals and other materials in many critical structural applications,, fatigue tests became important. Examples of, products subject to fatigue when they are, stressed repeatedly or in some defined cyclic, manner are a snap-action plastic latch that, is constantly opened and closed, a reciprocating mechanical part on a machine, a gear, tooth, a bearing, and any structural component subjected to vibration, such as an aircraft, wing or any product that will be subjected, to repeated impacts. Such cyclic loading can, cause mechanical deterioration and progressive fracturing of the material, leading to its, ultimate failure., Under a repeated applied cyclic load, fatigue cracks begin somewhere in the product and extend during the cycling. Eventually, the crack will expand to such an extent that, , the remaining material can no longer support, the stress, at which point the product will, fail suddenly. However, failure for different service conditions may be defined differently than just as the separation of two parts., ASTM D 671 defines failure as occurring also, when the elastic modulus has decreased to, 70% of its original value., The failure effect is generally a loss of, toughness, lowered impact strength, and lowered tensile elongation. Failure includes the, melting of any part of a product, excessive, change of dimensions or the warping of the, product, and the crazing, cracking, or formation of internal voids or deformation markings. These types of defects all may seriously, affect performance strength., Plastics are susceptible to brittle crackgrowth fractures as a result of cyclic stresses, in much the same way as metals. In addition, because of their high damping and low, thermal conductivity, plastics are prone to, thermal softening if the cyclic stress or cyclic, rate is high. Examples of the TPs with the best, fatigue resistance include PP and ethylenepropylene copolymers., Fatigue data are normally presented as a, plot of the stress (S) versus the number of, cycles (N) that cause failure at that stress;, the data plotted defined as an S-N curve, (Fig. 2-43). The use of an S-N curve is used to, establish a fatigue endurance limit strength., The curve asymptotically approaches a parallel to the abscissa, thus indicating the endurance limit as the value that will produce, failure. Below this limit the material is less, susceptible to fatigue failure., Examples of fatigue curves for unreinforced (top) and reinforced (bottom) plastics, are shown in Fig. 2-44. The values for stress, amplitude and the number of load cycles to, failure are plotted on a diagram with logarithmically divided abscissa and English or, metrically divided ordinates., The fatigue behavior of a material is normally measured in a flexural but also in a, tensile mode. Specimens may be deliberately, cracked or notched prior to testing, to localize fatigue damage and permit measuring the crack-propagation rate. In constantdeflection amplitude testing a specimen is

Page 101 : 2 Design Influencing Factor, .;;;, , 300, , ndividual fatigue tnts, , c-, , o, , 83, , 250, Endurance limit !23.000 P5i1, (159 MPa\, , VI, , '", .!:, , 150, , "tI, , c:, , OJ, , al, , 100, Number of Cycln 10 Failure, , Fig.2-43 SoN curve establishes fatigue endurance limit strength., repeatedly bent to a specific outer surface, strain level. The number of cycles to failure is, then recorded. In constant flexural load amplitude testing a bending load is repeatedly, applied to the specimen. This load causes a, specified outer-surface stress level. The number of cycles to failure is then recorded. Both, modes of flexural fatigue testing can be related to the performance of real structures,, one to those that are flexed repeatedly to a, constant deflection and the other to those, , 7, Phenolic, Epoxy, , 6, , o~----~----~----~----~~----~, , 10 3, , 104, , 10', 10", Cycles of failure, , Carbon/epoxy, , ~, .;, , ~, , 1ii, , 5, , .~, , ~, , 200, 180, 160, 140, 120, 100, 80, 60, 40, 20, , Boron/epoxy, Aramid/epoxy, , ), , 1.4, , 1.2, 1.0, 0.8, , t''5", , 0.6, , 0.2, , O~~--~~~~~~O, , 1Ii 10", , 104, , 10', , 10" 10', , Number of cycles to failure. N, , Fig.2-44 Examples of room temperature fatigue, curves., , that are repeatedly flexed with a constant, load., Since fatigue cracks often start at a random surface imperfection, considerable scatter occurs in fatigue data, increasing with the, increasing lifetime wherever crack initiation, occupies most of the fatigue life of a specimen. When a line of the best fit is drawn from, the available data points on an SoN curve,, this represents the mean life expected at any, given stress level or the stress that would, cause, say, 50% of the product failures in a, given number of cycles., If sufficient data are available, much more, information can be provided when different, curves for various percentages of failure are, plotted. Where such data are available, reasonable design criteria would be based on, some probability for failure, depending on, how critical the effects of failure occur. If a, large, expensive repair of a complex mechanism would result from the fatigue failure of, one product, then a 10 or even 1 % probability of failure would be a more likely design, criterion than the 50% suggested above., The fatigue strength of most TPs is about, 20 to 30% of the ultimate tensile strength determined in the short-term test but higher for, RPs. It decreases with increases in temperature and stress-cycle frequency and with the, presence of stress concentration peaks, as in, notched components., ASTM Special Technical Publication No., 91 discusses in detail the important ramifications to be considered in the various statistical aspects of fatigue testing. Most often, the, fatigue curves as well as the tabulated values

Page 102 : 84, , 2 Design Influencing Factor, , of endurance strengths and endurance limits, are based on the 50% probability curve. As a, result, designers do not resort to using scatterband curves unless they are involved with a, design that takes a statistical approach. The, designer requiring information on the highest order of reliability should always contact, the plastic manufacturer a nd/or run tests., Testing mode Basically material fatigue, failure is the result of damage caused by repeated loading or deformation of a structure., The magnitudes of the stresses and strains induced by this repeated loading or deformation are typically so low that they would not, be expected to cause failure if they were applied only once., Constant deflection amplitude fatigue testing is probably the less demanding of the two, techniques, because any decay in the modulus, of elasticity of the material due to hysteretic, heating would lead to lower material stress, at the fixed maximum specimen deflection., In the constant load amplitude tests, maximum material stress is fixed, regardless of any, decay in the modulus of elasticity of the, material., The test frequency used during fatigue, evaluation of plastics is typically 30 Hz, and, test temperature is typically 23°C (73°F). The, behavior of viscoelastic materials is very temperature and strain rate dependent. Consequently, both test frequency and test temperature has a significant effect upon the, observed fatigue behavior. Material fatigue, data are normally presented in one of two, ways: constant stress amplitude or constant, strain amplitude plotted versus the number of cycles (N) to specimen failure to, produce a fatigue endurance S-N curve for, the material. The fatigue testing of TPs is, normally terminated at ten million (107 ), cycles., Two conclusions can be drawn from an inspection of the S-N curve: (1) the higher the, applied material stress or strain, the fewer, cycles the specimen can survive; and (2) the, curve gradually approaches a stress or strain, level called the fatigue endurance limit below which the material is much less susceptible to fatigue failure. Different materials may, , show different fatigue behavior at the same, test temperature and test frequency., The standard way to deal with fatigue effects is by a statistical approach. A curve of, stress to failure vs. the number of cycles to this, stress level to cause failure is made by testing a large number of representative samples, of the material under cyclical stress, each one, at a progressively lowered stress level. This, S-N curve is used in designing for fatigue failure by determining the allowable stress level, for a number of stress cycles anticipated for, the product. In the case of materials such as, metals, this approach is relatively not complicated. Unfortunately, in the case of plastics the loading rate, the repetition rate, and, the temperature all have a substantial effect, on the S-N curve, and it is important that the, appropriate data be used., Endurance limit To develop S-N curves, the fatigue specimen is loaded until, for example, the maximum stress in the sample is, 275 MPa (40 ksi) (Fig. 2-43). At this stress, level it may fail in only 10 cycles. These data, are recorded and the stress level is then reduced to 206 MPa (30 ksi). This specimen may, not break until after 1,000 stress cycles at this, rather low stress level., This procedure is repeated until a stress, level is determined below which failure does, not occur. In this example of a relatively high, fatigue performance material develops a flat, portion ofthe S-N curve at a stress level of 159, MPa (23 ksi). Test duration of 107 stress cycles, is usually considered infinite life. This type,, of testing is expensive, principally because, it involves a large number of samples and, much statistical evaluation. The end result,, determining the fatigue endurance limit of, a material, is an extremely important design, property. This property should be used in determining the allowable stresses in products,, rather than just the short-term yield strength,, any time a product will see cyclic loading in, service., Cyclic loading significantly reduces the, amount of allowable stress a material can, withstand. If data are not available on the endurance limit of a material being considered, for use, a percentage of its tensile strength can

Page 103 : 2 Design Influencing Factor, be used. This percentage varies with the different material systems. For engineering plastics the endurance limit could be about 50%, of its tensile strength, as with metals. Taking, this 50% approach requires the designer to, become familiar with fatigue testing results, on plastics and other materials, so that the, proper evaluation can be applied. However,, to design correctly, requires obtaining reliable S-N curves with the required endurance, limit, as in Fig. 2-43. Plastics are subject to, fatigue, with a wide range of performance,, and efforts should be made to arrive at endurance limit information if a fail-safe design, is desired., Heat generation Since plastics are viscoelastic, there is the potential for having a, large amount of internal friction generated, within the plastics during mechanical deformation, as in fatigue. This action involves the, accumulation of hysteretic energy generated, during each loading cycle. Examples of products that behave in this manner include coil, or leaf springs and shoe soles., Because this energy is dissipated mainly in, the form of heat, the material experiences, an associated temperature increase. When, heating takes place the dynamic modulus decreases, which results in a greater degree of, heat generation under conditions of constant, stress. The greater the loss modulus of the, material, the greater the amount of heat generated that can be dissipated. Plastics for, fatigue applications can therefore have low, losses., If the plastic's (TP's) surface area is insufficient to permit the heat to be dissipated, the, specimen will become hot enough to soften, and melt. The possibility of adversely affecting its mechanical properties by heat generation during cyclic loading must therefore, always be considered. The heat generated during cyclic loading can be calculated from the, loss modulus or loss tangent of the plastics., The rate dependence of fatigue strength, demands careful consideration of the potential for heat buildup in both the fatigue test, and in service. Generally, since the buildup, is a function of the viscous component of, the material, the materials that tend toward, , 85, , viscous behavior will also display sensitivity, to cyclic load frequency. Thus TPS, particularly the crystalline polymers like polyethylene that are above their glass-transition temperatures, are expected to be more sensitive, to the cyclic load rate, and highly cross-linked, plastics or glass-reinforced TS plastics are less, sensitive to the frequency of load., From this review it should be obvious that, care must be taken in the use of the type of, accelerated fatigue testing that is common for, metals. For example, a frequency of 30 Hz is, not uncommon for metal tests. However, significant change in the fatigue life of PMMA, occurs as measured by excessive thermal softening at frequencies well below 30 Hz. Depending on the type of plastic, testing at frequencies of a few Hz or less is required, to, avoid such softening. In contrast, if the component is to be subjected to high-frequency, loads in service, the test should be performed, at similar frequencies. High-frequency loadings may show no significant heat buildup,, provided stresses are small, particularly when, the product is to be cooled., Fatigue results in a shift from ductile to, brittle failure with the increased number of, load cycles. Strength-regression behavior obtained under sustained stress with the regression under a 0.5 Hz cyclic stress can be applied, in a square waveform. The curves for an equal, duration of tensile stress, is represented by either the time under sustained load or the cumulative time under stress during the squarewave loading of the fatigue test. Compared to, the static loading, the fatigue loading results, in both a pronounced shift from ductile to, brittle fracturing and a marked decrease in, the time to failure at a given stress., Fracture mechanic The fracture mechanics theory developed for metals is also adaptable for use with plastics. The basic concepts remain the same, but since metals, and plastics are different they require different techniques to describe their fatiguefailure behaviors. Some of the comments, made about crack and fracture influences, on fatigue performance relate to the theory of fracture mechanics. The fracture mechanics theory method, along with readily

Page 104 : 86, , 2 Design Influencing Factor, , ---- -., , - - - - - - - - - - - - - - - - - - P P e r c e n t of unlmate Static Slrength--100, , _ _ _ _ 0107, , ----, , Cycle. - . J 10', , .,---=::::----80, , Fig.2-45 Summary of high-performance fatigue properties of different materials based on their percent of ultimate static tensile strength., , measured material properties, component, geometry, and loading information, can be, used to design against fatigue failure. The, fracture mechanics model also gives insight, into materials' development by showing how, their resistance to crack propagation depends, on both molecular and structural factors., Service failures in plastics can be caused, by fatigue. When time is the critical factor,, this type of failure is called static fatigue or, creep rupture. For mechanical load reversal, or the number of cycles controls failure, the, term employed is cyclic fatigue. Interaction, between the material and an environment, capable of damaging it can lead to stress, cracking in the static case and fatigue in the, cycle one. An additional failure mode is thermal degradation, in which the temperature, increases within the sample from hysteretic, energy dissipation., Traditional fatigue testing produces the familiar S-N diagram. In this type of testing, the crack initiation phase usually represents, a large fraction of a product's life. However,, the crack propagation phase reveals a material's inherent fracture resistance under fracture mechanics testing. The mechanical description of a fracture is usually divided into, three stages: crack initiation, stable or incremental fatigue crack propagation, and rapid, or catastrophic fracture., Reinforced plastic In common with metals and unreinforced plastics, RPs also is susceptible to fatigue. However, they provide, high performance when compared to un-, , reinforced plastics and many other materials (Fig. 2-45). If the matrix is a TP, there, is a possibility of thermal softening failures, at high stresses or high frequencies. However, in general the presence of fibers reduces, the hysteretic heating effect, with a reduced, tendency toward thermal softening failures., When conditions are chosen to avoid thermal, softening, the normal fatigue process takes, places as a progressive weakening of the material from crack initiation and propagation., Plastics reinforced with carbon, graphite,, boron, and aramid are stiffer than the, glass-reinforced plastics (GRP) and are less, vulnerable to fatigue. E-glass is the most popular type used; S-glass improves both shortand long-term properties (10). In short-fiber, GRPs cracks tend to develop easily in the, matrix, particularly at the interface close to, the ends of the fibers. It is not uncommon, for cracks to propagate through a TS matrix, and destroy the material's integrity before, fracturing of the fabricated product occurs, (Fig. 2-46). With short-fiber composites fatigue life can be prolonged if the fiber aspect, ratio of its length to its diameter is large, such, as at least a factor of five, with ten or better, for maximum performance., In most GRPs debonding can occur after, even a small number of cycles, even at modest levels. If the material is translucent, the, buildup of fatigue damage can be observed., The first signs (for example, with glassfiber TS polyester) are that the material becomes opaque each time the load is applied., Subsequently, the opacity becomes permanent and more pronounced, as can occur in

Page 105 : 2 Design Influencing Factor, (i ), , Crack ini~atioo, , l, , r, , Fibre buckles, (ii), , Fibre breaks, , Crack propogotioo, , Adjoining, fibres buckles, (iii), , Slot/crack, , Fracture, , II, II, , Adjoining, fibres break, , I, , Crock, propagates, , t, , o~wl~ ~jl~., support during compressioo, half of loading, , half of loading, , Fig. 2-46 Sequence of push-pull fatigue in unidirectional glass-fiberlTS polyester RPs by microbuckling processes., , corrugated RP translucent roofing panels., Eventually, plastic cracks will become visible, but the product will still be capable of, bearing the applied load until localized intense damage causes separation in the component. However, the first appearance of, matrix cracks may cause sufficient concern,, whether for safety or aesthetic reasons, to, limit the useful life of the product. Unlike, most other materials, GRPs give visual warning of their fatigue failure., Since GRPs can tend not to exhibit a fatigue limit, it is necessary to design for a specific endurance, with safety factors in the region of three to four being commonly used., Higher fatigue performance is achieved when, the data are for tensile loading, with zero, mean stress. In other modes of loading, such, as flexural, compression, or torsion, the fatigue behavior can be worse than that in, tension due to potential abrasion action between fibers if debonding of fiber and matrix occurs. This is generally thought to be, caused by the setting up of shear stresses in, sections of the matrix that are unprotected, , 87, , by some method such as having properly, aligned fibers that can be applied in certain, designs. Another technique, which has been, used successfully in products such as highperformance RP aircraft wing structures, incorporates a very thin, high-he at-resistant, film such as Mylar between layers of glass, fibers. With GRPs this construction significantly reduces the self-destructive action of, glass-to-glass abrasion and significantly increases the fatigue endurance limit., , Designing with fatigue data The ranking, of fatigue behavior among various plastics, should be conducted after an analysis is made, of the application and the testing method to, be used or being considered. It is necessary to, also identify whether the product will be subjected to stress or strain loads. Plastics that, exhibit considerable damping may possess, low fatigue strength under constant stress, amplitude but exhibit a considerably higher, ranking in constant deflection amplitude and, strain testing. Also needed consideration is, the volume of material under stress in the, product and its surface area-to-volume ratio., Because plastics are viscoelastic, this ratio is, critical in that it influences the temperature, that will be reached. At the same stress level,, the ratio of stressed volume to area may well, be the difference between a thermal short-life, failure and a brittle long-life failure, particularly with TPs., Another factor is whether the product will, be in an isothermal or adiabatic heat condition or its thermodynamic behavior. This heat, condition is strongly dependent on the loading rate and environmental influences such, as temperature, water, solvents, ultraviolet, light, air speed, and others. There are different design approaches to eliminating the, basically hysteretic heating. For example, using a plastic with a low viscous response to, mechanical stress minimizes heat generation, because this material is usually very stiff., Heat-transfer conditions can be improved by, increasing the flow of air or other coolant, (water, gases, etc.) across the surface of the, product. The product's design can also be, altered to decrease mechanical energy input, slow the cyclic loading rate, increase the

Page 106 : 88, Table 2-8, , 2 Design Influencing Factor, Elevated temperature properties of glass fiber/nylon 6/6 RPs, Short Fiber, , Property, , 30%, , Long Fiber, 50%, , 30%, , 50%, , 13.8, 7.8, 14.3, 5.27, , 14.3, 5.3, 17.4, 5.50, , 19.2, 5.6, 23.7, 8.90, , 7.3, 9.5, 7.4, 4.80, , 7.8, 6.2, 8.9, 5.19, , 8.3, 6.8, 10.0, 7.51, , At 300°F, psi), Tensile strength, Elongation (%), Flexural strength (10 3 psi), Flexural modulus (105 psi), (103, , Tensile strength (10 3 psi), Elongation (%), Flexural strength (103 psi), Flexural modulus (105 psi), , 12.8, 9.3, 13.8, 4.64, At 400°F, 6.3, 8.6, 6.9, 3.96, , Data on long-fiber glass-reinforced grades are for Verton compounds., , * To convert psi to pascals (Pa), multiply by 6.895 x 103 ., , surface area for dissipating heat through fins, and the like, and other alterations., As usual with plastics and other materials,, sharp comers or abrupt changes in their crosssectional geometry or wall thickness should, be avoided because they can result in weakened, high-stress areas. The areas of high, loading where fatigue requirements are high, need more generous radii, combined with, optimal material distribution. Radii of ten, to twenty times are suggested for extruded, parts, and one quarter to one half the wall, thickness may be necessary for moldings to, distribute stress more uniformly over large, areas. In evaluating plastics for a particular, cyclic loading condition, the type of material, and the fabrication variables are quite important. Remember that the many plastics perform differently, whether they are TPs, TSs,, unreinforced and reinforced plastics., The basic rules to providing fatigue endurance can be summarized. Fiber reinforcement provides significant improvements in, fatigue with carbon fibers and graphite and, aramid fibers being higher than glass fibers, (Fig. 2-45). The effects of moisture in the service environment should also be considered,, whenever hygroscopic plastics such as nylon,, pes, and others are to be used. For service, involving a large number of fatigue cycles, in TPs, crystalline-types offer the potential, of more predictable results than those based, on amorphous types, because the crystalline, , ones usually have definite fatigue endurance., Also, for optimum fatigue life in service involving both high-stress and fatigue loading, the reinforced high-temperature performance plastics like PEEK, PES, and PI are, recommended (Table 2-8)., High Speed Property, , For the most part, many of the behavioral, characteristics discussed are valid for a wide, range of loading rates. There may be significant shifts in behavior, however, at load or, strain durations that are much shorter than, those discussed, usually take about a second, or less to perform (Figs. 2-47 and 2-48). This, section deals with loading rates significantly, faster than those covered so far, namely rapid, and impact loading., An example of the type, significance, and, character of the data obtainable under rapid, loads is shown in Fig. 2-49. The data shown, describe behavior over a spectrum of elongation rates up to several orders of magnitude higher than those obtained in standard tests. These data illustrate trends for, the specific materials examined. (a) Tensile, strength usually increases with higher strain, rate, for all plastics. (b) The elongation at, break decreases with the strain rate. (c) Energy to failure, as determined from the area, under the stress-deformation plot, generally

Page 107 : 89, , 2 Design Influencing Factor, 10 14, 10 12, , 10 10, c::, , .2, , 10 8, , §, , 10 6, , '", , 10 4, , OJ, , .2, 't:l, , I\~, .<::, <.>, , '"~, , $a, , 100, 10- 2, , 10- 4, , u, , 10- 6, , 0, , ~, , a~d, , more, , 1 da., , 10 2, , '"c, , 't:l, , 1 day, , 1 sec., , I, , Creep and, stress rupture, , I I, Standard, static testing, , I I, I I, , 10- 8, 10- 10, 10- 12, , II, 10- 10, , 10- 8, , 10- 6, , 10- 4, , I, I, I, I Rapid, I Ioadin2, I, I, I, , I, I, I, I, 10 0, , Strain rate, in./in./sec., , Impact, , 102, , 10 4, , 10 6, , Fig. 2-47 Relation of rapid loading strain rates to those developed in other methods of testing., , decreases or remains the same with an increasing test rate. Moreover, different plastics show a markedly different rate of decay, of failure energy with increased test speed., VElOCITY., FT./SEC., , 1.000, , TYPICAL CASES, , -FIREO PROJECTIlE, , - BA TTEO BASEBAll, -PITCHED BASEBAll, , 100, , -FOOTBALL HELMET, , - TEN-FOOT FAll, -IZOO IMPACT TEST, 10, , -REFRIGERATOR OOOR·SLAM, , 1.0, , 0.1, , -CONVENTIONAL TENSilE STRENGTH, , TeSTS, , 0.01, , Fig. 2-48 Typical velocities that refer to rapid, loading., , Designers with a background in using other, materials will recognize both the similarities, and the differences in the behavior of the, plastics discussed. As an example, impact resistance has been a continuing issue with engineering materials, particularly certain metals, with similarities to many of the phenomena, observed in plastics., The concept of a ductile-to-brittle transition temperature in plastics is likewise well, known in metals, notched metal products being more prone to brittle failure than unnotched specimens. Of course there are major, differences, such as the short time moduli of, many plastics compared with those in steel,, that may be 30 x 106 psi (207 x 106 kPa). Although the ductile metals often undergo local necking during a tensile test, followed by, failure in the neck, many ductile plastics exhibit the phenomenon called a propagating, neck. These different engineering characteristics also have important effects on certain, aspects of impact resistance., There are a number of basic forms of, energy loads or impingement on products, to which plastics react in a manner different from other materials. These dynamic, stresses include loading due to impact, impulse, puncture, frictional, hydrostatic, and, erosion. They have a difference in response, and degree of response to other forms of, stress. Analyzing these differences provides

Page 108 : 90, , 2 Design Influencing Factor, TEST RATE, mm/min., , 10, '00, , "'£", f-, , 102, , 103, , 104, , 105, , 106, , 107, , 150, , 20, 16, , £, , 100, , (!), , z, , w, , a:, , a. Tensile Strength, , '", ~, , 0.., , 12, , S, z, w, , a:, , f-, , f-, , en, , w, -', Ci5, z, w, , en, , 8, , 50, , 4, , f-, , 0, , w, Ci5, z, w, , -', , f-, , 0.1, , 10, , 102, , 103, , 104, , 105, , 0, 106, , TEST RATE, in.lmin., , 10, , 500, , TEST RATE, mm/min., , 102, , 103, , if., "::i: 400, «, , !;;:, z, , a, , 105, , 106, , 107, b. Tensile Elongation, at Break, , ~, , w, , a:, , CD, , 104, , 300, , nylon, , 200, , ~, z 100, , (!), , a-', w, , 102, , 10, , 103, , 104, , 105, , 106, , TEST RATE, in.lmin., , '"to, , 1000, , ~, ui, , 800, , :::J, , 600, , ..a, '", , a:, , «, -', u., , 400, , (!), , 200, , >w, , 102, , TEST RATE, mm/min., , 103, , 104, , 105, , 106, , 107, 2, , '"E, , ~, , c. Energy to Failure, , '", , "3, , 1.5 .~, w, a:, , :::J, , -', , af-, , a:, , 10, , z, , UJ, , 0, , ~, , af-, , 0.5 >-, , (!), , a:, , 0, 10, , 0.1, , 102, , 103, , 104, , 105, , 106, , w, w, , z, , TEST RATE, in.lmin., , Fig. 2-49, , Examples of rapid loading or high speed tests., , the designer with information applicable to, product performances., Impact loading, , Whenever a product is loaded rapidly, it, can be said to be sUbjected to impact loading., Any product that is moving has kinetic energy. When this motion is somehow stopped, , because of a collision, its energy must be dissipated. The ability of a plastic product to, absorb energy is determined by such factors, as its shape, size, thickness, type of material,, method of processing, and environmental, conditions of temperature, moisture, and so, on. Although the impact strengths of plastics, are widely reported, these properties have, no particular design value. However, they, are important, because they can be used to

Page 109 : 2 Design Influencing Factor, provide an initial comparison of the relative, responses of materials. Impact strength can, pick up a discriminatory response to notch, sensitivity. A better value via impact tensile values, is unfortunately not generally reported., With limitations, the impact value of a material can broadly separate those that can, withstand shock loading from those that fare, poorly in this response. Of great importance, is that they can be compared to the impact, performance on the fabricated products. The, results provide guidelines that will be more, meaningful and empirical to the designer. To, eliminate broad generalizations, the target is, to conduct impact tests on the final product or, if possible, at least on its components., In conducting impact tests on products the, usual problem that has to be resolved as well, as possible is how it should be conducted., The real test is after the product has been, in service and field reports are returned for, evaluation. Regardless, the usual impact tests, conducted on test samples can be useful if, they are properly coordinated with product, requirements., Design feature The overall impact resistance of a structure is defined as its ability to, absorb and dissipate the energy delivered to, it during relatively high speed collisions with, other objects without sustaining damage that, would jeopardize its intended function. Several design features affect impact resistance., For example, rigidizing elements such as, ribs may decrease a part's impact resistance,, while less-rigid sections may absorb more, impact energy without damage by deflecting, elastically., Likewise, dead sharp corners or notches, subjected to tensile loads during impact may, decrease the impact resistance of a product by, acting as stress concentrators, whereas generous radii in these areas may distribute the, tensile load and enhance the impact resistance. This point is particularly important for, products comprised of materials whose intrinsic impact resistance is a strong function, of a notch radius. Such notch sensitive materials are characterized by an impact resistance that decreases drastically with notch, , 91, , radius. Wall thickness may also affect impact, resistance. Some materials have a critical, thickness above that the intrinsic impact resistance decreases dramatically., Impact loads are a particularly important, kind of load for plastics. While many materials such as PE and nylon have good impact strength, other plastics such as crystal, PS and some grades of PVC have low impact strength. Many of the tests for impact, strength have been based on tests for steel, and other metals and the applicability of, such tests to plastics has always been questionable. For example PVC which rates low, in notched Izod impact tests performs well, in normal applications that involve impact, loading. However, some grades of rubbermodified high impact styrenes that show, up well in the Izod test break on impact, under field test conditions. These results, have led to continual reexamination of the, tests used to determine the toughness of, plastics., Methods employed to determine the impact resistance of plastics include: pendulum, methods (Izod, Charpy, tensile impact, falling, dart, Gardner, Dynatup, etc.) and instrumented techniques. In the case of the Izod, test, what is measured is the energy required, to break a test specimen transversely struck, (the test can be done either with the specimen notched or unnotched). The tensile impact test has a bar loaded in tension and, the striking force tends to elongate the bar, (Chapter 5, Impact Strength)., There are plastics that tend to be very notch, sensitive on impact. This is apparent from the, molecular structure of the materials that consist of random arrangements of plastic chains., If the material exists in the glassy state at, room temperature the notch effect is to cut, the chains locally and increase the stress on, the adjacent molecular chains which will scission and propagate the effect through the material. At the high loading rate encountered, in impact loading the only form of molecular, response is the chain bending (spring) reaction which is limited in extent and generally, low in magnitude compared to the viscoelastic response which responds at longer loading, times.

Page 110 : 92, , 2 Design Influencing Factor, , There are several ways in which the impact properties of plastics can be improved, if the material selected does not have sufficient impact strength. One method is by altering the composition of the material so that, it is no longer a glassy plastic at the operating temperature of the product (Chapter 6)., In the case of PVC this is done by the addition of an impact modifier which can be a, compatible plastic such as an acrylic or a nitrile rubber. The addition of such a material, lowers the glass transition temperature and, the material becomes a rubbery viscoelastic, plastic with much improved impact properties. This is one of the methods in which PVC, materials are made to exhibit superior impact, properties., Another way in which to improve impact, properties is by orienting the material. Nylon, has a fair impact strength but oriented nylon, has a very high transverse impact strength., The intrinsic impact strength of the nylon, comes from the polar structure of the material and the fact that the polymer is crystalline. The substantial increase in impact, strength as a result of the orientation results, from the molecular chains being aligned. This, makes them very difficult to break and, in, addition, the alignment improves the polar, interaction between the chains so that even, when there is a chain break the adjacent, chains hold the broken chain and resist parting of the structure. The crystalline nature of, the nylon material also means that there is a, larger stress capability at rapid loading since, the crystalline areas react much more elastically than the amorphous glassy materials., Other methods in which impact strength, can be substantially improved is by the use of, fibrous fillers. These materials act as a stress, transfer agent around the region that is highly, stressed by the impact load. Since most of the, fibrous fillers such as glass and asbestos have, high elastic moduli, they are capable of responding elastically at the high loading rates, encountered in impact loading (39)., One general method of improving the performance of plastic products in impact loading is to prevent, by design and handling, the, formation of notched areas which act as stress, , risers. Especially under impact conditions the, possibility of localized stress intensification, can lead to product failure. In almost every, case the notched strength is substantially less, than the unnotched strength., It is important to recognize that impact, strength is sensitive to temperature conditions. The impact strength of plastics is reduced drastically at low temperatures with, the exception of fibrous filled materials that, improve in impact strength at low temperature. The reduction in impact strength is especially severe if the material undergoes a, glass transition where the reduction in impact, strength is usually an order of magnitude., , Impulse Loading, A related form of stress to impact is impulse loading that differs in two ways from, impact loading. Impact loading implies striking the object and consequently there is a, severe surface stress condition present before the stress is transferred to the bulk of, the material. In addition, in impact loading, the load is applied instantly, limited in straining rate only by the elastic constants of the, material being struck. A significant portion, of the energy of impact is converted to heat, at the point of impact and complicates any, analytically exact treatment of the mechanics of impact., In the case of impulse loading the load is, applied at very high rates of speed limited by, the member applying the load. However, the, loading is not generally localized and the heat, effects are similar to conventional dynamic, loading in that the hysteresis characteristics, of the material determines the extent of heating and the effects can be analyzed with reasonable accuracy. For example, the load of, two billiard balls striking is definitely an impact condition. The load applied to a brake, shoe when the brake is applied or the load, applied to a fishing line when a strike is made, is an impulse load. The time constants are, short but not as short as the impact load and, the entire structural element is subjected to, the stress.

Page 111 : 2 Design Influencing Factor, Plastics generally behave in a much different manner under impulse loading than they, do under loading at normal straining rates., Some of the same conditions occur as under, impact loading where the primary response, to load is an elastic one because there is not, sufficient time for the viscoelastic elements, to operate. The primary structural response, in the polymer is by chain bending and by, stressing of the crystalline areas of crystalline, polymers. The response to loading is almost, completely elastic for most materials, particularly when the time of loading is of the order, of milliseconds., Since the entire load is applied to the elastic elements in the structure and the longrange strain adaptation is precluded, the material will exhibit a high elastic modulus and, much lower strain to rupture. It is difficult, to generalize as to whether the material is, stronger under impulse loading than under, normal loading. For exa~ple, PMMA and, rigid PVC materials that appear to be brittle under normal loading conditions, exhibit, high strength under impulse loading conditions. Rubbery materials such as thermoplastic urethane elastomers and some other elastomers behave like brittle materials under, impulse loading. This is an apparently unexpected result that upon analysis is obvious, because the elastomeric rubbery response is, a long time constant response and the rigid, connecting polymer segments which are brittle are the ones that respond at high loading, rates., The comments regarding improvements, made with respect to impact loading for structures apply equally well to impulse loading, conditions. Fibrous fillers improve impulse, loading strength. Oriented materials withstand impulse loading much better than unoriented materials. As an example fibrous, forms of materials are used in rope because, they take impulse loading well. Crystalline, polymers generally perform well under impulse loading, especially polar materials with, high interchain coupling., Using plastics under impulse loading conditions requires a careful design approach., Test data taken with high-speed testing, , 93, , machines are essential before using a plastic for these applications since it is difficult to, predict the response of the material from the, available data. High-speed testing machine, are used to determine the response of materials at millisecond loading rates. In the absence of such test data, the only first sorting, evaluation that can be done is from the results, of the tensile impact test. The test should be, done with a series of loads below break load,, through the break load, and then estimating, the energy of impact under the non-break, conditions as well as the tensile impact break, energy. As indicated above, apparently brittle, materials perform well and rubbery materials, that would seem to be a natural for impulse, loading behave in a brittle manner., , Puncture Loading, Resistance to puncture is another type of, loading. It is of particular interest in applications involving sheet and film as well as thinwalled tubing or molding and other membrane type loaded structures. The surface, skins of sandwich panels are another area, where it is important. A localized force is applied by a relatively sharp object perpendicular to the plane of the sheet of material being, stressed. If the material is thick compared to, the area of application of the stress, it is effectively a localized compression stress with, some shear effects as the material is deformed, below the surface of the sheet., In the case of a thin sheet or film the, stresses cause the material to be displaced, completely away from the plane of the sheet, and the restraint is by tensile stress in the, sheet and by hoop stress around the puncturing member. Most cases fall somewhere, between these extremes, but the most important conditions in practice involve the second condition to a larger degree than the first, condition., To analyze the second condition take the, material at the point where the puncturing, object has almost pierced the membrane but, has not broken through. At this point one, can see the nature of the forces which are

Page 112 : 94, , 2 Design Influencing Factor, , resisting the puncture and qualitatively relate, them to the primary physical characteristics, of the material so that we can indicate which, materials are suitable for resistance to this, type of stress and how to improve the resistance to puncture., There are three principal stresses that result from the puncture forces through relatively thin material. They are a compressive, stress under the point of the puncturing member, a tensile stress caused by the stretching of, the material under the penetrating force, and, a hoop stress caused by the material being displaced around the penetrating member. Part, of the hoop stress is compressive adjacent, to the point which changes to tensile stress, to contain the displacing forces. It is evident, that anisotropic materials will have a more, complicated force pattern and, in fact, uniaxially oriented materials will split rather than, puncture under this type of loading. To improve the puncture resistance materials are, needed with high tensile strength. This is evident as required to have both the stretching, load and the hoop stress. In addition, the material should have a high compression modulus to resist the point penetration into the, material. Resistance to notch loading is also, important., Based on this analysis it is evident that, materials which are biaxially oriented will, have good puncture resistance. Highly polar, polymers would be resistant to puncture failure because of their tendency to increase in, strength when stretched. The addition of randomly dispersed fibrous filler will also add, resistance to puncture loads. From some examples such as oriented polyethylene glycol, terephthalate (Mylar), vulcanized fiber, and, oriented nylon, it is evident that these materials meet one or more of the conditions reviewed. Products and plastics that meet with, puncture loading conditions in applications, can be reinforced against this type of stress, by use of a surface layer of plastic with good, puncture resistance. Resistance of the surface layer to puncture will protect the product from puncture loads. An example of this, type of application is the addition of an oriented PS layer to foam cups to improve their, performance., , Frictional Loading, The frictional properties of plastics are, of particular importance to applications in, machine products and in sliding applications, such as belting and structural units such as, sliding doors. The range of friction properties, are rather extensive. The relationship between the normal force and the friction force, is used to define the coefficient of static, friction., Friction coefficients will vary for a particular material from the value just as motion starts to the value it attains in motion. The coefficient depends on the surface, of the material, whether rough or smooth,, as well as the composition of the material. Frequently the surface of a particular plastics will exhibit significantly different friction characteristics from that of a cut, surface of the same smoothness. These variations and others that are reviewed make it, necessary to do careful testing for an application which relies on the friction characteristics of plastics. Once the friction characteristics are defined, however, they are stable, for a particular material fabricated in a stated, manner., The molecular level characteristics that, create friction forces are the intermolecular, attraction forces of adhesion (2). If the two, materials that make up the sliding surfaces in, contact have a high degree of attraction for, each other, the coefficient of friction is generally high. This effect is modified by surface, conditions and the mechanical properties of, the materials. If the material is rough there is, a mechanical locking interaction that adds to, the friction effect. Sliding under these conditions actually breaks off material and the, shear strength of the material is an important, factor in the friction properties. If the surface, is not rough, but smoothly polished, the governing factor induced by the surface conditions is the amount of area in contact between, the surfaces. In a condition of large area contact and good adhesion, the coefficient of friction is high. In the case of smoothly polished, surfaces and adhesion forces the coefficient, is very high since there is intimate surface, contact.

Page 113 : 2 Design Influencing Factor, Several other factors affect the frictional, forces. If one or both of the contacting surfaces have a relatively low compression modulus it is possible to make intimate contact between the surfaces which will lead to high friction forces in the case of plastics having good, adhesion. It can add to the friction forces in, another way. The displacement of material in, front of the moving object adds a mechanical, element to the friction forces., All sliding friction forces are dramatically, affected by surface contamination. If the surface is covered with a material that prevents, the adhesive forces from acting, the coefficient is reduced. If the material is a liquid, which has low shear viscosity the condition, exists of lubricated sliding where the characteristics of the liquid control the friction, rather than the surface friction characteristics, of the materials. It is possible by the addition, of surface materials that have high adhesion, to increase the coefficient of friction., The use of plastics for gears and bearings is, the area in which friction characteristics have, been examined most carefully. As an example highly polar polymers such as nylons and, the TP polyesters have, as a result of the, surface forces on the material, relatively low, adhesion for themselves and such sliding surfaces as steel. Laminated plastics also make, excellent bearings. The physical properties of, these materials make them a good choice for, both bearing and gear materials. The typical, coefficient of friction for such materials is 0.1, to 0.2., In the injection molded condition the skin, formed when the plastic cools against the, mold tends to be harder and slicker than a, cut surface so that the molded product exhibit lower sliding friction and are excellent, for this type of application. Good design for, this type of application is to make the surfaces, as smooth as possible without making them, glass smooth which tends to increase the intimacy of contact and to increase the friction, above that of a fine surface. The problems, in this type of application related to friction, are heat effects due to the rubbing surfaces., For successful design the heat generated by, the friction must be dissipated as fast as it is, generated to avoid overheating and failure., , 95, , Obviously the addition of appropriate lubricants will lower the friction and help to remove the heat. There are several other ways, in which the friction can be reduced. One is, by the incorporation of fillers. The fillers can, be used to increase the thermal conductivity of the material such as glass and metal, fibers. The filter can be a material like TFE, plastic that has a much lower coefficient of, friction and the surface exposed material will, reduce the friction. Another approach that is, used is the incorporation of slightly incompatible materials such as silicone oil into the, molding material. After molding the material migrates to the surface of the product and, acts as a renewable source of lubricant for the, product. In the case of bearings it is carried, still further by making the bearing material, porous and filling it with a lubricating material in a manner similar to sintered metal, bearings, graphite and molybdenum sulfide, are also incorporated as solid lubricants., A different type of low friction or low drag, application is encountered with sliding doors, or conveyor belts sliding on support surfaces., In applications like this the normal forces are, generally quite small and the friction load, problems are of the sticking variety. Some, plastics exhibit excellent track surfaces for, this type of application. TFEs have the lowest coefficient of any solid material and represent one of the most slippery surfaces known., The major problem with TFE is that its abrasion resistance is low so that most of the, applications utilize filled compositions with, ceramic filler materials to improve the abrasion resistance., There is a whole field of applications for, TFE in reducing friction using solid materials, as well as films and coatings. Another material with excellent properties for surface sliding is ultra high molecular weight polyethylene (UHMWPE). Polyethylene and the, polyolefins in general have low surface friction, especially against metallic surfaces. The, UHMWPE has an added advantage in that, it has much better abrasion resistance and is, preferred for conveyor applications and applications involving materials sliding over the, product. In the textile industry loom products, also use this material extensively because it

Page 114 : 96, , 2 Design Influencing Factor, , can handle the effects of the thread and fiber, passing over the surface with low friction and, relatively low wear., The specific friction characteristics of plastics at the high friction end are also an, area of significant applications. Some plastics, notably polyurethanes and some plasticized vinyl compositions, have very high, friction coefficients. These materials make, excellent traction surfaces for products ranging from power belts to drive rollers where, the plastics either drives, or is driven, by another member. Conveyor belts made of oriented nylon and woven fabrics are coated, with polyurethane elastomer compounds to, supply both the driving traction and to move, the objects being conveyed up fairly steep, inclines because of the high friction generated. Drive rollers for moving paper through, printing presses and business machines are, frequently covered with either urethane or, vinyl to act as the driver members with minimum slippage. The materials are also used as, the torque surfaces in clutches and brakes., In all of the friction applications suggested, as well as in many others, there are two areas, where the design effort is introduced. The, first is in material selection and modification, to provide either high or low friction as required by the application. The other is in determining the required geometry to supply, the frictional force level needed by controlling contact area and surface quality to provide friction level. A controlling factor limiting any particular friction force application is, heat dissipation. This is true if the application, of the friction loads is either a continuous process or a repetitive process with a high duty, cycle. The use of cooling structures either incorporated into the products or by the use of, external cooling devices such as coolants or, air flow should be a design consideration., Hydrostatic Loading, This is another behavior to be considered, in this type of loading. The surface properties of the material are quite significant. If the, water does not wet the surface, the tendency, will be to have the droplets that do not impact, , close to the perpendicular direction bounce, off the surface with considerably less energy, transfer to the surface. Non-wetting coatings, reduce the effect of wind and rain erosion., Impact of air-carried solid particulate matter is more closely analogous to straight impact loading since the particles do not become disrupted by the impact. The main, characteristic required of the material, in addition to not becoming brittle under high rate, loading, is resistance to notch fracture. The, ability to absorb energy by hysteresis effects, is also important as is the case with the water. In many cases the best type of surface, is an elastomer with good damping properties and good surface abrasion resistance. An, example is polyurethane coatings and products that are excellent for both water and, particulate matter that is air-driven. Besides, such applications as vehicles, these materials are used in the interior of sand and shot, blast cabinets where they are constantly exposed to this type of stress. These materials, are fabricated into liners in hoses for carrying pneumatically conveyed materials such as, sand blasting hoses and for conveyor hose for, a wide variety of materials such as sand, grain,, and plastics pellets., In general when the surface impact loading by fluid-borne particulate matter, liquid, or solid, or cavitation loading is encountered,, the method of minimizing the effects of erosion produced are by material selection and, modification. The plastics used should be, ductile at impulse loading rates and capable, of absorbing the impulse energy and dissipating it as heat by hysteresis effects. The surface characteristics of the materials in terms, of wettability by the fluid and frictional interaction with the solids also playa role. In, this type of application the general data available for materials should be supplemented, by that obtained under simulated use conditions since the properties needed to perform, are not readily predictable from the usually, available data., Another loading condition in underwater applications is the application of external hydrostatic stress to plastic structures, (also steel, etc.). Internal pressure applications such as those encountered in pipe and

Page 115 : 2 Design Influencing Factor, tubing or in pressure vessels such as aerosol, containers are easily treated using tensile, stress and creep properties of the plastic with, the appropriate relationships for hoop and, membrane stresses (108). The application of, external pressure, especially high static pressure, has a rather unique effect on plastics., The stress analysis for thick walled spherical, and tubular structures under external pressure are available., The interesting aspect that plastics have, in this situation is that the high compressive, stresses increase the resistance of plastic materials to failure. Glassy plastics under conditions of very high hydrostatic stress behave, in some ways like a compressible fluid. The, density of the material increases and the compressive strength is increased. In addition, the, material undergoes sufficient internal flow to, distribute the stresses uniformly throughout, the product. As a consequence, the plastic, products produced from such materials as, PMMA and PC make excellent view windows, for undersea vehicles that operate at extreme, depths where the external pressures are, 1000 psi (7MPa) and more., , 97, , Aircraft radomes have also been extensively, studied for the effects of wind-driven water, and solids. The erosion effects are very dramatic and the surfaces are usually protected, with elastomeric materials that have good resistance to this type of stress., To determine the type of physical properties materials used in this environment should, have, it is necessary to examine the mechanics of the impact of the particulate matter on, the surfaces. The high kinetic energy of the, droplet is dissipated by shattering the drop,, by indenting the surface, and by frictional, heating effects. The loading rate is high as in, impact and impulse loading, but it is neither, as localized as the impact load nor as generalized as the impulse load, Material that can, dissipate the locally high stresses through the, bulk of the material will respond well under, this type of load. The plastic should not exhibit brittle behavior at high loading rates., In addition, it should exhibit a fairly high, hysteresis level that would have the effect, of dissipating the sharp mechanical impulse, loads as heat. The material will develop heat, due to the stress under cyclical load. Materials used are the elastomeric plastics used in, the products or as a coating on products., , Erosion Loading, This subject is emphasizing a specialty high, speed loading that is part of the previous section on hydrostatic loading. It is the effect of, erosion forces such as wind driven sand or, water, underwater flows of solids past plastic, surfaces and even the effects of high velocity, flows causing cavitation effects on material, surfaces. One major area for the utilization, of plastics is on the outside of moving objects, that range from the front of automobiles to, boats, aircraft, missiles, and submarine craft., In each case the impact effects of the velocity driven particulate matter can cause surface damage to plastics. Stationary objects, such as radomes and buildings exposed to, the weather in regions with high and frequent winds are also exposed to this type of, effect., A type of wind erosion analysis that has, been extensively studied is the effect of water, drop erosion on rapidly moving missile parts., , Cavitation erosion With increasing ship, speeds, the development of high-speed hydraulic equipment, and the variety of modem, fluid-flow applications to which metal materials are being subjected, the problem of cavitation erosion becomes ever more important., Erosion may occur in either internal-flow systems, such as piping, pumps, and turbines, or, in external ones like ships' propellers (36)., Osborne Reynolds identified the phenomenon of cavitation as early as 1873. By, the turn of the century it had been called by, its present name by R. E. Froude, the director, of the British Admiralty Ship Model Testing, Laboratories., Cavitation occurs in a rapidly moving fluid, when there is a decrease in pressure in the, fluid below its vapor pressure and the presence of such nucleating sources as minute, foreign particles or definite gas bubbles. As, a result, vapor bubble forms that continues, to grow until it reaches a region of pressure

Page 116 : 98, , 2 Design Influencing Factor, , higher than its own vapor pressure, when it, collapses. When these bubbles collapse near, a boundary, the high-intensity shock waves, that are produced radiate to the boundary,, resulting in mechanical damage to the material. The force of the shock wave or of the, impinging may still be sufficient to cause a, plastic flow or fatigue failure in a material, after a number of cycles, depending on the, properties of the material, the existing hydrodynamic conditions, and the foil-design, parameters., The behavior of materials, particularly, steel, in cavitating fluids results in an erosion, mechanism, including mechanical erosion, and electrochemical corrosion. The straightforward way to fight cavitation is to use hardened materials, chromium, chrome-nickel, compounds, or elastomeric plastics. Other, cures are to reduce the vapor pressure with, additives, reduce the turbulence, change the, liquid's temperature, or add air to act as a, cushion for the collapsing bubbles., , Rain erosion One that walks through a, gentle spring rain seldom considers that raindrops can be small destructive "bullets" when, they strike high-speed aircraft. These bulletlike raindrops can erode paint coatings,, plastic products, and even steel, magnesium,, or aluminum leading edges to such an extent, that the surfaces may appear to have been, sandblasted. Even the structural integrity of, the aircraft may be affected after several, hours of flight through rain. This problem is, of special interest to aircraft engaged in all, weather flying., It affects commercial aircraft, missiles,, high-speed vehicles on the ground, spacecraft, before and after a flight when rain is encountered, and even buildings or structures, that undergo high-speed rainstorms. The critical situations exist in flight vehicles, since, flight performance can be affected to the extent that a vehicle can be destroyed. Research and development concerning rain erosion on aircraft has been extensive since the, 1940s., Erosion by rain of the exterior of so, called (at that time) high-speed aircraft, during flight was observed during World, , War 11 on all-weather fighter airplanes capable then of only flying at 400 mph. The, aluminum edges of wings and particularly of, the glass-fiber-reinforced TP polyester-nose, radomes (particularly the long Eagle Wing, on B-29s flying over the Pacific) were particularly susceptible to this form of degradation., The problem continues to exist as can be seen, on the front of commercial and military airplanes with their neoprene protective coated, RP radomes; the paint coating over the rain, erosion elastomeric plastic erodes and then, is repainted prior to the rain erosion elastomeric coating is affected., Actual flight tests to determine the severity of this phenomenon of rain erosion carried, out in 1943 established that aluminum and RP, leading edges of airfoil shapes exhibited serious erosion after exposure to rainfall of only, moderate intensity. Inasmuch as this problem originally arose with military aircraft,, the u.s. Air Force initiated research studies, at the Wright-Patterson Development Center's Materials Laboratory in Dayton, Ohio., Based on the results of a young girl physicist (worked for DVR), it resulted in applying an elastomeric neoprene coating adhesively bonded to RP radomes. The usual, 5-mil coating of elastomeric material used, literally bounces off raindrops, even from a, supersonic airplane traveling through rain., There is a slight loss of radar transmission, of about 1 % per mil of the plastic thickness,, but this is better than losing 100% when the, radome is destroyed., Thermal Expansion and Contraction, , Unconstrained specimens of almost all materials respond to temperature increases by, expanding and to temperature decreases by, contracting. The coefficient of linear thermal expansion (CLTE) of a material is determined by varying the temperature of a, representative test specimen. Measurement, is made of its length as a function of temperature over the desired range, computing, the total change in specimen length over, that range, and then dividing that change in, length by both the specimen length at the

Page 117 : 2 Design Influencing Factor, reference temperature and the total temperature excursion. In determining the coefficient of linear thermal expansion of plastics, per ASTM D696, the temperature range is, -30 o e to + 300 e (-22 to + 86°F); and the, reference temperature is 23°e (73°F)., There are plastics that have equal or less, than those of other materials of construction, (metals, glass, or wood). In fact with certain, additives such as graphite powder contraction can occur rather than the expected expansion with the application of heat. However many plastics typically have coefficients, that are considerably higher than those of, other materials of construction such as metals. This difference may amount to a factor of 10 to 30. Also available are plastics, particularly TS-RPs, with practically no, change., Obviously, the designer must take thermal expansion and contraction into account, if critical dimensions and clearances are to, be maintained during use where material is, in a restricted design. Less obvious is the fact, that products may develop high stresses when, they are constrained from freely expanding, or contracting in response to temperature, changes. These temperature-induced stresses, can cause material failure., Plastic products are often constrained from, freely expanding or contracting by rigidly, attaching them to another structure made of a, material (plastic, metal, etc.) with a lower coefficient of linear thermal expansion. When, such composite structures are heated, the, plastic component is placed in a state of compression and may buckle, etc. When such, composite structures are cooled, the plastic, component is placed in a state of tension,, which may cause the material to yield or, crack. The precise level of stress in the plastic depends on the relative compliance of the, component to which it is attached, and on assembly stress., To minimize the stresses induced by differential thermal expansion/contraction one, must: (1) employ fastening techniques that, allow relative movement between the component parts of the composite structure, (2), minimize the difference in coefficient of linear thermal expansion between the materials, , 99, , comprising the structure; and/or (3) minimize, the temperature differences the structure will, experience during use or shipment. Examples, of proper fastening methods include the use, of screws, bolts, spring clips, etc. with oversize, holes, slots, or compliant bushings., , Hysteresis Effect, The hysteresis heating failure occurs more, commonly in plastic members subject to dynamic loading. It would be well to point out, what comprises dynamic loading and what, types of stresses are encountered. One example commonly encountered is a plastic gear., In the course of operation the gear teeth are, periodically, once per revolution, subjected, to a bending load that transmits the power, from one gear to another. Another example, is a link that is used to move a paper sheet in a, copier or in an accounting machine from one, operation to the next. The load may be simple tensile or compressive stresses, but more, commonly it is a bending load., There are some less obvious but quite, important dynamic stress situations that illustrate the importance of dynamic loading., A belt that is used to drive a pulley is subject to repeated bending and tensile stresses, during operation. A tire on a vehicle is subjected to a complicated combination of bending, bearing, and compressive stresses during, the movement of the vehicle that it supports., The keys on a computer or printer are subjected to repeated impulse loading during use, even though the action is not strictly cyclical, in nature. Add to this the effects of vibration induced by vehicle motion or machine, action that is an induced cyclical stress in, products that are attached to the vibrationinducing object and it becomes apparent, that cyclical loading is a widely encountered, type of loading. In many instances the dynamic stress exists in conjunction with static, stresses and with other longer-term periodic, loads., An example will be given to show how dynamic loading can lead to product failure by, hysteresis heating. When this condition exists, the failure will be catastrophic rather than

Page 118 : 100, , 2 Design Influencing Factor, , gradual. This is not generally true of creep, failure or of normal fatigue failure. The example is a link that is loaded in tension and is, the connecting link that drives a flywheel type, of unit by means of a linear actuating force., The primary load on the product is alternate, tension and compression loading. The compression loading is low since it represents the, flywheel driving the link back against friction, forces. The tensile force is the driving force, and it varies from zero to a maximum that, is determined by the torque load on the flywheel member., The relationship of force to time is, determined using engineering equations, (Appendix A: PLASTICS DESIGN TOOLBOX). Result is the force function per revolution and this divided by the time of a revolution will give the force as a function of, time. Increasing temperature increases heat, transfer from the product to the surroundings and if the rate of heat transfer equals, the rate of heat generation at a temperature, below the softening temperature of the material, the process will stabilize and the product, will not fail. It is apparent that the major factor in hysteresis failure is not the ability of the, product to dissipate the heat generated to its, surroundings (190)., The designer can use several approaches, to prevent hysteresis failure. The first is material selection. The stiffer the material is,, the smaller the strain is for a given stress, level and the lower the hysteresis loss per, cycle. Some materials are additionally fairly, linear in stress-strain characteristics and have, smaller hysteresis loops. These would be preferred in dynamic loading applications., Another approach is to improve the heat, transfer conditions from the product. This, can be accomplished in several ways. One, way is to operate in a coolant medium that, would also act as the lubricant for the system. The heat transfer to a liquid is usually, much better than to air, and the liquid can be, cooled by passing it through a heat exchanger, device. A second approach is to improve the, heat transfer to air. This can be done by increasing the surface area of the product by, means of fins or other surface projections., The larger area will increase the heat flow, , out of the product substantially. The third approach is the use of air circulating techniques, which can be areas added to the stressed unit, such as air deflector sections or the use of fan, cooling as part of the system. An approach, that may fit some applications is the use of, metal heat-sink elements buried in the plastic that conducts the heat into other parts of, the complete machine to dissipate it to the, surroundings., Basically, anything that can be done to reduce the temperature of the product by removal of heat generated by the cyclical stress, will improve the possibilities of surviving the, cyclical stress. If the heat transfer capability is, limited, then the only alternative is to use stiff, materials and low stress levels on the product, compared with the strength capability of the, material. The heavier products that result will, be relatively inefficient in the use of material., In some cases when the load applied is an inertial load (such as an impeller on a pump) it, may be that only a trade-off of weight for low, stress level can cause failure., Energy and Motion Control, There are plastics such as TP elastomers, that are frequently subjected to dynamic, loads where heat energy and motion control, systems are required. One of the serious dynamic loading problems frequently encountered in machines and vehicles is vibrationinduced deflection (Chapter 4, DYNAMIC, LOAD ISOLATOR)., Such effects can be highly destructive, particularly if a product resonates at one of the, driving vibration frequencies. One of the best, ways to reduce and in many cases, eliminate, vibration problems is by the use of these viscoelastic plastics. Some materials such as silicone elastomers, flexible vinyl compounds, of specific formulations, polyurethane plastics, and a number of others have very large, hysteresis effects. By designing them into, the structure it is possible to have the viscoelastic material absorb enough of the vibration inducing energy and convert it to heat, so that the structure is highly damped and, will not vibrate. In each case the viscoelastic

Page 119 : 2 Design Influencing Factor, , material is arranged in such a way that movement or flexing of the product results in, large deflections of the viscoelastic materials, so that a large hysteresis curve is generated, with a large amount of energy dissipated per, cycle., By calculating the energy to heat it is possible to determine the vibration levels to which, the structure can be exposed and still exhibit, critical damping. There is one area that must, be evaluated. Plastics exhibit a spectrum of, response to stress and there are certain straining rates that the material will react to almost, elastically. If this characteristic response corresponds to a frequency to which the structure is exposed the damping effect is minimal, and the structure may be destroyed. In order, to avoid the possibility of this occurring, it is, desirable to have a curve of energy absorption vs. frequency for the material that will be, used., Viscoelastic damping The same approach, can be used in designing power transmitting, units such as belts. In most applications it is, desirable that the belts be elastic and stiff, enough to minimize heat buildup and to minimize power loss in the belts. In the case of a, driver which might be called "noisy" in that, there are a lot of erratic pulse driven forces, present, such as an impulse operated drive,, it is desirable to remove this noise by damping out the impulse and get a smooth power, curve., This is easily done using a viscoelastic belt, that will absorb the high rate load pulses. The, same approach can be used by making one, gear in a gear train or one link in a linear, drive mechanism an energy absorber. The viscoelastic damping can be a valuable tool for, the designer to cope with impulse loading that, is undesirable and potentially destructive to, the product., There is another type of application where, the damping effect of plastic structures can, be used to advantage. It has a long although, not obvious history. The early airplanes used, doped fabric as the covering for wings and, other aerodynamic surfaces. The dope was, cellulose nitrate and later cellulose acetate, that is a damping type of plastic. Conse-, , 101, , quently, surface flutter was a rare occurrence., It became a serious problem when aluminum, , replaced the fabric because of the high elasticity of the metal surfaces. The aerodynamic, forces acting on the thin metal coverings can, easily induce flutter and this was a difficult, design problem that was corrected for minimizing the effect., WeatheringlEnvironment, , Plastics have been used, and used very, successfully, in applications where continuous or intermittent exposure to weather and, different environments has been involved., The successes, however, have been the result of thoughtful and discriminating sifting, of the weatherability data, rather than blind, choice or wishful thinking. Due to their extreme versatility, plastics are used in almost, every imaginable type of media. Not only, must they resist weather and temperature, extremes ranging from cryogenic to above, 1,370°C (2,500 P) heat generated in rocket, motors, but also extreme conditions of corrosion, irradiation, fluid degradation as typified, by liquid rocket propellants, and mechanical, energy such as abrasion., Like other materials with which designer's, work, different plastics can be sensitive to, the environments. Even ordinary exposure, from sunlight or to household cleaning agents, can change the properties of certain plastics., Whereas rust, corrosion, and loss of its properties can plague metals, the cracking, crazing, and loss of its properties can affect certain, plastics in the presence of different environments., The age-old problem of predicting what, will happen to any material after it is, subjected to service also exists with plastics., Different data on plastics are available, but, typical of so-called progress, there is never, sufficient or adequate useful information to, predict the service life of products being, designed. It is suggested that rather than assume that a lack of data exists, one should, determine what is logically available and apply it most efficiently. A potential example of, improper design with plastics concerns toys., 0

Page 120 : 102, , 2 Design Influencing Factor, , Toys can be made of plastics that will resist, mechanical destruction even though some, people consider all toys "immediately destructible.", Designing and developing plastics for use, in different environments requires the usual, practical or design approach for any material; namely, knowledge of its behavior and, capability. Since insufficient data will continually exist for some materials, particularly, the newer ones or those being subjected to, different environments, different methods of, evaluation and developing data can be used., These include both experimental and theoretical approaches. Experimental techniques, include static or dynamic specimen or product testing, simulated service testing of specimen, or product and field-testing indoors, and/or outdoors. In order to shorten the time, cycle required during testing, theoretical tests, can be conducted such as studies in rheology (science dealing with the deformation, and flow of matter) and aging (Chapter 5,, WEATHERING)., Temperature Review, As reviewed throughout this book, certain plastics can be affected in different ways, by temperature. Among other things, it can, influence short- and long-time static and, dynamic mechanical properties (Fig. 2-50),, aesthetics, dimensions, electronic properties,, and other characteristics. Some plastics cannot take boiling water, most others can operate up to at least 150°C (300°F), and the, so-called high-temperature types can take, various degrees of continuous use way above, 150°C and there are plastics that reach at, least 538°C (I,OOO°F). Then there are the reinforced plastics used as heat-shield ablative, materials on the nose cones of space vehicles that reach temperatures up to 1,370°C, (2,500°F) for fractions of a second upon reentering the atmosphere. As reviewed practically all plastics can take heat up to at least, what the human body can endure, which is, one important reason they are extensively, used., , TPs soften to varying degrees at elevated, temperatures, but TSs are much less affected., The maximum temperatures under which, plastics can be employed are generally higher, than the temperatures found in buildings,, including walls and roofs, but some such as, LDPE are marginal and others cannot carry, appreciable stresses at moderately elevated, temperatures without undergoing noticeable, creep. Many plastics can take shipping conditions that are more severe than their service conditions, as in an automobile trunk or, railroad boxcar that can reach at least 52°C, (126°F)., The response of a plastic to an applied, stress depends on the temperature and the, time at that temperature to a much greater, extent than does that of a metal or ceramic., The variation of an amorphous TP over an, extended temperature range can be exemplified by the behavior of its elastic modulus as, a function of temperature., With a temperature change the short-term, static strength, the elastic modulus, and the, elongation behavior of a material will be similar for it's tensile, compressive, flexural, and, shear properties. A material's strength and, modulus will decrease and its elongation increase with increasing temperature at constant strain. Curves for creep isochronous, stress and isometric stress are usually produced from measurements at a fixed temperature. Complete sets of these curves are, sometimes available at temperatures other, than the ambient. It is common, for instance,, to find creep rupture or apparent modulus, curves plotted against log time, with temperature as a parameter. Figure 2-51 shows, time-temperature shifting of apparent modulus curves shifting to estimate the extended, time values at lower temperatures., These curves suggest that it would be, reasonable to estimate moduli at somewhat, longer times than the data available from the, lower temperatures. However, a set of creeprupture curves from various temperatures, as, in Fig. 2-52, would suggest that projecting the, lowest-temperature curves to longer times, as a straight line could produce a dangerously high prediction of rupture strength, so

Page 121 : 2 Design Influencing Factor, •, , •, •, , •, •, , •, , •, , 103, , • BASED ON TEMPERATURE AND TIME, •, , • RETAINING 50 PERCENT OF MECHANICAL, OR PHYSICAL PROPERTIES OBTAINABLE AT, ROOM TEMPERATURE. WITH RESIN EXPOSURE, AND TESTNG AT ELEVATED TEMPERATURE., , 1000, , 900, , 800, , u.., , 0, , w, , a:, , 700, , ::l, , ~, w, , a:, , c..., , 600, , :2, , w, , I-, , 500, , 400, , 300, , 200, , 0.1, , 10, , 100, , 1000, , 10,000, , 100,000, , TIME (HOURS), , Fig.2·50 Guide to maximum short-time tensile stress vs. temperature., , this approach is not recommended. As previously reviewed one advantage of conducting, complete creep-rupture testing at elevated, temperatures is that although such testing for, endurance requires long times, the strength, levels of the plastic at different temperatures, can be developed in a relatively short time,, usually just 1,000 to 2,000 h. The Underwriters Laboratories and other such organiza-, , tions have employed such a system for many, years., Testing different impact properties at various temperatures produces a plot that looks, very much like an elongation vs. temperature, curve. As temperatures drop significantly below the ambient temperatures, most TPs, lose much of their room-temperature impact strength. A few, however, are on the

Page 122 : 2 Design Influencing Factor, , 104, , Stress Cracking and Crazing, , ~, , S, , §:---i, , INCREASING TEMPERA TURE, , ~~ ~----:-----::.....----, , Q, ~, , ....., , --, , ----.", , 8, , ....., , TIME-TEMPERATURE SHIFTING, , -..J, , 10, -1, , 0, , 50, , YEARS, , 23456789, LOG TIME (HOURS), , Fig.2-51 Apparent modulus at different temperatures., , lower, almost horizontal portion of the curve, at room temperature and thus show only a, gradual decrease in impact properties with, decreases in temperature. One major exception is provided by the glass fiber RPs, which, have relatively high lzod impact values, down, to at least -40o e (-40°F). The S-N (fatigue), curves for TPs at various temperatures show, a decrease in strength values with increases, in temperature. However the TSs, specifically, the TS RPs, in comparison can have insignificant or very low losses in strength., , I, , INCREASING, , -1, , o, , TEMPERA TURE, , 123, , 4, , LOG TIME (HOURS), , Fig. 2-52 Creep-rupture curves indicating the, danger of making linear projections to longer, times at lower temperatures., , Environmental stress cracking is the cracking of certain plastic products that becomes, exposed to a chemical agent while it is under stress. This effect may be caused by exposure to such agents as cleaners or solvents., The susceptibility of affected plastics to stress, cracking by a particular chemical agent varies, considerably among plastics, particularly the, TPs., The resistance of a given plastic to attack, may be evaluated by using either constantdeflection or constant-stress tests in which, specimens are usually coated with the chemical or be immersed in the chemical agent., After a specified time the degree of chemical, attack is assessed by measuring such properties as those of tensile, flexural, and impact, (Figs. 2-53 and 2-54). The results are then, compared to specimens not yet exposed to, the chemical. In addition to chemical agents, and the environment for testing may also require such other factors as thermal or other, energy-intensive conditions., A classic example illustrating the effects, of stress cracking is the case of the PE milk, bottle from the 1950s. A PE plastic and a process to blow mold the bottles were successfully integrated to the point where the lactic, acid in the milk would not cause a premature, split in the highly stressed neck area of the, bottle. As noted, stress cracking is intensified, by an increase in temperature. As an example, the results from testing HDPE pressurepipe specimens in water at 82°e (180°F) show, results in a life span of just a few hundred, hours but when the water temperature is, at 23°e (74°F) the life expectancy becomes, fifty years. In both tests, water was moving, through the pipes., It is possible with solvents of a particular, composition to determine quantitatively the, level of stress existing in certain TP products where undesirable or limited fabricatedin stresses exist. The stresses can be residual, (internal) stresses resulting from the molding, extrusion, or other process that was used, to fabricate the plastic product. Stresses can, also be applied such as bending the product., As it has been done for over a half century, the

Page 123 : 2 Design Influencing Factor, , c, , 105, , Conlrol. no oil or previosly, applied slress, 0 psi· (0 MPa), , ~, , iii, , Strain.e, Previously no stress or applied stress lasting .16 hours, with sample coated with vegetable all prior to testing, for the short-term stress-strain behavior shown., , apsi· (0 MPo), , 1000 psi· (6.9 Mpa), , 2000 psi· (13.8 MPo), , 3000 psi · (20.7 MPo), c, , Strain. e, , Strain. e, , Strain. e, , Sirain. e, , Fig. 2-53 Example of the influence of tensile stress-strain curves subjected to an environment that, influences the ductility of a specific plastic., , product is immersed in the solution that attacks the plastic for various time periods. Any, initial cracks or surface imperfections provides information that stresses exist. Other, tests conducted can be related to the stresstime information. Information on the solvent, mixtures suitable for this type of test and how, to interrupt them are available from plastic, material suppliers or determining from industry test data which show solvents that effect, the specific plastic to be evaluated., TP cracking develops under certain conditions of stress and environment sometimes, on a microscale. Because there are no fib-, , Fig. 2-54 Tensile test bars of two different plastics under the same stress were sprayed with acetone. The top one cracked quickly, but the other, did not fail., , rils to connect surfaces in the fracture plane, (except possibly at the crack tip), cracks, do not transmit stress across their plane., Cracks result from embrittlement, which is, promoted by sustained elevated temperatures and ultraviolet, thermal, chemical, and, other environments., For the designer it is not important whether, cracking develops upon exposure to a benign, or an aggressive medium. The important considerations are the embrittlement itself and, the fact that apparently benign environments, can cause serious brittle fractures when imposed on a product that is under sustained, stress and strain, which is true of certain, plastics., Crazing or stress whiting is damage that, can occur when a TP is stretched near its yield, point. The surface takes on a whitish appearance in regions that are under high stress., Crazing is usually associated with yielding., For practical purposes stress whiting is the result of the formation of microcracks or crazes,, which is another form of damage. Crazes, are not true fractures, because they contain, strings of highly oriented plastic that connect the two flat faces of the crack. These, fibrils are surrounded by air voids. Because, they are filled with highly oriented fibrils,, crazes are capable of carrying stress, unlike

Page 124 : 106, , 2 Design Influencing Factor, , true fractures. As a result, a heavily crazed, product can still carry significant stress, even, though it may appear to be fractured., It is important to note that crazes, microcracking, and stress whiting represent irreversible first damage to a material, which, could ultimately cause failure. This damage, usually lowers the impact strength and other, properties of a material compared to those, of undamaged plastics. One reason is that it, exposes the interior of the plastic to attack, and subsequent deterioration by aggressive, fluids. In the total design evaluation, the formation of stress cracking or crazing damage, should be a criterion for failure, based on the, stress applied., Weather Resistance, , Ultraviolet rays and the heat from solar radiation degrade the natural molecular structure of certain plastics. Acrylics, pes, PPO,, 1FE, silicone, and TS polyester are examples of plastics that have outstanding durability under UV exposure. The resistance to, sunlight of those that degrade can become, weather resistant by using chemical heat stabilizers and/or various fillers that can screen, and protect the plastic from radiation such, as is done with acrylics, polypropylene, etc., Weather resistant paints and coatings can, also protect plastics from UV damage. These, chemical heat stabilizers are also used to ensure no damage occurs to the plastic during heat processing such as during extrusion, or injection molding. If the processing heat, is increased above its normal requirement, (to reduce cycle time, etc.), the stabilizer that, should have remained to provide weather, protection is consumed causing the product, to be destroyed in outdoor service. This situation actually occurred when the first 1M PP, outdoor stadium seats were installed many, moons ago., The effects of UV radiation on degradable, plastics are usually confined to the exposed, surface layers. The general effect is one of, embrittlement. Tensile strength may either, increase or decrease, but the elongation upon, breaking is always reduced. A loss of impact, , strength is the usual measure of UV degradation. The creep rupture strength will also, be reduced dramatically, and the onset of the, knee in the stress-strain curve of certain plastics such as PE will be accelerated. UV degradation is aggravated by stresses or strains, and, the plastic may stress crack or craze after deterioration has occurred. The secondary effect of UV degradation is usually a yellowing, or browning of certain plastic., Other elements of weather and outdoor, exposure can interact with UV radiation to, accelerate degradation in degradable types, of plastics. They include humidity, salt spray,, wind, industrial pollutants, and atmospheric, impurities such as ozone, biological agents,, and temperature. The wavelengths that have, the most effect on plastics range from 290 to, 400 nm (2,900 to 4,000 A)., One of the insidious disadvantages of certain plastics is their tendency to absorb moisture from ambient air and then change their, size and properties. There are protective, measures that can be taken with these plastics such as coatings, chemical treatments, additives, and so on. To be practical, the best, way to circumvent problems of this type is to, select a plastic with the lowest possible absorption rate., Sterilization-Irradiation, , Fundamentally, radiation is the emission, of energy in such forms as light and heat, or the transfer of energy through space by, electromagnetic waves. Irradiation basically, identifies the radiant energy per unit of intercepting area. The effect of these energies on, degrading certain plastics and in changing, or improving their properties is measurable., Most nontechnical people consider only that, radiation results in degradation, but the irradiation of plastics is an important science for, plastic packaging sterilized medical products,, curing TS plastics, converting certain TPs to, TSs, and so on., Sterilization is an important process that, involves a major market for the use of plastics in packaging. The most common methods, of sterilization are those using heat, steam

Page 125 : 2 Design Influencing Factor, , (autoclaving), radiation, and gas (EtOethylene oxide). Unfortunately, each of these, methods has its limitations. There are, however, plastics that do meet performance requirements based on the various different, processes, including radiation., Harmful Weather Component, , Weather is a complex all-embracing term, that includes many components. However,, these elements can be listed and would seem, to be amenable to analysis, since the recognized segments are not too great in number. Among the portions that affect the properties of plastics are such things as solar, radiation, temperature, oxygen, humidity,, precipitation, wind, biological agents, and atmospheric impurities. Different aspects complicate the picture because factors such as, their concentrations and degree of two or, more components influence results. Normally these components reduce performances. However there are data in the literature that show that some TS plastics grow, stronger for periods of 2-4 years due to, postcuring when exposed to the elements., One of the most common impurities in, coastal areas which acts in a chemical manner rather than a physical one is salt water. However, with the ever-increasing spread, of the chemical industries, and the steppedup use of gasoline powered vehicles, the, problem of chemical degradation are also of, interest particularly in inland areas. While, plastics in general are corrosion resistant,, the multiplicity of chemical agents which, can be in the air in industrial atmospheres,, plus the chemical nature of the various plastics indicates that it cannot be assumed that, all plastics are chemically resistant to all, atmospheres., Assessing Weathering Effect, , In assessing the effects of weathering, some, change in property is measured. The relative, rankings of the various plastics (and to a large, extent the degree of correlation between, , 107, , artificial tests and outdoor exposure) will depend upon the property chosen for measuring. When consideration is given to the various types of properties and the number of, possible choices within each type, the list becomes legion., Depending upon the interests of the person, conducting the program, and the potential, uses foreseen, the test may be of a mechanical, optical (including appearance), electrical,, or thermal nature. In some cases, support of, a biological culture or change in dimension, could be the criterion of success or failure of, the material to resist exposure. Within each, of the above general groups, there are still, many choices., The ASTM Book of Standards lists many, different tests such as over 25 mechanical, tests applicable to plastics, more than a dozen, thermal tests, etc. (128). These tests will differ, in sensitivity and in applicability to a potential use. For instance, a test that establishes, a value dependent upon volume properties, might very well rank materials in an order, differing from a test dependent upon surface, properties. In a similar fashion, if the material will not be extended in use, a measurement of tensile elongation loses significance., The multiplicity of available test methods has, led to the paradoxical situation wherein extensive data are available but knowledge as, to the performance of a specific material in, a specific use must be based in many cases, upon educated guesses rather than substantial data. This free choice is highly defensible, and can lead to a disturbing dilemma., In many cases, even the method of conditioning prior to test will influence the ratings. For example, flexural tests run on standard conditioned specimens (50% relative, humidity and 73.5°F) may rank materials differently from tests conducted on specimens, which have been immersed in water or which, have been heated to some elevated temperature after outdoor exposure., No one can afford to run all the tests even, on one material. Yet the test or tests chosen may not be related to a contemplated, use. This has lead to an enormous amount, of duplication of time-consuming exposures., Consideration has been given to means of

Page 126 : 108, , 2 Design 1nfluencing Factor, , eliminating this duplication by the different, testing organizations (particularly ASTM,, UL, and ISO). To date no entirely satisfactory answer has been found. One means of, obtaining comparable data would be to have, all investigators perform the same test by, a standard procedure on the same type of, specimens prepared in the same fashion. This, would still not tell how weather would affect, some other property that might be of legitimate interest. Another argument against this, would be the reluctance of a manufacturer, to report data that would make their product, appear inferior., As might be expected from some of the, previous discussion, the results of any weathering tests will be largely influenced by the exposure method used. While it is obvious that, the general environment will have a bearing, on the ranking assigned, it is normally not, enough to know that the climate is hot, dry,, and rural, or cold, wet, and industrial. In addition, the local conditions specific to a location, are important. Such relatively minor aspects, as angle of exposure, height above the background and the nature of the background and, the season of the year when exposure is initiated all have a bearing on the results obtained., Due to the unpredictable scheduling and, high dollar costs of all weather natural testing, much of the environmental testing has, been brought into laboratories or other such, testing centers. Artificial conditions are provided to simulate various environmental phenomena and thereby aid in the evaluation, of the test item before it goes into service, under natural environments. This environmental simulation and testing does require, extensive preparation and planning. It is generally desirable to obtain generalizations and, comparisons from a few basic tests to avoid, prolonged testing and retesting. The type and, number of tests to be conducted, natural or, simulated, as usual are dependent on such, factors as end item performance requirements, time and cost limitations, past history,, performance safety factors, shape of specimens, available testing facilities, and the environment. Specifications, such as ASTMs',, provide guidelines., , When considering environment it generally becomes difficult since actual service conditions are most of the time unpredictable., As an example, there is a systematic difference in the frequency distributions of liquid water content in rain. It appears that, the areas most likely to have high values, of liquid water are where there is a plentiful supply of moisture and a high instability in the atmosphere. The lowest values, of liquid water are obtained from the climatic areas of light continuous rains such as, that found along the northwest coast of the, United States., Outer Space, The space environment, seen as beginning, in the center of the earth, fxtends to infinity., In the past few decades outer space has been, penetrated. These initial successful steps depended on a number of factors, one of which, was the use of plastics. As in terrestrial uses,, plastics have their place in space., Plastics will continue to be required in, space applications from rockets to vehicles, for landing on other planets. The space, structures, reentry vehicles, and equipment, such as antennas, sensors, and an astronaut's personal communication equipment, that must operate outside the confines of, a spaceship will encounter bizarre environments. Temperature extremes, thermal, stresses, micrometeorites, and solar radiation are sample conditions that are being encountered successfully that include the use of, plastics., Perhaps the most striking phenomenon encountered in outer space is the wide variation in temperature that can be experienced, on spacecraft surfaces and externally located, equipment. Temperatures and temperature, gradients not ordinarily encountered in the, operation of ground or airborne structures, and equipment are ambient conditions for, spacecraft equipment. On such hardware, not, suitably protected externally or housed deep, within the space vehicle in a controlled environment, these temperature extremes can, wreak destruction. Designers of earthbound

Page 127 : 2 Design Influencing Factor, , electronics must fight temperatures that will, produce system degradation, but spacecraft, electronic designers may be fighting temperatures that will cause their equipment to melt., On either ends of the temperature scale,, the ground- or airborne-equipment designer, has a simpler environment problem. In, addition, the space designer has a temperature paradox to consider. A black box cannot simply be placed in a superinsulated, enclosure anymore than a human being can., All other factors aside, both would rapidly, be destroyed because of self-generated heat., The equipment must therefore be exposed to, its environment in some manner, but it also, needs a great deal of protection. The problem, is not as simple as putting on or taking off a, sweater, depending on whether the temperature is 21 or 70cF (6 or 21 cC). The problem is, to put something on and keep it on, regardless of whether the temperature is -250 or, +250cF (-155 or + 121 cC). Many factors give, rise the temperature extremes encountered., Ocean, , Plastics are already vital for operation on, top and within the sea, even though comparatively little is known about the sea. To, develop more knowledge, radically new basic ideas and approaches were needed, such, as consideration of plastic structural hulls for, deep submersibles, or elastomeric plastics for, undersea housing and storage., Oceans occupy 70.8% or 125 million, square miles of the surface of the earth., Within or beneath this "inner space" are, foods, fuels, and minerals. Thus interest in, the sea is obvious. At least 4/5 of all life on, earth exists in saltwater. It is predicted that, of the oil and gas demand in future years will, come from oil at 2,000 ft. depths operated by, manned submarines and marine robots. All, the equipment needed to collect and store oil, or gas will be installed and operated on the, sea floor. Underwater housing and decompression chambers will be required. The sea, bottom is also reported to include trillions of, tons of copper, nickel, cobalt, iron, and other, important minerals., , 109, , From ships to submarines to mining the sea, floor, certain plastics can survive sea environments, which are considered more hostile than those on earth or in space. For, water-surface vehicles many different plastic, products have been designed and used successfully in both fresh and the more hostile, seawater. Figure 2-55 is an example where, extensive use is made using unreinforced, and reinforced plastics meeting structural, and nonstructural product requirements. Included are compartments, electronic scanners, radomes, optically transparent devices,, food storage and dispensing containers, medical products, buoyant devices, temperature, insulators, and many more., Boats have been designed and built up to, at least 37 x 9 m (120 x 30 ft.) in RP. Plastics, have become vital for operating within the, sea. In 1965 extensive test were conducted, by the U.S. Navy' Sealab 11 to assay man's, ability to live and work in ocean depths for, long periods of time (Fig. 2-56). For fortyfive days three groups of ten men each lived, fifteen-day periods in a 57 ft. x 12 ft. habitat, at a depth of 188 m (205 ft.) one half mile off, La Jolla, Calif. Plastic parts as well as other, materials were used to provide a highly successful experiment., This frontier's practical opportunities were, first developed with submarines, which until the nuclear ones were limited to depths, of only a few hundred feet. Many thousands, of feet can now be navigated. The crushing, pressures below the surface, which increase, at a rate of about t;z psi per foot of depth,, make corrosion a major threat to the operation and durability of many materials. For example, the life of uncoated magnesium bolts, in contact with steel nuts is less than seventytwo hours, aluminum buoys will corrode and, pit after only eleven months at just four hundred feet, and low-carbon steel corroded at a, rate one-third greater than in surface waters., Tests on plastics in deep water have, been extremely successful. As an example, filament-wound RP cylinders and PVC buoys, retained their strength. PVC washers and the, silicone-seating compound used in steel-toaluminum joints helped prevent their corrosion. Black twisted nylon and polypropylene

Page 129 : 111, , 2 Design Influencing Factor, , '."" ...,...., , ARCTIC ATlANTIC, PACIFIC, TONGUE OF, THE OCEAN, ARCTIC, , "., , ---.• __ .-, , --MEAN, DEPTH, -.---, , 5,000, ~"'.", , -, , --==, , ==, , ==, , ..".....,... ............. . ,, =...., ==-, , ==, ==, , AtlANTIC --._., , HULL, , ~EIGHT. rO.DISP~ACEMENr, , =:~~:"HY" ~ENOTE~ ~TREHGT1, YIELD, , o, , 10, , 10,000, , ,fI. . . . . . . ., , 15,000 ~, z, 20,000 ;;;;, , ..........,...., , ~, , 10.5, , :EArr~UM, , MARIANAS, TRENCH .---PACIFIC, , ,, , ==, ==, ==, , RATIO, , ASSUMIED IN CtlCUllTlONS, , 70, 50, 30, 40, 60, 80, 20, PERCENT OF OCEAN lESS THAN INDICATED DEPTH, , 90, , ......., , 25,000, , ~, , 30,000, 35,000, , 100, , Fig. 2-57 Example of boat hull materials subjected to seawater depths., , ropes used to rig and retrieve test platforms, are unaffected. Grappling lines attached to, platforms, made of steel wire jacketed with, extruded HDPF prevented corrosion of the, steel., PE is also used to protect submerged, telephone cables for over a half century., Plastic primers such as epoxy are used to, prevent antifouling plastic paints from corroding metals. These paints generally use, cuprous oxide to prevent the growth of barnacles. Plastics are used successfully in instruments to determine depth, velocity of, currents, temperature, and as echo sounders., Products operating to depths of 4,500 m, (15,000 ft.) include molded polystyrene rotors, neutrally buoyant polyethylene control, vanes, PVC buoy supports, O-ring seals, PE, flotation, and watertight electrical connectors, using PVC, polyurethane, and DAP. Plastics, such as PE, PP, and PUR are used to develop, the shapes and provide different combinations of desirable characteristics such as ease, of wrapping around standard winches, resistance to the water environment and abrasion,, good electrical insulation in wire-conducting, cables, and ease of fabrication and repair., The materials studied for deep-submergence hulls are generally limited to steel, (Hy 170), aluminum, titanium, reinforced, , plastics, and glass. Figure 2-57 shows the, depth limitations of various hull materials, in near-perfect spheres, superimposed on the, familiar distribution curve of ocean depths., To place the materials in their proper perspective, the common factor relating their, strength-to-weight characteristics to a geometric configuration for a specified design, depth is the ratio showing the weight of the, pressure hull to the weight of the seawater, displaced by the submerged hull, a factor referred to as the weight displacement (WID), ratio. The portions of the bars above the, depth-distribution curve correspond to hulls, having a 0.5 WID ratio, the portion beneath, showing the depth attainable by heavier hulls, with a 0.7 WID., The ratio of 0.5 and 0.7 is not arbitrary, as it, may appear, for small vehicles can normally, be designed with WID ratios of 0.5 or less, and, vehicle displacements can become quite large, as their WID ratio approach 0.7. Using these, values permits making meaningful comparisons of the depth potential of various hull, materials. An examination of the data reveals, that for all the metallic pressure-hull materials taken into consideration, the best results, would permit operation to a depth of about, 18,288 m (20,000 ft.) only at the expense, of increased displacement. The nonmetallic

Page 130 : 112, , 2 Design Influencing Factor, , materials of reinforced plastics (those with, just glass-fiber TS polyester) and glass alone, would permit operation to 20,000 ft. or more, with minimum-displacement vehicles., The submergence materials show the variation of the collapse depth of spherical hulls, with the weight displacement of these materials. All these materials initially would permit, building the hull of a rescue vehicle operating, at 1,800 m (6,000 ft.) with a collapse depth of, 2,700 m (9,000 ft.)., For a search vehicle operating at 6,000 m, (20,000 ft.) with collapse depth of 9,000 m, (30,000 ft.), the only materials that appear, suitable are solid glass and RP. No metals can, be used, because they potentially do not have, sufficient strength-to-weight values. One of, the drawbacks to using glass in hulls is its, lack of toughness. The inside of the glass, hull would need protection from impacts, etc.:, thus an elastomeric plastic would be used to, cover the glass. Another serious problem is, the difficulty in designing penetrations and, hatches in a glass hull. A solution to these, problems could be a filament winding around, the glass or using a tough plastic skin., These glass structural problems show that, the RP hull is very attractive on a weightdisplacement ratio, strength-weight ratio,, and for its fabrication capability. A significant, advantage of RP over solid glass is that it is, available today and the technology of fabricating large, thick-wall structures already, exists. Also, with an increased modulus of, elasticity in fibers other than glass additional, gains are obtained beyond what is presently, available in conventional RPs., RPs have already been used in different, structural applications, to replace conventional metal in seawater-compressed air surfacing ballast tanks in the Alvin depth vehicle., This vehicle, a first-generation deep research, vehicle, also used RP in its outer hull construction to enclose the pressure tanks and, aluminum frame. In the unmanned acoustical research vehicle of the Ordnance Research Laboratory called Divar, an RP cylinder with a 16 in. OD, 3/4 in. wall thickness,, 12112 in. ID with nine ribs, a 60 in. length and, weight of 180 pounds went to depths of 950 m, (6,500 ft.)., , In addition to developing solid RP structures, work has been conducted on sandwich structures such as filament-wound plastic skins with low-density foamed core or a, plastic honeycomb core to develop more efficient strength-to-weight structures. Sandwich, structures using a syntactic core have been, successfully tested so that failures occurred, at prescribed high-hydrostatic pressures of, 28 MPa (4,000 psi)., The design of a hull is a very complex, problem. Under varying submergence depths, there can be significant working of the hull, structure, resulting in movement of the attached piping and foundations. These deflections, however slight, set up high stresses in, the attached members. Hence, the extent of, such strain loads must be considered in designing attached components., Buoyancy in some form is employed in, nearly all categories of underwater and surface systems to support them above the, ocean bottom or to minimize their submerged weight. The buoyant material can assume many different structural forms utilizing a wide variety of densities. The choice of, materials is severely restricted by operational, requirements, since different environmental, conditions exist. For example, lighter, buoyant liquids can be more volatile than heavier liquids. This factor can have a deleterious, effect on a steel structure by accelerating, stress corrosion or increasing permeability in, reinforced plastics., The typical syntactic foam used for buoyancy in many vehicles is made of hollow glass,, ceramic, or plastic microspheres of 30 to 300, micron size, uniformly dispersed in a plastic, such as epoxy. The navy, desiring to develop, a material to replace the more conventional, gasoline flotation one, produced an excellent, syntactic foam. Strict processing and quality, control in producing the foam can develop a, static hydrostatic pressure of 10,000 psig and, fatigue testing of 1,000 cycles., In the Woods Hole Oceanographic Institute's three-man 1,800 m (6,000 ft.) depth, vehicles, approximately 5,000 lb. of syntactic, foam were used to provide buoyancy. With, a specific gravity of 0.68, it required three, pounds of material to gain one pound of

Page 131 : 2 Design Influencing Factor, buoyant effect. However, its main attributes, were that of being able to tailor it to fit the, available space and being useful to at least a, 5,000 psi (35 MPa) load., , Time-Dependent Data, Different developments and theoretical, approaches are always being considered for, predicting expected service of plastics. Since, there appears to be an endless list of new, materials being developed, or improvements, continually are developed in the science of, plastics, the problem of obtaining immediate, 5 to 20 year service data sets up problems., Even though this situation exists, recognize, that there are plastics with 10 to over 50 years, service; i.e., polyvinyl chloride, acrylic, silicone, phenolics, glass fiber-TS polyester RPs,, etc. So from a truly designers, engineering,, or scientific approach one has to be realistic that certain plastics exist with actual service data. In regard to those who desire long, time data on plastics that have not been subjected to field tests, or accelerated tests, other, approaches such as the following evaluations, exist., , Viscoelastic and rate theory To aid the designer the viscoelastic and rate theories can, be used to predict long-term mechanical behavior from short-term creep and relaxation, data. Plastic properties are generally affected, by relatively small temperature changes or, changes in the rate of loading application., Time dependence Viscoelastic deformation is a transition type behavior that is characterized by the occurrence of both elastic, strain and time-dependent flow. It is the time, dependence of the mechanical properties of, plastics that makes the behavior of these materials difficult to analyze by mathematical, theory., Creep behavior Creep is the deformation, that occurs over a long period of time in a, material subjected to a continuous load, and, stress relaxation is the reduction in stress with, time that occurs in a material when it is de-, , 113, , formed to some specific strain which is maintained constant., Failure can be considered as an actual rupture (stress-rupture) or an excessive creep, deformation. Correlation of stress relaxation, and creep data has been covered as well as, a brief treatment of the equivalent elastic, problem. The method of the equivalent elastic problem is of major assistance to designers of plastic products since, by knowing the, elastic solution to a problem, the viscoelastic solution can be readily deduced by simply, replacing elastic physical constants with viscoelastic constants., , Linear viscoelasticity Linear viscoelastic, theory and its application to static stress, analysis is now developed. According to this, theory, material is linearly viscoelastic if,, when it is stressed below some limiting stress, (about half the short-time yield stress), small, strains are at any time almost linearly proportional to the imposed stresses. Portions of, the creep data typify such behavior and furnish the basis for fairly accurate predictions, concerning the deformation of plastics when, subjected to loads over long periods of time., It should be noted that linear behavior, as defined, does not always persist throughout the, time span over which the data are acquired;, i.e., the theory is not valid in nonlinear regions and other prediction methods must be, used in such cases., The basic viscoelastic theory assumes a, timewise linear relationship between stress, and strain. Based on this assumption and using mechanical models thought to represent, the behavior of a plastic material, it can be, shown that the stress, at any time t, in a plastic held at a constant strain (relaxation test),, is given by:, (2-14), , where (I is the stress at any time t, Y is the, relaxation time, (Io is the initial stress, and e, is the natural logarithmic base number., Using the same mechanical models and assumptions, it cam also be shown that the total deformation experienced in a creep process (with the same under constant stress (I)

Page 132 : 114, , 2 Design Influencing Factor, , is given by:, 8, , = (a/ Eo), , + (a/ E)(1 -, , e- t / y ), , + (at/I]), (2-15), , where 8 is the total deformation, Eo is the initial modulus of the sample, E is the modulus, after time t, and I] is the viscosity of the plastic. Excluding the permanent set or deformation and considering only the creep involved,, Eq. 2-15 may be stated as:, , + (a/ E)(1 -, , e-tIY ), (2-16), Note that the term y in Eqs. 2-15 and 2-16, has a different significance than that in Eq., 2-14. In the first equation it is based on a concept of relaxation and in the others on the basis of creep. In the literature, these terms are, respectively referred to as a relaxation time, and a retardation time, leading for infinite elements in the deformation models to complex quantities known as relaxation and retardation functions. One of the principal accomplishments of viscoelastic theory is the correlation of these quantities analytically so that, creep deformation can be predicted from relaxation data and relaxation data from creep, deformation data., Using viscoelastic theory, it is possible to, demonstrate that:, (ao/a) relaxation = (8/80) creep, (2-17), Thus, by determining values of (ao/ a) from, a relaxation test, creep strains can be calculated using Eq. 2-17 in the form of:, 8 = 80(ao/a) = (ao/a)(ao/ Eo)(ao/a), (2-18), 8, , = (a/ E), , where (I/Eo)(ao/a) may be thought of as, a time-modified modulus, i.e., equal to 1/ E,, from which the modulus at any time t, is:, , E = Eo(ao/a), , (2-19), , that is the value to replace E in the conventional elastic soultions to mechanical problems. Where Poisson's ration, y, appears in, the elastic solution, it is replaced in the viscoelastic solution by:, y = (3B - E)6B, (2-20), where B is the bulk modulus, a value that, remains almost constant throughout deformations., , Creep and stress relation Creep and stress, relaxation behavior for plastics are closely related to each other and one can be predicted, from knowledge of the other. Therefore, such, deformations in plastics can be predicted by, the use of standard elastic stress analysis formulas where the elastic constants E and y can, be replaced by their viscoelastic equivalents, given in Eqs. 2-19 and 2-20., If data are not available on the effects of, time, temperature, and strain rate on modulus, creep tests can be performed at various, stress levels as a function of temperature over, a reasonable period of time. In this regard,, reasonable is a relative term. For applications, like rockets and missiles, data obtained over a, time period of 4-5 sec to an hour provide the, essential information. For structural applications, such as pipelines, data over a period of, years are required., This is the one serious limitation in plastic, design problems. Even if the designer did wait, for data on one material, chances are the final, design might be switched to another plastic, or formulation. Thus, as a compromise, data, from relatively short-term tests are extrapolated by means of theory to long-term problems. However, when this is done, the limitations inherent in the procedure should be, kept in mind., Rate theory An alternate method available involves the manipulation of the rate, theory based on the Arrhenius equation. This, procedure requires considerable test data but, the indications are that considerably more, latitude is obtained and more materials obey, the rate theory. The method can also be used, to predict stress-rupture of plastics as well as, the creep characteristics of a material, which, is a strong plus for the method., If it is assumed that the physical and chemical properties of the material are the same, before and after rupture (so that the concentration of material undergoing deformation, is related to the rate constant, K, by x = Kt,, where t is time) then it can be shown, as in, the following equation, that for plastics:, , A/R= Kl = [TTo/(To - T)](20+logt), (2-21)

Page 133 : 2 Design Influencing Factor, where A is the activation energy for the process, R is the gas constant, T is the absolute temperature of the process, To is the, absolute temperature at which the material, has no strength, Kl is a constant, and t is, time., For some materials, rupture curves can be, computed for all values of T related to the, magnitude of the stress applied. For design, purposes, if the required time and operating, temperature are specified, Kl can be computed and the value of stress required to, cause rupture at that time and temperature, can be read off charts., Creep deformations are calculated by dividing the stress by the modulus of the material. The deformation observed in a shortterm tensile test at an elevated temperature, is related to the deformation that takes place, at a lower temperature over a longer period, of time. The short-term data thus obtained, can be used to obtain long-term modulus data, through the development of a master modulus curve. Being able to determine the modulus at any time t and knowing the constant, value of stress to which a material is subjected, it is then possible to predict the creep, which will have been experienced at time t, by simply dividing the stress by the modulus using conventional elastic stress analysis, relationships., Designing plastic Basically the general, design criteria applicable to plastics are the, same as those for metals at elevated temperature; that is, design is based on (1) a deformation limit, and (2) a stress limit (for, stress-rupture failure). There are, of course,, cases where weight is a limiting factor and, other cases where short-term properties are, important., In computing ordinary short-term characteristics of plastics, the standard stress analysis formulas may be used. For predicting creep and stress-rupture behavior, the, method will vary according to circumstances., In viscoelastic materials, relaxation data can, be used in Eqs. 2-16 to 2-20 to predict creep, deformations. In other cases the rate theory, may be used., , 115, , Molecular Weight and Aging, MW and aging may each be cause and/or, effect on plastics. Reactivity with oxygen,, ozone, moisture, and UV light sensitization, via outdoor weathering and/or high temperature all become important with aging, particularly the NEAT plastics. Different, additives are used with different plastics to, provide long-time aging. Certain plastics will, improve with aging based on actual service, tests and extensive creep tests. However, certain plastics have limited endurance. This action is somewhat related to MW where low, MW materials tend to degrade and the higher, MWs become stronger through cross-linking, (Chapter 8)., Arrhenius Plot Theory, Another technique known and available, for evaluating and predicting performance in, special applications concerns the Arrhenius, plot., Why materials age Aging involves both, chemical and physical changes, although, many of the latter are just the visible manifestation of the former. While most of these, should be obvious to the chemist and engineer, it is important that they be reviewed, as background to the basic approach to be, taken., The chemical changes are due to reactions between materials of different energies, and may involve some complex reaction kinetics. Whenever two materials are, combined, many products may be formed., Thus, oxygen may be absorbed and oxidation of the materials result. The exact reaction depends on the presence of catalytic, agents. The oxidation may cause the materials to cross-link and cause hardening or, shrinkage that may show up as stress cracking. It may degrade the molecules to lower, molecular weight or volatile products, causing a volume decrease or stress cracking. Or, it may lead to acidic products which will, discolor the material or bring about further, degradations.

Page 134 : 116, , 2 Design Influencing Factor, , Other degradative reactions can occur in, the absence of oxygen. The presence of water may bring about hydrolitic reactions and,, if oxygen is also present, may increase oxidation reactions. All of these may be going on, simultaneously and in the most complicated, manner. The lower molecular weight units, can cause changes in flow, shape, strength, or, other desired properties., Physical changes may result from the, chemical changes, but even without a chemical reaction the low molecular weight materials may be lost by volatilization, and the, material may be undergoing a stress relaxation. Volatilization is a slow process that depends on the partial vapor pressure of the, lower molecular weight volatile constituents,, unless they are polar or have electrostatic attraction for other molecules. It may result in, hardening from the loss of plasticizers identified as such and also from the loss of low, molecular weight materials, or even water,, which can act as plasticizers. Stress relaxation may occur due to mechanical or thermal stress. Differential expansion of organic, and inorganic parts often results in cracking. These effects are particularly possible at, temperatures near those where changes or, property transitions occur (for example, softening or melting points or brittle points of, materials)., Rate of aging process It has been known, for a long time as an empirical fact that, many reactions approximately double or treble theirrates with a lOoC rise in temperature., A more quantitative relation is given by the, classical Arrhenius modified equation:, logk = (EI2.303R)(1IT), , +C, , (2-22), , where k = specific reaction rate; E = activation energy for the reaction; R = gas constant, per gram molecular weight; and T = absolute, temperature, OK., A straight line is produced when the logarithm of a specific reaction rate is plotted, against the reciprocal of the absolute temperature. Temperature has a marked influence, on the reaction rates, but the range between, reactions that are too slow or too fast to measure is really quite narrow., , Similarly, the rate of evaporation of materials depends on the vapor pressure, p, of, the volatile constituent, which in turn varies, directly as its molar concentration and the, temperature:, logp, , = (MIT) + C, , (2-23), , Volatilization is also affected by the ventilation rate over the surface of the material,, but when this is constant, a straight-line result, from the plot of the logarithm of the vapor, pressure against the reciprocal of the absolute temperature., Diffusion of a reactive component or a, volatile constituent into or out of a material, is also a temperature dependent rate phenomenon, as:, log D, , =K, , - (EI RT), , (2-24), , where D is the diffusion rate and K is a force, factor dependent on the velocity of motion of, the molecule and the frictional resistance to, this motion., Thus, whether the changes in the material, are due to chemical reactions, volatilization,, or diffusion, one can expect a linear relationship between the logarithm of life (i.e.,, time to failure) and the reciprocal of absolute temperature. But there is no sound basis, for extrapolating the effect of changing the, concentration of the environmental exposure, medium or the physical functions., It is possible, in some situations, that, two different phenomena which proceed at, different rates with different temperature, coefficients or activation energies will affect the physical properties. In such complex, cases, it is not expect to obtain a linear relation between the logarithm of life and reciprocal absolute temperature. If one obtains, a nonlinear curve, however, it may he possible to identify the reaction causing the nonlinearity and correct for it. When one can, make such a correction, one obtains a linear, relationship., Using the Arrhenius equation to predict performance It has been shown that temperature alone is a sufficient accelerating means., Now one must consider how best to apply this, criterion to a prediction of performance. The

Page 135 : 2 Design Influencing Factor, conditions of an accelerated aging test should, correspond as closely as possible to the conditions encountered in actual service, and the, material must be tested in the form and in, the function in which one wants to evaluate, its performance., The accelerated aging test should take into, account the associated materials as well as the, atmosphere that will be encountered in actual, use, since they are also controlling factors. It is, helpful to include materials of known performance against which to rate the new material,, since this allows a check of controlling factors, and further validates the extrapolation. Thus,, existing data from long term tests may be of, considerable value., For a criterion of failure, life tests should, measure the time required for a material, to deteriorate to a condition where it is no, longer capable of performing its intended, function. Careful analysis and testing are required to determine the most important condition or property at the time of failure or the, point when a material becomes inadequate to, its intended function., Test temperature. Tests should be run at a, minimum of three temperatures and preferably four to confirm the linear relation between the logarithm of life and the reciprocal of absolute temperature. Several samples, are necessary to plot the results of changes, occurring versus time for each testing temperature. The time available and the accuracy of the extrapolation desired determine the lowest test temperature. Usually, the most desirable lowest temperature is one, that will give results in about 1,000-2,000 h, (6-12 weeks)., Normal oxidative degradation. There is, seldom any reason to go below a 75% or a, 50% retention of properties, as the material, has usually changed rather drastically at these, levels., Cross-linking. In cross-linking the materials often improve before they begin to degrade; otherwise, the results are the same as, in the oxidative degradation., , 117, , Catalytic degradation. There are materials that show no change for a period of, time, then degrade rapidly. As an example the, degradation of certain polypropylenes, which, initiates at a site and then propagates by chain, scissor, would give this effect, resulting from, the depletion of a protective ingredient such, as a heat stabilizer or antioxidant. In this case,, the only significant end point is the very early, loss of properties., Arrhenius plot. In an Arrhenius plot the, ordinate is the log of the material life. The, abscissa is the reciprocal of the absolute temperature. The linear curves obtained with the, Arrhenius plot overcome the deficiency of, most of the standard tests, which provide only, one point and indicate no direction in which, to extrapolate. Moreover, any change in any, aspect of the material or the environment, could alter the slopes of there curves. Therein, lies the value of this method., There is supporting evidence in the literature for the validity of this method; two cases, in particular substantiate it. In one, tests were, made on plastics heated in the pressure of air., Differential infrared spectroscopy was used, to determine the chemical changes at three, temperatures, in the functional groups of a, TP acrylonitrile, and a variety of TS phenolic, plastics. The technique uses a film of un-aged, plastic in the reference beam and the aged, sample in the sample beam. Thus, the difference between the reference and the aged, sample is a measure of the chemical changes., The results showed that the rate of change, was markedly temperature dependent and, that the degradation at each of the three temperatures was identical. In other words, the, amount of degradation that occurred in 4 h, at 200°C (392°F) was identical to the amount, in 725 h at 100°C (212°F). The same tests, in a vacuum showed no degradation, indicating that the initiating step in the degradation, process in air must be the attack of oxygen., With acid catalyzed phenolic plastic, similar, results were obtained. These results are important; they lend some authenticity to this, technique., The second case concerns the results, published by du Pont, of actual service life tests

Page 136 : 118, , 2 Design Influencing Factor, , on Zytel 101 and 103, which were run for, more than 12 years. Some of these data were, plotted on an Arrhenius plot. It is not surprising that the heat stabilized Zytel 103, is markedly more stable to heat oxidation, than the Zytel101, since the heat stabilizers, were developed by high temperature evaluations until a stabilizing additive was found., What may not have been readily apparent,, however, is that the two materials would, have about the same life expectancy at room, temperature., Data was collected over a two-year period, on the effect of water on DuPont's Zytel101., In an Arrhenius plot of this data the failure point was the time when the elongation, and impact strength started to decrease. This, is not a chemical degradation, but rather a, permeation or diffusion rate phenomenon. It, shows that high temperature water tests can, be used to predict normal temperature exposure results., Usefulness of thermal evaluation technique, The following list includes examples where, the technique can be used., Fundamental Studies, Guiding research in tailor-making plastics, Fast evaluations and comparisons will, show if desired improvements are being, made, Curing studies-pot life, Engineering data for design, Stress relaxation at low loads under different exposures, Long term strength retention of glass fiber, in wet service, Fatigue testing-flexure, rotation or fold, Product or end use evaluations, Selecting or screening materials specifications, Control testing, Predicting end use applications, Water immersion, Vacuum or space conditions, Pipe burst, Storage effects on solid propellant binders, , Resistance to chemicals, Radiation, Soil burial, Weathering-UVexposure, Ozone, Permeation through films, Detergent effects on blown bottles, Discoloration, , High Temperature, , Plastics have found numerous uses in specialty areas such as hypersonic atmospheric, flight and chemical propulsion exhaust systems. The particular plastic employed in these, applications is based on the inherent properties of the plastics or the ability to combine, it with another component material to obtain, a balance of properties uncommon to either, component. Some of the compositions and, important properties of plastics are given in, Tables 2-9 and 2-10 that have been developed, over the years for use in flight vehicles and, propulsion systems that are dependent upon, chemical, mechanical, electrical, nuclear, and, solar means for accelerating the working fluid, by high temperatures., Since 1950, plastics have been development for uses in very high temperature environments. By 1954, it was demonstrated, that plastic materials were suitable for thermally protecting structures during intense, propulsion heating. This discovery, at that, time, became one of the greatest achievements of modern times, because it essentially initially eliminated the "thermal barrier" to hypersonic atmospheric flight as, well as many of the internal heating problems associated with chemical propulsion, systems., Only chemical propUlsion will be further, discussed, and in particular, that associated, with liquid, solid, and hybrid motors and, engines. These motors and engines are, uniquely different from other chemical, propUlsion systems in that they carryon, board the necessary propellants, as contrasted to jet engines that rely on atmospheric, oxygen for combustion of the fuel.

Page 137 : 2 Design Influencing Factor, Table 2-9, , Typical ablative compositions, , Plastic-Base, Polytetrafluoroethylene, , Epoxy-polyamide resin, with a powdered, oxide filler, , Phenolic resin with an, organic (nylon),, inorganic (silica),, or refractory (carbon), reinforcement, Precharred epoxy, impregnated with a, noncharring resin, , Ceramic-Base, , Elastomer-Base, , Metal-Base, , Porous oxide (silica), matrix infiltrated, with phenolic resin, , Silicone rubber filled, Porous refractory, with microspheres, (tungsten) infiltrated, and reinforced with, with a low melting, a plastic honeycomb, point metal (silver), PolybutadienePorous filament, Hot-pressed refractory, wound composite, acrylonitrile elastomer, metal containing an, of oxide fibers and an, modified phenolic, oxide filler, inorganic adhesive,, resin with a, impregnated with an, subliming powder, organic resin, Hot pressed oxide,, carbide, or nitride in, a metal honeycomb, , Hypersonic Atmospheric Flight, Progress in aeronautics and astronautics, within the past decades has been remarkable because people have learned to master the difficult feat of hypervelocity flight., A variety of manned and unmanned aircraft, have been developed for faster transportation from one point on earth to another., Similarly, aerospace vehicles have been constructed for further exploration of the vast, depths of space and the neighboring planets, in the solar system., Table 2-10, , II9, , All bodies traveling in a fluid experience, dynamic heating, the magnitude of which, depends upon the body characteristics and, the environmental parameters. Modern supersonic aircraft, for example, experience, appreciable heating. This incident flux is, accommodated by the use of an insulated, metallic structure, which provides a near, balance between the incident thermal pulse, and the heat dissipated by surface radiation. Hence, only a small amount of heat has, to be absorbed by mechanisms other than, radiation., , Plastics for propulsion environments, , Major Property of Interest, , Type of Polymer, , Ablative, Chemical resistance, , Phenol-formaldehyde, Fluorosilicone, , Cryogenic, Adhesion, , Polyurethane, Epoxy, , Dieletric, Elastomeric, Power transmission, Specific strength, , Silicone, Polybutadiene-acrylonitrile, Diesters, Epoxy-novolac, , Thermally nonconductive, , Polyamides, , Absorptivity:emissivity ratio, Gelling agent, , Alkyd silicone, Poly( vinyl chloride), , Propulsion System Application, Charring resin for rocket nozzle, Seals, gaskets, hose linings for liquid, fuels, Insulative foam for cryogenic tankage, Bonding reinforcements on external, surface of combustion chamber, Wire and cable electrical insulation, Solid propellant binder, Hydraulic fluid, Resin matrix for filament wound motor, case, Resin modifier for plastic thrust, chamber, Thermal control coating, Thixotrophic liquid propellant

Page 138 : 2 Design Influencing Factor, , 120, , to 25,000,000 Btu. This magnitude of energy, greatly exceeds that required too completely, vaporize the entire vehicle. Fortunately, only, a very small fraction of the kinetic energy, converted to heat reaches the body while the, remainder is dissipated in the gas surrounding the vehicle., , As flight speeds increased to about, 8,000 fps heating increases to a point where, some added form of thermal protection was, necessary to prevent thermo structural failure. In a somewhat similar manner, hypervelocity vehicles transcending through a planetary atmosphere also encounter gas-dynamic, heating. The magnitude of heating is very, large, however, and the heating period is, much shorter. This latter type of thermal, problem is frequently referred to as the, "reentry heating" problem, and it posed one, of the most difficult engineering problems of, the twentieth century., The intended mission of a hypervelocity vehicle will dictate its flight velocity, and trajectory. This point is illustrated in, Fig. 2-58, which presents the general altitudevelocity. The severity of the gas-dynamic, heating problem increases with flight velocity. It becomes particularly acute when a vehicle must be slowed from a very high speed, to a much lower impact or landing speed. In, other words, hypervelocity vehicles possess a, tremendous amount of kinetic and potential, energy that must be dissipated during deceleration., As shown in Fig. 2-58, a body entering the, earth's atmosphere at 25,000 fps has a kinetic energy equivalent to 12,500 Btu/lb of, vehicle mass. Assuming the vehicle weighs a, ton, it possesses a thermal energy equivalent, , Hyperenvironment Materials performance during hypersonic atmospheric flight, depends upon certain environmental parameters. These thermal, mechanical, and, chemical variables differ greatly in magnitude and with body position. In general, they are concerned with temperatures, from about 2,000 to over 20,000°F (1,1001l,000°C), gas enthalpies up to 40,000 Btu/lb,, convective/radiative heating from 10 to over, 10,000 Btu/ft2/sec, stagnation pressures less, than 1 to over 100 atm., surface shear stresses, up to about 900 psf, heating times from a, few to several thousand seconds, and gaseous, compositions involving molecular, dissociated, and ionized species. The type and magnitude of effects produced by these environmental parameters are dependent upon the, local aerothermo-chemical and gas-dynamic, state of the flow field., Thermal protection The design of vehicles for hypersonic atmospheric flight represents a compromise between the intended, , Stagnatfon Enthalpy, 2, , 400, , 10, , 5, , Ballistic Entry, ---- lilting Engry, , I,X-IS-2A, I, , 300, E, , ,, I, , OJ, , I, , .",, , ~, , I, , 100, I, , 00, , ,, ,,... ", , ,",,, , ., ,, ", , ", , #', , 20, , Btu/lbl, 25, , 35, , 30, , lunar, Return, , 40, , Mars, R turn, , ,,,, ,, ,,,, , I, I, , IRBM, , I, , ~, , (1, OOJ, , Orbital, Satellite, ICBM, , I, , :::::200, .a, , 15, , .........., , .., , ~.,, , ~, , 10-6 E, !!, }O"5 ~, , I, , I, , ,,, , (., , ::J, , 10- 4, , 0.., , 1:, 10-3 ~, , e, , ,I, , 10-2 «, 10- 1, , 10, , '"f, , 20, , 30, , 40, , Flight Velocity 0, OOJ It! sec), , Fig.2-58 Hypersonic atmospheric flight regime., , 50

Page 139 : 2 Design Influencing Factor, mission, the thermostructural aspects of the, environment, the rate and magnitude of, vehicle deceleration permitted, and the, amount of lift necessary for flight control and, landing at a predetermined point on some, planet. The heating problem associated with, high performance vehicles has been solved, by a variety of design techniques. These include radiative cooling, heat sinks, transpiration cooling, ablation, and combinations, thereof. Each thermal protective scheme is, applicable to a particular portion of the flight, regime, with reduced efficiency or no utility, at other flight conditions., , Ablation The most common design approach for handling intense heating and extremely high temperatures is ablation. In, this process, surface material is physically, removed or a temperature-sensitive component of a composite is preferentially removed. The injected vapors alter the chemical composition, transport properties, and, temperature profile of the boundary layer,, thus reducing the beat transfer to the material surface. At high ablation rates, the heat, transfer to the surface may be only 15 % of the, thermal flux to a non-ablating surface. Up to, tens of thousands of Btu's of heat can be absorbed, dissipated and blocked per pound of, ablative material through the sensible heat, capacity, chemical reactions, phase changes,, surface radiation and boundary layer cooling, of the ablator (Fig. 2-59)., ENERGY EXCHANGES, , CONVECTION, , Ablative systems are not limited by the, heating rate or environmental temperature,, but rather by the total heat load. In spite of, this limitation, however, the versatility of ablation has permitted it to be used on various hypervelocity atmospheric vehicles. No, single, universally acceptable ablative material has been developed. Nevertheless, the, interdisciplinary efforts of materials scientists and engineers have resulted in obtaining a wide variety of ablative compositions, and constructions. These thermally protective materials have been arbitrarily categorized by their matrix composition, and typical, materials are given in Table 2-9., Plastic-base composites that employ an, organic matrix, is the most widely used, class of plastic ablative heat protective, materials. They respond to a hyperthermal, environment in a variety of ways, such, as depolymerization-vaporization (polytetrafluoroethylene), pyrolysis-vaporization, (phenolic, epoxy) and decompositionmelting-vaporization (nylon fiber reinforced, plastic). The principal advantages of plasticbase ablators are their high heat shielding, capability and low thermal conductivity., The major limitations are high erosion rates, during exposure to very high gas-dynamic, shear forces and, limited capability to, accommodate very high heat loads., Elastomeric-base materials represent a, second major class of ablators. They thermally decompose by such processes as, Glass Droplets, Dense Char, Nascent Porous Char, Resin Volatilization, , RADIATION, GAS-PHASE, COMBUSTION, SURFACE, COMBUSTION, RERADIATION, , -4f---, , TRANSPIRATION, -4f--COOLING, CHEMICAL REACTIONS - 4 f - - PHYS ICAL CHANGES - 4 - f - - -, , Fig. 2-59, , 121, , Surface heat balance of an ablating glass fiber reinforced phenolic plastic.

Page 140 : 122, , 2 Design Influencing Factor, , depolymerization, pyrolysis, and vaporization. Most of the interest to date has been focused on the silicone plastics because of their, low thermal conductivity, high thermal efficiency at low to moderate heat fluxes, low, temperature properties, elongation of several hundred percent at failure, oxidative resistance, low density, and compatibility with, other structural materials. They are generally, limited by the amount of structural quality, of char formed during ablation, that restricts, their use in hyperthermal environments of, relatively low mechanical forces., Thermoplastic and elastomeric plastics, tend to thermally degrade into simple, monomeric units with the formation of considerable liquid and a lesser amount of, gaseous species. Little or no solid residue generally remains on the ablating surface. On the, contrary, most thermoset plastics and highly, cross-linked plastics (especially those with, aromatic ring structures) form a hard surface residue of porous carbon. The amount, of char formed depends upon various factors., (1) The carbon-to-hydrogen ratio present in, the original plastic structure. (2) Degree of, cross-linking and tendency to further crosslink during heating. (3) Presence of foreign, elements like the halogens, asymmetry and, aromaticity of the polymer structure. (4) Degree of vapor pyrolysis of the ablative hydrocarbon species percolating through the char, layer. (5) Type of elemental bonding., With the formation of a carbonaceous, layer, the primary region of pyrolysis gradually shifts from the surface to a substrate, zone beneath the char layer. The newly, formed char structure is attached to the virgin substrate material and remains thereon, for at least a short period of time. Meanwhile, its refractory nature serves to protect, the temperature-sensitive substrate from the, environment. Gaseous products formed in, the substrate pass through the porous char, layer, undergo partial vapor phase cracking,, and deposit pyrolytic carbon (or graphite), onto the walls of the pores., As the organic plastic or its residual char, are removed by the ablative aspects of the, hyper-environment, the reinforcing fibers or, particle fillers are left exposed and unsup-, , ported. Being vitreous in composition, they, undergo melting. The resultant molten material covers the surface as liquid droplets, irregular globules, and/or a thin film. Continued addition of heat to the surface causes the, melt to be vaporized. A fraction of the melt, may be splattered by internal pressure forces,, or sloughed away when acted upon by external pressure and shear forces of the dynamic, environment., , Chemical Propulsion Exhaust, The basic purpose of a propulsion system, is to convert the thermal energy of a chemical reaction into useful kinetic energy by, directing the flow of the resultant products., In other words, the propulsion system is to, provide thrust for the movement of a vehicle. Expulsion of material is the essence of, thrust production, and without material to expel no thrust can be produced, regardless of, how much energy is available. The amount, of thrust generated is equal to the rate of, propellant consumption multiplied by the exhaust gas velocity. In order to maximize the, exhaust velocity, it is necessary to have the, combustion process take place at the highest, possible temperature and pressure. Energy is, released in the process, with a major fraction, appearing as thermal (heat) energy., The combustion process is carried out in a, thrust chamber or a motor case, and the reaction products are momentarily contained, therein. The newly formed species are heterogeneous in composition and involve a, wide variety of low molecular weight products. The temperature of these products is, generally high, and it ranges from about, 2,000°F (1,100°e) in gas generators to well, over 8,000°F in advanced liquid propellant, engines. The combustion products leave the, chamber and are directed and expanded in a, nozzle to obtain velocities from about 5,000, to 14,000 ft/sec., , Cooling techniques Various methods, have been developed to cope with high, temperature and heating problems. They are, based on absorptive, dissipative, and mass

Page 141 : 123, , 2 Design Influencing Factor, transfer cooling systems. More specifically,, they include regenerative cooling, inert, or endothermic heat sinks, ablation, and, combinations of the preceding techniques., A form of cooling, and the one of prime, interest, concerns ablative cooling. It is essentially a heat and mass transfer process in, which mass is expended to achieve thermal, dissipation, absorption, and blocking. The, process is passive in nature, serves to control, the surface temperature, and greatly restricts, the flow of heat into the material substrate., As a result of these desirable attributes, ablative cooling (includes use of plastic compositions) has been widely used for thermal, protection of solid propellant motors and less, extensively in liquid propellant motors., , Flammability, When plastics are used, their behavior in, fire must be considered. Ease of ignition,, the rate of flame spread and of heat release,, smoke release, toxicity of products of combustion, and other factors must be taken into, account. Some plastics bum readily, others, only with difficulty, and still others do not, support their own combustion A plastic's behavior in fire depends upon the nature and, scale of the fire as well as the surrounding, conditions. Fire is a highly complex, variable phenomenon, and the behavior of plastics in a fire is equally complex and variable, (Chapter 5, FIRE)., Early in the past century it was thought, that the matter of fire hazard was simple, enough: does the material bum, or not? Wood, burns; steel does not. Although these statements are certainly true, they are almost irrelevant to the relative fire risk of the two, materials. Compare fires in two different, buildings, one framed of heavy timbers, (or plastic bonded-laminated wood arches,, RP-TS plastics, etc.) and the other of steel, framing. The steel frame could collapse after only a few minutes of exposure to fire,, but it may require a fire of very long duration (days) to bring down the timber-framed, building (and other materials). Fire reaches, 1,370°C (2,500°F). Steel basically takes only, , 100, Composite and Engineered Plastics, , 90, , ..,, , '"><, ~, , 80, , .~, , 70, , .;;, <II, !!, , 60, , Ii), , .", , iii, , 50, , >=, , 40, , ..., , 20, , .!!!, 'c;;, c:, , l', , Typical Steel, , 30, , II>, , Commodity Plastics, , 10, 0, ·100, , o, , 100 200 300 400 500 600 700 800 900 1000, Temperature, FO, , Fig. 2-60, plastics., , Strength vs. temperature of steels and, , up to about 538°C (l,OOO°F), making it collapse like a pretzel (Fig. 2-60). Wood, like certain plastics, can take the heat, and it takes a, rather long time to self-destruct, thus giving, time for people to leave the scene of the fire, and so on., Fire tests of plastics, like fire tests generally,, are frequently highly specific, with the results, being specific to the tests. The results of one, type of test do not in fact often correlate directly with those of another and may bear, little relationship to actual fires. Some tests, are intended mainly for screening purposes, during research and development, whereas, others, such as large-scale product tests, are, designed to more nearly approximate actual, fires. Consequently, such often-used terms as, self-extinguishing, nonburning, flame spread,, and toxicity must be understood in the context of the specific tests with which they are, used., Some materials may bum quite slowly but, may propagate a flame rapidly over their surfaces. Thin wood paneling will burn readily,, yet a heavy timber post will sustain a fire on, its surface until it is charred, then smolder at, a remarkably slow rate of burning. Bituminous materials may spread a fire by softening and running down a wall. Steel of course, does not burn, but is catastrophically weakened by the elevated temperatures of a fire., PVC does not bum, but it softens at relatively, low temperatures. Other plastics may not, burn readily but still emit copious amounts of, smoke. And some flammable plastics, such as

Page 142 : 124, , 2 Design Influencing Factor, , polyurethane, may be made flame retardant, (FR) by incorporating in them additives such, as antimony oxide. Other plastics basically do, not bum, such as silicone and fluorine., The principles of good design for fire safety, are as applicable to plastics as to other materials. The specific design must be carefully, considered the properties of the materials, taken into account, and good designer judgment applied. When evaluating the fire risk, that exists with plastic products it is always, best to perform appropriate tests on the end, items (Chapter 4, RISK). However, it is often, helpful to select plastic materials for specific, applications by first evaluating the flammability of the plastics under consideration in, laboratory tests if the data is not available., These tests, often used for specifying materials, fall into the category either of small-scale, or large-scale tests. Of course, as in evaluating any properties, having prior knowledge, or obtaining reliable data applicable to fire, or other requirements is the ideal situation., , Smoke Toxic smoke and fumes have became generally recognized as the major cause, of fire deaths, making the combustion products released by burning plastics and other, materials particularly important. Smoke is, recognized by firefighters as being in many, ways more dangerous than actual flames because (1) it obscures vision, making it impossible to find safe means of egress, thus often, leading to panic, (2) it makes helping or rescuing victims difficult if not impossible; and, (3) it leads to physiological reactions such, as choking and tearing. Smoke from plastics,, wood, gasoline, coal, oil, and other materials, usually contains toxic gases such as carbon, monoxide (CO), which has no odor, often accompanied by noxious gases that may lead to, nausea and other debilitating effects as well, as panic warning the fire victim of danger., With only CO the victim would die whereas, the start of a fire with noxious gases could, alert a person that a fire has started and leave, the area., Whether a plastic gives off light or heavy, smoke and toxic or noxious gases depends on, the basic plastic used, its composition of additives and fillers, and the conditions under, , which its burning occurs. Some plastics burn, with a relatively clean flame, but some, may give off dense smoke while smoldering. Others are inherently smoke producing, (Fig. 2-61)., In a particular application, therefore,, careful consideration should be given to the, relative importance of smoke and flame, including creating designs favoring the rapid, elimination of smoke by venting, for fending, off smoke, and other approaches., Different regulations, such as those of the, Federal Aviation Administration, Department of Transportation, and local building, codes, mandate that the designs of certain, products comply with specific flammability test requirements. Flame-retardancy requirements generally include limits on flame, spread, burning time, dripping, and smoke, emission. A multitude of flammability tests, has been developed, with more than 100, known just in the United States. Different, organizations are actively involved providing, information, software, etc.; they include UL,, ASTM, ISO, and NIST (Chapter 5)., One of the most stringent and most widely, accepted test is UL 94 that concerns electrical devices. This test, which involves burning, a specimen, is the one used for most flameretardant plastics. In this test the best rating, is UL 94 v-a, which identifies a flame with a, duration of to 5 s, an afterglow of to 25 s,, and the presence of no flaming drips to ignite, a sample of dry, absorbent cotton located below the specimen. The ratings go from v-a,, V-I, V-2, and V-5 to HB, based on specific, specimen thicknesses., , °, , °, , Intumescence coating Historically, smoke and the resultant toxic fumes caused by, the burning of a flammable substrate were, part of any fire, regardless of whether or not, a fire retardant treatment was applied. What, was needed was to smother the fire and thus, stop the generation of toxic smoke and save, the flammable substrate from further damage. Intumescence coatings were developed, over a half century ago via the US Navy R&D, programs for use on board ships and thereafter industry projects developed different, types of water resistant intumescent coatings.

Page 143 : 2 Design Influencing Factor, , 125, , -800 TEST CONDITIONS, , -700, -600, , 3.2 mOl (0.126 in.) samples, ~, , Flaming condition, , r--, , -500, , r--, , -400, , r- 300, , -, , r--, , r 200, , nn, , rlOO, , 0, r!;-flJ, , 9J'?, , ~, , . .v.., , ~'l.oe;, q<::i, , jt<:oi, , ,'1>, , ~, , q,,~, , Ib, ,,'lJt;f., , i}~, ~-4,, , ~, , ..~~, , r!;-flJ, , ~'IJ, , ~, , ~, , q<::i, , ~<:oi, , ~~, , ii:-~v, , ~«.«", , q", , ~v, , f}Q, ~'fj, , n, , q,,4r, , ~, , ~, , Fig. 2-61 Example of smoke emission results., , These intumescent coatings, when subjected, to fire, form a char between the substrate and, the fire source. The basic product coated becomes flameproof (36, 159)., Instability Behavior, , Shrinkage/Tolerance, Among the inherent characteristics of each, plastics material is its tendency to shrink or, expand. While the problems of shrinkage is, of major concern to the designer of tools, (molds, dies, etc.) and in turn the fabricators of the products, it should also be understood, as reviewed in this and other Chapters, that the product designer has a major, role in setting the required and proper product dimensions. By setting up the required, shrinkage and tolerance requirements, the, product designer can significantly influence, eliminating or reducing problems in production that directly increases costs. Where, tight tolerances are not required, they may, , be desired to reduce material and fabricating costs (Chapter 8, INFLUENCE ON, PERFORMANCE, Tolerance and Dimensional Control)., Shrinkage is defined as the difference, between corresponding linear dimensions, of the product and fabricating tool (under, controlled atmospheric conditions). Though, the shrinkage characteristics of plastics are, known and compensated for by a tool design,, the complex and overlapping nature of the, factors affecting shrinkage prevents exact scientific prediction. These factors include the, temperature range to which the plastic is exposed during the fabricating operation, the, material's coefficient of thermal expansion,, and the degree to which the plastic has been, compressed during the fabricating operation., Shrinkage can influence product performances such as mechanical properties., Anisotropy directional property can be used, when referring to the way a material shrinks, during processing, such as in injection molding (Fig. 2-62) and extrusion. Shrinkage is, an important consideration when fabricating

Page 144 : 126, , 2 Design Influencing Factor, properties of plastics the range of useful components is increased., , BEING, MOLDED, , Annealing, , MOLD CAViTY, , (HIGHLY, EXAGGERATED), , / - - ........., , j, , AFTER, CROSS, FLOW, SHRINKAGE, , Fig.2-62 Example of directional shrinkage in an, injection molded product., , plastics, particularly crystalline TPs or those, with glass fibers. The plastic melt flow direction can have more shrinkage than the crossflow direction. The control of shrinkage is, made to meet design requirements by factors, such as the design of the mold or die shape,, the processing-machine controls, the change, of product shape, and the type of plastics., , Heat Generation, This chapter has covered the reaction of, plastics to varying loads and environments., The heating of plastics by hysteresis and the, methods of designing to avoid frictional heat, failures of such products has been discussed., Fatigue effects on plastics subject to periodic loading as a failure mechanism was reviewed with emphasis on the design engineering approach to avoid fatigue failure. The, treatment is concluded with a discussion of, the use of viscoelastic effects to damp vibration and transient loads to reduce flutter, and, in general, to absorb mechanical energy, and prevent damage from induced mechanical vibration. By using the energy absorbing, , Also called hardening, tempering, physical aging, and heat treatment. The annealing, of plastics can be define as a heat-treatment, process directed at improving performance, by removal of stresses or strains set up in, the material during its fabrication. These unwanted stresses in the fabricated product can, cause service instability such as warping and, cracking. Depending on the plastic used, it, is brought up to a required temperature for, a definite time period, and then liquid (usually water; also use oils and waxes) and/or, air-cooled (quenched) to room temperature, at a controlled rate., Basically the temperature is usually near,, but below the melting point. At the specified temperature the molecules have enough, mobility to allow them to orient to a configuration removing or reducing residual stress., The objective is to permit stress relaxation, without distortion of its shape and obtain, maximum performances and/or dimensional, control. For certain plastics and product configurations, a holding frame is used during, the annealing process to eliminate unwanted, warpage., Annealing is generally restricted to thermoplastics, either amorphous or crystalline., Result is increasing density, thereby improving the plastics heat resistance and dimensional stability when exposed to elevated, temperatures. It frequently improves the impact strength and prevents crazing and cracking of excessively stressed products. The magnitude of these changes depends on the nature of the plastic, the annealing conditions,, and the product's geometry., The most desirable annealing temperatures for amorphous plastics, certain blends,, and block copolymers is just above their glass, transition temperature (Tg) where the relaxation of stress and orientation is the most, rapid. However, the required temperatures, may cause excessive distortion and warping.

Page 145 : 2 Design Influencing Factor, The plastic is heated to the highest temperature at which dimensional changes owing, to strain are released. This temperature can, be determined by placing the plastic product in an air oven or water liquid bath and, gradually raising the temperature by intervals of 3° to SoC until the maximum allowable change in shape or dimension occurs., This distortion temperature is dictated by the, thermomechanical processing history, geometry, thickness, and size. Usually the annealing temperature is set about SoC lower using, careful quality control procedures., Rigid, amorphous plastics such as PS and, PMMA are frequently annealed for stress relief. Annealing crystalline plastics, in addition, to the usual stress relief, may also bring about, significant changes in the nature of their crystalline state. The nature of the crystal structure, degree of crystallinity, size and number of spherulites, and orientation control it., In cases when proper temperature and pressure are maintained during processing, the induced internal stresses may be insignificant,, and annealing is not required., Plastic blends and block copolymers typically contain other low and intermediate, molecular weight additives such as plasticizers, flame-retardants, and UV or thermal stabilizers. During annealing, phase and, micro-phase separation may be enhanced, and bleeding of the additives may be observed. The morphologies of blends and, block copolymers can be affected by processing and quenching conditions. If their, melt viscosities are not matched, compositionallayering perpendicular to the direction, of flow may occur. As in the case of crystalline plastics, the skin may be different both, in morphology and composition. Annealing, may cause more significant changes in the, skin than in the interior., , Plastic Material and Equipment Variable, The subject of plastic materials and, equipment variables are important to understand so products can be properly designed, and processed. Details on MATERIAL, , 127, , VARIABLE are in Chapter 6 and, on EQUIPMENTIPROCESSING VARIABLE are in Chapter 8., , Finite Element Analysis, , Introduction, Designing products is usually performed, based on experience since most products, only require a practical approach (Fig. 1-4)., Experience is also used in producing new, and complex shaped products usually with, the required analytical evaluation that involves stress-strain characteristics of the plastic materials. Testing of prototypes and/or, preliminary production products to meet, performance requirements is a very viable, approach used by many., Classical equations and formulas from engineering handbooks for stress-strain static, and dynamic loads are utilized. Computeraided design analysis such as the use of finite, element analysis (FEA) can be used. FEA, can help a designer to take full advantage, of the unique properties of plastics by making products lighter, yet stronger while at the, same time also saving processing time and, money. The use of FE A has expanded rapidly, over the past decades. Unlike metals, plastics are nonlinear, so they require different, software for analysis, The early software programs were difficult and complex, but gradually the software for plastics has become easier to use. Graphic displays are better, they, consume less time, and are easier to understand (162)., One uses FEA to shorten the lead-time to, less than half. FEA helps to reduce material, costs while lessening the expense of building, prototypes and remachining tools. By eliminating excess material, it can save weight., It can simulate what will happen, allowing, immediate redesign to prevent premature, failure, The designer does less guessing and, more engineering, thereby improving reliability. Accuracy is increased., With the computer hundreds of simultaneous equations can be solved that would take

Page 146 : 128, , 2 Design Influencing Factor, , literally years to solve without a computer., FEA can be defined as a numerical technique, involving breaking a complex problem down, into small subproblems via computer models, that can be solved by a computer. The key to, effective FEA modeling is to concentrate element details at areas of highest stress. This, approach produces maximum accuracy at the, lowest cost., The first step in applying FEA is the construction of a model that breaks a component into simple standardized shapes or, (usual term) elements located in space by a, common coordinate grid system. The coordinate points of the element corners, or nodes,, are the locations in the model where output, data are provided. In some cases, special elements can also be used that provide additional nodes along their length or sides. Nodal, stiffness properties are identified, arranged, into matrices, and loaded into a computer, where they are processed with certain applied loads and boundary conditions to calculate displacements and strains imposed by the, loads (Appendix A: PLASTICS DESIGN, TOOLBOX)., In this method, the modeling technique is, critical because it establishes the structural, locations where stresses will be evaluated. If, a component is modeled inadequately for a, given problem, the resulting computer analysis could be quite misleading in its prediction, of areas of maximum strain and maximum deflection values. An inadequate model could, be quite expensive in terms of computer time., A cost-effective model concentrates on the, smallest elements at areas of highest stress., This configuration provides greater detail in, areas of major stress and distortion, and minimizes computer time in analyzing regions of, the component where stresses and local distortions are smaller., Unfortunately modeling can be a stumbling block because the process of separating a component into elements is not essentially straightforward. Some degree of insight, along with an understanding of how, materials behave under strain, is required to, determine the best way to model a component for FEA. The procedure can be made, , easier by setting up a few ground rules, before attempting to construct the model., For example, in the case of plane stress, analysis, quadrilateral elements should be, used wherever possible. These elements provide better accuracy than corresponding triangular elements without adding significantly, to calculation time. Also, 2-D and 3-D elements should have corners that are approximately right-angled, and should resemble, squares and cubes as much as possible in regions of high strain gradient. Generally, element size should be in inverse proportion to, the anticipated strain gradient with the smallest elements in regions of highest stress., Fundamental, In its most fundamental form, FEA is limited to static, linear elastic analyses. However,, there are advanced finite element computer, software programs that can treat highly nonlinear dynamic problems efficiently. Important features of these programs include their, ability to handle sliding interfaces between, contacting bodies and the ability to model, elastic-plastic material properties. These, program features have made possible the, analysis of impact problems that only a few, years ago had to be handled with very approximate techniques. FEA have made these, analyses much more precise, resulting in better and more optimum designs., , Operational Approach, The opportunity for creative design by, viewing many imaginative variations would, be blunted if each variation introduced a new, set of doubts as to its ability to withstand, whatever stress might be applied. From this, point of view the development of computer, graphics has to be accompanied by an analysis technique capable of determining stress, levels, regardless of the shape of the product., This need is met by FEA., The FEA computer-based technique determines the stresses and deflections in a

Page 147 : 2 Design Influencing Factor, structure. Essentially, this method divides, a structure into small elements with defined stress and deflection characteristics. The, method is based on manipulating arrays of, large matrix equations that can be realistically solved only by computer. Most often, FEA is performed with commercial programs. In many cases these programs require, that the user know only how to properly prepare the program input., FEA is applicable in several types of analyses. The most common one is static analysis, to solve for deflections, strains, and stresses, in a structure that is under a constant set of, applied loads. In FEA material is generally, assumed to be linear elastic, but nonlinear, behavior such as plastic deformation, creep,, and large deflections also are capable of being, analyzed. The designer must be aware that as, the degree of anisotropy increases the number of constants or moduli required to describe the material increases., Uncertainty about a material's properties,, along with a questionable applicability of the, simple analysis techniques generally used,, provides justification for extensive end use, testing of plastic products before approving, them in a particular application. As the use, of more FEA methods becomes common in, plastic design, the ability of FEAs will be simplified in understanding the behavior and the, nature of plastics., FEA does not replace prototype testing;, rather, the two are complementary in nature., Testing supplies only one basic answer about, a design that either passed or failed. It does, not quantify results, because it is not possible, to know from testing alone how close to the, point of passing or failing a design actually, exists. FEA does, however, provide information with which to quantify performance., Safety Factors, , In order to take uncertainties into account, in a product's design, there exist what is familiarly called the safety factory (SF) or sometimes the "factor of ignorance." Observe that, the safety factors have been omitted from, , 129, , most calculations, because different designers working on varying products use the, appropriate criteria for choosing SFs. In general, a SF used based on experience is 1.5 to, 2.5, as is commonly used with metals., Many designers have already used or calculated a safety factor on material, perhaps, without recognizing it such as deciding what, approach is used in determining the tensile secant modulus. The process appears to, be simple and straightforward, but unfortunately things are never quite that simple., The designer must be fully aware of what, one means when one calculates such a factor, or bases a design on it. Improper use of a presumed safety factor may in some case result in, a needless waste of material or in other cases, even product failure. Thus, one must define, what is meant when using a safety factor., Designers unfamiliar with plastic products can use the suggested preliminary safety, factor guidelines in Table 2-11. They provide for extreme safety. Any product designed with these guidelines in mind should, conduct tests on the products themselves, to relate the guidelines to actual performance (Chapter 4, RP PIPES, Stress-Strain, Curves). With more experience, moreappropriate values will be developed targeting to use 1.5 to 2.5. After field service of, Table 2-11, guidelines, , Safety factors a for preliminary, , Type of Load, , Factorb, , Static short-term loads, Static long-term loads, Variable of changing loads, Repeated loads, Fatigue or load reversal, Impact loads, , 1.5-2.5, 2.0-5.0, , 4-10, 5-15, 5-15, 10-20, , aThe material strength determined is the minimum required, not the average or maximum, which is what, is normally provided on manufactures' published data, sheets., Low-range values represent situations where failure is, not critical; the higher values are for where failure is, critical., Note: These values are intended for preliminary design, analysis only and are not to be used in place of thorough, product design.

Page 148 : 130, , 2 Design Influencing Factor, , the preliminary designed products have been, obtained, action should be taken to evaluate, reducing your SF in order to reduce costs., Structures are designed where the SF approaches 1.2 such as in aircraft because extreme close controls are made that range, from the raw materials to their final assembly, with initial flight tests., There are no hard-and-fast rules to follow, in setting safety factors for any given material, unless experience exists. The most important, consideration is of course the probable consequences of failure. For example, a little extra deflection in an outside wall or a hairline, crack in one of six internal screw bosses might, not cause concern, but the failure of a pressure vessel or aircraft wing might have serious, safety or product-liability implications., Before putting any product onto the market, prototype tests should be run at their, most extreme operating conditions. For instance, the maximum working load should, be applied at the maximum temperature and, in the presence of any chemicals that might, be encountered in the end use. Furthermore,, the loads, temperatures, and chemicals to, which a product will be exposed prior to, reaching its end use must not be overlooked., Impact loading should be applied at the lowest temperature expected, including what occurs during shipping and assembly. The effects of variations in plastic lots and molding, conditions must also be considered. The results should be to provide more logical SFs, pertinent to the product and the materials, used in it., Many situations discovered during the, testing of preproduction products can be, corrected with a selective use of increased, thickness in walls, ribs, and gussets or by, eliminating stress concentrations. Changing a, material to another grade of the same plastic or to a different plastic with a suitable, , mechanical property profile might also be the, solution., Uncertainty, , In addition to the basic uncertainties of, graphic design, a designer may also have to, consider additional conditions such as:, 1. Variations in material properties. Because no two plastic (or steel, for that matter), melts are exactly alike, some may have inclusions and so on, the strength properties given, in materials tables are usually average values., If the value stated is a manufacturer's value, it, probably is the minimum value, which can significantly reduce or eliminate its uncertainty., 2. Effect of size in stating material strength, properties. Property tables, unless otherwise, stated for plastics, metals, and so on, list, strength values based on a specified size, yet, larger components generally fail at a lower, stress than a similar smaller component made, of the same material., 3. Type of loading. A simple static load, is relatively easy to recognize, but there are, cases that fail between impact and suddenly, applied loads. One thus takes into account infrequently applied fatigue loading mixed with, some shock loads, as for example cams, links,, or feeding devices., 4. Effect of processes. The fabricating operations for plastics, steel, glass, and so forth, may, and usually do, introduce unwanted, stress concentrations and residual stresses if, not properly processed., 5. Overall concern for human safety. All, design must consider safety of the user who, may be near or in contact with the product. Unexpected overloads or other situations may cause breakage and considerable, bodily harm.

Page 149 : 3, Product Design Feature, , Introduction, , Design problems with the other conventional materials of construction are usually, solved with the aid of textbooks or handbooks that refer the reader to data sheets, where the characteristics of a specific material are listed. However, products designed, with plastics involve some special considerations when using these textbooks or handbooks as reviewed in Chapter 2., Plastic material suppliers provide material, data sheets for each grade they produce. At, first glance, there could be a tendency to apply the plastic information in a similar fashion to that of other materials. If such a procedure were to be followed, the result would, not only lead to disappointment but also perhaps even to failure for many products. The, reason for the difference in treating the plastic data sheets from those of other materials, is the behavior of plastics under load and under varying environmental conditions, which, normally are not factors with other materials, such as steel (Chapter 2)., The reaction of plastics under test conditions to their behaviors is explained in other, Chapters, particularly Chapters 2, 5 to 7. Until this phase of the information is properly, understood, it is best not to apply the numbers from the data sheet, for they can be a, source of misinterpreted information. A con-, , siderable segment of the data is usually only, usable for preliminary comparative evaluation of various grades of materials. Even in, this case one must be sure that the test procedure and the test conditions were the same., In many cases, product use conditions are, very different from material suppliers data, sheet test conditions; therefore, it would not, be safe to attempt interpolating the available information. The needed data should be, obtained under conditions simulating factors, such as the same specific test procedure, fabricating, and end use requirements. The reader, should recognize that knowledge of plastic, material tests is a prerequisite to understanding the meaning and value of data for design, purposes as presented in the suppliers' sheets, (Chapter 5)., Another factor to consider in the early, stages of design is material selection in relation to cost per volume rather than by weight., This subject volume vs. weight will be reviewed latter in this chapter entitled Analysis, Method. Since the material value in a plastic, product is usually over one-half of its overall, cost, it becomes important to select a candidate material with extraordinary care., After a material type and grade that will, fulfill performance requirements has been, decided upon, steps should be taken to ensure, that degrading features such as inside sharp, comers, nonuniform wall thicknesses, etc., are

Page 150 : 132, , 3 Product Design Feature, , eliminated or reduce as much as possible, from the design. There are features that can, degrade properties such as those reviewed, latter in this Chapter entitled FEATURES, INFLUENCING PERFORMANCE., Design Analysis, , Overview, In structural applications for plastics,, which generally include those in which the, product has to resist substantial static and/or, dynamic loads, it may appear that one of, the problem design areas for many plastics, is their low modulus of elasticity. The moduli, of unfilled plastics are usually under 1 x 106, psi (6.9 x 103 MPa) as compared to materials, such as metals and ceramics where the range, is usually 10 to 40 X 106 psi (6.9 to 28 x 104, MPa). However with reinforced plastics, (RPs) the high moduli of metals are reached, and even surpassed as summarized in Fig. 2-6., Since shape integrity under load is a major consideration for structural products, low, modulus plastic products are designed shapewise for efficient use of the material to afford maximum stiffness and overcome their, low modulus. These type plastics and products represent most of the plastic products, produced worldwide (1, 3, 6, 9,10,14,20,28,, 35,36, 62, 64)., , Pseudo-Elastic Design Method, Throughout this book as the viscoelastic, behavior of plastics has been described it has, been shown that deformations are dependent, on such factors as the time under load and, the temperature. Therefore, when structural, components are to be designed using plastics it must be remembered that the standard equations that are available (such as in, Figs. 3-1 and 3-2) for designing springs, beams,, plates, and cylinders, and so on have all been, derived under the assumptions that (1) the, strains are small, (2) the modulus is constant,, (3) the strains are independent of the loading rate or history and are immediately re-, , versible, (4) the material is isotropic, and (5), the material behaves in the same way in tension and compression., Since these assumptions are not always justifiable when applied to plastics, the classic, equations cannot be used indiscriminately., Each case must be considered on its merits,, with account being taken of such factors as, the time under load, the mode of deformation, the service conditions, the fabrication, method, the environment, and others. In particular, it should be noted that the traditional, equations are derived using the relationship, that stress equals modulus times strain, where, the modulus is a constant. From the review in, Chapter 2 it should be clear that the modulus of a plastic is generally not a constant., Several approaches have been used to allow, for this condition. The drawback is that these, methods can be quite complex, involving numerical techniques that are not attractive to, designers. However, one method has been, widely accepted, the so-called pseudo-elastic, design method., In this method appropriate values of such, time-dependent properties as the modulus, are selected and substituted into the standard equations. It has been found that this, approach is sufficiently accurate if the value, chosen for the modulus takes into account the, projected service life of the product and/or, the limiting strain of the plastic, assuming that, the limiting strain for the material is known., Unfortunately, this is not just a straightforward value applicable to all plastics or even to, one plastic in all its applications. This type of, evaluation takes into consideration the value, to use as a safety factor. If no history exist a, high value will be required. In time with service condition inputs, the SF can be reduced, if justified., This modulus value is often arbitrarily chosen, although several methods have been suggested for arriving at a suitable value. One is, to plot a secant modulus based on 1 % strain, or that is 0.85% of the initial tangent modulus (Chapter 2, SHORT-TERM LOAD BEHAVIOR). However, for many plastics, particularly the crystalline TPs, this method is, too restrictive, so in most practical situations, the limiting strain is decided in consultation

Page 151 : 3 Product Design Feature, , r., ~BI, RECTANGULAR, , 133, I-BEAM, , A~bd, , na, , I_b--!, , A~, , bd- h(b- t), , c~~, , c~f, , '~~f, , I ~, , bd 3 - h3(b - t), 12, , Z~, , bif - h3 (b - t), 6b, , z~!2f-, , H-BEAM, CIRCULAR, , A~1t:t, , A~bd-h(b-t), , c~~, , c~~, 2sb3 +ht 3, 12, , '~~f, , I~---, , z=~~3, , 2sb3 + ht3, 6b, , Z~---, , C-BEAM, , TUBE, , A ~ 1t(do' - d,z), 4, , A~, , bd- h(b- t), , c~~, , do, , c~2, , I~ 1t(do4 - d;4), , 64, , 1t(do'- d;4), , z~~, , Tor RIB, , I~, , bd3 _ h3(b - t), 12, , Z~, , bd3 _ h3 (b_ t), 6d, , A~, , bd- h(b- t), , U-BEAM, , A~bs+ht, , c~d- d 2t+s 2(b_t), 2(bs+ ht), , c~b- 2tfs+ht2, 2A, , I~ 2sb3 + ht 3, 3, , _, , A(b- c/, , Z'~_I­, , d- c, , I~ tc3 + b(d- c}'- (b- t)(d- c- si, 3, , Z'~_I­, , b-c, , Fig.3-1 Properties of some common cross-sections based on mechanical engineering analysis (na =, neutral axis)., , between the designer and the plastic material's manufacturer. Once the limiting strain, is known, design methods based on its static, and/or dynamic load becomes rather straightforward., , Analysis Method, Plastics have some mechanical characteristics that differ significantly from those of, , the familiar metals. Consequently, design analysts may have less confidence in these materials and in their own ability to design with, them. Materials selection thus may tend to, confine itself to familiar materials, or else, products may be overdesigned, and failures, may even occur in service due to faulty, design., Also, the statistics available on materials, are often presented so as to favor a particular bias, which complicates the process of

Page 152 : 3 Product Design Feature, , 134, , S/MPL Y SUPPORTED BEAM, CONCENTRA TED LOAD AT CENTER, , o=~, , (at load), , CANTILEVERED BEAM (ONE END FIXED), CONCENTRATED LOAD AT FREE END, , (at support), , o=~, , (at load), , y=~, , Z, , 4Z, , y=~, , (at load), , 3EI, , 48EI, SIMPL Y SUPPORTED BEAM, UNIFORML Y DISTRIBUTED LOAD, , CANTILEVERED BEAM (ONE END FIXED), UNIFORML Y DISTRIBUtED LOAD, , e:::=rt, I, , F (total load), , (at center), , (at center), , 0, , = FL, , (at support), , 8Z, , Y = SFL3, , (at support), , 384EI, , 0=, , FL, 2Z, , y=~, 8EI, , BOTH ENDS FIXED, CONCENTRATED LOAD A T CENTER, , BOTH ENDS FIXED, UNIFORML Y DISTRIBUTED LOAD, , F (total load), , 1 4 - - - L------tl~, y, , (at supports), , 0=, , FL, 8Z, , (8t load), , Y, , (at supports), , o=~, , (at center), , Y=, , 12Z, , FL3, 384EI, , Fig. 3·2 Maximum stress and deflection equations for selected beams., , assessing their relative merit and adds to the, confusion. Essentially, what the design analyst requires is relevant and credible design, data, together with valid methods for calcu-, , lating, predicting, and optimizing a product's, performance. This type information has been, available for over a half century. These methods may involve design formulas and charts

Page 153 : 3 Product Design Feature, , 135, , Table 3-1 Examples of the mechanical properties of metal and plastic materials, , Glass-fiber, Reinforced, Plastics (GRP), , Property, , Aluminum, , Mild Steel, , Polypropylene (PP), , Tensile modulus (E), 106 GN/m2 (psi), Tensile strength (a), 1()3 MN/m2 (psi), Specific gravity (S), , 70 (10), , 210 (30), , 1.5 (0.21), , 15 (2.2), , 400 (58), , 450 (65), , 40 (5.8), , 280 (40.5), , 2.7, , 7.8, , 0.9, , 1.6, , GN/m2 kPa., , such as those induded in computer-aided designs (CADs) that provide an opportunity for, plastics to be handled on a basis equivalent to, that of other materials. The CAD's software, includes applicable static and dynamic data., In the past almost all the methods for the, design analysis of plastics were base on models of material behavior relevant to traditional metals, as for example elasticity and, plastic yield. These principles were embodied, in design formulas, design sheets and charts,, and in the modern techniques such as those, of CAD using finite element analysis (FEA)., The design analyst was required only to supply appropriate elastic or plastic constants for, the material, and not question the validity of, the design methods. Traditional design analysis is thus based on accepted methods and, familiar materials, and as a result many designers have little, if any, experience with such, other materials as plastics, wood, and glass., Under these circumstances it is both tempting and common practice for designers to, treat plastics as though they were traditional, materials and to apply familiar design methods with what seem appropriate materials, constants. It must be admitted that this pragmatic approach does often yield acceptable, results. However, it should also be recognized, that the mechanical characteristics of plastics, are different from those of metals, and the, validity of this pragmatic approach is often, fortuitous and usually uncertain., It would be more acceptable for the design analysis to be based on methods developed specifically for the materials, but this, action will require the designer of metals to, accept new ideas. Obviously, this acceptance, becomes easier to the degree that the new, , methods are presented as far as possible in, the form oflimitations or modifications to the, existing methods discussed in this book., Table 3-1 gives typical mechanical property data for four materials, the exact values of which are unimportant for this discussion. Aluminum and mild steel have been, used as representative metals and polypropylene (PP) and glass fiber-TS polyester reinforced plastics (GRP) as representative plastics. Higher-performance types could have, been selected for both the metals and plastics,, but those in this table offer a fair comparison, for the explanation being presented., Also, it appears from the data that these, metals are much stiffer and significantly, stronger than the plastics. This approach to, evaluation could eliminate the use of plastics, in many potential applications, but in practice it is recognized by those familiar with the, behavior of plastics that it is the stiffness and, strength of the product that is important, not, its material properties., To illustrate the correct approach, consider, applications in which a material is used in, sheet form, as in automotive body panels, and, suppose that the service requirements are for, stiffness and strength in flexure. First imagine four panels with identical dimensions that, were manufactured from the four materials, given in Table 3-1. Their flexural stiffnesses, and strengths depend directly on the respective material's modulus and strength. All the, other factors are shared in common with the, other materials, there being no significantly, different Poisson ratios. Thus, the relative, panel properties are identical with the relative material properties illustrated in Fig. 3-3., Obviously, the metal panels will be stiffer and

Page 154 : 136, _ 200, , 3 Product Design Feature, , ~oo, , ~, , E, , .._, , E, , :z, , !, , 200, , t>, , Fig. 3-3 The relative stiffness (open bars) and, strength (shaded bars) of sheets made from the, materials listed in Table 3-1., , significantly stronger than the plastic ones,, based on the identical panel dimensions resulting in the use of equal volumes of materials., Obviously, the lower densities of plastics, allow them to be used in thicker sections than, metals, which will have a significant influence, on panel stiffness and strength. For example, assume that the four panels have equal, weights and therefore different thickness (t)., When the panels are loaded in flexure, their, stiffnesses depend on (Et 3 ) and their strength, on (at 2 ) where E and a are the material's, modulus and its strength. For panels of equal, weight it follows that their relative stiffnesses, are governed by (E/s 3 ) and their relative, strengths by (0'/ s2) where s denotes specific, gravity. These relative panel properties illustrated in Fig. 3-4, show that the plastics, now appear in a much more favorable light., Figures 3-3 and 3-4 present the same basic data from Table 3-1, but in two different, forms and the superficial use of either form, can be misleading., In practice, metals and plastics usually do, not have to compete under either of the extreme conditions of equal volume or equal, weight, and their positioning between these, extremes will depend on the requirements of, , ..., , ~, , E 4, , Z, , ~, , '"III, , iU 2, , 100, , ~, ~, , E, , ~, , -.., , so ..., , 0, , Fig. 3-4 The relative plate stiffness (open bars), and strength (shaded bars) in flexure for panels of, equal weight., , the particular application. For vehicle body, panels, plastics may be used with thicker sections than their metals counterparts (that is,, not of equal volume), but the desire to save, weight will ensure that they are not used to, their extremes. Thus the designer has the opportunity to balance out the requirements for, stiffness, strength, and weight saving., For the materials data given in Table 3-1 a, G RP panel having 2.4 times the thickness of a, steel panel has the same flexural stiffness but, 3.6 times its flexural strength and only half, its weight. The tensile strength of the GRP, panel would be 50% greater than that of the, steel panel, but its tensile stiffness is only 17%, that of the steel panel. The designer's interest, in this GRP panel would then depend in this, context on whether tensile stiffness was what, was required., No general conclusions should be drawn, on the relative merits of various materials, based on this description alone. These examples have been presented merely to illustrate, the dangers of superficially interpreting property data and of making dogmatic or generalized statements about the relative merits of, various classes of materials. Similar remarks, could be made with respect to various materials' costs and energy contents, which can also, be specified per unit of volume or weight. If, these factors are to be treated properly, they, too must relate to final product values, including the method of fabrication, expected lifetime, repair record, in-service use, and so on., One important conclusion illustrated by, the example given is that plastic products, are often stiffness critical, whereas metal, products are usually strength critical. Consequently, metal products are often made stiffer, than required by their service conditions, to, avoid failure, whereas plastic products are often made stronger than necessary, for adequate stiffness. Thus, in replacing a component in one material with a similar product in, another material is not usually necessary to, have the same product stiffness and strength., It follows that general statements about energy content or cost per unit of stiffness or, strength, as well as other factors, should be, treated with caution and applied only where, relevant.

Page 155 : 3 Product Design Feature, This review identifies the need for using, design analysis methods appropriate for plastics. It also indicates the uncertainty of using, with plastics methods derived from metals,, and demonstrates the dangers of making generalized statements about the relative merits, of different classes of materials. The designer, who has basically no familiarity with plastics, needs to be receptive to the different methods of handling them., It is necessary to keep an open mind when, designing products with plastics, rather than, limiting the design to being an exact replica, of the metal product. Let us assume from this, point on that this approach is accepted, so, a more-detailed examination of the needs of, the design analysis methods can follow., Analysis Requirement, It should be evident that the full spectrum, of the possible materials and applications in, load-bearing situations involves many factors, that may have to be taken into account. Fortunately, most products involve only a few, factors, and others will not be significant or, relevant. Regardless, the methods of design, analysis must be made available to handle, any possible combinations of such factors as, the materials' characteristics, the product's, shape, the loading mode, the loading type,, and other service factors and design criteria., , Material Characteristic, The wide choice available in plastics makes, it necessary to select not only between TPs,, TSs, reinforced plastics (RPs), and elastomers, but also between individual materials within each family of plastic types (Chapters 6 and 7). This selection requires having, data suitable for making comparisons which,, apart from the availability of data, depends, on defining and recognizing the relevant plastics behavior characteristics. There can be,, for instance, isotropic (homogeneous) plastics and plastics that can have different directional properties that run from the isotropic, to anisotropic. Here, as an example, certain, , 137, , engineering plastics and RPs that are injection molded can be used advantageously to, provide extra stiffness and strength in predesigned directions., Reinforced plastic It can generally be, claimed that fiber based RPs offer good potential for achieving high structural efficiency, coupled with a weight saving in products, fuel, efficiency in manufacturing, and cost effectiveness during service life. Conversely, special problems can arise from the use of RPs,, due to the extreme anisotropy of some of, them, the fact that the strength of certain constituent fibers is intrinsically variable, and because the test methods for measuring RPs', performance need special consideration if, they are to provide meaningful values., Some of the advantages, in terms of high, strength-to-weight ratios and high stiffnessto-weight ratios, can be seen in Figs. 3-5 and, 2-6, which shows that some RPs can outperform steel and aluminum in their ordinary forms. If bonding to the matrix is good,, then fibers augment mechanical strength by, accepting strain transferred from the matrix, which otherwise would break. This occurs until catastrophic debonding occurs. Particularly effective here are combinations of, fibers with plastic matrices, which often complement one another's properties, yielding, products with acceptable toughness, reduced, thermal expansion, low ductility, and a high, modulus (10, 62, 92)., As a further advantage, RPs make effective use of some materials that are otherwise, , Stress, , Epoxy resin with, 30%gl ..., Epoxy resin, , Strain, , Fig.3-5 Examples of the tensile properties of different materials.

Page 156 : 138, , 3 Product Design Feature, , unable to stand alone. When incorporated, into plastics, in particular those such as TS, unsaturated polyesters or phenolics, particles, (fibers, flakes, etc.) can reduce manufacturing, shrinkage and yield a more usable product. In, service, zero thermal expansion coefficients, can be achieved by a suitable choice of starting materials., , points, and ribs will determine its shape. Also, influencing the design decision will be the, method offabricating the product. The load's, magnitude and distribution can be difficult, to specify, especially in a system composed, of several interacting components of the, product (37)., , Load, Design Concept, , Design analysis is required to convert applied loads and other external constraints, into stress and strain distributions within a, product and calculate the associated deformations. The nature and complexity of these, calculations will be strongly influenced by the, product's shape. The designing will be simplified if the product approximates a simple engineering form like a plate or shell, beam or, tube, or some combination of idealized forms, such as a box structure. In such cases standard design formulas can be used, with appropriate parameters relating to the factors, being reviewed: short- and long-time loadings, creep, fatigue, impact, and so on using, viscoelastic materials (Chapter 2)., There are of course products whose shapes, do not approximate a simple standard form, or where more detailed analysis is required,, such as a hole, boss, or attachment point in, a section of a product. With such shapes the, component's geometry complicates the design analysis for plastics, glass, metal, or other, material and may make it necessary to carry, out a direct analysis, possibly using finite element analysis (FEA) followed with prototype testing. Examples of design concepts are, presented., , Loading Mode, Loads applied on products induce tension,, compression, flexure, torsion, and/or shear,, as well as distributing the loading modes. The, product's particular shape will control the, type of materials data required for analyzing, it. The location and magnitude of the applied, loads in regard to the position and nature of, such other constraints as holes, attachment, , In a simplified approach the first step in analyzing any product is to determine the loads, to which it will be subjected. These loads will, generally fall into one of two categories, directly applied loads and strain-induced loads., Directly applied loads are usually easy to understand. They are defined loads that are applied to defined areas of the product, whether, they are concentrated at a point, line, or, boundary or distributed over an area. The, magnitude and direction of these loads are, known or can easily be determined from the, service conditions. Figure 3-2 shows examples, of directly applied loads., Frequently, a product becomes loaded, when it is SUbjected to a defined deflection., The actual load then is a result of the structural reaction of the product to the applied, strain. Unlike directly applied loads, straininduced loads are dependent on the modulus, of elasticity and, with TPs, will generally decrease in magnitude over time. Many assembly and thermal stresses could be the result, of strain-induced loads. They include metal, insert press fits in the plastic and clamping or, screw attachments., When a load is applied, if the product, is to remain in equilibrium there must be, equal force acting in the opposite direction., These balancing forces, as an example, are, the reactions at the supports. For purposes of, structural analysis there are several supports, conditions that have been defined. The free, (unsupported), simply supported, and fixed, supports are the most frequently encountered. The free (unsupported) condition occurs where the edge of a body is totally free to, translate or rotate in any direction. The fixed, (clamped or built-in) support condition at the, end of a beam or plate prevents transverse, displacement and rotation. The condition can

Page 157 : 3 Product Design Feature, be thought of as its ends support firmly embedded into fixed solid walls. In practice this, condition rarely exists in its pure form, especially with plastic, since the mounting points, of the products usually have some give via, factors such as relaxation., The other support conditions include a, guided system that is similar to the free, end except that its edge is prevented from, rotating. In a simple support condition transverse displacement in one direction is restricted. There is the held (pinned) situation, that is similar to the simply supported, one except that here only rotations are, allowed., , 139, , 5 tress levels, ---- 2000 p.s.i., - - 3000 p.s.i., , 3, ..".,.~-----.,, , '", , '", , I, I, , I, I, , I, I, , I, \, , .~ 1, iii, , \, , Co, Q), Q), , u O~~--~----~~--~~----~--o, 40, 80, 120, 160, Time, hr., , Loading Type, The mechanical behavior of plastics on, time-dependent applied loading can cause, different important effects on materials viscoelasticity. Loads applied for short times and, at normal rates (Chapter 2) causes material, response that is essentially elastic in character. However, under sustained load plastics,, particularly TPs, tend to creep, a factor that, is included in the design analysis., Products can also be SUbjected to intermittent loading involving successive creep and, recovery over relatively long time scales. It, is not unusual, for instance, for creep deformation arising during one loading phase to, be only partly recovered in the unloading, cycle, leading to a progressive accumulation, of creep strain (Figs. 3-6 and 3-7) and possibly resulting in creep rupture. An analogue, of creep behavior is the stress-relaxation cycle that can occur under constant strain., , Fig.3-7 Examples are shown of elasticity changes for engineering TPs involving one cycle of, loading and unloading. The curves show effects, of stress and time under load and strain recovery, after loading., , This behavior is particularly relevant with, push-fit assemblies and bolted joints that rely, on maintaining their load under constant, strain. Special design features or analysis may, be required to counteract excessive stressrelaxation., In many applications, intermittent or dynamic loads arise over much shorter time, scales. Examples of such products include, chair seats, panels that vibrate and transmit noise, engine mounts and other antivibration products, and road surface-induced, loads carried to wheels and suspension systems. Plastics' relevant properties in this regard are material stiffness and internal damping, the latter of which can often be used to, advantage in design (Chapter 2). Both properties depend on the frequency of the applied, loads or vibrations, a dependence that must, be allowed for in the design analysis. The possibility of fatigue damage and failure must, also be considered., Load-Bearing Product, , Tim.~, , Fig. 3-6 An example of intermittent loading involving successive creep strain and recovery., , A fundamental concept in structural analysis is that the structure as a whole and each, of its elements together are in a state of

Page 158 : 140, , 3 Product Design Feature, , equilibrium. This means that there are no unbalanced forces of tension, compression, flex,, or shear acting on the structure at any point., All the forces counteract one another, which, results in equilibrium. When all the forces, acting on a given element in the same direction are summed up algebraically, the net effect is zero, with no acceleration. However,, the object does respond to the various forces, internally. It can be pushed or pulled and, otherwise deformed, with internal stresses of, varying types and magnitudes accompanying, these deformations., Basically, designing a load-bearing product with any material involves first selecting a suitable material and then specifying, the shape into which it is to be formed or, assembled. One important aspect of shape, is its effect on internal stress. As the crosssectional area of a product increases for a, given load, the stresses are reduced. Design, is concerned with determining the stresses, for a given or hypothetical shape and subsequently adjusting the shape until the stresses, are neither high enough to risk fracture nor, low enough to suggest that material is being, wasted., Stress analysis involves using the descriptions of the product's geometry, the applied, loads and displacements, and the material's, properties to obtain closed-form or numerical expressions for internal stresses as a function of the stress's position within the product, and perhaps as a function of time as well. The, term engineering formulas refers primarily, to those equations reviewed previously and, given in engineering handbooks by which the, stress analysis can be accomplished., Multiaxial Stresses and Mohr's Circle, , Sophisticated design engineers unfamiliar, with plastics' behavior will be able to apply the information contained in this and, other chapters to applicable sophisticated, equations that involve such analysis as multiple and complex stress concentrations. The, various machine-design texts and mechanical engineering handbooks listed in the Appendix A: PLASTICS TOOLBOX and REF-, , ERENCES section at the end of this book, provide detailed analysis of these stressconcentration factors and other load-bearing, parameters., Many structural products are stressed in, a manner that is more complex than simple tension, compression, flex, or shear. Because yielding will also occur under complex, stress conditions, a yield criterion must be, specified that will apply in all stress states., Any complex stress state can be resolved, into three normal components acting along, three mutually perpendicular (X, Y, Z) axes, and into three shear components along the, three planes of those axes. Then, by making, a proper choice it is possible to find a set of, three axes along which the shear stresses will, be zero. These are the principal axes, with the, normal stresses along them being called the, principal stresses. Determining these principal stresses in a complex loaded member, is the responsibility of the designer, a task, normally performed by using approaches, such as Mohr's circle and its associated, relationships., Design Criteria, , The nature of design analysis obviously, depends on having product-performance requirements. The product's level of technical, sophistication and the consequent level of, analysis that can be justified costwise basically relate to control of these requirements., The analysis also depends on the design criteria for a particular product. If the design is, strength limited, to avoid component failure, or damage, or to satisfy safety requirements,, it is possible to confine the design analysis, simply to a stress analysis. However, if a plastic product is stiffness limited, to avoid excessive deformation from buckling, a full stressstrain analysis will likely be required., Even though many potential factors can, influence a design analysis, each application, fortunately usually involves only a few factors. For example, TPs' properties are dominated by the viscoelasticity relevant to the, applied load. Anisotropy usually dominates, the behavior of long-fiber RPs.

Page 159 : 141, , 3 Product Design Feature, , HAT SECTION, CROWNING, CORRUGA TION, , METAL, REINFORCEMENT, , BI·DIRECTIONAL, CORRUGA TION, , Fig. 3-8, , DOMING, , Geometric shapes., , Geometrical Shape, There are different techniques that have, been used for over a century to increase the, modulus of elasticity of plastics. Orientation, or the use of fillers and/or reinforcements, such as RPs can modify the plastic. There, is also the popular and extensively used approach of using geometrical design shapes, that makes the best use of materials to improve stiffness even though it has a low modulus. Structural shapes that are applicable to, all materials include shells, sandwich structures, and folded plate structures (Fig. 3-8)., These widely used shapes employed include, other shapes such as dimple sheet surfaces., They improve the flexural stiffness in one or, more directions., , E1 theory In each case displacing material from the neutral plane makes the improvement in flexural stiffness. This increases, the EI product that is the geometry material, index that determines resistance to flexure., The EI theory applies to all materials (plastics, metals, wood, etc.). It is the elementary, mechanical engineering theory that demonstrates some shapes resist deformation from, external loads., This phenomenon stems from the basic, physical fact that deformation in beam or, sheet sections depends upon the mathemat-, , ical product of the modulus of elasticity, (E) and the moment of inertia (1), commonly expressed as E1. This theory has been, applied to many different plastic constructions including solid and different sandwich, structures., In the case of plastics, emphasis is on the, way plastics can be used in these structures, and why they are preferred over other materials. In many cases plastics can lend themselves to a particular field of application only, in the form of a sophisticated lightweight stiff, structure and the requirements are such that, the structure must be of plastics. In other, instances, the economics of fabrication and, erection of a plastics lightweight structure, and the intrinsic appearance and other desirable properties make it preferable to other, materials., When compared to other materials, formability into almost any conceivable shape is, one of plastics' design advantages. It is important for designers to appreciate this important characteristic. Both the plastic materials, and different ways to manufacture products, provide this rather endless capability (Chapter 8). Shape, which can be almost infinitely, varied in the early design stage, is capable, for a given volume of materials to provide a, whole spectrum of strength properties, especially in the most desirable areas of stiffness, and bending resistance. With shell structures,

Page 160 : 142, , 3 Product Design Feature, , plastics can be either singly or doubly curved, via the different processes and so on., There are different design approaches to, consider as reviewed in different engineering, textbooks concerning specific products (Appendix A: PLASTICS TOOLBOX). They, range from designing a drinking cup to a compIe x shape such as the roof of a house to, a wing structure. As an example shapewise, consider a house to stand up to the forces of, a catastrophic hurricane. Low pitch roofs are, less vulnerable than steeper roofs because the, same aerodynamic factors that make an airplane fly can lift the roof off the house. Also,, the roof requires being properly attached to, the building structure., Other examples include the advantage of, basic beam structures as well as hollow channel, I -shape, T-shape, etc. They are used, to provide more efficient strength-to-weight, products and so forth. While this construction may not be as efficient as the sandwich, panel, it does have the advantage that it can, be molded, extruded, etc. directly in the required configuration at a low cost and the, relative proportions be designed to meet the, flexural, etc. requirements. One of the pot entiallimitations is that generally it imparts increased stiffness in one direction much more, than in the other. However processing techniques can be used to develop bidirectional, or any other directional properties such as, combining extrusion with filament winding., In most cases, plastic products can take advantage of a basic beam structure in their, design. Hollow-channel, 1-, and T-shapes designed with generous radii (and other basic, plastic flow considerations) rather than sharp, corners are more efficient on a weight basis in, plastics because they use less material, thus, provide a high moment of inertia, etc. The, moments of inertia of such simple sections,, and hence their stresses and deflections, can, be fairly easily calculated, using simple engineering equations (Fig. 3-1)., Rib, , In the discussion of uniform wall thickness,, ribbing was one of the suggested remedies., Ribs are also used to increase load-bearing, requirements when calculations indicate wall, , thicknesses are above recommended values., They are provided for spacing purposes, for, supporting components, etc. The first step, in designing a rib is to determine dimensional limitations followed by establishing, what shape the rib is to have in order to realize a product with good strength and satisfactory appearance that can be produced, economically., Unless the reinforcing ribs are added in the, correct engineered proportions, some additional material may be used and placed so, that it creates high stresses, actually decreasing the loads that cause yielding or fracture., Lengthy equations for the moment of inertia and for deflection and stress are normally, required to determine the effect of ribs on, stress. However, nondimensional curves have, been developed to allow quick determination, of proper rib proportions and a corresponding program for a pocket calculator or computer will allow for obtaining greater precision when required (Fig. 3-9)., If performance calculations indicate wall, thicknesses well above those recommended, for a particular material, one of the solutions, to the problem is to find equivalent crosssectional properties by ribbing. Heavy walls, can be responsible for reduction in properties, due to poor heat conductivity during fabrication, thus creating temperature gradients, throughout the cross section, and thereby, causing residual stresses. Cycle times are usually longer, thus adding another potential, cause for stresses when using too short a cycle time. Also, close tolerance dimensions are, more difficult to maintain, material is wasted,, quality is degraded, and material and processing costs are increased., Solid plastic wall thicknesses for most materials should be targeted to be below 0.2 in., and preferably around 0.125 in. in the interest, of avoiding the above pitfalls. In most cases, ribbing will provide a satisfactory solution; in, other cases sandwich structures or reinforced, materials may have to be considered. As reviewed elsewhere when presenting the ideal, target to meet the best design such as the thinner wall just reviewed, does not mean that a, thicker wall can not be processed, etc. The, thicker wall can be processed requiring closer, process controls (Chapter 8).

Page 161 : 3 Product Design Feature, , 143, , primary rib, , Section, , A~A, , Conventional isogrid, , Lt'"_.-../' Node, , A, , b, (width), , ~s, , -I r- tl, , :=:::::;t'---., , T'T, Secondary rib, Section 8-8, , Fig. 3-9, , Thin-skinned structures with integral ribbing to carry edge loads., , Rib design An example of how ribbing, will provide the necessary equivalent moment of inertia and section modulus will be, given. A flat plastic bar of 1% in. x 3/8 in., thick and 10 in. long, supported at both ends, and loaded at the center, was calculated to, provide a specified deflection and stress level, under a given load. The favorable material, thickness of this plastic is 0.150 in. Using, , judgment as a guide, it would appear that, the l 11z in. width would require about two, ribs. So, as a starting point, calculate the, equivalent cross-sectional data as if we were, dealing with two "T" sections., According to the handbooks under "Stress, and Deflections in Beams" and "Moments of, Inertia," etc., the moment of inertia and resistance to deflection expresses the resistance

Page 162 : 3 Product Design Feature, , 144, , Case, , Moment, Of, Inertia, , 1, , Increase, In, Weight, , .0208, , 700%, , 100%, , 7, , Add Vs"wx, W'HRib, , .0048, , 85%, , 6.25%, , 14, , AddV."wx, W'HRib, , .0064, , 146%, , 12.5%, , 12, , Add Vs"wx, W'HRib, , ,0118, , 354%, , 12.5%, , 28, , AddW'wx, W'HRib, , .0194, , 646%, , 25%, , 26, , Shape, , Change, , ~, , Base, 2"x v.", , .0026, , 2, , -f3-, , Double, Height, , 3, , -E?-, , 4, , -~-, , -T-qy-, , 5, 6, , Increase, In, , Ratio, , _1_, WI., , Fig. 3-10 Examples of ways in using ribs to increase rigidity and reduce weight., , to stress by the section modulus. By finding a, cross section with the two equivalent factors,, we will ensure equal or better performance., Summarizing this subject, the moment of inertia can be changed substantially by adding, ribs or gussets or some combination of them., As shown in Figs. 3-10 and 3-11 and, Table 3-2, there is a better way to achieve, this result and still keep weight at a minimum by using ribbing, if space exists for it., The views include sections of equal stiffness., Adding ribs to a part maintains its thin walls, and thus allows faster fabricating cycles. Summarizing this subject, it is possible to reduce, the cross-sectional area of a product and con-, , sequently reduce the amount of material used, in it, with a corresponding weight reduction., Beam, , In simple beam-bending theory a number, of assumptions must be made, namely that, (1) the beam is initially straight, unstressed,, and symmetrical; (2) its proportional limit is, not exceeded; (3) Young's modulus for the, material is the same in both tension and compression; and (4) all deflections are small so, that planar cross-sections remain planar before and after bending. The maximum stress, , Aluminum, , Zinc, , Valox 420 plastic, , E = 10.3 x 10 6, , E = 2.0 x 10 6, , E = 1.2 x 10 6, , 1, E1, , = 0.0049, =, , Area, Wt/in, , I, , = 0.0254, =, , 5.08 x 10 4, , E1, , = 0.283, , Area, , = 0.446, , In., , oz. Wt/in, , 5.08 x 10 4, , = 0.489, = 2.01, , I, , = 0.0424, , El, , = 5.08, , Area, , oz, , x 10 4, , = 0.170, , Wt/in = 0.149 oz, , Fig.3-11 Different cross-sectional TP polyester profiles with equivalent stiffness in bending.

Page 163 : 145, , 3 Product Design Feature, Table 3-2, , Design examples to obtain the same part rigidity for a section 1 ft. x 2 ft., , Property, , Steel, , Solid Plastic, , Structural Foam, , Ribbed Solida, , Thickness (in.), E (psi), I (in.4), E x I (rigidity), Weight (lbs.), , 0.040, 3 x 107, 0.000064, 1,920, 3.24, , 0.182, 3.2 X 105, 0.006, 1,920, 1.98, , 0.196, 2.56 X 105, 0.0075, 1,920, 1.78, , 0.125, 3.2 X 105, 0.006, 1,920, 1.60, , a Rib, , height = 0.270 in., thickness = 0.065 in., rib spacing = 2.0 in., , occurs at the surface of the beam farthest, from the neutral surface, as given by the following equation:, a, , = McjI = MjZ, , (3-1), , where M = the bending moment in in.llbs.,, c = the distance from the neutral axis to the, outer surface where the maximum stress occurs in inches, I = the moment of inertia, in in.4, and Z = Ijc-, the section modulus, in in. 3 ., Observe that this is a geometric property,, not to be confused with the modulus of the, material, which is a material property. I, c, Z,, and the cross-sectional areas of some common cross-sections are given in Fig. 3-1, and, the mechanical engineering handbooks provide many more. The maximum stress and, defection equations for some common beamloading and support geometries are given in, Fig. 3-2. Note that for the T- and U-shaped, sections in Fig. 3-1 the distance from the neutral surface is not the same for the top and, bottom of the beam. It may occasionally be, desirable to determine the maximum stress, on the other nonneutral surface, particularly, if it is in tension. For this reason, Z is provided, for these two sections., , a variety of shapes to meet different product, requirements. Switching from metal to plastic thus lets the designer overcome configuration barriers and environmental operations, to new spring designs., As an example plastic replaced a metal, pump in a PVC plastic bag containing blood., The plastic spring hand-operating pump did, not contaminate the blood., Figure 3-12 is an example of a TP spring, action with a different shape. It is an injection molded Du Pont Delrin acetal plastic, stapler illustrating spring design with the, body and curved spring section molded in, a single part. This complex shape could not, have been achieved in a single operation in, steel. The designer has taken advantage of, molding'S versatility to reinforce the curved,, frequently stressed back section. When the, stapler is depressed, the outer curved shape, is in tension and the ribbed center section is, put into compression. When the pressure is, released, the tension and compression forces, are in turn released and the molded stapler, returns to its original position. With this, type of plastic having these inherently desirable properties as well as other desirable, properties, this repeated spring action has a, virtually unlimited life span., , Beam Bending and Spring Stress, To illustrate how traditional materials such, as metals limit the design process, consider a, spring. The manufacturing process in metals, limits the options available in producing a variety of shapes in this material. As a result,, steel springs are produced in basically only, three shapes: the torsion bar, the helical coil,, and the fiat-shaped leaf spring. By comparison, TPs and TSs can be easily fabricated into, , Fig.3-12 TP spring action.

Page 164 : 146, , 3 Product Design Feature, , Leaf springs constructed of unidirectional, fiber-reinforced plastics have come to be, recognized as viable replacements for steel, springs in truck and automotive suspension, applications and have been used in aircraft, landing systems since the early 1940s taking advantage of weight savings. Because of, the material's high specific strain energy storage capability as compared to steel, a direct replacement of multileaf steel springs, by monoleaf composite springs can be justified on a weight-saving basis. Such springs, have in fact been in use since the 1960s in, ground transportation vehicles. Further advantages of RP springs accrue from the ability with them to design and fabricate spring, leaves having continuously variable widths, and thicknesses along their lengths (3, 10,62)., Such design features will no doubt lead, to new suspension arrangements in which, leaf springs will serve multiple functions,, thereby providing a consolidation of parts, and simplification of suspension systems. One, distinction between steel and plastic is that, complete knowledge of shear stresses is not, important in a steel part undergoing flexure,, whereas with RP design shear stresses, rather, than normal stress components, usually control the design. Procedures have thus been, developed for evaluating design stresses because of simple flexure as well as secondary, loads like axle windup., Developments with RP leaf springs have, highlighted the need to reassess standards, for testing and evaluating them. Because of, the anisotropic properties of RPs, the standards previously developed for steel components in the laboratory and on the proving ground can give misleading test results, in plastics. The concept of spring design has, been well documented in various SAE and, ASTM-STP design manuals from the 1970s, on. These also give the equations for evaluating design parameters, which are simply, derived from geometric and material considerations. Further information enables the calculation of windup (that is, accelerating and, braking) and roll stiffnesses for springs as a, check against the design requirements. (See,, for instance, SAE J788A, Oct. 1970, and STP, 376, Jan. 1973.), , The design of any RP product is unique and, rather difficult, because the stress conditions, within a given structure depend on its manufacturing methods, not just its shape. Programs have therefore been developed on the, basis of the strain balance within the spring, to enable suitable design criteria to be met., Stress levels are then calculated, after which, the design and manufacture of RP springs become feasible., The cantilever spring can be employed to, provide a simple format from a design standpoint. Cantilever springs, which absorb energy by bending, may be treated as beams,, with their deflections and stresses being calculated as short-term beam-bending stresses., The calculations arrived at for multiplecantilever springs (that is, two or more, beams joined in a zigzag configuration, as in, Fig. 3-13) are similar to, but may not be as, accurate as, those for a single-beam spring., A zigzag configuration may be seen as a, number of separate beams each with one end, fixed. The top beam is loaded (F) either along, its entire length or at a fixed point. This load, gives rise to deflection y at its free end and, moment M at the fixed end. The second beam, is then loaded by moment M (upward) and, load F (the effective portion of load F, as, determined by the various angles) at its free, end. This moment results in deflection Y2 at, the free end and moment M2 at the fixed end, (that is, the free end of the next beam). The, , Fig. 3-13 Zigzag configured multiple-cantilever, beam spring.

Page 165 : 147, , 3 Product Design Feature, , third beam is then loaded by M2 (downward), and force F2 (the effective portion of FI ), and, so on., The total deflection, y, is the sum of the, deflections of the individual beams. The, bending stress, deflection, and moment at, each point can be calculated by using standard equations. To reduce stress concentration, all corners should be fully radiused. This, type of spring is often favored because of its, greater design flexibility over the single-beam, spring. The relative lengths, angles, and crosssectional areas can be varied to give the desired spring rate Fly in the available space., Thus, the total energy stored in a cantilever, spring is equal to:, Ec, , = 1/2Fy, , (3-2), , where F = total load in lb, y = deflection in.,, and E = energy absorbed by the cantilever, spring, in-Ibs., Torsional Beam Spring, , A torsional beam spring absorbs energy by, twisting through an angle 0 (Fig. 3-14) and, may thus be treated as a shaft in torsion., A shaft subject to torque is generally considered to have failed when the strength of, the material in shear is exceeded. For a torsionalload the shear strength used in design, should be the published value or one half the, tensile strength, whichever is less. The maximum shear stress on a shaft in torsion is given, by the following equation:, T, , =, , Tel J, , (3-3), , CROSS SECTION, , M, , ~, , POLAR MOMENT, OF INERTIA, J, , LDCA TION OF MAX., SHEAR STRESS, , c, , Rei', 32, , 2, , R(do 4·d,4), , do, , 32, , 2, , nb 3 h, , b, , 32, , 2, , b 3h, , b, , 9, , 2, , h4, , h, , 9, , 2, , d, , Pdo, , TO, , 10m, , hID, M, , Fig.3-15 Polar moments of inertia for common, cross-sections., , where T = applied torque in in-Ib, c = the, distance from the center of the shaft to, the location on the outer surface of shaft, where the maximum shear stress occurs, in., (Fig. 3-15), and J = the polar moment of inertia, in.4 (Fig. 3-15)., The angular rotation of the shaft is caused, by torque is given by:, , e = TLIGJ, , (3-4), , where L = length of shaft, in., G = shear, modulus, psi = E12(1 + v), E = tensile, modulus of elasticity, psi, and v = Poisson's, ratio., The energy absorbed by a torsional spring, deflected through angle e equals:, Et, , = 1/2Me x e, , (3-5), , where Me = the torque required for deflection e at the free end of the spring, in-lb., Folded Plate, , Fig. 3-14 Shaft with diameter d and length L, under torque T undergoing angular deformation., , The methods of analysis and design presented for beams can be applied to the morecomplex products such as folded plate structures, which range from bottles to roofing to

Page 166 : 148, , 3 Product Design Feature, , outer-space structures. They are basically assemblies of rectangular, triangular, spherical,, or other shapes that behave much like beams,, portal frames, arches, or shells., The stresses in some folded structures can, be determined with acceptable accuracy by, applying elementary beam theory to the overall cross-sections of the plate assemblies., When assemblies are plates whose lengths, are large relative to their cross-sectional dimensions (thin-wall beam sections, ribbed, panels, and so on) and are in large plates, , whose fold lines deflect identically, such as the, interior bays of roofs, they can be analyzed, as beams. More elaborate procedures must, be used to determine the transverse bending, stresses in assemblies of large plates and longitudinal stresses in structures with "pinned", connections along folded lines that do not deflect identically., There are also bellows-style collapsible, plastic containers such as blow molded bottles (jars) that are foldable. As shown in Figs., 3-16 and 3-17, the technology of foldable, , -, , ri\cd POl1ion, , Mo\ ing Portion, - - OUI~r Rc,1 PINI1l1J1, ~ O\l~rccntcring, , Point, , ____ Inner RC\I PO\lIion, II I = 111 = oJ, , Fig. 3-16 Theory and operation of the collapsible bottle: (a) an uncallapsed bottle, (b) a collapsed, bottle, (c) top view of the bottle, and (d) definitions.

Page 167 : 149, , 3 Product Design Feature, , (b), , (a), , Fig.3-17, , (c), , Design ideas for the collapsible bottle., , containers in contrast to that of the usual, "passive" bottles provides advantages and, conveniences such as reduced storage, transportation, and disposal space; prolonged, product freshness by reducing oxidation and, loss of carbon dioxide; and provides continuous surface access to foods like mayonnaise, and jams., The bellows of collapsible containers overlap and fold to retain their folded condition, without external assistance, thus providing a, self-latching feature. This latching is the result of bringing together under pressure two, adjacent conical sections of unequal proportions and different angulations to the bottle, axis. On a more technical analytical level the, latching is created by the swing action of one, conical section around a fixed pivot point,, from an outer to an inner, resting position., The two symmetrically opposed pivot points, and rotating segments keep a near-constant, diameter as they travel along the bottle axis., This action explains the bowing action of the, smaller, conical section as it approaches the, overcentering point., After fabrication an initial collapsing of, such a bottle should occur as soon as possible, (no later than one to two hours after manufacture; the sooner the better). Additional, pressure is needed for this first-time collapse in order to create permanent fold rings, and completely orient the plastic molecules, (Chapter 8, PROCESSING AND PROP-, , ERTIES, Orientation). The subsequent collapsing and expansion of such bottles before filling them can be performed at the, recommended ambient temperature of 20 C, (68 F) or higher depending on the type of, plastic used. In most disposable applications, these bottles would undergo three changes of, volume: (1) an initial collapsing of the container before shipment and storage; (2) expansion of the container at its destination,, before or during filling; and (3) finally collapsing the bottle for reuse or disposal., The fold rings designed on the bellows for, such containers have proven to be durable, and sturdy. Prototype bottles made of PETG, and 75 durometer PVC were able to withstand dozens of collapses and still pass their, stress tests. A guide is proved as shown in, Fig. 3-17. The two adjacent conical sectors, providing the latching should not exceed an, angle of 110° to make a sharp fold ring. The, size of rotating conical section B should not, exceed 80% of conical section A, to prevent, confusion and wobbling as the bottle is being, collapsed., Product labeling can be accomplished by, attaching a floating sleeve to the neck or, shoulder section of the bottle. This cylindrical sleeve then accommodates the bellows as, they fold from the bottom up and contains, them within the sleeve as the jar is collapsed., The maximum length of the sleeve is limited, by the collapsed dimension of the bottle. An, D, , D

Page 168 : 150, , 3 Product Design Feature, , extended cap can also be used to hold the, label to the side of the bottle., Sandwich Construction, , Increasing the stiffness capability of any, material (plastic, metal, etc.) can be accomplished by thickening the product. Result is, use of more materials and more processing, costs. As reviewed, other approaches include, the use of ribs, corrugations, and sandwich, constructions., Each have their place with plastic sandwiches being very popular when space is, available providing high performance, lightweight, noise suppression, heat insulation,, permit fabricating special shapes, and for, certain products provide cost reductions, (Fig. 3-18). They are similar to the I-beam, shape in which its facings (plastics unreinforced or reinforced) correspond to the, flanges and the cores (plastic foams; honeycomb structure of plastics, etc.) representing the webs. The facings, also called skins,, resist axial loads and provide stiffness. The, sandwich core stabilizes the facings against, buckling or wrinkling under axial compression, and provides resistance to shear in, bending (109)., A sandwich panel performs by improving, loading characteristics such as in bending in, the direction perpendicular to the plane of, , the panel. It basically exhibits no improvement in performance in other directions such, as parallel to the plane of the sandwich (unless high strength facings are used). It is, in, fact, subject to failure under lower load conditions under edge loading because of the, susceptibility to failure of the skins by buckling. Despite these potential limitations structural sandwich panels are a very efficient, lightweight structural element widely used, in buildings, aircraft, surface vehicles, spacecrafts, and many commercial and industrial, applications., Different core materials are used. They, include foam, honeycomb core (plastic, paper, aluminum, etc.), ribs, balsa wood, filler, spacers, corrugated sheet spacers, etc. Materials such as polyurethane foam, cellulosic, foams, and polystyrene foams are widely, used as core materials. Plastics, such as glassreinforced polyester, are frequently used as, the skins for panels. Different skin materials, are used such as metallic skins alone or in, conjunction with plastic skins., They range from structural foam molded, products (which come from the mold as completed molded products) incorporating low, density cores and high density skins of the, same materials to products vacuum formed, of a plastics material, the core of which becomes cellular during the heating process, (Chapter 8). RP translucent structural panels, for curtain wall building construction using, , Load, , Completed sandwich structure, , Fig. 3-18, , Example of a sandwich construction with a honeycomb core.

Page 169 : 3, , honeycomb cores or other decorative cores, are examples of the widespread use of the, panel concept. Plated plastics products covered with substantial layers of metal are another use of reinforcing skins to improve, the stiffness of plastics products as well as, to provide a different appearance. Extruded, cellular plastic shapes with applications that, range from molding substitutes for wood to, structural shelving are other examples where, the sandwich panel stiffening principle is, applied., ., In the usual building and constructlOn, practice a structural sandwich construction is, a special case of a laminate with flat, cur~ed,, or otherwise two thin facings. The facmgs, are of relatively stiff, hard, dense, strong material that are bonded to a relatively thick, core of a lightweight material that is considerably less dense, stiff, and strong than the, facings. Structural sandwiches can be all plastics, all metals, or combination of plastic and, metal, etc., With this geometry and relationship of, mechanical properties, facings are subjected, to almost all the stresses in transverse, bending or axial loading. The geometry of, the arrangement provides for high stiffness, combined with lightness, because the stiff, facings are at a maximum distance from, the neutral axis, similar to the flanges of an, I-beam (Fig. 3-1). The continuous core, takes the place of the web of an I-beam or, box beam, absorbs most of the shear, and, stabilizes the relatively thin facings against, buckling or wrinkling under compressive, stresses. The bond between the core and its, facings must resist shear and any transverse, tensile stresses set up as the facings tend to, wrinkle or pull away from the core., Stiffness For an isotropic material with a, modulus of elasticity E, the bending stiffness, factor (El) of a rectangular beam b wide and, h deep stiffness is:, E1 = E(bh 3 /12), , 151, , Product Design Feature, , the bending stiffness factor El is:, , This equation is exact if the facings are, of equal thickness, and approximate if they, are not, but the approximation is close if t~e, facings are thin relative to the core. If, as IS, usually the case, E is much smaller than E f', the last term in the equation can be ignored., For asymmetrical sandwiches with different, materials or different thicknesses in their facings or both, a more general equation may be, used (109)., In many isotropic materials the shear modulus G is high compared to the elastic modulus E, and the shear distortion of a transversely loaded beam is so small that it can be, neglected in calculating deflection. In a stru~­, tural sandwich the core shear modulus G, IS, usually so much smaller than E f of the facings, that the shear distortion of the core may be, large and therefore contribute significantly to, the deflection of a transversely loaded beam., The total deflection of a beam is thus composed of two factors: the deflection caused, by the bending moment alone, and the deflection caused by shear, that is, 8 = 8m + 8s ,, where 8 = total deflection, 8m = moment deflection, and 8s = shear deflection., Under transverse loading, bending moment deflection is proportional to the load, and the cube of the span and inversely proportional to the stiffness factor, El. Shear deflection is proportional to the load and span, and inversely proportional to shear stiffness, factor N, whose value for symmetrical sandwiches is:, N, , =, , [(h, , + c)bI2]Gc, , (3-8), , where Gc = the core shear modulus., The total deflection may therefore be, written:, , (3-6), , In a rectangular structural sandwich with, the same dimensions just given whose facings and core have moduli of elasticity E f, and Ec , respectively, and a core thickness C,, , The values of Km and Ks depend on the, type of load. Examples of these values are, given in Table 3-3.

Page 170 : 152, , 3 Product Design Feature, , Table 3-3 Typical loading conditions, Beam Ends, , Deflections at, , Km, , Ks, , Both simply supported, Both clamped, Both simply supported, Both clamped, Both simply supported, Both simply supported, Cantilever, 1 free, 1 clamped, Cantilever, 1 free, 1 clamped, , Midspan, Midspan, Midspan, Midspan, Midspan, Load point, Free end, Free end, , 5/384, 1/384, 1/48, 1/192, 11/768, 1/96, 1/8, 1/3, , 1/8, 1/8, 1/4, 1/4, 1/8, 1/8, 1/2, 1, , Loading, Uniformly distributed, Uniformly distributed, Concentrated at midspan, Concentrated at midspan, Concentrated at outer quarter points, Concentrated at outer quarter points, Uniformly distributed, Concentrated at free end, , Reinforced Plastic Directional Property, , The term reinforced plastic (RP), also, called composites (more accurately plastic, composites), refers to combinations of plastic (matrix) and reinforcing materials that, predominantly come in fiber forms such as, chopped, continuous, woven and nonwoven, fabrics, etc.; also in other forms such as powder, flake, etc. They provide significant oriented property and/or cost improvements, than the individual components (10, 14, 35,, 38,39--43,62)., Primary benefits include high strength, and modulus, lightweight, high strength-toweight ratio, high dielectric strength and corrosion resistance, long term durability, and, particularly oriented strength or controlled, directional properties. Their exists with many, unreinforced and reinforced plastics directional properties requirements. Included are, materials such as oriented film, pressure pipe,, support beams, laminates, reinforced plastics,, and so on. (Chapter 8, PROCESSING AND, PROPERTIES, Orientation)., Both thermoset (TS) and thermoplastic, (TP) are used. Included in the RTPs (thermoplastic RPs) are stamp able reinforced thermoplastics (SRTPs). At least 90wt% use, glass fiber and about 40% of all RPs use, TS polyester plastic of the RP products fabricated. Improved understanding and control of processes continue to increase performance and reduce variability (Chapter 8)., Fiber strengths have risen to the degree that, 2-D and 3-D RPs can be used producing very, high strength and stiff RP products having, long service lives of over a half century. In-, , cluded in these RTPs are stamp able reinforced thermoplastics (SRTPs)., Thermoplastic RPs (RTPs), even with their, relatively lower properties when compared, to thermoset RPs (RTSs), consume about, 55wt% of all RP products. Practically all of, the RTPs are injection molded with very, fast cycles using short glass fiber producing highly automated and high performance, products., Isotropic material In an isotropic material, the properties at a given point are the same,, independent of the direction in which they, are measured (Fig. 3-19). The term isotropic, means uniform. As one moves from pointto-point in this type of homogeneous plastic the material's composition remains constant. Also, the smallest samples of material, Polar, Directional Properties, , o OrthotfoptC or Unidirectional, !§, , D, , o, , Bodlrecbonal, I sotropK: or Planar, Unretnforced Plasncs, , Fig.3-19 Examples of the performance of RPs, with different orientations of their fiber reinforcements.

Page 171 : 3 Product Design Feature, cut from any location has the same properties., A cast, unfilled plastic is a good example of a, reasonably homogeneous material. With RPs, and other similar materials, isotropic refers, only to the plane of the fiber layup; that is,, it is only two-directional (2-D), rather than a, complete isotropic behavior in three planes., However there are 3-D RPs; they use a 3-D, fabric layup., Anisotropic material In an anisotropic, material the properties vary, depending on, the direction in which they are measured., There are various degrees of anisotropy, using different terms such as orthotropic or, unidirectional, bidirectional, heterogeneous,, and so on (Fig. 3-19). For example, cast plastics or metals tend to be reasonably isotropic., However, plastics that are extruded, injection molded, and rolled plastics and metals, tend to develop an orientation in the processing flow direction (machined direction)., Thus, they have different properties in the, machine and transverse directions, particularly in the case of extruded or rolled materials (plastics, steels, etc.)., Wood is anisotropic with distinct different, properties in three directions. Its highest mechanical properties are in the growth (fiber), direction, with the perpendicular (or second, plane) direction having lower properties and, the other perpendicular (or third plane) directi on having much lower properties., During World War llRTPs were developed. These glass fiber-TS polyester plastics, were used in many high-performance, structurally loaded products in aircraft, ground, vehicles, to ships. The RPs used many different glass-fiber nonwoven and woven constructions to produce the required directional properties for the different products., The design equations and engineering technology approaches used were based on the, technology and engineering knowledge of, the anisotropic wood performance (based on, centuries of wood applications in buildings,, bridges, etc.) that the Forest Products Laboratory (FPL) in Madison, WI used. The, Materials Laboratory's Plastic Section at the, Wright-Patterson Air Force Laboratories in, Dayton, Ohio, with the help of FPL provided, , 153, , the original engineering equations and technical approach to designing with RPs that latter were applied to unreinforced plastics (14,, 41,43, 106)., Monocoque Structure, Plastics provides a means to producing, monocoque constructions such as has been, done in different applications that include, toys to automotive body, motor truck, railroad car, aircraft fuselage and wings, and, houses. Its construction is one in which the, outer covering "skin" carries all or a major, part of the stresses. The structure can integrate its body and chassis into a single structure. Unreinforced and RPs are used in these, constructions (14, 34)., Integral Hinge, Although integral hinges are feasible with, a number of TPs, the concept is generally, associated with injection or blow molding, polypropylene. This section discusses the integral hinge as it is generally applicable to, polypropylene. There are various techniques, used to fabricate integral hinges; molded-in, (by injection or blow molding), cold worked,, extruded, and coining. These so-called "living hinges" take advantage of molecular orientation to provide the bending action in the, plastic hinge. As an example an integral hinge, can be molded by conventional processing, techniques providing certain factors are observed. The required molecular orientation, runs transverse to the hinge axis. This can, best be achieved by a proper fast melt flow, through a thin hinge section, using a proper, high melt temperature (Fig. 3-20)., The main concern in integral hinge molding is to avoid conditions that can lead to, delamination in the hinge section. These include filling the mold too slow, having too, low a melt temperature, having a nonuniform flow front through the hinge section,, suffering material contamination as from pigment agglomerates, and running excessively, high mold temperatures near the hinge area.

Page 172 : 154, , 3 Product Design Feature, Shffenino, , 0.060, Web land, , shoulder, , 0.005 to 0.015 as, necessary for stiffness, of hinoe action or for, mold· fill requirements, , 0.030, , f, , 0.030, Thickness approxlrnotely, , equal to sidewalls, , All, , Fig. 3-20 Example of a PP living hinge., , Immediate post-mold flexing while it is still, hot is usually required to ensure its proper, operation., Conventional coining mechanical operation is used where the plastic at the hinge, section is compressed to the desired thickness using matching bars that produce the required shape of the hinge (Fig. 3-21). Pressure applied to properly cut metal plates,, heated or unheated depending on type plastic used, produces the hinge. The plastic, in the hinge section is stressed beyond its, yield point after creating a necking down effect that causes stretching or orienting of its, molecules perpendicular to the hinge folding, direction., A press, a homemade toggle job, or a hotstamping machine can be used to perform, the cold working operation. When heat is required (usual requirement) the male forming die should be about 132 to 138°C (270, to 290°F). Pressure should be maintained for, about 10 seconds. This time can be reduced if, the product still retains residual molding heat, or is preheated. The recommended preheating temperature is from 80 to 110°C (175 to, 230°F)., , T-;,;m,m, , ,,",<h, '0",, , ';m", , Thickness 0.012 to 0.020 in., , Fig. 3-21, , Coining dimensions., , <h;,k,,", , The die backings may be either hard or flexible. With a hard backing, such as steel, the, softened polypropylene is die formed into the, desired hinge contour. Using a flexible backing like stiff rubber usually makes thinner, hinges. The deformation of this type of backing produces the hinge contour by stretching, the softened plastic and generally results in, thinner cross-sections., Hinge dimensions of lids, boxes, and many, other products made of TPs, particularly, polypropylene, have been well established, (Fig. 3-22). The successful operation of such, hinges depends not only on processing technique, but determining the proper dimensions based on the type plastic used. The, dimensions in Figs. 3-20 and 3-21 are typical. Recognize dimensions can differ if the, hinge is to move 45° or 180°. If the web land, length is too short for the 180° it will selfdestruct. Also during injection molding of, large size products, there may be a tendency, to place a mold gate at the center of the box, and another at the center of the lid. The result is that the flow patterns are not an ideal, combination to creating a favorable hinge, strength, in fact a weld line can develop in the, hinge area., Forming the hinge cross-section by using, an extruder die results in a hinge with poor, flex life. Because hinges are formed in the, direction of the polymer flow, they cannot, be sufficiently oriented when flexed. However, if an extruded hinge is formed by the, take-off mechanism while the polypropylene

Page 173 : 155, , 3 Product Design Feature, (1) Self-hinged spray closure, , (2) Box lid hinge, , (3) Single flap cal hinge closure, with snap spud, , ~d:C, , Orifice, Finger recess, , land length, , Land Length, To Thickness Ratio, At Least 3 TD 1, , Lower hinge, , (4) Action of package design combining a hinge with snap fits., \ ",.CHAVII', , I, , ~""""'ot=.., , Fig_ 3·22, , Examples of living hinges., , still retains internal heat, the hinge will, have properties approaching those of cold, working., , Snap Joint, A snap joint is economical in two respects: it allows the structural member to, be molded simultaneously with the molded, product, and it allows rationalizing the assembly, compared with such other joining processes as screws. Table 3-4 provides a comparison of its advantages and disadvantages., Some examples of the various types and their, design considerations are shown in Figs. 3-23, to 3-25., The geometry for snap joints should be, chosen in such a manner that excessive increases in stress do not occur (Table 4-3). The, arrangement of the undercut should be chosen in such a manner that deformations of, the molded product from shrinkage, distortion, unilateral heating, and loading do not, , disturb its functioning. The following guidelines are recommended regarding the position of the snap joint to the injection molded, gate and the choice of the wall thicknesses, in the area of flow to the place of joining:, (1) there should be no binding seams at critical points; (2) avoid binding seams created by, stagnation of the melt during filling; (3) the, plastic molecules and the filler should be oriented in the direction of stress; and (4) any, uneven distribution of the filler should not, occur at high-stress points (Chapter 4, JOIN·, ING AND ASSEMBLING. Snap Fit)., , Product Size and Shape, Product size is limited to available equipment that can handle the size and pressure, as well as other processing requirements., Also involved are factors such as packaging, and shipment to the customer. The ability to, achieve specific shapes and design details is, dependent on the way the process operates.

Page 174 : 156, Table 3·4, , 3 Product Design Feature, Advantages and disadvantages of snap joints, Disadvantages, , Advantages, Can be easily integrated into the, structural member, Compact, space-saving form, Takes over other functions like, bearing, spring cushioning,, fixing, Higher forces can also be, transmitted with proper, designing, Small number of individual parts, Assembly of a construction system, with little expenditure of, production facilities and time, , The fixing of the joined parts is weaker than in welding,, bonding, and screw joining, The conduct of force at the joining place is lesser than in areal, joining (bonding, welding), Effects of processing on the properties of the snap joints, (orientation of the molecules and of the filler, distribution, of the filler, binding seams, shrinkage, surface, roughness, and structure), Narrow tolerances are required in complicated applications, (in plastics, this is associated in some cases with considerable, expenditure), Influence of environmental effects (for example, distortion, due to temperature differences) on the functioning, Difficulties with a continuous loading of the snap joint, , Generally the lower the process pressure,, the larger the product that can be produced., With most labor-intensive fabricating methods, such as RP hand lay-up with TS plastic,, relatively slow process curing reaction time, of the plastic can be used so that there is virtually no limit on size (Fig. 8-63)., A general guide to practical processing, thickness limitations follows based on heat, transfer capability through plastics is in, inches: injection molding 0.02 to 0.5; extrusion 0.001 to 1.0; blow molding 0.003 to 0.2;, thermoforming 0.002 to 1.0; compression, molding 0.05 to 4.0; and foam injection molding 0.1 to 5.0. However with the proper process controls on materials and equipment,, products are produced that range below these, figures (Chapter 8)., Although there is no limit theoretically to, the shapes that can be created, practical considerations must be met. These relate not only, to product design but also to mold or die design, since these must be considered one entity in the total creation of a usable, economically feasible product. In the sections that, follow, various phases considered important, in the creation of such products are examined, for their contribution to and effect on design, and function., Prior to designing a product, the designer should understand such basic factors as, those summarized in Fig. 3-26 and Table 3-5., Success with plastics, or any other material, , for that matter, is directly related to observing design details. For example, something, as simple as a stiffening rib is different for, an injection molded or structural foam product, even though both may be molded from, the same plastic (Fig. 3-26). However, a stiffening rib that is to be molded in a lowmold-shrink, amorphous TP will differ from a, high-mold-shrinkage, crystalline TP rib, even, though both plastics are injection molded., Ribs molded in RP have their own distinct, requirements. Hollow stiffening ribs of the, type produced by thermoforming, blow, or, rotational molding have the same function,, but they are designed to be totally different., The important factors to consider in designing can be categorized as follows: product thicknesses, tolerances, ribs, bosses and, studs, radii and fillets, drafts or tapers, holes,, threads, colors, surface finishes and gloss levels, decorating operations, parting lines, gate, locations, shrinkages, assembly techniques,, mold or die designs, production volumes,, tooling and other equipment amortization, periods, as well as the plastic and process, selected. As previously reviewed (Fig. 1-11), with the gains obtain by these type factors,, there could be losses such as surface imperfections, sink marks, or voids that could occur., Preparing a complete list of design constraints is a crucial first step in the design;, failure to take this step can lead to costly errors. For example, a designer might have an

Page 175 : 157, , 3 Product Design Feature, (a) Snap-in fit, , (b) Snap-on fit, , em?, o 0 bJld, , (c) Separable snap joints for box cover, , (d) Cap with two cantilever and two rigid lugs, , (e) Discontinuous annular snap jOint, , (f) Detachable and non-detachable snaps, , 1. h = 0.00 75d if, , (~~ 12), , 2. h = d (0.0024*, , G=t--~-~~, , I, , __ I _, /, I, , "'" _7, /', , I, , (, \, , ,-"......, , I, , \I \, I, , LL, , _.~30", , T, , o, , j, , d, , 1_~_~~_.t2~~, , detachable, , Fig.3-23, , r- ..-., , + 0.005) if (~. ;:: 12), , non-detachable, , Different snap-fit designs., , expensive injection mold prepared, designed, for a specific material's shrink value to meet, specific product dimensions, only to discover, belatedly that the initial material chosen did, not meet some overlooked design requirement or constraint., The designer may have the difficult if not, impossible task of finding a plastic that does, meet all the design constraints, including the, important appropriate shrink value for the, , existing mold cavity(s) otherwise expensive, mold modifications may be required, if not, replacing the complete mold. Such desperation in the last stages of a design project can, and should be avoided. As emphasized from, one end of this book to the other, it is vital, to set up a complete checklist of product requirements, to preclude the possibility that a, critical requirement may be overlooked initially. Fortunately there are occasions where

Page 176 : 158, , 3 Product Design Feature, tion of properties during fabrication and/or in, service., Such features may be called property detractors since most of them are responsible, for internal stresses that can result in products, cracking, surface crazing, reducing the available stress level for load-bearing purposes,, etc. Other features may be classified as precautionary measures that may influence the, favorable performance if not properly incorporated. Examples of these property detractors along with other features suggest means, of circumventing their potential negative effects are presented. This subject will be reviewed in detail latter in this chapter., , Sealing rib, , Tamper seal, , Fig. 3-24 Section of a linerless cap with a tamperproof snap seal., , Tolerance, changes in process control during fabrication can be used to produce the required, dimensional product and meet product performance properties without any or excessive, cost., , Basic Feature, Design involves establishing the configuration of the products that will form the basis, on which suitable material selected for anticipated requirements and processes can be, applied. During the drawing of shapes and, cross sections, there are certain design features with plastic materials that have to be, kept in order to avoid failure or degradaStandard, threads drive, Snap Cap, into place, , ", , l, , ---t, , 1----, , ..I., ~-, , I, , Tight tolerances can be met. However, the, specific dimensions that can be obtained on, a finished fabricated plastic product basically, starts with the design configuration. In turn it, depends on the performance and control of, the fabrication process, the plastic material,, and, in many cases, upon properly integrating, the materials with the process. A number of, variable characteristics exist with designing,, materials, and processes as described at the, end of this chapter and Chapters 6 and 8. Unfortunately, many designers tend to consider, dimensional tolerances on plastic products to, be complex, unpredictable, and not controllable. This is simply not true since there is a, logical approach to controlling and operating, within tolerances that can be met., , r, I, , /5 nap rin g ,, , ", , "hreadS, disengage when, Sn ap Cap seals,, th en re-engage, to drive cap, down tighter, , '\, , .A, , Fig.3-25, , ", , Nonbackoff snap cap provides liquid-tight closure.

Page 177 : 3 Product Design Feature, , ?LT, , Injection molded, Polypropylene, , Structural foam molded, , Injection molded, , Reaction injection molded, , .. _~o85 W, , Compression molded, SMC, , .. _;...... ;.9,.070" min., Thermoformed., , -lar-WLT·:~~~~;"~~'·~f,nc~, ... U,QJ5W, , F, , ! ..lDW, , J;"'1 Z!LQ_9.U;W__, o, , Fig.3·26 Examples of how different plastics and, processes affect the design details of a stiffening, rib., , Plastics are no different in this respect than, other materials. If steel, aluminum, and ceramics were to be made into a different complex shapes and no prior history on their, behavior for that processing shape existed, a, period of trial and error would be required to, ensure their meeting the required measurements. If relevant processing information or, experience did exist, it would be possible for, these metallic (or plastic) products to meet, the requirements with the first product produced. Experience on new steel shapes always took trial and error time that included, different shaped high pressure hydraulic steel, cylinders that failed in service when used in a, new injection molding hydraulically operating machine (author'S experience)., This same situation exists with plastics. To, be successful with plastics requires experience with their melt behavior, melt-flow behavior during processing, and the process, controls needed to ensure meeting the dimensions that can be achieved in a complete, processing operation. Based on the plastic, to be used and the equipment available for, processing, certain combinations will make it, possible to meet extremely tight tolerances., Fortunately, there are many different types, of plastics that can provide all kinds of properties, including specific dimensional tolerances. It can thus be said that the real problem, is not with the different plastics or processes, but rather with the designer, who requires, knowledge and experience to create products to meet the desired requirements. The, designer with no knowledge or experience, , 159, , has to become familiar with the plastic design concepts expressed throughout this book, and work initially with capable people such, as qualified and independent consultants,, suppliers of plastic materials, and/or the processors., Some plastics, such as the TSs and in particular the TS-RPs (RTSs), can produce products with exceptionally tight tolerances that, practically meet zero tolerances. In injection, or compression molding of relatively thin to, thick and complex shapes, tolerances can be, held to less than 0.001 in. or to even zero, as, can also be done using hand layup RP fabricating techniques., At the other extreme are the unfilled, unreinforced extruded TPs. Generally, unless a, very thin uniform wall is to be extruded, it, is impossible to hold the tight tolerances just, given. The thicker and more complex an extruded shape is, the more difficult it becomes, to meet tight tolerances. However extruded, products meet satisfactory tolerances such as, those required in products such as window, frames, rain gutters electrical/electronic devices, and medical device (6, 242). What is, important to the designer is to determine the, tolerances that can be met and then design, using these tolerances., To maximize control in setting tolerances, there is usually a minimum and a maximum limit on thickness, based on the process to be used such as those in Tables 3-6, to 3-9. Each plastic has its own range that depends on its chemical structure, composition, (additives, etc.), and melt-processing characteristics. Any dimensions and tolerances are, theoretically possible, but they could result, in requiring special processing equipment,, which usually becomes expensive. There are, of course products that require and use special equipment such as polycarbonate compact discs (CDs) to meet extremely tight, tolerances., An influence on dimensions and tolerances, involves the coefficient of linear thermal expansion or contraction. This CLTE value has, to be determined at the product's operating, temperature (Chapter 2, THERMAL EXPANSION AND CONTRACTION). Plastics can provide all extremes in CLTEs. As an

Page 178 : 3 Product Design Feature, , 160, Table 3·5, , Design guides for processes vs. product requirements, Compression Molding, Sheet, Molding, Compound, , Bulk, Molding, Compound, , Preform, Molding, , Injection, Molding, (Thermo·, plastics), , Cold, Press, Molding, , Spray-up, and, Hand, Lay-up, , Minimum inside, radius. in. (mm), , LV, , 1/16", (1.59), , 1/16", (1.59), , I/S", (3.IS), , 1/16", (1.59), , 1/4", (6.35), , 1/4", (6.35), , Molded-in holes, , S~~, , Yes, , Yes, , Yes, , Yes, , No, , Large, , Trimmed in mold, , ~, , Yes, , Yes, , Yes, , No, , Yes, , No, , Core pull & slides, , C_V, , Yes, , Yes, , No, , Yes, , No, , No, , Undercuts, , rr~_._~, , Yes, , Yes, , No, , Yes, , No, , Yes, , (!fJ, , 1/4" to 6" (6.35-152 mm) depth: 1" to 30, 6" (152 mm) depth and over: 3°or as required, , 20, 3D, , 00, , Minimum, recommended, draft, in./o, , Minimum practical, thickness, in. (mm), , D, , Maximum practical, thickness, in. (mm), , @, , -r, , .050", (1.3), , .060", (1.5), , .030", (0.76), , 0.35", (0.89), , .080", (2.0), , .060", (1.5), , 1", (25.4), , 1", (25.4), , .250", (6.35), , .500", (12.7), , .500", (12.7), , No limit, , N annal thickness, variation, in. (mm), , ~, , ±.OO5, (±0.1), , ±.OO5, (±O.I), , ±.OOS, (±0.2), , ±.OO5, (±O.I), , ±.OlO", (±0.2S), , ±.020", (±0.51), , Maximum thickness, buildup, heavy, buildup and, increased cycle, , 47, , As req'd., , Asreq'd., , 2-to-1, max., , Asreq'd., , 2-to-l, max., , As req'd., , Corrugated sections, , ~, , Yes, , Yes, , Yes, , Yes, , Yes, , Yes, , Metal inserts, , ~, , Yes, , Yes, , Not, recommended, , Yes, , No, , Yes, , Bosses, , 0, , Yes, , Yes, , Yes, , Yes, , Not, recommended, , Yes, , Yes, , Not, recommended, , Yes, , Not, recommended, , Yes, , Ribs, , m, , As req'd, , Molded-in labels, , C9, , Yes, , Yes, , Yes, , No, , Yes, , Yes, , Raised numbers, , @.. ....-:-.-,,'...., , Yes, , Yes, , Yes, , Yes, , Yes, , Yes, , Finished surfaces, (reproduces, mold surface), , ffl, , Two, , Two, , Two, , Two, , Two, , One

Page 179 : 0.005, , 0.006, 0.008, 0.009, 0.011, 0.012, 0.003, , 0.004, , 0.003, , 0.002, 0.002, 0.003, 0.004, , 0.003, 0.004, 0.005, , 0.015, 0.030, , 0.009, , To 1.000, , 1.000--2.000, 2.000--3.000, 3.000--4.000, 4.000--5.000, 5.000--6.000, 6.000--12.000, for each, additional inch, , ............. ., , .............., , 0.000--0.125, 0.125-0.250, 0.250-0.500, 0.500 and over, , 0.000-0.250, 0.250-0.500, 0.500--1.000, , 0.000--3.000, 3.000--6.000, , TIR, , Commercial, , ABS, , 0.005, 0.003, 0.003, 0.004, 0.005, 0.004, 0.004, 0.006, 0.010, 0.015, , 0.002, 0.001, 0.002, 0.002, 0.003, 0.002, 0.003, 0.004, 0.006, 0.010, , 0.004, 0.004, 0.002, 0.003, 0.004, 0.006, 0.004, 0.005, 0.006, 0.011, 0.020, , 0.002, 0.002, 0.003, 0.010, 0.020, 0.005, , 0.001, 0.001, 0.002, 0.002, , 0.002, , 0.002, , 0.010, , 0.003, , 0.002, , 0.006, , 0.006, 0.007, 0.008, 0.009, 0.011, 0.003, , 0.005, 0.006, 0.007, 0.008, 0.009, 0.002, , 0.008, 0.009, 0.011, 0.013, 0.014, 0.004, , 0.010, , 0.005, , 0.004, , 0.006, , 0.004, 0.005, 0.006, 0.007, 0.008, 0.002, , 0.003, , Commercial, , Fine, , Acrylic, , Commercial, , Fine, , Acetal, , Examples of dimensional tolerances for injection molded TP products, , Dimensions, in, , Table 3-6, , 0.006, , 0.007, 0.010, , 0.002, 0.002, 0.003, , 0.001, 0.002, 0.002, 0.003, , 0.003, , 0.003, , 0.004, 0.005, 0.006, 0.007, 0.008, 0.002, , 0.003, , Fine, , 0.010, , 0.010, 0.015, , 0.004, 0.004, 0.005, , 0.002, 0.003, 0.003, 0.005, , 0.005, , 0.004, , 0.006, 0.007, 0.009, 0.010, 0.012, 0.003, , 0.004, , Commercial, , Nylon, , 0.006, , 0.004, 0.007, , 0.002, 0.003, 0.004, , 0.001, 0.002, 0.002, 0.003, , 0.003, , 0.003, , 0.003, 0.005, 0.006, 0.007, 0.008, 0.002, , 0.002, , Fine, , 0.005, , 0.005, 0.007, , 0.002, 0.003, 0.004, , 0.002, 0.002, 0.003, 0.003, , 0.003, , 0.003, , 0.005, 0.006, 0.007, 0.008, 0.009, 0.003, , 0.004, , Commercial, , ( Continues), , 0.003, , 0.003, 0.004, , 0.002, 0.002, 0.003, , 0.001, 0.015, 0.002, 0.002, , 0.002, , 0.002, , 0.003, 0.004, 0.005, 0.005, 0.006, 0.015, , 0.0025, , Fine, , Polycarbonate, , ~, , ......., , ~, , l::, , ~, tl, ....., , ~, atj., ;:s, , tl, , ("), ....., , l::, , >:l..., , c~, , ~

Page 180 : 0.003, 0.004, 0.006, 0.014, 0.021, , 0.003, 0.004, 0.005, 0.008, 0.005, 0.006, 0.009, 0.021, 0.035, , 0.020, 0.030, , 0.005, 0.007, 0.009, , 0.023, 0.037, , 0.027, , 0.000-0.250, 0.250--0.500, 0.500--1.000, , 0.000--3.000, 3.000--6.000, , TIR, , 0.010, , 0.015, 0.022, 0.008, , 0.015, 0.020, , 0.003, 0.004, 0.006, , 0.002, 0.003, 0.004, 0.005, , 0.003, 0.005, 0.006, 0.008, , 0.000--0.125, 0.125-0.250, 0.250--0.500, 0.500 and over, , 0.010, , 0.003, 0.004, 0.005, , 0.003, 0.004, 0.005, 0.006, , 0.004, , 0.006, , .............., , 0.003, 0.004, 0.006, , 0.002, 0.003, 0.004, 0.005, , 0.005, , 0.004, , 0.006, , .............., , 0.016, , 0.002, 0.003, 0.004, 0.006, , 0.006, , 0.004, , 0.005, , 0.008, 0.011, 0.013, 0.016, 0.Q18, 0.003, , 0.010, 0.013, 0.015, 0.018, 0.020, 0.006, , 0.007, , 0.013, , 0.003, , 0.003, , 0.006, , 0.004, , 0.010, , 0.007, 0.013, , 0.0035, 0.004, 0.005, , 0.002, 0.002, 0.002, 0.0035, , 0.007, , 0.0055, , 0.005, 0.007, 0.008, 0.010, 0.011, 0.004, , 0.005, 0.007, 0.008, 0.009, 0.011, 0.003, , 0.009, 0.011, 0.013, 0.015, 0.018, 0.005, , 0.006, 0.008, 0.010, 0.011, 0.013, 0.004, , 0.010, 0.012, 0.015, 0.017, 0.020, 0.005, , 0.004, , 0.007, , 0.004, , 0.004, , Commercial, , Commercial, , 0.008, , 0.004, 0.005, , 0.002, 0.002, 0.003, , 0.001, 0.001, 0.0015, 0.002, , 0.0035, , 0.003, , 0.003, 0.004, 0.005, 0.006, 0.007, 0.002, , 0.0025, , Fine, , Polystyrene, , Fine, , Polypropylene, , Fine, , Commercial, , 1.000--2.000, 2.000-3.000, 3.000--4.000, 4.000--5.000, 5.000--6.000, 6.000--12.000, for, each additional, inch add, , 0.006, , Fine, , 0.008, , Commercial, , Polyethylene,, low-density, , To 1.000, , Dimensions, in, , Polyethylene,, high-density, , Table 3-6 ( Continued), , 0.015, , 0.010, 0.020, , 0.004, 0.005, 0.006, , 0.004, 0.005, 0.006, 0.008, , 0.007, , 0.007, , 0.012, 0.014, 0.015, 0.017, 0.018, 0.005, , 0.011, , Commercial, , 0.010, , 0.007, 0.015, , 0.003, 0.004, 0.005, , 0.003, 0.004, 0.005, 0.006, , 0.003, , 0.003, , 0.008, 0.009, 0.011, 0.012, 0.013, 0.003, , 0.007, , Fine, , Vinyl, flexible, , 0.010, , 0.015, 0.020, , 0.004, 0.005, 0.006, , 0.004, 0.004, 0.005, 0.006, , 0.007, , 0.007, , 0.009, 0.010, 0.012, 0.013, 0.014, 0.005, , 0.008, , Commercial, , 0.005, , 0.010, 0.015, , 0.003, 0.004, 0.005, , 0.003, 0.003, 0.004, 0.005, , 0.003, , 0.003, , 0.005, 0.006, 0.007, 0.008, 0.009, 0.003, , 0.0045, , Fine, , Vinyl, rigid, , ~, , ....., , $:l, ...., ;::, , ~, , ~, , '", aQ., , ~, , \::), , ("), , ...., , ;::, , ~, , ~, ....., 0, , U.;, , Rl, , .......

Page 181 : 163, , 3 Product Design Feature, Table 3-7 Guide on allowable undercut, tolerances TPs, , Material, , Average Maximum, Strippable Undercut, [mm (in)], , Acrylic, Acrylonitrile butadiene, styrene, Nylon, Polycarbonate, Polyethylene, Polypropylene, Polystyrene, Polysulfone, Vinyl, flexible, , 1.5 (0.060), 1.8 (0.070), 1.5 (0.060), 1.0 (0.040), 2.0 (0.080), 1.5 (0.060), 1.0 (0.040), 1.0 (0.040), 2.5 (0.100), , example graphite-filled molding compounds, could work in reverse. Upon heating, they, contract rather than expand, and vice-versa., To assist the designer the Society of the, Plastics Industry (SPI) issued Standards and, Practices of Plastics Molders that contains, tolerance ranges for various plastics as an, initial guide. These ranges theoretically encompass the accuracy involved in moldmaking, shrink variations, and molding variations., Each material supplier converts these data to, suit their specific plastics. Tables 3-10 to 3-14, are examples of this information. This type of, information is intended to give the designer a, guide for tolerances that are to be shown on, the drawings; these tolerances include variaTable 3-8, , tions in product manufacture and some degree of variation in the tooling for TPs and, TSs., These SPI tables can also be used as the, basis for establishing standards for molded, products between the designer, molder, and, customer. Users will find that two separate, sets of values are represented. Commercial, values represent common production tolerances that can be achieved at the most economical level. Fine values represent closer, tolerances that can be held, but at a greater, cost. The selection of one or the other will depend on the application under consideration, and the economics involved., Refer to the hypothetical molded article, and its cross-section, illustrated in the tables., Then using the applicable code number (such, as A that represents the diameter) in the first, column of the table and the exact dimensions, indicated in the second column, one can find, the recommended tolerances either in the, chart at the top of the table or in the two, columns underneath. Note that the typical article shown in cross-section in the table may, be round or rectangular or some other shape., Thus, dimensions A and B may be either, diameters or lengths., Tight tolerances on dimensions should be, specified only where absolutely necessary., Too many drawings show limits of sizes where, other means of attaining desired results, would be more constructive or the tolerances, , Guide for wall thicknesses of TS molding materials, , Alkyd-glass filled, Alkyd-mineral filled, Diallyl phthalate, Epoxy-glass filled, Melamine--cellulose filled, Urea--cellulose filled, Phenolic-general purpose, Phenolic-flock filled, Phenolic-glass filled, Phenolic-fabric filled, Phenolic-mineral filled, Silicone glass, Polyester premix, , Minimum Thickness, in. (mm), , Average Thickness, in. (mm), , Maximum Thickness, in. (mm), , .040 (1.0), .040 (1.0), .040 (1.0), .030 (0.76), .035 (0.89), .035 (0.89), .050 (1.3), .050 (1.3), .030 (0.76), .062 (1.6), .125 (3.2), .050 (1.3), .040 (1.0), , .125 (3.2), .187 (4.7), .187 (4.7), .125 (3.2), .100 (2.5), .100 (2.5), .125 (3.2), .125 (3.2), .093 (2.4), .187 (4.7), .187 (4.7), .125 (3.2), .070 (1.8), , .500 (13), .375 (9.5), .375 (9.5), 1.000 (25.4), .187 (4.7), .187 (4.7), 1.000 (25.4), 1.000 (25.4), .750 (19), .375 (9.5), 1.000 (25.4), .250 (6.4), 1.000 (25.4)

Page 182 : 164, , 3 Product Design Feature, Table 3-9, , Guide to tolerances of TP extrusion profiles, , Wall thickness (%, =), Angles (Deg., =), , PVC, , HIPS, , PC,, ABS, , PP, , Rigid, , Flex., , LDPE, , 8, 2, , 8, 3, , 8, 3, , 8, 2, , 10, 5, , 10, 5, , 0.007, 0.012, 0.017, 0.025, 0.030, 0.035, 0.050, 0.065, 0.093, 0.125, , 0.010, 0.020, 0.025, 0.027, 0.Q35, 0.037, 0.050, 0.065, 0.093, 0.125, , 0.010, 0.015, 0.020, 0.027, 0.035, 0.037, 0.050, 0.065, 0.093, 0.125, , 0.007, 0.010, 0.015, 0.020, 0.025, 0.030, 0.045, 0.060, 0.075, 0.093, , 0.010, 0.D15, 0.020, 0.030, 0.Q35, 0.040, 0.065, 0.093, 0.125, 0.150, , 0.012, 0.025, 0.030, 0.035, 0.040, 0.045, 0.065, 0.093, 0.125, 0.150, , Profile dimensions (in., ±), To 0.125, 0.125 to .500, .500 to 1, 1 to 1.5, 1.5 to 2, 2 to 3, 3 t04, 4 to 5, 5 to 7, 7 to 10, , where not sufficiently specific. For example,, if the outside dimensions of an electric drill, housing halves were to have a tolerance of, ±0.003 in., this would be a tight limit and can, be met. And yet if half of the housing were, to be on the minimum side and the other on, the maximum side, there would be a resulting, step that would be uncomfortable to the feel, of the hand while gripping the drill., A realistic specification would call for, matching of halves that would provide a, smooth joint between them, and the highest, step should not exceed 0.002 in. The point is, that limits should be specified in a way that, those responsible for the manufacture of a, product will understand the goal that is to be, attained. Thus we may indicate dimensions, for gear centers, holes as bearing openings, for shafts, guides for cams, etc. This type of, designation would alert a mold maker as well, as the molder to the significance of the tolerances in some areas and the need for matching products in other places and clearance for, assembly in still other locations., Most of the engineering plastics reproduce, faithfully and easily conform to the mold configuration, and when processing parameters, are appropriately controlled, they will repeat, with excellent accuracy tolerancewise, etc. As, an example for the past many decades, we, see plastic gears and other precision products made of acetal, nylon, polycarbonate,, , etc. Their tooth contour and other precision, areas are made with a limit of 0.0002 in., and, the spacing of the teeth is extremely uniform, to meet the most exacting requirements., The problem with any precision-type product is to recognize what steps are needed, to reach the objective and follow through, in a detailed manner every phase of the, process to safeguard the end product. Generally speaking, if we segregate the tolerances we should come up with feasible tolerances that will be reasonable and useful., The segregation can be into (a) functional, need, such as running fit, sliding fit, gear, tooth contour, etc.; (b) assembly requirements that are to accommodate products, with their own tolerances; and (c) matching parts for appearance or utility. This approach would be more productive than trying, to apply tolerances strictly on a dimensional, basis., Adaptation of metal tolerances to plastics is not advisable. With plastics reaction to, moisture and heat, for example, is drastically, different from metals, so that pilot testing under extreme use conditions is almost mandatory for establishing adequate tolerance requirements. Also important to control cost, is that close tolerances should be indicated, only where needed, carefully analyzed for, their magnitude, and proven out as to their, usefulness.

Page 183 : 3 Product Design Feature, Table 3-10, , 165, , High density polyethylene (HDPE), , Drawing, Code, , A = Diameter, (See note II), B = Depth, (See note 13), C= Height, (See note 13), , Dimensions, (Inches), ---0.000, ---0.500, ---1.000, , Plus or Minus in Thousands of an Inch, , ---4.000, , :, , lR ,:, , :, , :, :, :, :, , :, , : :, , ~~, ~IP~, ;, , :, , .., ., , :, :, , :, , :, , :, , K~ "i, , Comm.±, , Fine ±, , 0.006, , 0.003, , (See note 13), , O.OOS, , 0.004, , E=SideWall, , (See note '4), , O.OOS, , 0.004, , 0.000 to 0.125, , 0.003, , 0.002, , 0.12S to 0.250, , 0.004, , 0.002, , 0.251 to 0.500, , O.OOS, , 0.004, , 0.501 & over, , 0.008, , 0.005, , 0.000 to 0.250, , 0.005, , 0.003, , 0.251 to 0.500, , 0.007, , 0.004, , 0.501 to 1.000, , 0.009, , O.OOS, , H = Corners,, Ribs, Fillets, , (See note IS), , 0.025, , 0.010, , Flatness, , 0.000 to 3.000, , 0.023, , 0.015, , (See note 14), , 3.001 to S.OOO, , 0.037, , 0.022, , Thread Size, (Class), , Internal, , 1, , 2, , External, , 1, , 2, , (See note '4) (F.I.M.), , 0.027, , 0.010, , Draft Allowance, Per Side, , (See note IS), , 2.0', , 0.75·, , Surface Finish, , (See note m, , Color Stability, , (See note m, , Concentricity, , ,, , .., , 'IN, , D = Bottom Wall, , G= Hole Size, Depth, (See note IS), , ., , 1, , :, , F= Hole Size, Diameter, (See note 11), , 25, , :, , :, , 'i~~;, ! : :~, , ---5.000, ---6.000, 6.000 to 12.000, for each additional, inch add (inches), , 20, , 15, , I~, , :, , ---2.000, ---3.000, , 10, , 5, , Shrinkage, One factor associated with tolerance is, shrinkage. Generally, shrinkage is the difference between the dimensions of a fabricated, product at room temperature and after cooling,checked usually twelve to twenty-four, hours after fabrication. Having an elapsed, , ~A~, ~~, /1'H, , -, , ~~1, , ~, , REFERENCE NOTES, , 1. These tolerances do not include allowance for, aging characteristics of material., , 2. Tolerances are based on 0.125 inch wall section., 3. Parting line must be taken into consideration., , 4. Part design should maintain a wall thickness as, nearly constant as possible. Complete uniformity, in this dimension is sometimes impossible to, achieve. Walls of non-uniform thickness should, be gradually blended from thick to thin., 5. Care must be taken that the ratio of the depth of, a cored hole to its diameter does not reach a, point that will result in excessive pin damage., 6. These values should be increased whenever, compatible with desired design and good, molding techniques., 7. Customer-Molder understanding is necessary, prior to tooling., , time is necessary for many plastics, particularly the commodity TPs, to allow products to complete their inherent shrinkage, behavior after processing. The extent of this, postshrinkage can be near zero for certain, plastics or may vary considerably., Shrinkage can also be dependent on, such climatic conditions as temperature and

Page 184 : 166, , 3 Product Design Feature, , Table 3·11 Polypropylene (PP), Drawing, Code, , A = Diameter, (See note '1), B = Depth, (See note '3), C= Height, (See note #3), , Dimensions, (Inches), ---0.000, ---0.500, ---1.000, , Plus or Minus in Thousands of an Inch, , 10, , 5, , f\ N, ~i_hJi"'~, :, :::, :'\~~, , ---3.000, :, , ---4.000, , '~+-~, ~ ~ j, , ~ ~, , Comm.±, , j, , :, , 0.005, , 0.003, , D = Bottom Wall, , 0.003, , E=SideWall, , (See note 14), , 0.006, , 0.003, , 0.000 to 0.125, , 0.003, , 0.002, , 0.126 to 0.250, , 0.004, , 0.003, , 0.251 to 0.500, , 0.005, , 0.004, , 0.501 &over, , 0.008, , 0.006, , 0.000 to 0.250, , 0.005, , 0.003, , 0.251 to 0.500, , 0.006, , 0.004, , 0.501 to 1.000, , 0.009, , 0.006, , H = Comers,, Ribs, Fillets, , (See note #6), , 0.029, , 0.016, , Aatness, , 0.000 to 3.000, , 0.022, , 0.014, , .(See note 14), , 3.001 to 6.000, , 0.036, , 0.021, , Thread Size, (Class), , Internal, , 1, , 2, , External, , 1, , 2, , (See note '4) (F.l.M.), , 0.D15, , 0.012, , Draft Allowance, Per Side, , (See note '5), , 1.5', , 0.5', , Surface Finish, , (See note 17), , Color Stability, , (See note 17), , humidity, under which the product will exist, in service, as well as its conditions of storage. If proper stipulations are not in the fabricators job order, molded products could be, delivered at the time the ideal climatic conditions exist to meet the customer's tolerance requirements. As ridiculous as this may, , '''\, , :, , N:, , Fine ±, , 0.006, , Concentricity, , : 1, , N, , (See note '3), , G =Hole Size, Depth, (See note 15), , .\, .., , ---5.000, , F= Hole Size, Diameter, (See note 11), , 25, , :\, , ---2.000, , ---6.000, 6.000 to 12.000, for each additional, inch add (inches), , 20, , 15, , ~AW, _ - E-0, , GJi. ~~, , ~FW~l, ~, REFERENCE NOTES, , 1. These tolerances do not include allowance for, aging characteristics of material., 2. Tolerances are based (In 0.125 inch wall section., 3. Parting line must be taken into consideration., 4. Part design should maintain a wall thickness as, nearly constant as possible. Complete uniformity, in this dimension is sometimes impossible to, achieve. Walls of non-uniform thickness should, be gradually blended from thick to thin ., 5. Care must be taken that the ratio of the depth of, , a cored hole to its diameter does not reach a, point that will result in excessive pin damage., 6. These values should be increased whenever, compatible with desired design and good, molding techniques., 7. Customer-Molder understanding is necessary, prior to tooling., , appear, it has happened unfortunately to, customers., Plastic suppliers can provide the initial information on shrinkage that has to be added, to the design shape and will influence its processing. The shrinkage and postshrinkage will, depend on the types of plastics and their

Page 185 : 167, , 3 Product Design Feature, Table 3·12, , Polyvinyl chloride (PVC), , Drawing, Code, , A = Diameter, (See note #1), B = Depth, (See note #3), C= Height, (See note #3), , Dimensions, (Inches), ---0.000, ---0.500, ---1.000, , Plus or Minus in Thousands of an Inch, , 5, :, , ---4.000, , :\ ~:, \. :\1, , :, , :, :, :, , :, , :, , Comm.±, , Fine ±, , 0.005, , 0.003, , D = Bottom Wall, , (See note #3), , 0.007, , 0.003, , E= SideWall, , (See note /4), , 0.007, , 0.003, , 0.000 to 0.125, , 0.004, , 0.003, , F = Hole Size, Diameter, (See note #1), , 0.126 to 0.250, , 0.005, , 0.004, , 0.251 to 0.500, , 0.006, , 0.005, , 0.501 & over, , 0.008, , 0.006, , 0.000 to 0.250, , 0.004, , 0.003, , 0.251 to 0.500, , 0.005, , 0.004, , 0.501 to 1.000, , 0.006, , 0.005, , (See note #6), , 0.030, , 0.010, , Flatness, , 0.000 to 3.000, , 0.010, , 0.007, , (See note '4), , 3.001 to 6.000, , 0.020, , 0.Q15, , Thread Size, (Class), , Internal, , H = Corners,, Ribs, Fillets, , ::, :, , :, , \., , ::::, ., , 25, , :, , :, , :, , ~., , :\., :, , :N :'N, ., , ., , :, , ",, , .., , IfK-A~, .~~, vii, , -~, , ~~, --, , G, , ~, , REFERENCE NOTES, , 1. These tolerances do not include allowance for, aging characteristics of material., 2. Tolerances are based on 0.125 inch wall section., , 3. Parting line must be taken into consideration., 4. Part design should maintain a wall thickness as, nearly constant as possible. Complete uniformity, in this dimension is sometimes impossible to, achieve. Walls of non-uniform thickness should, be gradually blended from thick to thin., 5. Care must be taken that the ratio of the depth of, a cored hole to its diameter does not reach a, point that will result in excessive pin damage., , External, (See note #4) (HM.), , 0.015, , 0.010, , Draft Allowance, Per Side, , (See note #5), , 1.5°, , 1.0°, , Surface Finish, , (See note #7), , Color Stability, , (See note #7), , Concentricity, , :, , : :: :l\:: : 1: :\ ( ::, :, :, , G= Hole Size, Depth, (See note '5), , 20, :, :, , :\A',:~:, ::, ~ : : : '%.: :, , :, :, :, :, :, , ---5.000, ---6.000, 6.000 to 12.000, for each additional, inch add (inches), , 15, , ..., , ---2.000, ---3.000, , 10, , additives/fillers that interrelate to the processing conditions. The type and amount of, filler, such as its reinforcement, can significantly reduce shrinkage and tolerances where, it could be at zero change. If a plastic product, is free to expand and contract (shrink) with, temperature change, then its thermal expan-, , 6. These values should be increased whenever, compatible with desired design and good, molding techniques., 7. Customer-Molder understanding is necessary, prior to tooling., , sion property is usually of little significance., However, if it is attached to another material, having a lower or different thermal expansion, then movement of the product will be restricted. Temperature change will then result, in the development of thermal stresses in the, product. The magnitude of the stresses will

Page 186 : 168, , 3 Product Design Feature, , Table 3-13, , Nylon (polyamide) (PA), , Drawing, Code, , Dimensions, Plus or Minus in Thousands of an Inch, (Inches), 5, 10, 15, 20, 25, 0.000 - - - .--.......,..-,..-:--r--:--:---:--:--r-:-..,-.,--:--T--:--:--:--,-.,--,,......,--:--:---r-~, - - - 0.500 - - - - 1.000 - - - t-~T\-;-'-!'."'d-!'.-t--;--;----;--+-if---;--;-+-+-t-"!'-!'--!---;--i--;--f, , -------l - - A= Diameter, (See note 11), B = Depth, (See note 13), C= Height, (See note 13), , - - - 2.000, , r\ r\, , N-;-:-;--;-., c, 1~:. . . ~ ~~~A:-t-:-:--7-+-I--;--;-;-;-+-;-;--+-~--:---f, _-1--"'~::.\:-:, . rt-+-'<'1-,-1_ .......... j - ..........-+-....-.--+-!f--+-l, , :...-.;-+-+-....;--+-H-;..-+-...;-~f--;--+-....;-.;-f-.;.--j, , _ _ 3.000 _ _ _ I--;---;._.;.-i, - - 4.000 - - - 1-.........., , -I-....., , '\:-+:-+--+-.-+-.;......<;'-;'-j--;'-";"""-+-i----l-+-l, , - - - 5.000 - - - f---;-+-+-"";-+-"--i-':T.N'-+:-+--;:~, - - 6.000 - - 6.000 to 12.000, for each additional, inch add (inches), , ';:==:=::;===-;-l...-.:.-'-~.:.....J.-'-~.:......:.--L.~.:......:.-'--'--.:....J, , Comm. ±, , Finu, , 0.003, , 0.002, , D = Bottom Wall, , (See note 13), , 0.004, , 0.003, , E=SideWall, , (See note 14), , 0.005, , 0.003, , 0.000 to 0.125, , 0.002, , 0.001, , F= Hole Size, Diameter, (See note #1), , 0.126 to 0.250, , 0.003, , 0.002, , 0.251 to 0.500, , 0.003, , 0.002, , 0.501 &over, , 0.005, , 0.003, , 0.000 to 0.250, , 0.004, , 0.002, , 0.251 to 0.500, , 0.004, , 0.003, , 0.501 to 1.000, , 0.005, , 0.004, , H = Comers,, Ribs, Fillets, , (See note 16), , 0.021, , 0.013, , Ratness, , 0.000 to 3.000, , 0.010, , 0.004, , (See note 14), , 3.001 to 6.000, , 0.D15, , 0.007, , Thread Size, (Class), , Internal, , 2, , External, , 2, , G= Hole Size, Depth, (See note 15), , Concentricity, , (See note 14) (F.I.M.), , Draft Allowance, Per Side, Surface Finish, , (See note #7), , Color Stability, , (See note 17), , 0.005, , 0.003, , 1.50, , 0.5 0, , depend on the temperature change, method, of attachment, and relative expansion and, modulus characteristics of the two materials, at the exposed heat., Expansion or contraction can be controlled, in the plastic by orientation, cross-linking,, adding fillers and/or reinforcements, etc. Any, cross-linking has a substantial beneficial ef-, , REFERENCE NOTES, 1. These tolerances do not include allowance for, , aging characteristics of material., , 2. Tolerances are based on 0.125 inchwall section., 3. Parting line must be taken into consideration., , 4. Part design should maintain a wall thickness, as, nearly constant as possible. Complete uniformity, in this dimension is sometimes impossible to, achieve. Walls of non-uniform thickness should, be gradually blended from thick to thin., 5. Care must be taken that the ratio of the depth of, a cored hole to its diaml)ter does not reach a, point that will result in excessive pin damage., 6. These values should be increased whenever, compatible with desired design and good, molding techniques., 7. Customer-Molder understanding is necessary, prior to tooling., , fect on TPs. With the amorphous type, expansion is reduced. In a crystalline TP, however,, the decreased expansion may be partially offset by the loss of crystallinity. A compounded, plastic can be made to match those of the, attached material (plastic, steel, etc.). With, certain additives, such as graphite filler, the, thermal change could be zero or near zero;

Page 187 : 169, , 3 Product Design Feature, Table 3-14, , Phenol-formaldehyde (PF), , Drawing, Code, , Plus or Minus in Thousands of an Inch, , A = Diameter, (See note"l), 8 = Depth, (See note "3), , , ,, ,, , C= Height, (See note "3), , ,,,, , D = Bottom Wall, E = Side Wall, , F= Hole Size, Diameter, (See note "1), , G = Hole Size, Depth, (See note /5), , 0.003, , 0.002, , (See note "3), , 0.006, , 0.004, , (See note "4), , 0.004, , 0.003, , 0.000 to 0.125, , 0.002, , 0.001, , 0.126 to 0.250, , 0.003, , 0.002, , 0.251 to 0.500, , 0.004, , 0.003, , 0.501 & over, , 0.005, , 0.003, , 0.000 to 0.250, , 0.004, , 0.002, , 0.251 to 0.500, , 0.005, , 0.003, , 0.501 to 1.000, , 0.007, , 0.004, , H = Corners,, Ribs, Fillets, , (See note #6), , 0.030, , 0.015, , Flatness, , 0.000 to 3.000, , 0.014, , 0.008, , (See note /4), , 3.001 to 6.000, , 0.021, , 0.014, , Thread Size, (Class), , Internal, , 2, , External, , 2, , (See note "4) (F.I.M.), , 0.007, , 0.004, , Draft Allowance, Per Side, , (See note "5), , 1.0·, , 0.5", , Surface Finish, , (See note #7), , Color Stability, , (See note #7), , Concentricity, , in fact during a temperature rise, the plastic, could contract rather than expand., The condition of anisotropy can be used, when referring to the way a material shrinks, during processing, such as in injection molding (Fig. 2-62) and extrusion. Shrinkage is, an important consideration when fabricating plastics, particularly crystalline TPs where, , REFERENCE NOTES, 1. These tolerances do not include allowance for, aging characteristics of material., 2. Tolerances are based on 0.125 inch wall section., , 3. Parting line must be taken into consideration., 4. Part design should maintain a wall thickness as, nearly constant as possible. Complete uniformity, in this dimension is sometimes impossible to, achieve. Walls of non-uniform thickness should, be gradually blended from thick to thin., 5. Care must be taken that the ratio of the depth of, a cored hole to its diameter does not reach a, point that will result in excessive pin damage., 6. These values should be increased whenever, compatible with desired design and good, molding techniques., 7. Customer-Molder understanding is necessary, prior to tooling., , the flow direction can have more shrinkage, than the cross-flow direction. The control, of shrinkage can be made to meet design, requirements by factors such as the design, of the mold with its gate locations or die, shape, the processing machine controls, the, change of product shape, and the type of, plastics.

Page 188 : 170, , 3 Product Design Feature, , If it has been determined in advance that, a product must be postcured, stress relieved,, or baked, allowance must be made for probable additional shrinkage. These requirements, must be specified on the initial drawings. Especially for long runs, mold or die design is an, important factor. The metals that will be used,, particularly in mold cavities, and the forces, required will largely be determined by the, complexity of the product design. This complexity will, of course, dictate in turn the intricacy of the tool design that will eventually, be used (Chapter 8, TOOLING). In general,, pack hardening, oil hardening, and prehardened steels are used, with materials such as, beryllium copper and clectroformed cavities, finding use in applications for specialized, purposes (2-7, 10,20)., , Processing and Tolerance/Shrinkage, , Processing is extremely important in regard to tolerance control; in certain cases it is, the most influential factor. The dimensional, accuracy of the finished product relates to the, process, the machining accuracy of mold or, die, and the process controls, as well as the, shrinkage behavior of the plastic., The mold or die should also be recognized as one of the most important pieces, of production equipment in the plant. These, controllable, complex devices must be an, efficient heat exchanger and provide the, product's shape. The mold or die designer, thus has to have the experience or training and knowledge of how to produce the, tooling needed for the product and to meet, required tolerances with the plastic to be, processed., Adequate process control and its associated instrumentation are essential to have, product quality control. In some cases the, goal is precise adherence to a control point., In others it is simply to maintain the temperature within a comparatively narrow range., A knowledge of processing methods will, be useful to the designer to help determine what tolerances can be obtained. With, such high-pressure methods as injection and, compression molding of 2,000 to 30,000 psi, , (13.8 to 206.9 MPa) it is possible to develop tighter tolerances, but there is also, a tendency to develop undesirable stresses, (orientations, etc.). The low-pressure or no, pressure processes, including RP contact,, casting, and rotational molding, usually do, not permit meeting tight tolerances. There, are exceptions, such as certain RPs that are, processed at contact pressures resulting in, meeting tight tolerances. Regardless of the, process used, exercising the required and, proper control over it will maximize obtaining and repeating of tolerances that are, achievable., Table 3-15 reviews factors affecting tolerances. Many plastics change dimensions after, molding principally because they're molecular orientations or molecules are not relaxed (Chapter 2). To ease or eliminate the, problem, one can change the processing cycle so that the plastic is "stress relieved,", even though that may extend the cycle time., Also applicable is annealing according to, one's experience or the plastic supplier's, suggestions., An easy method for estimating shrink allowance for injection molding is as follows:, SD1, , = FL(l + SR), , (3-10), , where SD1 = mold dimension, SR=plastic's, shrinkage (in/in or mm/mm), and F L = product dimension., If the products are small and have thin, walls, this estimate is the best guide. If they, are large (> 10 in. or 25 cm) or use rather highshrink plastics, consider using the following, method of analysis (214):, SD2 = FL(l- SR), , (3-11), , where S~ = the mold dimension as determined by the corrected equation., The error, ER, would simply be the difference between the SD1 and S~ equations. To be more accurate for calculating, mold dimensions where the product size and, shrink rate increase, this error value should, be considered or Table 3-16 is be used. This, table shows, as one example, which in the, low shrink (0.008 mil/in. or less) materials, the products must be larger than 15 in.

Page 189 : 3 Product Design Feature, Table 3-15, , 171, , Parameters that influence product performances, PART DESIGN:, MATERIAL:, , MOLD DESIGN:, , MACHINE CAPABILITY:, , MOLDING CYCLE:, , Part configuration (size/shape). Relate shape to flow of melt in mold, to meet performance requirements that should at least include, tolerances., Chemical structure, molecular weight, amount and type of fillers/, additives, heat history, storage, handling., Number of cavities, layout and size of cavities/runners/gates/cooling, lines/side actions/knockout pins/etc. Relate layout to maximize, proper performance of melt and cooling flow patterns to meet part, performance requirements; preengineer design to minimize wear, and deformation of mold (use proper steels); layout cooling lines, to meet temperature to time cooling rate of plastics (particularly, crystalline types)., Accuracy and repeatability of temperature/time/velocity/pressure, controls of injection unit, accuracy and repeatability of clamping, force, flatness and parallelism of platens, even distribution of, clamping on all tie rods, repeatability of controlling pressure and, temperature of oil, oil temperature variation minimized, no oil, contamination (by the time you see oil contamination damage to the, hydraulic system could have already occurred), machine properly, leveled., Set up the complete molding cycle to repeatedly meet performance, requirements at the lowest cost by interrelating material/machine/, mold controls., , before an error of 0.001 in. will be realized., The allowable error will depend upon each, product's particular application. In some, cases it will be important to ensure proper, mold-size calculations. In others, changing, the calculation method will be purely academic., Experience is still a basic requirement for, mold design with regard to determining cavity dimensions. The costs for changing mold, cavities are high, even when similar moldings, are to be produced. Until now, theoretical efforts to forecast linear shrinkage have been, limited because of the number of existing, variables. One way to solve this problem is to, simplify the mathematical relationship, leading to an estimated but still acceptable assessment. This means, however, that the number, of necessary processing changes will also be, reduced (3)., As a first approximation, a superposition method has been used that can provide a guide to predicting mold shrinkage, (Fig. 3-27). However, problems arise in measuring the influencing variables, because they, , are often interrelated, such as variations in, the pressure course in a mold with a varying, wall thickness., The parameters of the injection process, must be provided. They can either be estimated or, to be more exact, taken from the, thermal and rheological layout. The position, of a length with respect to flow direction is in, practice an important influence. This is used, primarily for glass-filled material but can also, be used for unfilled TPs., Regarding this relationship, when designing the mold it is necessary to know the flow, direction. To obtain this information, a simple flow pattern construction can be used, (Fig. 3-28) via computer analysis. However,, the flow direction is not constant. In some, cases the flow direction in the filling phase differs from that in the holding phase. Here the, question arises of whether this must be considered using superposition., In order to get the flow direction at the, end of the filling phase and the beginning, of the holding phase (representing the onset of shrinkage), an analogous model can

Page 190 : -0.06, -0.19, -0.32, -0.45, -0.58, -0.71, -0.84, -0.97, -1.10, -1.23, -1.35, -1.48, -1.61, -1.74, -1.87, -2.00, -2.13, -2.26, -2.39, -2.52, -2.65, -2.77, -2.90, -3.03, -3.16, , -0.02, -0.05, -0.08, -0.11, -0.14, -0.18, -0.21, -0.24, -0.27, -0.31, -0.34, -0.37, -0.40, -0.43, -0.47, -0.50, -0.53, -0.56, -0.59, -0.63, -0.66, -0.69, -0.72, -0.76, -0.79, , 1.0, 3.0, 5.0, 7.0, 9.0, 11.0, 13.0, 15.0, 17.0, 19.0, 21.0, 23.0, 25.0, 27.0, 29.0, 31.0, 33.0, 35.0, 37.0, 39.0, 41.0, 43.0, 45.0, 47.0, 49.0, , -0.1, -0.4, -0.7, -1.0, -1.3, -1.6, -1.9, -2.2, -2.5, -2.8, -3.1, -3.4, -3.6, -3.9, -4.2, -4.5, -4.8, -5.1, -5.4, -5.7, -6.0, -6.3, -6.6, -6.9, -7.1, , 0.012, , -0.3, -0.8, -1.3, -1.8, -2.3, -2.9, -3.4, -3.9, -4.4, -4.9, -5.5, -6.0, -6.5, -7.0, -7.5, -8.1, -8.6, -9.1, -9.6, -10.1, -10.7, -11.2, -11.7, -12.2, -12.7, , 0.016, -0.4, -1.2, -2.0, -2.9, -3.7, -4.5, -5.3, -6.1, -6.9, -7.8, -8.6, -9.4, -10.2, -11.0, -11.8, -12.7, -13.5, -14.3, -15.1, -15.9, -16.7, -17.6, -18.4, -19.2, -20.0, , 0.020, -0.9, -2.8, -4.6, -6.5, -8.4, -10.2, -12.1, -13.9, -15.8, -17.6, -19.5, -21.3, -23.2, -25.1, -26.9, -28.8, -30.6, -32.5, -34.3, -36.2, -38.0, -39.9, -41.8, -43.6, -45.5, , 0.030, , 0.060, -4, -11, -19, -27, -34, -42, -50, -57, -65, -73, -80, -88, -96, -103, -111, -119, -126, -134, -142, -149, -157, -165, -172, -180, -188, , 0.050, -3, -8, -13, -18, -24, -29, -34, -39, -45, -50, -55, -61, -66, -71, -76, -82, -87, -92, -97, -103, -108, -113, -118, -124, -129, , 0.040, -1.7, -5.0, -8.3, -11.7, -15.0, -18.3, -21.7, -25.0, -28.3, -31.7, -35.0, -38.3, -41.7, -45.0, -48.3, -51.7, -55.0, -58.3, -61.7, -65.0, -68.3, -71.7, -75.0, -78.3, -81.7, , -5, -16, -26, -37, -47, -58, -68, -79, -90, -100, -111, -121, -132, -142, -153, -163, -174, -184, -195, -205, -216, -227, -237, -248, -258, , 0.070, , -90, -100, -118, -132, -146, -160, -174, -188, -202, -216, -230, -243, -257, -271, -285, -299, -313, -327, -341, , -77, , -7, -21, -35, -49, -63, , 0.080, -9, -27, -45, -62, -80, -98, -116, -134, -151, -169, -187, -205, -223, -240, -258, -276, -294, -312, -329, -347, -365, -383, -401, -418, -436, , 0.090, -11, -33, -56, -78, -100, -122, -144, -167, -189, -211, -233, -256, -278, -300, -322, -344, -367, -389, -411, -433, -456, -478, -500, -522, -544, , 0.100, , 'Error values in table are in mil (0.001 inch); thus, for shrink rate of 0.050 in/in and part size of 11 in, the error is 29 mil (0.029 in)., , 0.008, , 0.004, , Plastic Shrink Rate (inches/inch), , Error in mold size as a result of using incorrect shrinkage equation, , Part Size, Inches, , Table 3·16, , -50, -150, -250, -350, -450, -550, -650, -750, -850, -950, -1050, -1150, -1250, -1350, -1450, -1550, -1650, -1750, -1850, -1950, -2050, -2150, -2250, -2350, -2450, , 0.200, -129, -386, -643, -900, -1157, -1414, -1671, -1929, -2186, -2443, -2700, -2957, -3214, -3471, -3729, -3986, -4243, -4500, -4757, -5014, -5271, -5529, -5786, -6043, -6300, , 0.300, -267, -800, -1333, -1867, -2400, -2933, -3467, -4000, -4533, -5067, -5600, -6133, -6667, -7200, -7733, -8267, -8800, -9333, -9867, -10400, -10933, -11467, -12000, -12533, -13067, , 0.400, , -500, -1500, -2500, -3500, -4500, -5500, -6500, -7500, -8500, -9500, -10500, -11500, -12500, -13500, -14500, -15500, -16500, -17500, -18500, -19500, -20500, -21500, -22500, -23500, -24500, , 0.500, , ~, , $::, , $::), , ...~, , r§., , t::::J, ~, , ("), , ...~, , 0, , ....'"t:I, , \j,), , t::l, , .......

Page 191 : 3 Product Design Feature, , "w o, , Holding-pressure, , Mo Id - temperatu re, , I!.SIIII, S, , So, , a, , a:, Flow-angle, , Superposition approaches to determine shrinkage., , _!----JS, , Fig. 3·28, , -----Ct, , Molding -thickness, , Fig. 3·27, , 173, , ~, , 3 mill, , Flow patterns., , be developed that provides the flow direction at the end of the filling phase. To control, flow with respect to the orientation direction,, color studies are used., , Cost advantage with tight tolerance Economical production requires that tolerances, , not be specified tighter than necessary. However, after a production target is met, one, should mold "tighter", if possible, for greater, profit by using less material and/or reducing cycle time. Sometimes tight tolerances are, specified when they are not needed. This action is usually taken when the designer is in, a hurry or at a lost to set up the correct values. If relatively wide tolerances are specified, consider specifying that tighter tolerances are, desirable., In fact if a cost savings occurs due to, less plastic being used and/or cycle time is, reduced also consider a financial reward, (split the savings) with the fabricator. True, the processor usually takes this action to, reduce costs particularly after prototypes, are accepted and production starts. If a, large amount of plastic is consumed for the, production run, the fabricating specification, could include the weight of the product., Thus if a weight reduction occurs, it will be, obvious. If tighter tolerances develop during, molding and no reduction in weight occurs,, the molder may be overpacking the cavity(s), providing you with possibly unwanted, residual stresses or other problems that did, not exist on the prototypes. To eliminate, production process changes after a product

Page 192 : 174, , 3 Product Design Feature, , is approved, the fabricated should follow, their fabricating process control setting. This, action would follow what FDA requires, plastic medical device fabricators to meet, called quality system regulation (QSR)., Blowing agent and tolerance For example, certain injection molded products can, be molded to extremely close tolerances of, less than a thousandth of an inch, or down to, 0.0 percent, particularly when TPs are filled, with additives or TS compounds are used. To, practically eliminate shrinkage and provide, a smooth surface, one should consider using, a small amount of a chemical blowing agent, «O.5wt%) and a regular packing molding, procedure. For conventional molding, tolerances can be met of ±5% for a product 0.020, in. thick, ±1 % for 0.050 in., ±0.5% for 1.000, in., ±0.25% for 5.000 in., and so on. Thermosets generally are more suitable than TPs, for meeting the tightest tolerances., , Thermal Stress, When materials with different coefficients, of linear thermal expansion (CLTE) are, bolted, riveted, bonded, crimped, pressed,, welded, or fastened together by any method, that prevents relative movement between, the products, there is the potential for thermal stress. Most plastics, such as the unfilled, commodity TPs, may have ten times the expansion rates of many nonplastic materials., However there are plastics with practically no, expansion. Details are reviewed in Chapter 2,, THERMAL EXPANSION AND CONTRACTION., In many assemblies the clearances around, fasteners, the degrees of failure or yield, in adhesives, and warpage or creep will, tend to relieve the thermal stress. As with, metal-to-metal attachments having different, CLTEs, proper design allows for such temperature changes, especially with large parts, that might be subject to wide temperature, variations., , Impact Load, Film, As reviewed in Chapter 2, loads are often, applied abruptly, resulting in significant stress, and strain increases. However, the elasticity, of most TPs lets recovery usually be complete. Therefore, the steady-state stress and, deflection of plastic can be considered identical to that of a product that is loaded gradually. However, when impact becomes severe,, failure can result from it., Many high impact resistant plastics can survive large deflections or strains during impact without suffering the permanent deformation or failure one might expect from the, stress-strain curves of the plastics as measured at the standard loading rates. Therefore, the calculated impact stress of successful, products will often appear to be unreasonably high. Recall that stress-strain behaviors are very different under rapid loading as, compared to slow, steady loading conditions., Many plastics tend to have an exceptional capability of dissipating large amounts of mechanical energy when subject to these impact, conditions., , Plastic films represent the largest worldwide market for plastics with practically all, extruded (6). They are used to meet different, performance requirements particularly for its, major packaging market. Worldwide just for, biaxial oriented (Chapter 8) polypropylene, consumption is about 5% billion lb. Their, use includes tape, food, tobacco, and confectionery. Thermoforming film (and extruded, sheets) is a major processing technique producing all kinds of products., History from Kodak relates to a product, design feature approach that is applicable, to the subject of developing film features., As reported by Kodak as of 1879 they were, coating its photographic emulsions only on, glass plates (187). Since 1920 cellulose triacetate safety plastic was used for the movie, film and since then there has been relatively little change in the film base material., By the late 1950s Kodak was using acetate, as the support across a range of products., But it was determined that polyethylene

Page 193 : 3 Product Design Feature, terephthalate (PET) had better dimensional, stability and tensile strength. The dimensional stability made it a better material than, acetate for microphotographic applications,, especially for four-color work., The tensile strength of PET provided characteristics that were important in X-ray applications. The modulus of acetate is half that, of PET therefore PET was adopted in X-ray, film so that images could be handled and displayed more easily, and in microphotographics for its greater accuracy., In the early 1990s interest developed in the, packaging material polyethylene naphthalate, (PEN), a close cousin of PET. PEN has thermal stability 20°C higher than PET. Kodak, had samples of the material sifting in its labs, from the makers Teijin in Japan, as early as, the beginning of the 1970s. Teijin is still the, premier producer of PEN film and plastic today, and is involved with DuPont on the film, manufacturing side., The Kodak Advantix format film utilizes, PEN. The material has two advantages in that, context. First the Advantix film has smaller, apertures for the film advance sprockets and, PEN locates more accurately in the camera. Secondly its relaxation characteristics, are better than PET. When film comes off, the cylinder core it has a tendency to curl, which can complicate both in-camera use and, photofinishing. With PEN, which is a little, stiffer than PET, the film relaxes into a flatter, profile more quickly., All consumer films and professional stock, continue to be offered on cellulose triacetate., All its X-ray and micro photographic film is, supported on PET. Only Advantix is on PEN., The primary issue is the cost of PEN, which, may be why it has not been adopted widely, in packaging. Its transport characteristics for, bottles is excellent because of its physical, characteristics. Its cost is high but a premium, price in a premium product is more acceptable than it would be in Kodak's mainstream, product range., Motion film has been moving from acetate, to PET because the tensile strength is better and the product is more durable. Going, to PET has no cost penalty in comparison, with acetate. Kodak uses a huge volume of, , 175, , PET and manufactures its own in Rochester,, NY, USA as well as at its polyester plants in, Colorado/USA, Chalon, France and London,, UK., In terms of trend the company is looking at a number of materials with interest., Photo manufacturers are studying sindiotactic polystyrene because it has very low moisture take-up. All its products need dimensional stability so materials which resist the, effects of temperature and humidity changes, are highly desirable., , Weld Line, Weld lines are also called knit lines. During processing, such as by injection molding, and extrusion, weld lines can occur. They can, form during molding when hot melts meet, in a cavity because of flow patterns caused, by the cavity configuration or when there, are two or more gates. With extrusion dies,, such as those with "spiders" that hold a center metal core, as in certain pipe dies, the, hot melt that is separated momentarily produces a weld line in the direction of the extrudate and machine direction. The results, of these weld lines could be a poor bond at, the weld lines, dimensional changes, aesthetic, damages, a reduction of mechanical properties, and other such conditions., To illustrate the influence of processing, on mechanical properties, the test specimens, in Fig. 3-29 can be analyzed and related to, what can happen in a fabricated product. It, shows three sets of injection-molded specimens where the same plastic is processed in, all specimens. There are three sets of similar specimens: a tensile one on top, a notched, Izod impact one on the right side, and a flexural one on the left. The top set has a single gate, for each specimen, the center set has double, gates that are opposite each other for each, specimen, and the bottom set has fan gates, on the side of each specimen. The highest, mechanical properties come with the top set, of specimens, because of its melt orientation, being in the most beneficial direction. The, bottom set of specimens, with its flow direction being limited insofar as the test method

Page 194 : 176, , 3 Product Design Feature, ing mechanism (3). Either splitting the mold, halves or using unscrewing devices in the, mold can produce external threads; split mold, produces a parting line on the threads. With, a split lower cost mold, it is basically easier, to design the mold and easier to remove the, threaded part from the mold during processing (Chapter 8, TOOLING). The proper design of the thread shape is required to prevent excessive shear, resulting in stripping, the threads when torque is applied, and also, to limit hoop stresses, which can result in, tensile failure. Although the mechanics of, stress analysis for screw threads are readily available, the equations for them can be, rather complicated., , Coating, Fig. 3-29 Injection molded test specimens that, include weld lines., , is concerned, results in lower test data performance. With the double-gated specimens, (the center set) weld lines develop in the critical testing area that usually results in this set's, having the potential lowest performance of, any of the specimens in this diagram., Fabricating techniques can be used to reduce this problem in a product. However,, the approach used in designing the product,, particularly its mold (relocate gates), is most, important to eliminate unwanted orientation, or weld lines. This approach is no different, from that of designing with other materials, like steel, aluminum, or glass., , Meld Line, A meld line is similar to a weld line except, the flow fronts move in parallel rather than, meet head. Usually the meld line is identified, as a weld line., , External Thread, Threads can be molded or tapped into a, plastic. Molded internal threads usually require some type of unscrewing or collaps-, , Coatings for all types of products (plastics,, steels, etc.) are essential to meet all kinds of, environmental requirement for certain plastic products but more with other materials, such as steel and wood. Plastics continue to, be the backbone in the coating industry since, practically all coatings are composed of some, type of plastics. The most widely used include acrylics, alkyds, vinyls, urea-melamine,, styrenes, epoxies, and phenolics. Growth has, been steady and reliable so that rational and, economic paint production can no longer be, regarded, as was the case until comparatively, recent, as an art or craft based solely on empirical experiences. Although color matching, tends to still be more of an art or craft., Coatings are generally identified as paints,, varnishes, and lacquers. Other nomenclature includes enamels, hot melts, plastisols,, organosols, aerospace coatings, masonry water repellents, polishes, magnetic tape coatings, and overlays. They each have their performance characteristic (2). There are 100%, plastic coatings such as vinyl-coated fabrics or, polyurethane floor coverings. The more popular, and the largest user of plastics, are the, paints. Almost all the binders in paints, varnishes and lacquers are made up principally, of plastics., The properties of the coating industry are, essentially for the protection and decoration, of the majority of manufactured products

Page 195 : 3 Product Design Feature, that characterize our complex material civilization. The protective function includes resistance to air, water, organic liquids and aggressive chemicals such as acids and alkalis,, and together with improved superficial mechanical properties such as greater hardness, and abrasion resistance. The decorative effect may be obtained through color, gloss or, texture, or combinations of these techniques., In the case of many surfaces such as walls, or floors, or objects such as interior fittings,, furniture and other articles, the surface coating can also fulfill hygienic requirements. The, surface should not be prone to collect dirt,, bacteria and other impurities. It should be, easy to clean with common cleaning agents., In certain cases special qualities are required, of the surface coatings, for example, in roadmarking paints, in safety-marking paints, in, factory floors, and in paints which make the, surface either a good or poor electrical conductor., Substrates protected from different environmental conditions basically include the, metals (steel, zinc, aluminum and copper),, inorganic materials (plaster, concrete and asbestos), and organic materials (wood, wallboard, wallpaper and plastics). Metals may, be surface coated to improve their workability in mechanical processing., Different technical developments have occurred in the coating industry which permit, the use of a variety of raw materials. It is possible to formulate surface coatings that are, suitable for each and every kind of material., In many cases a number of different coating systems may come into consideration for, painting a particular substrate., Functional Surface and Lettering, Surfaces of plastics may be provided with, designs that can give a good grip or that can, simulate wood, leather, etc. These types of, surfaces should be specified in a manner that, will not create undercuts to the withdrawal, action from a mold. The undercut effect can, be responsible for stresses and marring. A, similar condition applies to lettering, and the, location of such lettering should conform to, smooth withdrawal requirements., , 177, , Fiber Reinforcement, Fiber behavior in reinforced plastics usually occurs at strains of only 1-3%. Designers that are accustomed to designing to yield, with built-in safety factor margin of at least, 10% strain might hesitate in using these materials. However, designing with these strains, is logical and has been used since at least the, 1940s. Data has been developed and used that, includes variability in properties, creep, fatigue, static and dynamic sustained loading,, etc. Both short and long fibers are used (106)., The conclusion that short stable fibers will, not produce maximum physical properties is, not theoretically correct. Both experiment, and theory have concluded that with proper, adhesion or bond between fibers and plastic matrix, maximum properties can basically, be achieved by using relatively short stable, fibers rather than continuous filament construction (39). To date the higher performances is overwhelming achieved with the, continuous fibers. Also, the fibers used in RPs, have the important potential of reaching values that are far superior (7, 10)., Process, There are conditions during the fabrication of plastic products that ensure meeting, product performance requirements. However there are also constraints as reviewed, in Chapter 8., Prototype, , The basic approach in designing any product made from any material (steel, aluminum,, wood, plastic, etc.) involves knowing the behaviors and characteristics of the materials, and manufacturing influences on the materials. In turn this knowledge is to be correctly applied such as using, when required,, the processed material's static and/or dynamic properties. Should a need arise for, data at conditions different from those at, which test data are available, with few exceptions, it would not be too difficult or costly to, obtain.

Page 196 : 178, , 3 Product Design Feature, , Depending on product performance requirements, that could involve the safety, of people, the more costly engineering approach such as finite-element analysis may, be required (Chapter 2). Finally, in addition to taking into account all of the relevant elements that are targeted to ensure, a sound product design, it must be kept in, mind that prototype testing to verify performance is usually the most important step, in the overall design process of any product (Chapter 8, MODELIPROTOTYPING, BUILDING). These products would include, highly load types to those basically not exposed to loads. The no load product may, be one that has to meet certain requirements (abusive handling to meeting safety, requirements) or have a long production, run., A prototype is a 3-D model suitable for, use in the preliminary testing and evaluation, of a product (also used for modeling a die,, mold and other tool). It provides a means, to evaluate the product's performances before going into production. The ideal situation is for the prototype to be the actual, product made in production. However machining stock material and using rapid prototype techniques can make prototypes (Chapter 4, BOOK SHELVES)., Conventional machining operations are, used preferably from the same plastic to, be used in the product (Chapter 8, SECONDARY EQUIPMENT). Different casting techniques are used that provide low cost, even though they are usually labor intensive., The casting of unfilled or filled/reinforced, plastic used include TS polyurethane, epoxy,, structural foam, and RTV silicone. Also used, are die cast metals., These materials are reviewed elsewhere, in this book except RTY. The RTV (room, temperature vulcanization) silicone plastic, is a very popular type. It solidifies by vulcanization or curing at room temperature, by chemical reaction, made up of two-part, components of silicones and other elastomers/rubbers. RTV are used to withstand, temperatures as high as 290°C (550°F) and, as low as -160°C (-250°F) without losing, their strength. Their rapid curing makes them, , useful in different applications such as prototypes, prototype molds, etc., , Rapid Prototyping and Tooling, Rapid proto typing (RP) is technology used, for building physical models and prototype, products from 3-D computer-aided design, data. Rapid tooling is any method or technology that enables one to produce tooling, quickly. The term "rapid tooling" is derived, from rapid prototyping technology and its, application. It refers to RP-driven tooling., Even though these systems are more expensive than the past usual methods, they provide, the desirable end result to the industry that, is a much quicker way to obtain prototypes, (hours instead of days). These systems are, continuously being up dated and expanding, their capabilities (165, 174)., Methods are used to produce the more, costly rapid prototypes include those that, produce models within a few hours. They, include photopolymerization, laser tooling,, and their modifications. The laser sintering, process uses powdered TP rather than chemically reactive liquid photopolymer used in, stereo lithography. Models are usually made, from certain types of plastics. Also used in, the different processes are metals (steel, hard, alloys, copper-based alloys, and powdered, metals). With powder metal molds, they can, be used as inserts in a mold ready to produce prototype products. These systems enable having precise control over the process, and constructing products with complex geometries., As an example stereolithography is a 3-D, rapid process that produces automatically, simple to very complex shaped models in, plastic. Basically it is a method of building successive layers across sections of photopolymerized plastics on top of each other, until all the thin printed layers can be joined, together to form a whole product. The chemical key to the process, photopolymerization,, is a well established technology in which a, photo initiator absorbs UV energy to form, free radicals that then initiate the polymerization of the liquid monomers. The degree

Page 197 : 3 Product Design Feature, of polymerization is dependent upon the total amount of light energy absorbed., This process uses a moving laser beam, directed by a computer, to prepare the model., The model is made up of layers having, thicknesses about 0.005--0.020 in. (0.012-0.50, mm) that are polymerized into a solid product. Advanced techniques also provides fast, manufacturing of precision molds (152). An, example is the MIT three-dimensional printing (3DP) in which a 3-D metal mold (die,, etc.) is created layer by layer using powdered, metal (300- or 400-series stainless steel, tool, steel, bronze, nickel alloys, titanium, etc.)., Each layer is inkjet-printed with a plastic, binder. The print head generates and deposits, micron-sized droplets of a proprietary waterbased plastic that binds the powder together., Once the lay-up is completed, product is removed and placed in a sintering oven. It goes, through three cycles where plastic is burned, off, metal powder is sintered together, and, the product is solidified by infiltrating with, another material to fill the voids such as lower, melting point metal or a plastic (epoxy, etc.)., Total time is 50 h. Shape is accurate within, 0.005 in., plus 0.002 in.lin. (0.0127 cm, plus, 0.0051 cm) and may be acceptable for prototyping. The tool can be machined to tighter, tolerances and polishing. This process permits creation of any type of internal voids, such as cooling lines that conform to the part, shape (160)., , 179, , AND ASSEMBLING and Chapter 8, PROCESSING BEHAVIORS and PROCESSING AND PROPERTY)., One of the earliest steps in product design, is to establish the configuration that will form, the basis on which strength calculations will, be made and a suitable material selected to, meet the anticipated requirements. During, the sketching and drawing phase of working, with shapes and cross-sections there are certain design features with plastics that have, to be kept in mind to obtain the best costperformances and avoid degradation of the, properties. As previously reviewed, such features may be called property detractors or, constraints. Prior to designing a product, the, designer should understand such basic factors as those summarized in Table 3-5 and, Fig. 3-26. Success with plastics, or any other, material for that matter, is directly related to, observing design details., The important factors to consider in designing can be categorized as follows: part, thickness, tolerances, ribs, bosses and studs,, radii and fillets, drafts or tapers, holes,, threads, colors, surface finishes and gloss levels, decorating operations, parting lines, gate, locations, shrinkages, assembly techniques,, production volumes, mold or die designs,, tooling and other equipment amortization, periods, as well as the plastic and process selections. The order that these factors follow, can vary, depending on the product to be designed and the designer's familiarity with particular materials and processes., , Features Iuflueuciug Performauce, , This section provides more detail on this, important basic subject of design detractors, and constrains. They represent conditions, that can usually be incorporated in a design but it is to show that there is an easier way to fabricate the product so that you, have a target to meet if the design permits, it. Even though some of the analyses here, will pertain to a specific process, many will relate to other processes, so it is best to review, them all. Product designers should have some, idea of where problems can develop that includes how a tool (mold or die) is designed, and manufactured (Chapter 4, JOINING, , Residual Stress, Such processing-induced residual stresses, that influence properties as mechanical, physical, environmental, and aesthetic factors, (which also exist in other materials like metals and ceramics) can have favorable or unfavorable effects, depending on the application, of the load with respect to the direction of the, stresses or orientation., Residual stresses and molecular orientation play an important role in the toughness enhancement of plastics, because toughness is primarily based on the mechanics of

Page 198 : 180, , 3 Product Design Feature, , craze formation and shear band (crazes and, flaws) formation. The shear bands determine, the fracture mode and toughness of a plastic, when subjected to impact loads. The amount, of energy dissipated will depend on whether, the material surrounding the flaws deforms, plastically. For toughness enhancement the, residual stresses play an important role in the, suppression of craze formation, by avoiding, the stress state that promotes brittle fracture., The term residual stress identifies the system of stresses that are in effect locked into a, product, even without external forces acting, on it. For instance, minute stresses may be, induced in a material by nonuniform heating and cooling during processing. The production of residual stresses is usually the result of nonhomogeneous plastic deformation, occurring during thermal and mechanical actions, arising from changes in either volume, or shape. Thermal treatments like quenching (rapid cooling) and annealing (slow cooling) introduce changes in physical and mechanical properties. For example, with sheet, plastic the stresses created by quenching are, the result of uneven cooling, when the surfaces cool faster than the core. This produces, nonuniform volume changes and properties, throughout the thickness. The compressive, stresses on the surfaces of the quenched plastic produce tensile stresses in the core, which, maintain the equilibrium of the forces., , elastic recovery, this condition produces compressive residual stresses at the surface and, tensile residual stresses in the core., The logic of this situation is that the surface, material is forced to elongate more than the, relatively rigid core permits. When there is a, large diameter and much reduction, the deformation penetration occurs deeper in the, core and there is a tendency for the plastic, to lag at the surface, the result of friction, at the material-to-tool interface occurs. Thus,, the cold working processes like rolling, drawing, extrusion, and forging produce residual, stresses along with their molecular orientation., Generally, the more discussed and technically reviewed residual stresses are in injection molded products. It usually occurs because melt in the cavity next to the cavity is, cold and does not properly flow. Cause could, be the melt and/or the cavity surface was, cold. Their presence can often be detected by, (1) the product's performances being reduced or changed such as dimensions, or, (2) qualitatively by immersing TP products, in appropriate stress-cracking solvents for, a short time, then observing the crazing, caused by surface tensile residual stresses, (Chapter 5, STRESS ANALYSIS). Such, methods are ineffective for a product with, compressive or insufficient tensile stresses on, its surface. To determine their magnitude includes the layer removal technique of microtoming (Chapter 5, FLAW DETECTION)., , Cold Working, Generally, a variety of mechanical deformation processes cause the nonuniform deformation that results in the formation of, residual stresses. This nonhomogeneous deformation in a material is produced by the, material's parameters, largely its process parameters such as the tool geometry and frictional characteristics. For example, the rolling, of a strip can be accomplished by using relatively cold squeeze rolls. In the rolling process, parameters with a small roll diameter and little reduction produce deformation, penetration that is shallow and close to the, surface, whereas the interior of the strip remains almost undeformed. After the removal, of the deformation forces and a complete, , Stress Concentration, Sharp corners should always be avoided, in designing. Although sharp-cornered designs are common with certain sheet metal, and machined products, good design practice in any material dictates the use of generous radii, to reduce stress concentrations. RPs, and metal products will often tolerate sharp, corners, because the stresses at their corners are low compared to the strength of the, material or because localized yielding redistributes the load. However, neither of these, factors should be relied upon in TP products., Sharp corners, particularly the inside comers, can cause severe molded-in stresses as

Page 199 : 3 Product Design Feature, a material shrinks onto the corner, as well as, poor flow patterns, reduced mechanical properties, increased tool wear, and so on., The elementary formulas used in design, are based on structural members having a, more or less constant cross-section, or at, least only a gradual change of contour, but, these conditions are seldom found in practice., The presence of shoulders, bosses, grooves,, holes, threads, and corners result in modifying the simple stress distribution so there are, no localized, high stresses. This localization,, known as the stress concentration factor, is, defined as K = maximum stress divided by, nominal stress. Localized high stresses must, in most cases be determined experimentally, rather than theoretically. The photoelastic, technique is one of the more effective methods used to do this. To interpret a photoelastic diagram qualitatively it is sufficient to, know that the number of fringes (the density, of lines) is proportional to the absolute stress, level (Chapter 5, STRESS ANALYSIS)., Basically, in the vicinity of a sharp comer, all fringes converge toward the apex. Having a high density of lines at this point indicates the presence of high stress level. At, a rounded corner there will be considerably, less concentration. Besides the molding problems, sharp corners often cause premature, failure because of the stress concentration., To avoid these problems, inside comer radii, should be equal to one-half the nominal wall, , 181, , thickness, with a 0.020 in. radius considered, as a minimum for products sUbjected to stress, and a 0.005 in. minimum for the stress-free regions. Having inside radii less than 0.005 in., is not recommended for most materials. Outside comers should have a radius equal to the, inside corner plus the wall's thickness., Injection Molding, Design concept In designing a totally new, product or redesigning an existing one to improve the product, bring about cost savings,, or some combination of these or other reasons, consideration should be given to the, key advantages of 1M. These advantages include the ability to produce finished, multifunctional, or complex molded products accurately and repeatedly in a single, highly, automated operation (Chapter 8). While, keeping this in mind during the initial planning stage, one should also be aware of the, general design considerations presented in, this section (3)., Many injection molded products will influence the final product's performance, dimensions, and other characteristics. The mold, includes the cavity shape, gating, parting, line, vents, undercuts, ribs, hinges, and so on, (Table 3-17). The mold designer must take all, these factors into account to eliminate problems. At times, to provide the best design, , Table 3-17 Functions of an injection mold, Mold Component, Mold base, Guide pins, Sprue bushing (sprue), Runners, Gates, Cavity (female) and, force (male), Water channels, Side (actuated by cams., gears, or hydraulic, cylinders), Vents, Ejector mechanism (pins,, blades, stripper plate), Ejector return pins, , Function Performed, Hold cavity (cavities) in fixed, correct position relative to machine nozzle, Maintain proper alignment of the two halves of a mold, Provide means of entry into mold interior, Convey molten plastic from sprue to cavities, Control flow into cavities, Control size, shape, and surface texture of molded article, Control temperature of mold surfaces, to chill plastic to rigid state, From side holes, slots, undercuts, threaded sections, Allow escape of trapped air and gas, Eject rigid molded article from cavity or force, Return ejector pins to retraced position as mold closes for next cycle

Page 200 : 182, , 3 Product Design Feature, , the product designer, processor, and mold, designer may want to jointly review where, compromises can be made to simplify meeting product requirements. With all this interaction, it should be clear why it takes a, certain amount of time to ready a mold for, production., The subject of who is responsible for, designing the mold can become confusing., One might say it is not the product designer responsibility. The product designer, may provide a design that the mold maker can, produce but the products do not meet performance requirements, etc. because the original, design was not complete or accurate. It permitted the mold designer liberty to use whatever approach that made it easier to meet the, design configuration., Stretching this point let us assume that an, optical lens was designed with no mention, that a gate could not be located in the middle, of the lens. The mold was made with a gate in, the center of the mold cavity. The responsibility is on the product designer who should, have known better and specified no gate on, the lens' surface or without experience contacted a knowledgeable and cooperative person such as the mold designer that would explain the options available to meet the mold, design requirements. In this example we have, to assume that product designer was not familiar with gate location problems. However, one ofthe requirements should have included, that the lens' surface not be marred, meet, certain optics (index of refraction, etc.), and, so on. If these requirements had been listed, and translated to the mold designer the gate, would not have been located in the center of, the lens., Thus, in the design of any 1M product there, are certain desirable goals that the designer, should use. In meeting them, problems can, unfortunately develop. For example, the most, common mold design errors of a sort that, can be eliminated usually occur in the following areas: (1) thick/thin section transitions,, (2) multiple gates resulting in distorted products or weld lines, (3) wrong gate locations,, (4) inadequate provision for cavity air venting entrapping microscopic voids, (5) products too thin to mold properly for the plastic, , being used, (6) products too thick to mold, properly for the plastic being used, (7) plastic flow path too long and tortuous, (8) runners too small, (9) gates too small, (10) poor, temperature controls, (11) runner too long,, (12) product symmetry vs. gate symmetry, clashes, (13) orientations of plastic melt, in flow direction, (14) hiding gate stubs,, (15) stress relief for interference fits, (16) living hinges, and (17) thread inserts., As reviewed in other chapters, different, plastics have different melt and flow characteristics. What is used in a mold design for, a specific material may thus require a completely different type of mold for another, material. These two materials might, for instance, be of the same plastic but use different proportions of additives and reinforcements. This situation is no different than that, of other materials like steel, ceramics, and, aluminum. Each material will require its own, cavity shapes and possibly have its own runner system., What follows is a general summary of how, to reduce problems to tolerable limits. They, represent conditions that can be molded but, it is to show that there is an easier way to, mold so that you have a target to meet if the, design permits it., First as reviewed, inside comers should, normally not be shown as two intersecting, straight lines with a sharp corner. Corners, are stress-concentration areas, quite similar, to a notch in a test bar. The Izod impact, strength of notched and unnotched test bars, shows that the relative impact strength of, each material at these two conditions that has, a relationship to a radius vs. a sharp corner., Thus, for example, polycarbonate has an impact strength of the notched 1/8 in. test bar, of 12 to 16 ft.-Ib'/in., whereas the same bar, unnotched does not fail the test. Polypropylene has an impact strength 30 times greater, in the unnotched than the notched bar. Nylon, shows a drastic increase in impact strength, as the radius increases from sharpness to, 3/64 in. A similar trend exists for most other, materials., These examples point out that brittleness, increases with the decreasing of a radius in, a comer. Visually, a radius of 0.020 in. on a

Page 201 : 3 Product Design Feature, product may be considered sharp, with an, influence on strength that is much more favorable than a radius of 0.004 in. To the moldmaker, a sharp corner is usually easier to produce, but in the plastic product it is a source, of brittleness and, in most cases is highly undesirable. Inside sharp comers on plastic-part, drawings are a frequent occurrence., Second, varying wall thicknesses from, thick to thin sections can lead to problems in, molding. Having a uniform wall throughout, a part gives it good strength and appearance., Thick and thin sections could have molded-in, stresses, different rates of shrinkage (causing, warpage), and possibly void formation in the, thick portion. Since the molding solidify from, their outer surfaces toward the center, sinks, will tend to form on the surface of a thick, portion. When thick (3/16 in. and over) and, thin (1/8 in. or less) portions are unavoidable,, the transition should be gradual and coring, should be utilized whenever possible. Influencing these behaviors can be related to the, locations of mold gates. The usual approach, is gating at the thin section., Third, sinks are not only the result of the, causes listed above but also can occur whenever supporting or reinforcing ribs, flanges,, or similar features are used in an attempt to, provide functional service without changing, the basic wall thickness of a product. If the, appearance of a sink on the surface is objectionable, the ribs and transition radius should, be proportioned so that their contribution to, the sink is minimal. Sinks can usually be eliminated by changing the process controls that, usually results in the unwanted longer cycle, times., Fourth, molded-in metal should be avoided, whenever alternate methods will accomplish, the desired objective. If it is essential to incorporate such inserts, they should be shaped so, that they will present no sharp inside comers, to the plastic. The effect of the sharp edges, of a metal insert would be the same as explained in the first point above, namely, brittleness and stress concentration can occur., The cross-section that surrounds a metal insert should be heavy enough that it will not, crack upon cooling. A method of minimizing cracking around the insert is to heat the, , 183, , metal insert prior to mold insertion to a temperature of 250 to 300°F (121 to 149°C) so, that it will tend to form the plastic into its finished shape. The thickness of the plastic enclosure will vary from material to material. A, reasonable guide is to have the thickness 1.75, to 2 times the size of the insert diameter., Fifth, plastic threads have a very limited, strength and may be further degraded if, the thread form is not properly shaped. The, V-shaped portion at the outside of a female thread will present a sharp inside comer, that will act as a stress concentrator and, thereby weaken the threaded cross-section., A rounded form that can be readily incorporated in a molding insert will appreciably, improve the strength over a V-shaped form., When self- tapping, thread-cutting, or threadform screws are used, their holding power can, be increased if either the screws or plastics, are heated to a temperature of 180 to 200°F, (82 to 93°C) at joining time. This will provide, forming action to some degree and keep the, stress level caused by the joining action at a, low point. More on this subject is reviewed, latter under Internal plastic thread., These possible sources of problems in a, molded part should be marked on the product drawing and explained to the mold designer for corrective action or creating an, awareness of possible product defects. This, is a necessary step in the chain of events in, which the aim is to produce a tool that will, provide useful products. Even if the mold's, design, workmanship, and operation are carried out to the highest degree of quality, they, cannot overcome a built-in weakness due to, the product design., Sharp corner As reviewed, and never to, many times, when a drawing does not show, a radius, the tendency is for the toolmaker, while manufacturing a mold to leave the intersecting machined or ground surfaces as, they are generated by the machine tool., The result is a sharp comer on the molded, product. Such sharp comers on the insides, of products are the most frequent property, detractors., Sharp corners become stress concentrators. The stress-concentration factor

Page 202 : 184, , 3 Product Design Feature, , increases as the ratio of the radius R to the, part thickness T decreases. An R/T of 0.6 is, favorable, and an increase in this value will, be of some limited benefit. The ASTM Izod, impact strength value of nylon with various, notch radii change. With a radius of 0.005, in. the impact strength is about 1.3 ft-Ib.lin.,, with an R of 0.020 in. it is 4.5 ft-Ib.lin., and, with an R of 0.040 in. it is 12 ft-Ib'/in. In most, cases a radius of 0.020 in. can be considered, a sharp comer as far as end use is concerned, a size that is a decided improvement, over a 0 to 5 mil radius; therefore, it should, be considered a minimum requirement and, be so specified., The recommended radius not only reduces, the brittleness effect but also provides a, streamlined flow path for the plastic melt in, the mold cavity. The radiused corner of the, metal in the mold reduces the possibility of, its breakdown and thus eliminates a potential repair need. Too large a radius is also, undesirable because it wastes material, may, cause sink marks, and may even contribute, to stresses from having excessive variations, in thickness., , Uniform wall thickness Wall requirements are usually governed by the load, the, support needs for other components, attachment bosses, and other protruding sections., Designing a product to meet all these requirements while still producing a reasonably uniform wall will greatly benefit its durability. A, uniform wall thickness will minimize stresses,, differences in shrinkage, possible void formation, and sinks on the surface; it also usually, contributes to material saving and economy, in production., Most of the features for which heavy sections are intended can be modified by means, of ribbing, coring, and shaping of the crosssection to provide equivalent strength, rigidity, and performance. Top of Fig. 3-30 shows, a small gear manufactured from metal bar, stock. The same gear converted to a molded, plastic would be designed as shown in the, bottom of Fig. 3-30. This plastic gear design, compared to the metal gear saves material,, eliminates stresses from having thick and thin, sections, provides uniform shrinkage in teeth, , 1-1/2 t, , t, , = Thickness through, pitch line, , I, , I, , Root, , diameter, , Fig. 3-30 Design of the solid steel gear (top) is, redesigned using plastic (bottom)., , and the remainder of the gear, avoids the danger of warpage, with its thin web and tooth, base prevents bubble formation and potential weak spots, and, having no sink in the, middle of the thickness, provides a full loadcarrying capacity for the teeth., , Wall thickness tolerance When relatively, deep products are being designed, a tolerance for the wall thickness on the order of, ±0.005 in. is usually given. What this tolerance should mean is that a product will be, acceptable when made with this tolerance,, but that the wall thickness must be uniform, throughout the circumference., Let us analyze the molding condition of, such a product and assume that one side, is made to minimum specifications and the, opposite to maximum specifications where, the gate is unfortunately located. Result is, that the resistance to plastic flow decreases, with the third power of the thickness, which, means that the thick side will be filled first,, while the thin side will fill from all sides.

Page 203 : 3 Product Design Feature, This type of filling can create a pocket on the, thin side and compresses cavity air and gases, to such a point that the rising temperature, caused by compression results in the material, to be charred while the pocket is filling up., The charred plastic will create porosity, a, weak area, and an electronically defective, surface. Furthermore, the filling of the thick, side ahead of the thin side creates a pressure imbalance generated by the usual at least, 5 to 10 tons/sq. in. (69 to 138 MPa) injection, pressure that can cause the core to deflect, toward the thin side, further aggravating the, difference in wall thickness. This pressure imbalance could eventually contribute to mold, damage and make production of products difficult if not impossible. It can be conclude that, the wall uniformity throughout the circumference must be within narrow limits, such as, ±O.002 in., whereas the thickness in general, may vary from the specified value by ±O.005, in. Logical corrective action is to gate from, the thin section of the cavity., Flow pattern Ultimately, product quality, can be considered a direct outcome of a plastic melt's flow behavior in its mold cavity or, cavities. Excessive restrictions and obstructions to the flow of material spell trouble in, injection molding., , Parting line PLs on the surface of a, molded product, which are produced by the, parting line of the mold, when required can, often be concealed on a thin, inconspicuous, edge of the product. Doing so preserves the, good appearance of the molding and in most, cases eliminates the need for any finishing., Gate size and location Because of high, melt pressure, the area near a gate is highly, stressed, both by the frictional heat generated, at the gate and the high velocities of the flowing material. Using a small gate is desirable, for separating the product from the feed line,, but not for a product with low stresses. Gate, openings are usually two thirds of a product's, thickness. If they are that large or larger it, will reduce frictional heat, permit lower velocities, and allow the application of higher, pressures for increasing the product density, , 185, , of the material in the cavity resulting in better thickness tolerance control. Temperature, controlled valve gates are used to eliminate, these type problems as well as other problems that can develop such as overpacking, the melt near the gate., The product designer should caution the, tool designer to keep the gate area away from, load-bearing surfaces and to make the gate, size such that it will improve the quality of, the product. It so happens that the product, wall in the gate area develops the minimum, tolerance due to the high melt pressure in that, area., Taper of draft angle It is desirable for any, vertical wall of a molded product to have an, amount of draft that will permit its easy removal from a mold. The amount of draft may, vary from 1/8 degree up to several degrees, depending on what the circumstances permit, and behavior of the plastic. A fair average, may be from 1/2 degree to 1 degree. The, possibility of having voids close to the base, is avoided, and increased cycle time in manufacturing is minimized., The vertical cavity surfaces, particularly, with a draft of 1/8 degree, will demand a, much higher surface finish, with polishing, lines in the direction of product withdrawal., On shallow walls the draft angle can be considerably larger, since the influence of the, drawbacks will be minor. The designer should, be cognizant of the need for drafts on vertical walls. If problems are encountered during, the removal of products, stresses can result,, the shape of the product can be distorted and, surface imperfections be introduced., If a vertical wall is required with no taper, it can be accomplished. However cost, of mold is significantly increased since more, action will be required in the mold such as, moving its sidewalls to release the molding, and higher ejection pressure mechanisms are, required., Weld line With moldings that include, openings (holes), problems can develop. In, the process of filling a cavity the flowing melt, is obstructed by the core, splits its stream,, and surrounds the core. The split stream then

Page 204 : 186, , 3 Product Design Feature, , reunites and continues flowing until the, cavity is filled. The rejoining of the split, streams forms a weld line. It lacks the strength, properties that exist in an area without a weld, line because the flowing material tends to, wipe air, moisture, and/or lubricant into the, area where the joining of the stream takes, place and introduces foreign substances into, the welding surface. Furthermore, since the, plastic material has lost some of its heat, the, temperature for self-welding is not conducive, to the most favorable results., A surface that is to be subjected to load, bearing should be targeted not to contain, , c~--~>, , weld lines. If this is not possible, the allowable working stress should be reduced, by at least 15%. Under the ideal molding, conditions up to about 85% of available, strength in the solidified plastic can be developed. At the other extreme where poor, process controls exists the weld line could approach zero strength. In fact the two melt, fronts could just meet and not blend so, that there is relatively a microscopic space., Other problems occur such as influencing, aesthetics. Some examples of different aspects pertaining to weld lines are shown in, Fig. 3-31., , m-::::~---::;':,, , Flow around holes, , Flow around ribs, , It'"" -0------;, , .. : ..::___, \, , ',-.., ,, , \, , ~ ~eld, , I, I, , ...... _____ .. J, , Flow or gote, , Not this, , This, , G(, , I, "t........, , Weld/ine, , )", , Opposite flow fronts produce a weld line, that could also contain entrapped air., , -:;;;!"l'~~~u..lns jde, , or, , outs ide, , center, gote, , Direct flow in one direction to avoid undesirable welds., , Fig. 3-31 Examples of melt flow patterns to consider during the design stage to eliminate or at least, minimize weld lines to obtain maximum strength.

Page 205 : 3 Product Design Feature, Undercut Whether external or internal,, undercuts should be avoided if possible to, reduce mold cost (by about 25 to 30%) and, simplify melt flow during molding. However, many molds use external and/or internal undercuts. In cases where it is essential to incorporate them in a design, appropriate mold, design is required. The mold will include, action such as sliding components on tapered surfaces, split cavity cam actions to produce the needed undercut, etc. (Chapter 8,, TOOLING)., Some conditions will, however, permit, incorporating undercuts with conventional, stripping of the product from the mold. Certain precautions are necessary in order to attain satisfactory results. First, the protruding, depth of the undercut should be two thirds, of the wall thickness or less. Second, the, edge of the mold against which the product is ejected should be radiused to prevent, shearing action. Finally, the product being removed should be hot enough to permit easy, stretching and return to its original shape after removal from the mold., With particularly flexible type materials, their elasticity and springback can simplify, removal. As an example certain threaded, plastic caps are stripped from the cores instead of being unscrewed. Coarse threads, with the crest of the core thread rounded, and a material with good elongation and ability to spring back make it more feasible to, apply conventional stripping. The undercut, problem can be solved by the cooperation, of the designer, moldmaker, and processor,, since each product configuration presents different possibilities., Blind hole In regard to molding products, that include holes, it is important to ensure, that sufficient material surrounds the holes, and melt flows property. A core pin forming, blind holes is subjected to the bending forces, that exist in the cavity due to the high melt, pressures. Calculations can be made for each, case by establishing the core pin diameter, its, length, and the anticipated pressure conditions in the cavity (3)., From engineering handbooks we know, that a pin supported on one end only will, , 187, , deflect up to forty-eight times as much as, one supported on both ends. This suggests, that the depth of hole in relation to diameter, should be small in order to maintain a straight, hole. Sometimes a deep, small-diameter hole, is needed, as in pen and pencil bodies. In this, case the plastic flow is arranged to contact, the free end of the core, as an example, from, four to six evenly spaced gates. This design, will cause a centering action, and the plastic, will continue flowing over the diameter in an, umbrella like pattern to balance the pressure, forces on the core., When this type of flow pattern is impractical, an alternative may be a through hole or, tube formation combined with a postmolding sealing or closing operation by spinning, or ultrasonic welding. At the other extreme,, consider a 1/4 in. (0.6 cm) diameter core exposed to a pressure of 4,000 psi (28 MPa), with an allowance for deflection of 0.0001 in., (0.00025 cm) and determine how deep a blind, hole can be molded under these conditions., Boss Bosses and other projections from, the nominal wall are commonly found in 1M, products. These often serve as mounting or, fastening points. As with rib design, avoiding overly thick wall sections is important, to, minimize the chance of appearance or molding problems. When bosses are designed to, accommodate self-tapping screws, the inside, diameter and wall thickness must be controlled to avoid excessive buildup of hoop, stresses in the boss. Ribs are frequently used, in conjunction with bosses when lateral forces, are expected. Special care must be used with, tapered pipe threads, since they can create, a wedging action on the boss. If there is a, choice, the male rather than the female pipe, thread should be the one molded into the, plastic., Coring The term coring in 1M refers to, the addition of steel to the mold for the purpose of eliminating plastic material in that, area. Usually, coring is necessary to create a, pocket or opening in the product, or simply, for the purpose of reducing an overly heavy, wall section. For simplicity and economy in, injection molds, cores should be parallel to

Page 206 : 188, , 3 Product Design Feature, , the line of draw of the mold. Cores placed, in any other direction usually create the, need for some type of side action (such as a, mechanical cam or hydraulic cylinder) or, manually loaded and unloaded loose cores., Blind holes in molded plastics are created, by a core supported by only one side of the, mold. The length of the core and depth of, the hole are limited by the ability of the core, to withstand the bending forces produced, by the flowing plastic without excessive deflection. For this reason, the depth of a blind, hole should not exceed three times its diameter or minimum cross-sectional dimension., For small blind holes with a minimum dimension below 1/4 in., the LID ratio should be, kept to two. With through holes the cores can, be longer, since the opposite side of the mold, cavity supports them (3)., Sometimes the cores can be split between, the two sides and interlocked when the mold, is closed, allowing for the creation of long, through holes. With through holes, the overall length of a given-size core can generally, be twice as long as that of a blind hole. Some-, , times, even longer cores are necessary. The, tool can be designed to balance the pressure, on the core pin, thus limiting the deflection., Press fit Products or components of any, material in a press-fit assembly are assembled, to a plastic product using an interference fit to, maintain the assembly. The main advantage, of this system is that the tooling is kept, relatively simple. This method can, however, create very high stresses in the plastic., Amount of stress will depend on factors such, as temperature during and after assembly,, modulus of the mating material, type of stress,, usage environment, and the type of material being used. Some materials will creep, or stress relax, while others will fracture or, craze if the strain is too high. Except for light, press-fits, this type of assembly can be damaging due to the hoop stress in the boss that, might already be weakened by a knit-line., Figures 3-32 and 33 provide hoop stress equations for two typical press fit and alternate, methods of designing press-fits that result in, lower risk of failure., Ep = MODULUS OF ELASTICITY OF PLASTIC, Em, , = MODULUS OF ELASTICITY OF METAL, , vp = POISSON'S RA TlO OF PLASTIC, = ALLOWABLE DESIGN STRESS FOR, , 00, , PLASTIC, , Io+---d;, , = dB' d; = DIAMETRAL, , i, , INTERFERENCE, , i. = ALLOWABLE INTERFERENCE, CASE A, SHAFT AND HUB ARE BOTH THE SAME OR, ESSENTIALL Y SIMILAR MATERIALS, HOOP STRESS GIVEN "i" IS, o =~ Ep __, r_, d,, r+1, OR, THE ALLOWABLE INTERFERENCE IS, , i., , = d,.~ r+ 1, r, , Ep, , GEOMETRY FACTOR, , CASE B, SHAFT IS METAL, HUB IS PLASTIC, HOOP STRESS GIVEN "i" IS, r _, o _, - _ i ..... Ep _ .._..._, , r, , ds, r + vp, OR, THE ALLOWABLE INTERFERENCE IS, , io, , =, , ds .~, , Eo, , f, , + vp_., , r, , Fig. 3-32 Determining press fit stresses for two typical situations.

Page 207 : 189, , 3 Product Design Feature, , D, , _METAL, PIN, , STRAIGHT (INTERFERENCE), PRESS FIT CAN PRODUCE, HIGH STRAINS, , ~ ,mw., ';::::::::::, ALTERNATIVE PRESS FIT, DESIGNS FOR LOWER STRESS., , reasons related to the high induced stress, levels, or (3) undergo stress relaxation sufficient to reduce the stress to a lower level, which can be maintained., A simpler, although less accurate, method, of evaluating these press fits is to assume that, the shaft will not deform when pressed into, the plastic. This is reasonably accurate when, a metal shaft is used in a plastic hub. The hoop, strain developed that is reasonably accurate, in the hub is then given by the equation:, £, , ADD METAL, "HOOP" RING, PREVENTING, EXPANSION, OF PLASTIC, BOSS., , USE BARBS OR SPLINES, ON THE METAL, PIN TO CREATE, INTERFERENCE, FIT AND, RETENTION, , CREATE, INTERFERENCE, PRESS FIT BY, ADDING "CRUSH RIBS', TO THE INSIDE, DIAMETER OF, THE BOSS, , Fig. 3-33 Alternate press fit., , A common use is with a plastic hub or boss, accepting either a plastic or metal insert., The press fit operation tends to expand the, hub creating a tensile or hoop stress. If the, interference is too great, a very high strain, and stress will develop. The plastic product, will (1) fail immediately by developing a, crack parallel to the axis of the hub to relieve, the stress, a typical hoop stress failure,, (2) survive assembly but fail prematurely, when the product is in use for a variety of, , = i/d/, , (3-12), , The hoop stress can then be obtained by, multiplying by the appropriate modulus. For, high strains, the secant modulus will give the, initial stress (Chapter 2). The apparent or, creep modulus should be used for the longer, time stresses. The main point is that the maximum strain or stress must be below that value, which produces creep rupture in the material., It is to be noted that there is usually a weld, line present in the hub that can significantly, effect the creep rupture strength of most plastic materials. An additional frequent complication with press fits is that a round hub or, boss if often difficult to mold. There is a tendency for the hub to be slightly elliptical in, cross section increasing the stresses on the, product. In view of the above, all press fits, must be given prototype life testing under actual operating conditions to assure product, reliability (84)., 1nternal plastic thread The strength of, plastic threads is limited, and when molded in, a product involving either an unscrewing device or a rounded shape of thread similar to, bottle-cap threads, they can be stripped from, the core. Screw threads, when needed, should, be of the coarse type and have the outside, of the thread rounded so as not to present, a sharp V to the plastic that can produce a, notch effect., If a self-threading screw can be substituted,, it will not only appreciably decrease mold, maintenance and mold cost but most likely,, with proper type selection, also give better, holding power. A screw that has a thin thread, with relatively deep flights can give high holding power. If the screw or plastic is preheated

Page 208 : 190, , 3 Product Design Feature, , to about 121°C (250°F), a condition of forming in combination with material displacement will exist, thereby improving the holding power. When male plastic threads are being considered, the coarser threads are again, preferred, and the root of the thread should, be rounded to prevent the notch effect., M aIded-in insert If metal inserts are to be, molded into a plastic product consideration, should be given to wall thickness around the, insert (Table 3-18) and their shape. The shape, should present no sharp edges to the plastic, since the effect of the edges would be, similar to that of a notch. A knurled insert, Table 3-18, , should have the sharp point smoothed, again, to avoid the notch effect., The practice of molding inserts in place, is usually employed to provide good holding power for plastic products, but there are, drawbacks to this method. It normally takes, a pin to support the insert, and since this, pin is small in relation to the cored hole, for the insert, it is easily bent or sheared under, the influence of injection pressure. Should, the insert fall out of position, there is danger of mold damage. Also, the hand placement of inserts contributes to cycle variation and with it potentially product quality, degradation. Some of these problems can, be overcome by higher mold expenditures,, , Suggested minimum wall thicknesses for inserts of various diameters [in. (mm)], Diameter of Inserts, in., , Plastic Material, ABS, Acetal, Acrylics, Cellulosics, Ethylene vinyl, acetate, F.E.P., (fluorocarbon), Nylon, Noryl (modified, PPO), Polyallomers, Polycarbonate, Polyethylene (H.D.), Polypropylene, Polystyrene, PolysuIfone, Surlyn (ionomer), Phenolic G.P., Phenolic (medium, impact), Phenolic (high, impact), Urea, Melamine, Epoxy, Alkyd, Diallyl phthalate, Polyester (premix), Polyester T.P., , .125, (3.17), , .250, (6.35), , .375, (9.52), , .500, (12.7), , .750, (19.0), , 1.00, (25.4), , .125 (3.17), .062 (1.57), .093 (2.36), .125 (3.17), .040 (1.02), , .250 (6.35), .125 (3.17), .125 (3.17), .250 (6.35), .085 (2.16), , .375 (9.52), .187 (4.75), .187 (4.75), .375 (9.52), N.R., , .500 (12.7), .250 (6.35), .250 (6.35), .500 (12.7), N.R., , .750 (19.0), .375 (9.52), .375 (9.52), .750 (19.0), N.R., , 1.00 (25.4), .500 (12.7), .500 (12.7), 1.00 (25.4), N.R., , .025 (0.64), , .060 (1.52), , N.R., , N.R., , N.R., , N.R., , .125 (3.17), .062 (1.57), , .250 (6.35), .125 (3.17), , .375 (9.52), .187 (4.75), , .500 (12.7), .250 (6.35), , .750 (19.0), .375 (9.52), , 1.00 (25.4), .500 (12.7), , .125 (3.17), .062 (1.57), .125 (3.17), .125 (3.17), , .250 (6.35), .125 (3.17), .250 (6.35), .250 (6.35), , .750 (19.0), .375 (9.52), .750 (19.0), .750 (19.0), , 1.00 (25.4), .500 (12.7), 1.00 (25.4), 1.00 (25.4), , .062 (1.57), .093 (2.36), .078 (1.98), , .093 (2.36), .156 (3.96), .140 (3.56), , .375 (9.52) .500 (12.7), .187 (4.75) .250 (6.35), .375 (9.52) .500 (12.7), .375 (9.52) .500 (12.7), Not Recommended, Not Recommended, .125 (3.17) .187 (4.75), .187 (4.75) .218 (5.53), .156 (3.96) .203 (5.16), , .250 (6.35), .312 (7.92), .281 (7.14), , .312 (7.92), .343 (8.71), .312 (7.92), , .062 (1.57), , .125 (3.17), , .140 (3.56), , .187 (4.75), , .250 (6.35), , .281 (7.13), , .093 (2.36), .125 (3.17), .020 (0.51), .125 (3.17), .125 (3.17), .093 (2.36), .062 (1.57), , .156 (3.96), .187 (4.75), .030 (0.76), .187 (4.75), .187 (4.75), .125 (3.17), .125 (3.17), , .187 (4.75), .218 (5.53), .040 (1.02), .187 (4.75), .250 (6.35), .140 (3.56), .187 (4.75), , .218 (5.53), .312 (7.92), .050 (1.27), .312 (7.92), .312 (7.92), .187 (4.75), .250 (6.35), , .312 (7.92), .343 (8.71), .060 (1.52), .343 (8.71), .343 (8.71), .250 (6.35), .375 (9.52), , .343 (8.71), .375 (9.52), .070 (1.78), .375 (9.52), .375 (9.52), .281 (7.14), .375 (9.52)

Page 209 : 3 Product Design Feature, as for example shuttling cavities (Chapter 4,, JOINING AND ASSEMBLY)., However the desired results in fastening, can be attained by other means. One example, is by coring holes in the molding that will permit ultrasonic welding of inserts in place. Coring a hole in the product will be of a size when, the product is removed from the mold that, will permit a slight press fit plus a gain in the, holding power from postmolding shrinkage., Also is the approach of coring a hole in the, product that will permit dropping the insert, and providing a retaining shoulder by spinning or ultrasonic forming., All these type assembly methods usually, require the same time to perform as placing, inserts in the mold, but they also lower IMM, time. There are several other means of accomplishing the desired result that depend, on the circumstances at hand. In any event,, conventional molded-in inserts usually prove, costlier. There are highly automatic injection, molding machines available designed just for, insert molding that will reverse the cost., Screw Screw threads can be molded or, tapped into a plastic. Molded internal, threads, that can be produced meeting tighter, and performance requirements, usually require some type of unscrewing or collapsing, mechanism. External threads can be molded, either by splitting the mold halves or parting, the line across the thread if parting the line, on the threads is permitted. With a split mold, it is basically easier to design the mold and remove the threaded part from the mold during, processing., The design of the threads requires control, to prevent excessive shear, resulting in, stripping the threads when torqued, and also, to limit hoop stresses that can result in tensile failure. Although the mechanics of stress, analysis for screw threads are readily available, the equations for them can be rather, complicated., For mechanical assemblies using screws, can be detached indefinitely, with the exception of self-tapping screws, which can be loosened and retightened only a limited number, of times. The best guideline for the designer, is to prefer any assembly design that converts, , 191, , eventual tensile loads to compression loads., Those plastics generally are subject to crazing, or stress cracking. Compression loads tend to, reduce this problem., When feasible, use metal-to-metal forcelocking connections, particularly with many, of the TPs, to release plastics from stresses., The forces that can be applied with a single small screw can be surprisingly high. As, in metals, consider the use of torque-limiting, wrenches in designs where the degree ofloading is critical., External and internal threads can be, molded economically in plastic parts. Screw, threads produced by the mold itself using rotating cores, split inserts, or collapsible cores, will eliminate the normally expensive postmolding threading operations (Chapter 8,, TOOLING). Coarse threads can be molded, easier than fine ones, so threads less than, 32-pitch should be avoided. American Standard screw threads should be designed and, molded carefully. If the thread end form, notches, a reduction in impact strength and, ultimate elongation under tensile stress can, be significant, depending on the type of plastic used. With certain applications and materials, trapezoidal and knuckle threads are, better., Generally, the length of thread used should, be more than 1.5 times the diameter, the section thickness around the hole more than, 0.6 times the diameter. Avoid having feather, edges, and limit tightening with the bolt, shoulder., Bottle caps made from different plastics, are extensively used. Some closures are of the, simple cork snap type design, but most are of, the screw type. Strong, accurate threads can, be molded, which represent undercuts. Simple designs should be used when permitted,, such as wide-pitch threads. The thread should, be designed to start about 1/32 in. (0.08 cm), from the end of the face perpendicular to the, axis of the thread. It is usually practical to, mold up to 32 threads per in.; more than this, number can give certain molders trouble., Self-threading screws are an economical, means of securing separable plastic joints., They can be thread cuttings. To select the correct self-threading screw, the designer should

Page 210 : 192, , 3 Product Design Feature, , know which plastic will be used and what, its mechanical properties are, particularly its, modulus of elasticity. These self-threading, screws are driven into the molded product,, eliminating the need for a molded-in thread, or a secondary tapping operation. They differ in their thread spacing and body design., Thread-forming screws, which provide the, highest stripping torques, have less tendency, to damage threads in repeated assembly operations than do other types. The threadforming screw displaces material as it is being, installed in the receiving hole., This type of screw induces high stress levels, in the plastic part, so it is not recommended, for use with certain plastics such as those with, a low modulus, unless careful procedures are, used in forming the threads., Screws or threaded bolts with nuts require, through-going holes to provide an easy, assembly system. Washers are recommended, to distribute the load upon a larger area,, wherever feasible or required. If a screw, is tightened too far, excessive bending or, tensile stresses will easily be created, possibly, causing cracking based on stress-to-failure, data curves. A change in design or the use of, a spacer can convert tensile into compressive, stresses. Different screw- and bolt-heads can, be used, but flat-underside types of heads, are best., In regard to screw threads, certain observations should be considered. First, the torque, values are based on the coefficients of friction of the mating parts and can thus vary, significantly. The use of any compatible lubricant that reduces friction will increase the, shear and hoop stresses if the torque remains, the same. Therefore, with lubricants, reduce, the amount of allowable torque., Second, having high assembly torque to, prevent vibrational loosening is frequently, ineffective, since creep in the plastic will reduce the effective assembly torque even if, the fastener does not rotate. Using vibrationproof screws, lockwashers, locknuts, and, thread-locking adhesives are usually a better, alternative when loosening is considered a, problem., Finally, self-tapping screws require additional torque to cut or form their threads. This, , torque can usually be added to the allowable, safe-assembly torque, but for the first assembly only. The appropriate hole design for selftapping screws is quite dependent on the material and screw design., Rib As previously reviewed if there is sufficient space, the use of ribs is a practical,, economic means of increasing the structural, integrity of plastic products without creating, thick walls. Ribs are provided for spacing purposes, to support components, and for other, uses. Table 3-19 shows a summary of the results of using a rib design. Although the use, of ribs gives the designer great latitude in efficiently tailoring the structural response of a, plastic product, ribbing can result in warping, and appearance problems (sink marks, etc.)., In general, experienced designers do not use, ribs if there is doubt as to whether they are, structurally necessary. Adding ribs after the, tool is built is usually simple and relatively, inexpensive since it involves removing steel, in the mold., There are certain basic rib-design guidelines that should be followed (Fig. 3-9). The, most general is to make the rib thickness at, its base equal to one-half the adjacent wall's, thickness. With ribs opposite appearance areas, the width should be kept as thin as possible. In areas where structure is more important than appearance, or with very low, shrinkage materials, ribs are often 75 or even, 100 percent ofthe outside wall's thickness. As, can be seen in Fig. 3-10, a goal in rib design, is to prevent the formation of a heavy mass, of material that can result in a sink, void, distortion, long cycle time, or any combination, of these problems., , Extrusion, Basically, the size of the die orifice initially controls the thickness, width, and shape, of any extruded product dimension. In general, it is developed oversize to allow for, the drawing and shrinkage that occur during conveyor pulling and cooling operations, (Chapter 8, TOOLING and EXTRUSION)., The rate of takeoff has significant influences

Page 211 : 3 Product Design Feature, Table 3-19, , 193, , Example of the effect of rib and cross-section changes, , Geometry, , Maximum Deflection,, inches (mm), , Cross Section Area,, square inches (mm2), , Maximum Stress,, psi (mPa), , 0.0600, (38.7), , 6800, (46.9), , 0.694, (17.6), , 0.0615, (39.7), , 2258, (15.6), , 0.026, (0.66), , 0.1793, (115.7), , 2258, (15.6), , 0.026, (0.66), , (19.1 nun), , f- --j.l, 07S, , ~, ORIGINAL SECTION, , T, , 0.080, , (2.0), , ORIGINAL SECTiON, WITH RIB, , f-, , 0. 7S, , --Jj, , ~, THICK SECTION, , 0.239, , on dimensions and shapes. This action, called, drawdown, can also influence keeping the, melt extrudate straight and properly shaped,, as well as permitting size adjustments. The, drawdown ratio is the ratio of orifice die size, at the exit to the final profile size (6)., The range of extrudable profiles is practically unlimited, but to realize a full, practical design with economic potential, particular attention must be given to factors like, wall thickness, hollows and cores, legs and, projections, comers and radii, and so on. The, most important consideration in profile design is the balancing of various wall thicknesses. A profile with a uniform wall thickness throughout its cross-section is the easiest, to produce. Having uneven walls will cause, material flow variations between the large, and small portions of the profile. Also, thinner sections cool faster, causing bowing or, warpage toward the heavy side. To compensate, it is necessary to provide external cooling for the bulkier sections and, usually, some, , special orifice die design in which the land, lengths (distances along metal surfaces) are, changed significantly in respect to their crosssectional openings. This usually requires, additional costs, equipment, and reduced extrusion speed, resulting in higher production costs. Most important requirement is, experience., , Tolerance The penalty for having an unbalanced wall is the reduction of tolerance, control. Tolerance limits are usually at least, doubled. Also, with certain plastics it is more, difficult to process them, such as those with, low melt strength. Although the balanced, wall is the ideal, having it is not always possible. Recognize that the unbalanced wall can, be extruded with proper die design and control of the extruder line from upstream to, downstream equipment., As discussed in the previous section on injection molding, a sink mark almost always, occurs in extrusion on a flat surface that is

Page 212 : 194, , 3 Product Design Feature, , Fig.3-34 Sink marks can be eliminated by creating a design, rib, or serration., , opposite to and adjoining a leg or rib, because of unbalanced heat removal or similar factors. As with 1M, sink marks can be, practically eliminated or eliminated by slowing down the extrusion line permitting more, uniform cooling action. A popular method is, to conceal the marks by adding a design feature, such as a series of serrations on the area, where they occur (Fig. 3-34)., , Figure 3-35 provides design features in extrusion dies that influence product performance. The guiding principle should be to, keep it simple whenever possible. (a) The, method of balancing flow to produce this, shape requires having a short land where the, thin leg is extruded. This design provides the, same rate of flow for the thin section as for, the heavy one. (b) This die for making square, , (b), , (a), , (c), , (d), , (e), , Fig. 3-35, , Examples of die designs to produce different profiles.

Page 213 : 3 Product Design Feature, extrusions uses convex sides on the die opening so that straight sides are formed upon, melt exiting; the comers have a slight radius, to help obtain smooth comers. The rear and, sectional views show how part of the die has, been machined away to provide short lands, at the corners to balance the melt flow. (c) In, this die for a P shape, a pin mounted on the, die bridge forms the hole in the P. The rate of, flow in thick and thin sections is balanced by, the shoulder dam behind the small-diameter, section of the pin. The pin can be positioned, along its axis to adjust the rate of flow to, meet the melt characteristics. (d) In this die, to extrude a rather complicated, nonuniform, shape, a dam or baffle plate restricts the flow, at the heavy section of the extrudate to obtain uniform flow for all sections. The melt, flows between the die plate and the dam to, fill the heavy section. The clearance between, the dam and the die plate can be adjusted, as required for different plastics with different melt behaviors. (e) In this die for extruding a quarter-round profile the die opening, has convex sides to give straight sides on the, right -angled portion, and the comers have a, slight radius to aid in obtaining smooth comers on the extrusion., Figure 3-36 provides design tips for coextrusion. (a) A dual extrusion for a modular, cabinet wall panel. (b) If the flexible sealing portion wears out from abrasion, a replacement flexible insert can be slid into the, slot in a rigid portion. (c) A cross-section, of a dual extrusion (a ball-return trough for, a billiard table). (d) A bowling-ball return, trough made from a 6 in. (15 cm) diameter, extruded tube with one or more layers. The, tube is slit while still workable and guided, over a forming die. (e) Typical dual extrusions of rigid and flexible PVCs. (f) Typical, extrusions of rigid and flexible PVCs showing different applications. (g) A cross-section, of a window frame with a metal embedment., (h) Keying or fitting can join nonbondable, plastic. (i) noncircular hollows are easier to, form if each part of the surrounding wall is, made from the same family of plastic: (A) the, rigid PVC base will remain flat and not bulge, and (B) the air pressure inside the hollow will, cause the flexible base section to bulge. (j), , 195, , Different applications for metal-embedment, extrusions., , Blow Molding, Blow molding, provides designers with the, capability to make products ranging from, the simple to rather complex 3-D shapes, (Chapter 8, BLOW MOLDING). Designers, should become aware of the potentials BM, offers since intricate and complex shapes can, be fabricated. The BM process is especially, amenable to the designer's goal of consolidating as much function as possible into a single, product. Some of the features that can be incorporated include threads, inserts, fasteners,, hinges, and others somewhat similar to those, covered under injection molding. Hinges include the different mechanical types as well, as integral hinges (9, 20)., , Hinge In addition to the information concerning Fig. 3-20 on the general approach, to molding living hinges, this review specifically concerns BM. To produce a hinge during extrusion BM (Figs. 3-37 and 3-38) the, hinge is formed perpendicular to the parison, flow from the die. With injection blow molding, the hinge is perpendicular to the melt, flow in the preform mold (Chapter 8, BLOW, MOLDING)., Here are some guidelines to mold living, hinges with polypropylene (other plastics are, similar but may require their own specific, dimensions dependent upon their particular, viscoelastic behavior):, 1. The land of the hinge should be at least, 1.5 mm (0.06 in.) wide for a proper flow pattern and at least wide enough so that when the, product is bent in service it will not develop, strains. Too short a land length will cause the, hinge to have limited flex life., 2. The minimum plastic thickness or pinchoff gap at the center of the hinge should be, 0.25 to 0.38 mm thick (0.010 to 0.015 in.) and, 0.5 mm (0.020 in.) wide., 3. When the plastic melt flows across, the small hinge gap, frictional heat will be

Page 214 : 196, , 3 Product Design Feature, , (a), REPLACEME NT SEAL, ", , "\, , CUT OFF, , ',., , '., , REPLACEMENT SEA L, , (b), , (d), PUAI, , EXTRUSIONS, , ~ ${, , tfs ~, , '!GID, , ~,'", , ~XIBLE, , <., , ~ EDGE, , VINYL, , PROT ECTOR, , ...'.:. SEAL AND, '.~?, CAP, , VINYL, , . : ..... ., , ~NAP-ON, COVER, , RIGI D, VINYL, ,, , FLEX IBLE VINYL, , ~ID, , ~, , FLEXIBLE VINYL, RIGID VINYL, PROTECTIVE, BUMPER, , ~X I BLE, ,«« !!f:;!, , VINYL, ACCENT, STRIP, , (e), , (f), , Fig. 3-36 Designs for co extrusion.

Page 215 : 197, , 3 Product Design Feature, , ilJJ, 'iii 'I~ Ii:, FLEXIB L E, , "NYl, , ~ETAl ~GI O, , WINDOW, FRAME, , VINYl, , (g), , NONBONDABLE DUAL EXTRUSIONS, , (h), , METAL-EMBEDMENT, EXTRUSIONS, , Ji--a, "., , STORt.I-WIN OOW, , FRAME, , EASY, , A, , ~, ......., , .", , TUBULAR, . EXTRUSI ONS, , FLEX I BLE, V IN YL, , .", , I, , ~, , "., , /, , ."DIFFICULT, ..a, (i), , (j), , Fig. 3-36, , generated. There should be sufficient cooling, of the mold around the hinge area., 4. With injection blow, the hinge gap is a, difficult area to flow across. Therefore, the, gate should be placed so that the molten plastic can flow perpendicular to the hinge, to ensure a good fill. If the melt flows along the, length of the hinge, there is bound to be a, short shot or cold weld at the hinge., 5. Shoulders and lips should be included in, the two mating parts to help alignment., 6. The finished product should be flexed, immediately upon its ejection from the mold,, while the heat from the mold is still in it. De-, , (Continued), , pending on its service operation flex angle between 90° to 180° is recommended. The flexing action can stretch the hinge area by 200%, or more; thus, the initial 0.25 to 0.38 mm thickness (0.10 to 0.015 in.) will be thinned down, to less than 0.l3 mm (0.005 in.). This elongation helps align the plastic'S molecules and, increases its tensile strength from 34 x 106 to, 552 x 106 Pa (5,000 to 80,000 psi)., An extrusion-blown hinge can be compared to a stamping (Fig. 3-21). Hot- and, cold-stamped hinges are made by compressing a sheet of material down to the desired, thickness [12 to 20 in. (3 to 5 mm)]. Stamped

Page 216 : 198, , 3 Product Design Feature, Oie, , Hinge --, , Blow, , ~tdedPart, , possibilities. Because this hinge is practically, free, the cost of these products is just the cost, of the material and the molding., Summarizing this subject for a designer, concerns becoming familiar with the possibilities in designing BM products, particularly, the complex shapes. Gradually designers are, becoming more familiar with the capabilities, inherent in BM., , Thermoforming, Parison, , Fig. 3-37 Example of an extrusion blow molded, container with a living hinge., , hinges are less durable in flexing but strong, in tearing., , Consolidation Even though blow molding provides the capability of providing multiple products combined into one, by including, hinges the designer has an added feature. The, ability to produce many articulated products, in one shot has always opened new design, , Fig.3-38 A molded living hinge in the as-molded, position (a) and a flexed position (b)., , Designers should follow the inherent nature of thermoforming that basically uses flat, panels (film or sheet) instead of the solid, enclosed, boxlike, cylindrical, rodlike, or structural shapes of other processes (Chapter 8,, THERMOFORMING). They should be, aware of and observe the material's depth-ofdraw limitations. It can vary depending on the, type of TP, the thickness tolerance of the material, and the degree of pinhole freedom the, material enjoys. Generally, for straight vacuum forming into a female mold, the depthto-width ratio should not exceed 0.5/1. For, drape forming over a male mold, this ratio, should normally not exceed 1/1. For products to be used with the plug-assist, slip-ring,, or one of the reverse-draw methods, the ratio, can exceed 1/1 and perhaps even reach 2/1, under normal circumstances. However, shallow drafts are in general more readily formed, than deep ones and result in more uniform, wall thickness (1)., Undercuts and reentrant shapes are possible in many designs. They require movable, or collapsible mold members, but with small, undercuts they can often be sprung from a, female mold while the formed product is still, warm. This type of action works best when, the plastic has some flexibility, as do the TPEs,, or the material is very thin. Guidelines for the, maximum amounts of undercutting that can, be stripped from a mold are as follows: 0.04, in. (0.1 cm) for acrylics, PCs and other rigid, plastics; 0.060 in. (0.15 cm) for PEs, ABSs,, and PAs; 0.100 in. (0.25 cm) for flexible plastics such as the PVCs., When female tooling is split to permit the, removal of products with undercuts, a parting

Page 217 : 199, , 3 Product Design Feature, , -,c, NOI Ihis, , 0rall angle '/4 0 min. for female looling, ,. min. for moie laolmg, , 1t==R=.J. .2T"' ",'", This, , Fig. 3-39 Example of the draft on thermoformed side walls., , line of the split halves becomes visible on the, formed part. If this is objectionable, the designer can sometimes incorporate the parting line in the decoration of the product or, at some natural line on the product. Sharp, c~rners generally should never be specified,, smce they hamper the flow of material into, the mold's comers. This results in excessive, thinning of the materials and causes concentrations of stress. A minimum radius of two, times the stock's thickness is recommended., It is also more desirable from several standpoints to have large, flowing curves in a, thermoformed product than to have squared, comers or rectangular shapes. However there, are thermoforming techniques that can produce thicker corners (1)., The best products have smooth, natural, curves and drawn sections that are sphericalor nearly so in shape. Their walls will, be more uniform, they will be more rigid,, their surfaces will be less apt to show tool, marks, and their tooling and molds will be, lower in cost. Notches or square holes should, be avoided when punching formed products., Round holes are preferred to oval ones for, minimizing stress buildup., Some draft is required in side walls to, facilitate the easy removal of the product, from the mold. Female molds require less, draft since products tend to pull away from, m~ld walls as they shrink during cooling., WIth female or male tooling, for most plastics, the draft on each side wall should be at least, 1 degree (Fig. 3-39)., Metal inserts are usually not feasible, because thin walls are not sufficiently strong to, hold inserts, particularly if thermal expansion, and contraction of the product takes place in, service. Figure 3-40 shows a method of holding metal fittings. It may be desirable to in-, , j([, •, , Not this, , Melal insert, Thermoformed, plaslic sheet, , This, , Fig. 3-40 Recommended method for holding, metal fittings in thermoformed products., , crease the stiffness of thermoformed products. Many are panel shaped and made of, thin walls, so they may lack rigidity. Corrugations, which if used are preferable in two, directions, or an embossed pattern can add, to their rigidity. With short-run production it, may be more economical just to use thicker, sheet plastic to gain stiffness. If the function, of the product permits, use curved, dished, or, domed surfaces to gain stiffness., When thermoformed products such as, caps are stacked, without controlled spacing they will jam together (as with other, similar shaped processed products), which, could cause sufficient stress to cause products to split. To avoid jamming and control the space between parts, a stacking boss, or shoulder system can be used (Fig. 3-41)., Within this stacking area the plastic must be, sufficiently rigid to prevent the deflection of, bosses that would cause jamming. The height, of the bosses is generally greater than their, vertical cross-sections at the point of least, taper; otherwise the tapered walls will interfere before the stacking sections can engage., There are also other designs that can be used, to eliminate jamming., , Tolerance Thermoformed products lack, the dimensional accuracy of processes such as, injection and compression molded products.

Page 218 : 3 Product Design Feature, , 200, , Fig.3-41, , Example for stacking thermoformed products to avoid jamming., , With its low pressure, thermoforming reduces the degree to which the sheet or film being formed is forced to conform to the mold., Material variations, mainly in their thickness, and degree of existing pinholes, affect the final accuracy of the product. This is particularly true because tooling is generally one, sided where the product is pushed against a, female or male mold cavity. However there, is the thermoforming operation where a male, and female mold are used together which is, a take-off of compression molding. The objective should be to use material with tight, thickness controls that is pinhole free, rather, than just to determine its weight. Some fabricators buy by the lower-cost method where, weight is the controlling factor because they, do not have to meet any tolerance. However it is possible that by buying by thickness, amount of material consumption per product will provide a significant material cost, saving. Other factors that effects cost savings, also could include uniform heat absorption of, the sheet/film that could result in more uniform thickness tolerances and quicker cycle, times., Products are affected dimensionally by, the difference between their forming temperature and their product-use temperature., Thus, a plastic's coefficient of thermal expansion and contraction has a significant effect on, service conditions. The thermoforming pressure, time, and temperature variations that, can exist will affect the final dimensions. Of, these factors, evenness in heating throughout, the sheet thickness before forming is usually, the most important control. Type of heater, has a direct effect on obtaining uniform heat, , (1). An allowance must also be made for postforming shrinkage. Molds should be designed, oversize so that when shrinkage is complete, the product dimensions will be correct to, within the design tolerances., The dimensional tolerances with the more, conventional single-mold system are generally ±O.6% (±O.35% for close tolerances)., With female molds ±O.5% (±O.3% close), with male molds under 3 ft., ±O.8% (±O.4%, close) and with male molds over 3 ft., ±30%, (±1O% close) for wall thicknesses., , Rotational Molding, RM, which uses single or multiple arms to, hold the molds, is appropriate to different, sizes and shapes of products such as tanks, or containers ranging from small squeeze, bulbs of vinyl plastisol to large storage tanks, (Chapter 8, ROTATIONAL MOLDING)., This technique can produce uniform wall, thicknesses even when the product has a, deep draw off the parting line or small radii., The liquid or powdered plastic used in this, method flows freely into comers or other, deep draws upon the mold's being rotated, and is then fused by heat passing through the, mold's wall., , Mold This process is particularly suited, economically to producing small production, runs and large-sized products, because molds, are not SUbjected to relatively any pressure, during molding and inexpensive thin sheet, metal molds can thus be used in many applications. Lightweight cast aluminum and

Page 219 : 3 Product Design Feature, , clectroformed or vaporformed nickel molds,, which are light in weight and low in cost, can, also be used. Large RM machines can be purchased or built economically, because they, can use relatively inexpensive gas-fired, hotair ovens with relatively lightweight moldrotating mechanism., Cost When it is necessary to equal the, production rates of other processes, the mold, cost with RM may exceed that of other processes such as flow molding. The plastics used, in RM are generally more expensive than, the pelleted plastics used in many other processes, because they must be more finely and, evenly powdered, such as to a 35 mesh. However, this process generates low levels of regrind or scrap, even when it is operating, poorly. Products can have no flash at all if, properly designed molds are used., The molding of two or more different types, of plastics in a single product may be accomplished to combine their specific properties and/or a better performing or lower-cost, product. This process, called corotation, is, similar to coextrusion or coinjection in terms, of the performance of the designed product., An expensive plastic may be backed with a, less costly material (recycled, etc.), and a skin, surface layer can be backed with a foamed, plastic molded in one operation. The dissimilar molding powders, which may have different softening temperatures, can be molded, simultaneously or separately, depending on, the processing conditions and the end product's requirements. Any greater than normal, thickness must usually be designed to form, multilayered products, especially if a foam, component is to be included., Some combinations of materials are not, feasible with this method. For instance, after, molding the first layer against the mold wall,, the second material cannot have a higher melt, temperature, which, of course, would melt the, first layer, probably causing them to mix., With RM one inherent overall disadvantage exists. It is that the complete cycle for, a single mold is significantly longer than it is, for many other processes. However, in many, cases it is possible to run multiple molds on, each arm or arms, to offset the effect of hav-, , 201, , ing slower cycles. Also in many applications, total cost (mold, operator, etc.) is lower than, the other processes., The preferred contour for any parting line, is the straightest path possible. By this means,, mold construction costs can be reduced and, demolding will be the easiest means possible., When two products like a container and its lid, are to be molded together, as in blow molding, they may be separated after the molding, by employing a removable cutter or annular wedge at the parting line. Another technique is by molding it oversize to provide a, resting flange, then cutting it to separate the, products., Wall thickness/surface The wall thickness, in a mold can be changed just by increasing the amount of plastic put into the mold,, because the wall is basically produced by a, coating or plating process that operates on, the inside surface of the mold. However,, changes in heating time would be necessary, to fuse the plastic properly. Thus, adjustments to product's wall thicknesses can be, made to increase rigidity, impact strength,, or load-carrying capacity. A maximum thickness does exist, based on the type of material, used and the material chosen to construct the, mold as well as the heat source. These factors, all influence the rate of heat transfer through, the plastic. Because in this process the plastic is deposited on the mold without pressure,, the finished part is generally stress-free., Products in this process can have deep sections and relatively sharp comers. However, RM flat, particularly large relatively uniform, wall thickness surfaces are difficult if not impossible to produce. This process can be used, to mold complex products that may require, three or four split molds. Also, different finished surfaces are obtained. For example, the, products' surface finish is dictated by the inside surface of the mold. This makes it easy, to obtain smooth as well as textured surfaces, on the product. Raised or depressed letters,, fluting, and other decorative inscriptions may, also be molded., Processing technique The inside surfaces, are influenced by the type of plastic used and

Page 220 : 202, , 3 Product Design Feature, , may be made smoother by selecting an easily flowing melt with a high melt index. Because such plastics are sometimes chemically, or mechanically inferior, the better plastic, may be made smoother by resorting to higher, molding temperatures and longer cycle times,, short of damaging the plastic. In-mold decorating methods, such as decals that are deposited on the mold surface, are used that, can become part of the finished product's surface and can be designed to provide increased, structural performance, as also in injection, molding, blow molding, and other processes., Ample draft is suggested on sidewalls to, facilitate product removal. A recommended, minimum for most plastics is 1 degree. The, lower-shrinkage plastics like PC and PMMA, will require 11/2 to 2 degrees. Undercuts are, possible, but they should be kept to a minimum. Making provisions for undercuts usually requires higher mold costs, because of, having to use some type of action such as, core pulls or splitting a mold to allow separation parallel to the undercut groove. Undercuts may also require extra time for unloading, molds., Inside or outside comers should use large, radiuses, not sharp ones even though sharp, corners can be molded. By doing so any potential cracking, molded-in stresses, and undesirable thickening will be prevented. A, useful guide to the smallest allowable inside radius is 1/16 in. (0.16 cm) with 1/4 in., (0.66 cm) for optimal filling conditions. The, goal should be to have a radius equal to the, wall thickness for easier melt flow. Although, RM produces uniform wall thicknesses, comers in it can have greater variation than the, rest of the product. A sharp inside comer, tends to heat at a slower rate, causing the plastic to flow away from it, thus making it thinner. Conversely, sharp outside comers heat, at a faster rate and tend to hold the plastic longer, thus building up more thickness., If required techniques are used to reduce or, eliminate these type problems by controlling, the heat input at these corners., It is usually difficult to produce internal, or external bosses and T sections, because, they are not conducive to producing uniform, walls. It is possible to produce interior ext en-, , sions, by placing a metallic screen in contact, with the inner mold wall. This screen heats, up, attracts plastic, and becomes covered remaining in place after molding. By using this, method a hollow product can be molded to, have two or more separate chambers, with, the screen being extended entirely across the, inside of the mold., A hole can be formed by molding a dome, and cutting it after molding. One technique, that can be used for this design is to mount, securely on the inside mold wall a fluorocarbon (PTFE) plug to prevent plastic from, adhering to the mold at that location. Another method involves inserting machined, brass plugs, pins, or tubing through the mold, wall. During molding, the heat passes from, the mold to the insert, causing plastic to form, around it. Care must be taken to select inserts that will heat easily and a plastic that, will not crack, because stresses are created, as the plastic shrinks around the insert upon, cooling., Moldable holes and inserts can complicate, molding and may require extra postmolding, operations. Thus, the most economical designs are those that minimize the number of, holes. With many plastics, both external and, internal threads can be molded, but sharp, V threads should be avoided because they, can cause the plastic to bridge, resulting in, incomplete thread fill. Rounded or modified, buttress threads will allow improved thread, fill., The stiffening of solid ribs or projections is, possible and easily moldable if the requirement of maintaining uniform wall thickness, is followed. A narrowed rib will not fill and, will leave inside stringers. It also can prevent, the melt from reaching the bottom before fusing. A small, shallow, narrow rib will fill completely but have limited strengthening effect., The correct rib design requires a wide gap to, form the rib, with a generous draft so that, the melt is allowed to fill uniformly, without, bridging. As a guide, deep ribs that are four, times the wall's thickness generally require at, least five times the wall's thickness between, the parallel sides of the rib to prevent the, plastic from bridging as it flows into the rib, before fusing to the mold's wall.

Page 221 : 3 Product Design Feature, Design Failnre Analysis, , The process of analyzing designs includes, the modes of failure analysis. At an early, stage the designer should try to anticipate, how and where a design is most likely to, fail. A few examples of potential problems, due to loading conditions on products are reviewed., The most common conditions of possible, failure are elastic deflection, inelastic deformation, and fracture. During elastic deflection a product fails because the loads applied, produce too large a deflection. In deformation, if it is too great it may cause other parts, of an assembly to become misaligned or overstressed. Dynamic deflection can produce, unacceptable vibration and noise. When a, stable structure is required, the amount of deflection can set the limit for buckling loads or, fractures., Because many plastics are relatively flexible, analysis should consider how much deflection might result from the loadings and elevated temperatures the products might see, in service. The equations for predicting such, deflections should use the modulus of the, material; its tensile strength is not pertinent., Usually, the most effective way to reduce de-, , 203, , flection is to stiffen a product's wall by changing its cross-section., Inelastic deformation can cause product, failure arising out of a massive realignment of, the plastic's molecular structure. A product, undergoing inelastic deformation does not, return to its original state when its load is removed. It should be remembered that there, are plastics that are sensitive to this situation, and others that are not., The existence of an elevated temperature, with or without long-term or continuous loading, would suggest the possibility, that a material might exceed its elastic limits., As explained in Chapter 2 concerning momentary loading, the properties to consider, are the proportional limit and the maximum, shear stress. The presence of fracture reflects, a load that exceeds the strength of the design., The load may occur suddenly, such as upon, impact, or at a low temperature, which will, reduce the elongation of the material. A failure may develop slowly, from a steady, high, load applied over a long time (creep rupture), or from the gradual growth of a crack from, fatigue. If fracture is the expected mode of, failure, analysis should examine the greatest, principal stresses involved (Chapter 2, HIGH, SPEED PROPERTIES).

Page 222 : ____4, Designing Plastic Product, , Introdnction, , This chapter reviews the design of different, current and potential applications for plastics. Plastics are used uniquely in these applications because of factors such as availability, of their extensive capability in material modifications to meet specific material and processing requirements. By incorporating some, innate behaviors of the materials and adapting them to operate in unusual environments,, low cost products are produced as well as, some of the most significant and sophisticated, problems of man-kind are being solved by the, use of plastics., A product under consideration must have, some utility; it must fulfill a need which, may be aesthetic or functional and, generally, both. To proceed with the design we must, know what function it is to perform. We also, need to know the context or surroundings of, the product to determine what effect they will, have on its function. A careful definition of, the function will simplify the design and permit the widest latitude of alternatives possible in the design without compromising the, function of the product., Book Shelve, , A good example is designing a shelf. The, function served is a support that can hold, , several objects in a desired location for storage or for display. Unless a more specific function is defined, the shelf can take on a wide, range of possible shapes, structures, and materials. It would be necessary to define the, shelf as a bookshelf, for example, compatible, with the environment found in a library, suitable for: holding five or more books per foot, of shelf, and for constant reference use rather, than for storage (190)., This information will sufficiently define the, function so that a design can be started. It, defines the environment, sets the load level, and the type of loading situation, and gives, some idea of the shape requirements, as well, as the possible aesthetics of the unit. It still, permits a wide range of design choices as to, material, structure, and shape but they would, be limited to those normally used in a library environment. The more accurately and, completely the function is defined, the more, restricted are the design possibilities and, the more detailed the specifications for the, function., Size is the next factor to be considered. A, product has to fit its function within the confines of the space in which it is used. Continuing with the example of the shelf, it is obvious that we must know the length of the, shelf, either by deciding how many books it, will hold or by stating the size of the supporting rack that will be used. The size can, then be decided either by burden or by space

Page 223 : 4 Designing Plastic Product, , restrictions. In most cases, one or the other, of these considerations will apply and in a, typical case both may apply to some extent., In the example given, the width of the shelf, would be determined by the width of a book,, which ranges from 6 to 11 in. (15 to 28 cm), The typical bookshelf is supported at 3 ft, (0.9 m) intervals so that the shelf would be, this wide to fit a typical book rack. The, shelf will hold about 5 books per foot (5 per, 0.3 m) with an average weight of about 2 Ib, (0.91 kg) each to make a maximum load on, the shelf of 30 Ib (13.6 kg). If the shelf were, completely filled, it could be considered a distributed load, or it can be considered as a set, of discreet loads., Material, , The type of shelf design is the next consideration. The shelf can be a solid plate of plastic material, an inverted pan-like structure, with reinforcing ribs, a sandwich-type structure with two skins and an expanded core,, or even a lattice type sheet that has a series, of openings. The choice between these is dictated by a number of factors. One is appearance or aesthetics., The lattice-type shelf is functionally as, good as the others, but it may not look appropriate for a book shelf in the context of, a library. A second consideration is a combination of physical requirements and appearance. A simple plastic beam that will function, adequately in terms of strength and stiffness, may be rather thin. A shelf of this type can, look flimsy even if it is functional. This impression is useful to the designer since the, solid plate is probably an uneconomical use, of material. A requirement was added that, the design should look like a wood shelf, since this is the context in which it is to be, used. To produce the desired thickness appearance either a lipped pan with internal reinforcement can be used or, alternatively, a, sandwich-type structure with two skins and, a separator core. In either case the displacement of the material from the plane of bending will improve the stiffness efficiency of, the product. The appropriate procedure is to, , 205, , leave both as possibilities and do some trial, designs., The next step in the design procedure is to, select the materials. The considerations are, the physical properties, tensile and compressive strength, impact properties, temperature, resistance, differential expansion environmental resistance, stiffness, and the dynamic, properties. In this example, the only factor, of major concern is the long-term stiffness, since this is a statically loaded product with, minimum heat and environmental exposure., While some degree of impact strength is desirable to take occasional abuse, it is not really, subjected to any significant impacts., Using several materials such as Pp, glassfilled PS, and PS molded structural foam that, is a natural sandwich panel material, the design procedure follows to determine the deflection and stress limitations of the material, in each of the several designs., There are two criteria to use as the basis, for evaluation. The design life of the shelf, is determined by deciding what the product, will tolerate in deflection and still be useful. This is combined with the cost effectiveness value the product must meet. For example, we can say that if it costs $X the life, must be A months, if it costs $Y it must last, B months, and if it costs $Z, it must last C, months. This can be presented as a table or, it can be graphed as the criteria range that it, must meet., Using the several materials selected and, the basic design possibilities, products should, be designed to meet the criteria as far as deflection is concerned, and the cost of manufacture estimated. If the designer does not, have this type experience it is best done with, the assistance of the fabricator who will fabricate the product. In addition to the material cost and the production labor costs,, the amortization costs of the tools are to be, included., The various designs and costs can be tabulated and the ones that are the most economical can be determined. At this point, it, may become evident that the design life can, be long and the cost of increasing the design, life small, or, alternatively, it may be that the, cost of small increments in the design life are

Page 224 : 206, , 4 Designing Plastic Product, , quite costly. In the latter case, the design life, should be limited to the acceptable minimum., A value judgment must be made as to the, product quality requirements and the final, design made to meet these requirements. By, leaving the options open until this conclusion, is reached, the decision as to what is best in, terms of product can be based on more than, a single valued solution, with the probable, result that a more economical and practical, product will result., The next step is the performance evaluation. In order to do this the product must, be completely designed as to the dimensions, necessary to fit any surrounding products, as, well as to the necessary cross-section thickness for strength and stiffness. The material,, color and manufacturing process must be selected. The product must include in the design, the necessary features to make for proper, process ability and whatever design features, are necessary to improve the performance, in the service environment. The latter may, include reinforced areas, coating or plating,, inserts, etc., Prototype, Next is to make sample prototype tooling, and sample prototype products for the test., Samples made by machining or other simplified model making techniques do not have, the same properties as the product made by, molding or extrusion or whatever process is, to be used (Chapter 3, PROTOTYPES). A, product made this way is a sample rather than, a testable prototype. Simplified prototypes, may reduce trial mold cost and produce adequate test data in some cases. Its main value, is appearance and feel to determine whether, the aesthetics are correct. Any testing has to, be done with considerable reservation and, caution., If prototype tooling is not made, then production tooling must be made to provide samples for evaluation testing. This is justified if, the product does not represent a substantial, departure from previously made units whose, performance is known in similar applications., If there is no prior history and as an example, , there will be a very long production run on, producing the shelves, it mandates the use of, a production type prototype tooling., In the situation where a similar application existed, the risk that the tools may have, to be scrapped or drastically altered as a result of the testing is not high and is justified., The other reason that a production tool is, made with no prototype tooling is because of, the lack of lead time. Here the risk is usually not justified and the shelves of processors are littered with tools that were the result of bad guesses made under severe time, pressure., By proper organization of time and tool design, the sample tooling can be made to fit into, the normal tooling cycle with a minimum of, added time and expense. Sometimes the prototype tooling can be made part of an existing, master chase or holder or it can be made of, soft materials such as epoxy or kirksite that, can be worked rapidly. In any event, the information obtained in the prototype tooling, stage can have a major effect on the final, design and tooling to give a successful and, economical product while prejudgments may, result in a poor compromise as a result of, drastically reworked tooling., Testing, After obtaining the prototypes, tests must, be made to determine the utility. Generally, these include a short time destructive test to, determine the strength and to check out the, basic design. Another test that is done is to, use the product in the projected environment, with stress levels increased in a rational manner to make for an accelerated life test. Other, tests may include consumer acceptance tests, to determine what instructions in proper use, are required, tests for potential safety hazards, electrical tests, self-extinguishing tests,, and any others that the product requires. In, the case of high risk products, the test program is continued even after the product enters service., The remainder of the test program requires the generation of quality control (QC), monitoring tests. For example, in the case of

Page 225 : 4 Designing Plastic Product, an injection molded product such as the library shelf, the quality control monitoring, might include critical dimension checks and, an oven test to see if the product has a, tendency to warp or self destruct, indicating improper molding conditions. A solvent, test for monitoring proper process conditions, might be included to check for stress crack, resistance., The last step in the design cycle is the, end-use testing, or field trials. This can be, done using selected individuals or applications that are closely monitored or controlled., This information will indicate whether or not, the product performed as the designer anticipated because of some unexpected situation. For example, the library shelves are, often cleaned with lemon oil that disintegrates the polystyrene (this requirement was, not previously known). Some of the product, can be test marketed to uncontrolled users, and their reactions sampled with a standard, response form generated by the advertising, people. Sample responses from a larger group, of people frequently produces what might be, referred to as the "idiot response." It is unbelievable what some users can do to a product simply because they did not understand, its limitations., The results of the field testing must define, the basis for labeling and the instructions to, be used with the product. Unless there has, been a serious misjudgment by the product, development designers, the field tests do not, lead to redesign. There may be the need for a, more durable unit for the serious abuse situations, as well as the need for proper instructions, but the main need is for the labeling, and instructions. The designer can supply the, necessary data for the do's and don'ts and, the instructions will at least minimize liability on the product of the producer for failure, due to abuse. The most obvious case in which, this is not true is when the abuse may occur, easily and result in a personal hazard to the, user. In this case, loss of the instructions is, not an adequate defense against responsibility by the user. In all cases, the product must, be designed to prevent danger to the user., Potential failures that can cause personal injury must be avoided in all product designs, , 207, , (see near end of this Chapter, LAWS AND, REGULATIONS)., , Summary, A table can be prepared summarizing the, steps in the design of a plastic product. It, would indicate the different types of options, that can be used at different stages in the design sequence. It also would indicate the areas, of potential high risk failure and the alternative approaches to use under these conditions. Example of a design program approach, follows:, 1. Define the function of the product with, life requirements., 2. State space and load limitations of the, product., 3. Define all of the environmental stresses, that the product will be exposed to in its intended function., 4. Select several materials that appear to, meet the required environmental requirements and strength behaviors., 5. Do several trial designs using different, materials and geometries to perform the required function., 6. Evaluate the trial designs on a cost effectiveness basis. Determine several levels of, performance and the specific costs associated, with each to the extent that it can be done, with available data., 7. Determine the appropriate manufacturing process for each design., 8. Basedon the preliminary evaluation select the best apparent choices and do a detailed design of the product., 9. Based on the detailed design select the, probable product design, material, and process., 10. Make model if necessary to test the effectiveness of the product., 11. Build prototype tooling., 12. Make prototype products and test products to determine if they meet the required, function.

Page 226 : 208, , 4 Designing Plastic Product, , 13. Redesign the product if necessary, based on the prototype testing., 14. Retest., 15. Make field tests., 16. Add instructions for use., , UNIFORM INTERNAL PRESSURE. P, , HOOP STRESS, , Pipe, A major and important market for plastics is in producing pipe (tube) for use such, as on the ground, underground, in water,, and electrical conduit. The largest use is in, transporting water, gas, waste matter, industrial mining, etc. Use of extruded thermoplastic, such as HDPE, PVC, and PP, provide, most of the world markets. The other major product is reinforced plastic principally, using glass fiber with TS polyester plastic that, use fabricating methods such as bag molding, and filament winding fabricating techniques, (Chapter 8, REINFORCED PLASTIC)., Since the 1930s, the TP pipe industry continues to expand its use worldwide. It now, represents over 30% of the dollar share compared to other materials (iron/steel at 45%,, copper at 12%, concrete at 8%, aluminum at, 4%, etc.). Although RP TS pipe represents, a small portion of the market, it is a product, of choice for many special high performance, applications. Corrosion resistance, toughness, and strength contribute to its growing, acceptance., A common pressure vessel application for, pipe is with internal pressure. In selecting the, wall thickness of the tube, it is convenient, to use the usual engineered thin-waIl-tube, hoop-stress equation (top view of Fig. 4-1). It, is useful in determining an approximate wall, thickness, even when condition (t < d/l0) is, not met. After the thin-wall stress equation is, applied, the thick-wall stress equation given, in Fig. 4-1 (bottom view) can be used to, verify the design (Appendix A: PLASTICS, DESIGN TOOLBOX)., RP Pipe, , RP pipes are used in different applications., The following review concerns the use and acceptance of buried large-diameter glass fiber,, , " =!:!!21, This equation is reasonably accurate for, t < d/10. As the wall thickness increases the, error becomes quite large., UNIFORM INTERNAL PRESSURE, P, , u=P..!...:..!!..., , da, , 1- R, , WHERE, , R=(:}, This equation is for the maximum hoop stress, which occurs on the surface of the inside wall, of the tube., , Fig. 4-1 Cylindrical pressure pipe of thin-wall, construction (top view) and cylindrical pressure, pipe of thick-wall construction (bottom view)., , plastic reinforced, filament-wound pipe that, has increased steadily since the 1950s. Such, RP was selected for its superior corrosionresistance characteristics and installationcost savings. ASTM standards use the term, reinforced thermoset resin pipe (RTR pipe or, RTRP); the general plastic industry uses the, term reinforced thermoset plastic pipe (RTP, pipe). Filament-wound pipe with a double helical angle of continuous-glass reinforcement, (Chapter 8, REINFORCED PLASTIC) is, but one of several types of RTP pipe constructions. Since at least 1944 pipe design equations have been used that specifically provide, useful information to meet internal and/or, external pressure loads (37)., Attempts have been made to utilize performance standards based upon internal pressures and pipes' stiffness, but other factors, must be carefully considered in designing

Page 227 : 209, , 4 Designing Plastic Product, , buried piping systems, especially the longitudinal effects of internal pressure, temperature gradients, and pipe bridging. Failing, to recognize these factors incurs the risk, of under designing a system. Because of its, plastic-glass fiber construction, the physical, characteristics of RTR pipe and therefore the, design techniques needed for it differ considerably from those of older, traditional pipe, materials., It is true that RTR pipe design does to a degree parallel the design philosophy for steel, pipe, but there is a point where the steel and, RTR pipe design approaches part company,, even though steel and RTR pipe are by definition both flexible conduits. In other words,, both kinds of pipe can bend and deflect after, burial, within certain limitations, without suffering structural or functional failure. In this, regard they both differ from concrete pipe,, which is a rigid conduit that cannot tolerate, bending or deflection to the same extent as, RTR pipe. Since an appreciation of the differences between flexible and rigid conduit is, essential to a better understanding of RTR, pipe design, let us examine these differences., Load Testing, , The diagrams in Fig. 4-2(a) illustrate the, results of actual load testing on both types, of conduit by the Roadway Committee of, the American Railway Engineering Associ-, , ation. Both the flexible and the rigid pipes, were buried under thirty-five feet of identical fill material. Obviously, specific pressures, vary from installation to installation, but the, relationship in the way the two kinds of pipe, react to the same burial condition generally, remains constants., Let us start by examining a rigid pipe. Because of its rigid, inflexible characteristics,, surface load intensifies at the crown of a rigid, pipe and is transmitted through the pipe directly to the bed of the trench in which the, pipe rests. This is not true with flexible conduit. Because a flexible conduit deflects under, covering load of earth, this deflection transfers portions of the load to the surrounding, envelope of soil. This is true of both steel and, RTR pipe. The result is that the support of, the surrounding earth actually increases the, strength of the flexible conduit. Therefore,, analyzing the type and consolidation of backfill materials must be considered an integral, part of the design process., Two additional observations can be made., First, because a rigid pipe transmits almost, all the load of the earth cover to the trench, bed, someone will occasionally be heard to, say that rigid pipe, such as concrete pipe, does, not require side support. This is not true. Second, because of the difference in the ways, rigid and flexible conduit distribute the load, of their earth cover, flexible piping materials, are often said to require less bedding bearing, strength, because they impose less of a load, , Flexible Pipe, 26 psi Computed, , ~~, , Concrete, Rigid pipe, 26 PSI Computed, , '" 54.7%, , i!.,. 158%, 26, , 17 PSi+, , 14 psi, , Fig.4-2(a), , •, , 41 psi, , Load-testing profile of flexible and rigid underground pipes.

Page 228 : 210, , 4 Designing Plastic Product, , on the trench bed. This is indeed true. In fact,, it is one of several factors that help to reduce, the installed cost of RTR large-diameter flexible pipe., , Directional Property, Given these differences between rigid and, flexible conduit, let us examine the differences between steel and RTR pipe, both of, which are, of course, flexible conduits. First,, steel pipe is by definition constructed from a, material, steel, that for our purposes is a homogeneous isotropic substance. Therefore,, steel pipe can be considered to have the same, material properties in all directions; that is, it, is equally strong in both the hoop and longitudinal directions [Fig. 4-2(b)]., RTR filament-wound pipe is, however, an, anisotropic material. That is, its material, properties, such as its modulus of elasticity, and ultimate strength, are different in each, of the principal directions of hoop and longitude. It is here where the design approaches, for steel and RTR pipe part company, [Fig. 4-2(c)]. This behavior is a result of the, construction of filament-wound RTR pipe., , Filament Wound Structure, Its manufacturing is done by winding continuous strands of plastic-impregnated glass, fiber around a steel mandrel at a precisely, controlled helix angle, under controlled tension. A cross-sectional view of an RP layup, is shown in Fig. 4-2(d). As seen, the structural wall of the pipe is made up of con-, , Fig.4-2(b) Material properties of relatively homogeneous isotropic steel pipe., , Fig. 4-2(c), RTRpipe., , o, , Material properties of anisotropic, , tinuous strands of fiber glass embedded in, a plastic matrix, plus an internal corrosion, barrier liner. The liner can be constructed, from a number of different plastics and reinforcement materials, depending on what, will eventually be put through the pipe. Incidentally, the thicknesses of the liner are, not considered during design analysis, except, for calculating buckling and pipe deflection, (Chapter 8, REINFORCED PLASTICS,, Filament Wound Structure)., Broadly speaking, three factors control the, physical properties of RTR pipe. These are, the amount of continuous-glass filament used, to construct the pipe wall, the prescribed, dual-helix angle at which the glass is wound, around the mandrel, and the type and amount, of plastic matrix used to bind the glass filaments together. Controlling the strength of, the pipe in the hoop and longitudinal directions is done by selecting the winding angle, and ratio of glass to plastic content. The winding angle for the structural wall is usually, from 55 to 65 degrees to the horizontal, and, the glass-fiber content is not less than 45 wt%., The final material composition of the pipe, is determined by calculating the longitudinal, , Fig.4-2(d), , Cross-sectional view of RTR pipe.

Page 229 : 4 Designing Plastic Product, and hoop strengths needed to meet installation requirements demanded by the project., By now it should be apparent that, while, both steel and RTR pipe are by definition, flexible conduit, they are also quite different and therefore require different design approaches, even though initially at least their, design considerations are identical. As with, steel pipe, the RTR pipe designer must concern oneself with both pipe deflection and, buckling analysis. Unlike the steel pipe designer, however, the RTR pipe designer must, also examine a third area of concern., The third factor is a combined strain analysis in both the hoop and longitudinal directions. This analysis demands a thorough, examination of such important considerations as diametrical bending, internal pressure, temperature gradients, and the ability, of the pipe to bridge voids in bedding. In such, a design system the pipe is seen as part of a, buried pipe system in the ground., , Stiffness and Strength, In simplest terms the design goal is to select the correct RTR pipe configuration for a, specific application. In other words, we want, to design a pipe wall structure of sufficient, stiffness and strength to meet the combined, loads that the pipe will experience over the, long term. There are two primary ways to, achieve correct pipe stiffness. One is to design a straight-wall pipe in which the wall, thickness controls the stiffness of the pipe, [Fig.4-2(e)]., Another way is to design a rib-wall pipe on, which reinforcement ribs of a specific shape, , 211, , and dimension are wound around the circumference of the pipe at precisely calculated, intervals. The advantage of rib-wall pipe is, that the nominal wall thickness of the pipe, can be reduced while maintaining or even increasing its overall strength-to-weight ratio., Generally, a rib-wall pipe design is selected, for applications where burial conditions are, extreme or for difficult underwater installations. The ability to increase or maintain pipe, stiffness by means of reinforcement ribs also, provides the ability to design an RTR pipe, system to fit the economic as well as mechanical parameters of a project., , Deflection Load, The next step in design is to determine the, pipe deflection requirements, based on the, equation shown in Fig. 4-2(f). The accepted, maximum allowable pipe deflection should, be no more than 5%., This value is the basic standard that, AWWA M-II specifies for steel conduit and, pipe, as do the ASTM and ASME. As is, obvious, there are a number of factors that, contribute to pipe deflection. These are the, external loads that will be imposed on the, pipe, both the dead load of the overburden as, well as the live loads of such things as wheel, and rail traffic. The factors affecting RTR, pipe deflection can be summarized as follows:, 1. Design pipe deflection, 2. Dead load-trench shape, overburden, weight, depth of cover, 3. Live load-wheel load, spacing surcharge, , RTR Pipe Wall Structures, , i~'-~', Straight Wall, , Maximum 5% Deflection, (~Xmax :5 5%), by AWWA M-l \, ASTM, and ASME., , Rib Wall, , Fig.4-2(e), , Example ofRTR pipe wall structures., , Fig.4-2(f) How to calculate maximum allowable, pipe deflection.

Page 230 : 212, , 4 Designing Plastic Product, , 4. Modulus of soil reaction-native soils,, type of backfill, differential soil stress and, consolidation, 5. Deflection lag factor, 6. Bedding shape, 7. Pipe stiffness (El), 8. Pipe radius, In terms of dead loads, the shape of the, trench in which the pipe will be buried is also, a factor. Generally speaking, a narrow trench, with vertical sidewalls will impose less of a, load on the pipe than will a wider trench with, sloping side walls. It is necessary also to know, the modulus of soil reaction (E), which is dependent on the type or classification of the, native soil, the backfill material that is contemplated, and the desired consolidation of, the backfill material. Soil consolidation is important, because it contributes to the strength, of a flexible conduit in a buried pipe system., If the designer is to do the job properly, it is, important to have accurate data on which to, base calculations. That is why test borings and, proper laboratory analysis to determine the, E value of the soil sample are essential. An, arbitrary textbook selection of a soil modulus, should always be avoided. However, if a pipe, is to be buried deeper than the sampling zone, that underwent laboratory testing to determine E and if the test bore shows the deeper, material to be equal or better, then the designer may increase the E value proportionally to the square root of the differential soil, stress., Assuming that all the necessary data are, available, determining the necessary pipe, stiffness for the maximum allowable pipe deflection is relatively simple. The SpanglerIowa equation provides a useful, reasonable, determination of what wall structure will be, needed (111)., , criterion of no more than 5% deflection., Theoretically, we could choose a pipe-wall, structure to meet this required stiffness of either a straight-wall pipe with a thickness of, approximately 1.3 cm (0.50 in.), or a rib-wall, pipe that would provide the same stiffness., But would the wall structure selected be of, sufficient stiffness to resist the buckling pressures of burial, or superimposed longitudinal, loads? At this point we do not really know. To, find out, we must know a few more things, one, of being the amount of resistance to buckling that is wanted in the pipe. The ASME, Section III Standard of a four-to-one safety, factor on critical buckling, based on many, years of field experience, should be used. To, calculate the stiffness or wall thickness capable of meeting that design criterion one must, know what anticipated external loads will occur (Fig. 4-2(g)). This time, in addition to the, dead loads one must also consider the effects, of possible flooding on both an empty and full, pipe, as well as the vacuum load it is expected, to carry., The analysis should include the modulus of, soil reaction, because in a buried RTR piping system the elastic medium surrounding, the pipe helps increase the pipe's resistance, to buckling. The formula into which all these, factors can be inserted to determine the critical buckling pressure of the pipe is called the, Luscher & Hoeg formula (44, 56)., It has been determined that, with burial, depths greater than two thirds the radius of, the pipe, this equation provides a means of, determining the required pipe stiffness for, critical buckling. To make the equation easier, to use, it can be rewritten by substituting certain values and solving for the required stiffness for buckling. Suppose that this Luscher, & Hoeg equation says we will require a, pipe stiffness of 0.123 x 106 lb-in 2/lineal in. to, Flood Water-I, , Stiffness and Buckling, Assume for the purposes of this project, that the calculations indicate that this pipe, stiffness of 0.0365 x 106 Ib-in 2/1inear in. is in, fact required to meet this deflection-design, , Earth Load, , I I III II II II I II I I, , .----------:\ I I, , "', , Vacuum Load, , Fig.4-2(g), , \' I, , \,, , \,, , "', , Ground, , Level, , ,/, , ,/,, ".., , Confined Soil, Media, , Buckling analysis.

Page 231 : 4 Designing Plastic Product, meet a four-to-one critical buckling pressure, safety factor., This is a straight-wall thickness of approximately 1.9 cm (0.75 in.). But remember that, we earlier calculated that a 1.3 cm (0.50 in.), thick wall would be sufficient to withstand, the anticipated deflection pressure. Which of, these two wall thicknesses is correct? Quite, logically, it is the larger one of the 0.75 in., thickness, or a rib-wall pipe of equivalent, stiffness. To put it another way, after carefully, completing both a deflection and a buckling, analysis, always select the pipe stiffness that, is greater. Now if we were designing in steel, pipe, the work would be about over. But since, the design is a large diameter RTR buried, piping system, we are not. From experience, it has been learned that the final choice of, an RTR pipe configuration cannot be made, until the effects of strains in the longitudinal and hoop directions have been carefully, investigated., , Anisotropic Behavior, The reason is obvious since the material, continuous glass-reinforced TS polyester, plastic, is anisotropic. Unlike a homogeneous, isotropic material, such as steel, the strength, of RTR pipe in its longitudinal and hoop directions is not equal (Fig. 3-19). The effects, of this unequal strength in the two directions, must therefore be seriously considered during design if an RTR piping system is to meet, the long-term operating requirements of the, system being designed., Therefore, before a final wall structure can, be selected, it is necessary to conduct a combined strain analysis in both the longitudinal, and hoop directions. This analysis will consider thermal contraction strains, the internal pressure, and the pipe's ability to bridge, soft spots in the trench's bedding. In order to, do this we must know more about the inherent properties of the material we are dealing with; that is a structure made up of successive layers of continuous filament-wound, fiberglass strands embedded within a plastic, matrix. We must know the modulus of the, material in the longitudinal direction and the, , 213, , Hydrostatic Testing, , i"'- I 'l', Flexural, , Q, , Parallel Plate Testing, , : [:---J-..I :, , Coupon Testing, , Tensile, , Fig. 4-2(h) Examples of using strain gauges to, develop stress-strain curves., , hoop direction, plus the material's allowable, strain., These values are determinable through, standard ASTM-type tests, including those, for hydrostatic testing, parallel plate loading, coupon tests, and accelerated aging tests, [Fig. 4-2(h)]. The next step is to examine, Fig. 4-2(i), which shows the tensile stressstrain curve for typical steel-pipe materials., In the steel pipe business, designing is based, on the curve's yield point. As noted previously, the yield point on a stress-strain curve, beyond which steel pipe will enter into the, range of plastic deformation could lead to a, total collapse of the pipe. Generally to provide a safety factor, steel-pipe designers select an allowable design strain of approximately two thirds of the yield point., , Stress-Strain Curve, RTR pipe designers also use a stress-strain, curve similar to that used by steel pipe, 120, 100, 90, Stress, ax 103 PSI, , Stress/Strain Curve, Mild Steel Pipe, , 80, 70, 60, 50, 40, 30, 20, 10, 0, , 1000 2000, , 3000 4000 6000 8000, , 10,000, , Strain, £ x 10--6 in.lin., , Fig. 4-2(i) Example of a tensile stress-strain, curve for mild steel pipe material.

Page 232 : 4 Designing Plastic Product, , 214, 100, 90, 80, 70, 60, , Stress/Strain Curve, RTR Pipe, , Stress, ax 10' PSI 50, 40, 30, , Normal, Design Strain, , Strain to 1sl Crack or, , Empirical Weep Point, (0.009 in.!in.), , 15,000, Strain, e x 10-6 in.fln., , 20,000, , Fig. 4-2(j) Example of a tensile stress-strain, curve for RTR., , designers. However, instead of a yield point,, they use what is called an empirical weep, point, or the point of first crack [Fig. 4-2( j)]. It, is determined by either coupon or hydrostatic, tests. The weep point is the point at which the, matrix becomes excessively strained so that, minute fractures begin to appear in the structural wall., At this point it is probable that in time even, a more elastic liner will be damaged and allow, water or whatever else the pipe is carrying to, ooze or weep through the wall. As is the case, with the yield point of steel pipe, reaching, the weep point is not cataclysmic. The pipe, can still continue to withstand quite a bit of, additional load before it reaches the point of, ultimate strain and failure. Recognize that a, more substantial, stronger liner can easily extend the weep point., , tors of other pipe manufacturers following, (NBS/NIST) Voluntary Product Standard PS, 15-69, these safety factors may seem modest., However, PS 15-69 is based on the ultimate, tensile strength of the material (Chapter 2,, SAFETY FACTOR)., The next step is to proceed with a strain or, stress analysis in the longitudinal and hoop, directions. When conducting this analysis the, designer has the option to work in terms of, either stress or strain. Strain is generally used,, since it can be accurately measured using reliable strain gauges, whereas stresses have to, be calculated. From a practical standpoint, both the longitudinal and the hoop analysis, determine the minimum structural wall thickness of the pipe. However, since the longitudinal strength of RTR pipe is less than it is, in the hoop direction, it is wise to approach, longitudinal analysis first., In doing so there are three major factors, to consider: the effects of internal pressure,, the expected temperature gradients, and the, ability of the pipe to bridge voids in the bedding. Analyzing these factors requires that, several equations be superimposed, one on, another. Even though from a practical standpoint all these longitudinal design conditions, are solved simultaneously, it is interesting to, examine each individually., Poisson s Effect, , Weep Point, The weep point or strain-to-first-crack in, a wall for filament-wound pipe constructed, using isophthalic plastic is currently found to, be not less than 0.009 in.lin. This has been, repeatedly demonstrated by careful coupon, testing and burst testing of pipes with strain, gauge instrumentation attached., Thus, design values are based on the strainto-first-crack or the empirical weep point., For normal design conditions a strain of, 0.0018 in.lin. is used, which provides a fiveto-one safety factor. For transient design conditions a strain of 0.0030 in.lin. is used, for a, safety factor of approximately three to one., To those familiar with the design safety fac-, , Some tend to disregard the effects of internal pressure in the longitudinal direction, on buried pipe because they theorize that the, longitudinal load is cancelled out by the earth, surrounding the pipe. Or they may assume, that in a gasketed joined pipeline the gasket, joints will allow the pipe to move freely, so, that no longitudinal load will exist. However,, this situation is not necessarily true. Poisson's, ratio can have an influence (Chapter 2). This, effect occurs when an open-ended cylinder is, subjected to internal pressure. As the cylinder expands diametrically, it also attempts to, shorten longitudinally. These movements will, not be visible to the naked eye in all cases but, can be easily measured with strain gauges., Or the movements can be observed in the

Page 233 : 4 Designing Plastic Product, shortening of pressurized pipe where a test, fixture absorbs the pressure thrust., Since a buried pipe movement is resisted, by the surrounding soil, a tensile load is produced within the pipe. The internallongitudinal pressure load in the pipe is independent, of the length of the pipe. Thus, Poisson's effect must be considered when designing any, length of pipe, whether long or short that is, part of a buried pipe system. Buried pipes are, influenced by friction with their surrounding, media., Several equations can be used to calculate, the result of Poisson's effect on the pipe in, the longitudinal direction in terms of stress, or strain. Equation provides a solution for a, straight run of pipe in terms of strain. However, where there is a change in direction and, thrust blocks are eliminated through the use, of harness-welded joints, a different analysis, is necessary. This is so because, compared to, in straight runs of pipe, the longitudinal load, imposed on either side of an elbow is greater., This increased load is the result of internal, pressure, a temperature gradient, and/or a, change in momentum of the fluid. Because, of this increased load, the pipe joint and elbow thickness may have to be increased to, avoid overstraining. There is a special equation, shown in Fig. 4-2(k) to calculate the, longitudinal strain in pipe at harnessed elbows. For the sake of simplicity the effects of, internal pressure, temperature gradient, and, change in momentum of the fluid have been, combined into one equation., After examining the effects of internal, pressure in the longitudinal direction, the, next step is to investigate the longitudinal, tensile loads generated by a temperature gradient in the piping system. The goal is to, , :~::Ili~~,~~,"" '~F2F', Fl, , Pressure + Temperature +, Change in momentum, ltd2P, V, F,~ -4-+<'c,A+QP, ~, , g, , A, , ~, , Fl, , ltdt, , "lt~ ~ .<lTELoc, , Fig.4-2(k) Example of longitudinal tensile strain, with harnessed elbows., , 215, , determine the extent of the tensile forces imposed on the pipe because of cooling. When, an open-ended cylinder cools, it attempts to, shorten longitudinally. A tensile load is then, imposed by the resistance of the surrounding soil. As a matter of fact, any temperature, change in the surrounding soil or medium, that the pipe may be carrying can produce, a tensile load. The effects of temperature, gradient on pipe can be written in terms of, strain., In this analysis the designer must consider, two conditions and base the pipe design on, the one that is worse. One condition is where, the temperature differential is one half the, difference between the maximum temperature and minimum temperature. The second, condition considers the temperature differential between the maximum pipeline temperature at installation and the minimum design temperature., The next step in longitudinal analysis is, to examine the bridging. Bridging can occur,, and if so must be considered, wherever the, bedding grade's elevation or the trench bed's, bearing strength varies, when a pipe projects, from a headwall, or, of course, in all subaqueous installations. It is a good practice to, design the pipe to be strong enough to support the weight of its contents, itself, and its, overburden while spanning a void of two pipe, diameters [Fig. 4-2(1)]., Conservative Approach, For simplicity, the condition considers the, conservative case where the pipe acts simply, as a support. The normal practice is to solve, all these equations simultaneously, then determine the minimum wall thickness that has, strains equal to or less than the allowable design strain. Thus, the minimum structural wall, thickness is dictated by the longitudinal tensile load., The importance of combining longitudinal, strain analyses is that it often provides the, designer with a minimum wall thickness on, which to base the ultimate choice of pipe, configuration. For instance, assume that the, combined longitudinal analysis indicates a

Page 234 : 216, , 4 Designing Plastic Product, Ground Level, , ]1, Earth, , Fig. 4-2(1), , Example of the longitudinal tensile load on a pipe bridging a void of two pipe diameters., , minimum of 5/8 in. (1.59 cm) of wall thickness. However, deflection analysis calls for a, 1/2 in. (1.27 cm) wall, and the buckling analysis says we need a 3/4 in. (1.9 cm) wall. We, had already decided that the most likely candidate was the 3/4-in. wall. Now longitudinal, analysis says that a 5/8 in. wall is enough to, handle the longitudinal strains likely to be, encountered. Which wall thickness, or what, pipe configuration, straight wall or ribbed, wall, do we now settle on? Economic considerations would have to be weighed, but, the experienced designer would most likely, choose the 3/4 in. straight-wall pipe. This is,, of course, if the design analysis is complete,, but it is not since there still remains strain, analysis in the hoop direction. The target is, to determine if the combined loads of internal pressure and diametrical bending deflection will exceed the allowable design strain, [Fig. 4-2(m)]. This entails investigating the, effects of rerounding or decreasing the diametrical deflection that occurs because of internal pressure [Fig. 4-2(n)]., , There is a method that can be used for, this analysis. It is extremely complex so it, requires using a computer. In general, equations are generated to determine the moment, and thrust created in the invert area of the, deflected pipe, where a pressure term is superimposed. This analysis must examine the, strains in the outer and innermost fibers of, the pipe to verify that its wall structure is adequate and not overstrained. During this analysis the pipe must be examined under conditions of no pressure, minimum pressure, and, maximum pressure., Although this analysis should be conducted for both straight-walled and ribwalled pipe, it is particularly important in the, case of rib walled. That is, because the rib, is often thicker than the structural wall of, the pipe, by several times the wall's thickness. Strains along the ribs may be higher, than along the straight-walled sections, particularly at the top of the rib. For the sake, of this discussion, assume that strain analysis in the hoop direction has confirmed that, , ~x, , Fig. 4-2(m) Example of strain analysis in the, hoop direction with external load only; no internal, pressure rerounding., , Fig. 4-2(n) Example of strain analysis in the, hoop direction with external load only plus internal pressure rerounding.

Page 235 : 4 Designing Plastic Product, , 217, , Gasket, Spigot, , ~ ____ ~, , Close Tolerance Machined Surface, , Gaskets, , Single Gasket, , Fig. 4-2(0), , Double Gasket, , Example of using elastomeric bell-and-spigot seals., , a structural wall thickness of 3/4 in. is satisfactory. Does that mean the pipe design has, been completed? Not yet. There's more to a, piping system than just the pipe walls., , Pipe Joint, We must still design the joints to connect, the straight lengths of pipe together. The designing of joints perhaps tends to be one, of the most overlooked areas in any pipingsystem design. Since the performance of the, whole piping system is directly related to the, performance of the joints, this subject deserves serious attention., For example, use a bell-and-spigot joint, with an elastomeric seal [Fig. 4-2(0)]. This, type of joint permits rapid assembly of a piping system and thus offers an economic advantage in terms of installed cost. It should, be used as much as possible for connecting straight runs of pipe, especially at points, where the pipe projects from a rigid structure. In terms of flexibility, the joint should, be able to rotate at least two degrees without, a loss of integrity. Thus, the threat of failure, from unanticipated pipe subsidence is substantially reduced, and changes in the grade, line during installation can be the more easily accommodated. The joint must also be, designed with corresponding bell and spigot, stiffnesses. And the spigot should have a special control ridge to ensure proper gasket, seal, even when the pipes on either side of, the joint are not uniformly supported., Bell, , Fiberglass & Resin Overlay, , Adhesive Filler, , Spigot, , External Harness-Welded Joint, , Fig.4-2(p), , The next type of joint is weld overlays,, which are often utilized to eliminate the need, for costly thrust blocks [Fig. 4-2(p)]. In designing the pipe an analysis was made to ensure that it possessed sufficient longitudinal, strength. It makes sense, then, to make the, weld joints be at least as strong as the longitudinal strength of the pipe rather than just, as an internal pressure-seal pipe., This can be done by noting the pipe's structural wall thickness and the strength relationship between the pipe and the overlay weld., These equations show one way of relating the, structural wall thickness of a pipe to its longitudinal design's allowable values first in regard to the longitudinal strength of the pipe, and its overlay laminate, to determine the, proper thickness of the joint, and second to, the longitudinal pipe strength and the weld, overlay's bond strength., , Bearing, Similarly to gears, some plastic bearings, have a long history of successful performance. The injection molded TPs that are, considered for bearing applications are usually for relatively small, light duty work such, as food mixers, adding machines, and similar devices. However small to large bearings also go into the heavy duty applications. Some TPs have inherent lubricating, characteristics that can be enhanced by additives such as PTFE, molybdenum disulfide, and others. Other TPs, as well as TSs,, Adhesive Filler, Preformed Recession Area, , iii7"~, ., ~\~, , Inside Fiberglass & Resin Overlay, , Internal Harness-Welded Joint, , Joints with overlay on either side.

Page 236 : 218, , 4 Designing Plastic Product, , by the addition of PTFE and/or molybdenum disulfide, become excellent candidates, for bearing materials (Chapter 4, OTHER, BEHAVIOR, Friction, Wear, and Hardness, Property)., The laminated (RP) fabric, bonded with, phenolic plastic incorporating antifriction ingredients and cured under heat and pressure, gives excellent service when properly, applied in various applications. This group of, bearings has a low coefficient of friction, antiscoring properties, and adequate strength for, use in steel mills and other heavy-duty applications and is well established in the industry., PV Factor, , When designing a plastic bearing, one must, recognize that the primary cause for favorable performance will be keeping the frictional heat to a low value and having prevailing conditions that lead to dissipation of, such generated heat. It has been established, that the basic factors in a bearing system contributing to frictional heat are the pressure P, exerted on the projected area of the bearing, and the velocity V or the speed of the rotating, member. This is known as the PV factor, and, maintaining the values within the prescribed, limits of each material will lead to a successful, bearing., The overall elements that contribute to the, limiting of the PV factor are magnitude of, pressure, speed of rotation, coefficient of friction of mating materials, lubrication, clearance between bearing and shaft, surrounding temperature, and surface finish, as well, as hardness of the mating materials. Bearing wall thickness is also an element in, the PV factor since it determines the heat, dissipation., By treating individually each of the above, elements, the following occurs. The limit of, the PV factor for each material or the internally lubricated materials for the constant, wear of bearing is usually available from the, supplier of the plastic. Neither the pressure, nor the velocity should exceed a value of, 1000. Thus, if the PV limit of acetal is 3000, the, PV factor could be 1000 ft/min (300 mlmin), , times 3 pounds or 1000 pounds times 3 ft/min, at the extreme, provided heat conditions resulted in uniform rate of wear. The coefficient, of friction data, available from suppliers, can, also provide guidelines to the efficiency in, comparing the different materials., Lubrication whether incorporated as an, RP material or provided by feeding the lubricant to the bearing will raise the PV limit 2.5, or more times over the dry system. The possibility of a rusting shaft should be guarded, against in order to prevent excessive bearing, wear., Clearance between shaft and bearing will, be large in comparison with, for example, a, bronze bearing, mainly due to the high coefficient of expansion of these plastics-roughly, up to 10 times that of steel. The average allowed clearance is 0.004 to 0.005 in.lin. (0.010, to 0.013 cmlcm) of bearing diameter. This is, needed in order to counteract the tendency, to close in the bearing ID when temperatures, rise or assembly conditions cause a decrease, in the shaft hole., The surface roughness of the shaft can play, a large part in heat generation in the bearing., The protruding ridges from machining on the, shaft act as minute cutting tools and disturb, the smooth surface of the bearing thereby, creating heat due to interference with the, displaced material. A surface reading of, 5 microinches is almost mandatory on the, bearing portion of the shaft in order to ensure good life. Surface hardness of at least, 300 Brinell on the shaft is another favorable, feature for smooth operation. It prevents the, pick-up of loose particles that can abrade the, plastic material., Wall thickness of the bearing should be on, the low side to facilitate heat transfer into, the housing, and yet it should be of sufficient value to facilitate effective manufacturing that will be conducive to a quality, product. The thickness should be in proportion to shaft diameter, starting with 0.05 in., (1.27 cm) on the low side and ending with, 0.2 in. (0.51 cm) on the high side. For filled materials, these thicknesses can be 50% higher., Bearing length should be equal to or less, than 1.5 diameters. Concluding the remarks, on plastic bearings, one must appreciate the

Page 237 : 4 Designing Plastic Product, numerous variables that enter into their design, and for that reason a prototype test is, very much in order., Gear, , Gear design is one of the more complicated, areas for designing with plastics (but understood with the extensive past half century, experiences), because the bending, shear,, rolling, and sliding stresses all act upon a, mechanism whose purpose is to transmit, uniform motion and power. In this age of, lightweight and quieter operation, plastic, gears have become increasingly important as, a means of cutting cost, weight, and noise, without reducing performance., Because plastics are not as strong as steel,, they must often perform far closer to their, design limits than do metal gears (134)., Although many plastic gear designs are, derived from metal-gear technology, plastics, demand special consideration, for instance, to deal with heat buildup from hysteresis, (Chapter 2)., , Load Requirement, The basic difference between metal and, plastic in gear design is that designs for metal, are based on the strength of a single tooth,, whereas plastic shares the load among the, various gear teeth to spread it out. Thus,, in plastics the allowable stress for a specific, number of cycles to failure increases as the, tooth size decreases to a pitch of about 48., Very little increase is seen above a 48 pitch,, because of the effects of size and other considerations. The following guidelines for good, gear design with TPs should be observed:, (1) determine the gears' conditions of service,, such as temperature, load, velocity, space,, and environment; (2) establish the short-term, plastic properties as against the initial performance requirements; (3) compare the longterm property retention factor as opposed to, the life of the gear; (4) using physical property data, calculate the stress levels caused, by the various loads and speeds; and (5) then, , 219, , compare these calculated values with the allowable stress levels and redesign as needed, to provide an adequate safety factor., Plastic gears fail for many of the same reasons as metal gears that include wear, scoring, plastic flow, pitting, fracture, creep, and, fatigue. The causes of these failures are essentially the same. If a gear is lubricated, bending stress will be the most important parameter. Because nonlubricated gears may wear, out before a tooth fails, contact stress is the, prime factor in their design. Plastic gears usually have a full fillet radius at the tooth root,, so they are not as prone to stress concentrations as are metal gears. The bending stress in, engineering TPs is based on fatigue tests run, at specific pitch-line velocities. A velocity factor should be used if the operating pitch-line, velocity exceeds the test speed. Continuous, lubrication can increase the allowable bending stress by a factor of at least 1.5., As with bending stresses, calculating, surface-contact stress requires using a number of correction factors. For example, a, velocity factor is used when the pitch-line velocity exceeds the test velocity. A correction, factor is also used to account for changes in, operating temperature, gear materials, and, the pressure angle. Stall torque, another important factor, could be considerably more, than the normal loading torque., , Hysteresis Effect, At high speeds, plastic gears are also subject to hysteresis heating, which may be severe enough that they actually melt. Avoid, this failure by designing the gear drive so that, there is favorable thermal balance between, the heat that is generated and that, which is, removed by an inherent cooling process., Reducing the rate of heat generation or increasing the rate of heat transfer will stabilize the gear's temperature so that they will, run indefinitely until stopped by genuine fatigue failure. In such cases the wear resistance, and durability of plastic gears makes them, quite useful. Using unfilled engineering plastics usually gives them a fatigue life on an, order of magnitude higher than metal gears.

Page 238 : 220, , 4 Designing Plastic Product, , Hysteresis heating in plastics can be reduced by several methods, the usual one being to reduce the peak stress by increasing, the tooth root area available for torque transmission. Another way to reduce stress on the, teeth is by increasing the gear's diameter., Peak stress can also be reduced by geometrically repositioning it using various conventional published gear theories., Using stiffer plastics to reduce hysteresis, provides other improvements. For example,, the higher crystalline TPs like acetal and nylon (types of plastics extensively used) can, be further increased by compounding techniques that can reinforce their stiffness by, 25 to 50%. The most effective way to improve stiffness is through the use of fillers, and reinforcements, particularly the highstiffness fibers. Fillers and reinforcements, are available that will also significantly increase heat transfer. The surrounding fluid,, whether liquid or air, can have substantial, cooling effects. A fluid like oil is at least ten, times better at cooling than air. Agitating, these mediums increases their cooling rates,, particularly when employing a cooling heat, exchanger., Processing, , When discussing plastic gears, one has to, recognize that one is dealing with two basic, materials. One type is a gear hobbed (cut), in a conventional manner from sheet blanks, (the same as steel gears). The other type, that represents practically all produced are, injection molded into the required shapes., This type of gear has been in use for over at, least a half century in electric power tools, instruments, meters, registers, windshield wiper, mechanisms, steel mills, heavy duty machinery, or wherever the advantages of smoother, operation, longer life, lower noise levels,, lightweight, toughness, and lower costs existed. Timing gears for automobiles, for example, have been made on the same basic, principle in very large volume over a period, of many decades. This type of gear has established its reliability and is considered as, a proven candidate for many applications., , Use is made of unfilled and filled or reinforced TPs., Careful consideration of plastic material, characteristics and its processing requirements can lead to gears with the enumerated benefits and, above all, to a more successful product performance. Considerable, attention is given to the mold ability of gears., One can make all the perfect calculations and, insert the necessary values for plastic gears,, but if molding conditions and molding materials are not compensated for to obtain a highquality gear, one may end up with mediocre, or even unsatisfactory results., One of the first questions the designer faces, in connection with a gear drive is to determine the pitch diameter of the pinion, and, number of teeth required. Designs have to, take into consideration backlash and working clearance. Backlash is defined as the measurement by which the space between teeth, exceeds the thickness of the engaging tooth, on the pitch circle. Backlash is necessary, to prevent simultaneous contact on the two, sides of the space and thus eliminates the, possibility of binding. Backlash, tip relief,, and similar arrangements are the means of, providing satisfactory working clearance and, thus minimizing excessive wear and noise., The factors that cause a gear to mesh, tightly are: (1) tolerance on concentricity of, shaft hole with pitch diameter, (2) tolerance, on center distance, (3) tolerance on quality, (4) coefficient of thermal expansion, and, (5) change in dimensions due to moisture absorption, which is a consideration/detriment, in some materials. The first three apply to, gears of any material. Item 4, and in some, cases Item 5, for plastic gears deserves special consideration., The subject of transmitting motion and, power by means of gears, their construction, and detail requirements are fully covered in textbooks, technical handbooks, and, industrial literature of gear suppliers. The, knowledge of gear fundamentals is a prerequisite for the understanding of where and, how to insert the appropriate plastic behavioral information into the gear formulas, so that the application results in favorable, operation.

Page 239 : 4 Designing Plastic Product, Gasket and Seal, , Different plastics are used to fabricate gaskets and seats. With many applications, usually the chemical or heat resistance will suggest the choice of the plastic, but often it, can be below the optimum in stress relaxation. As an example PTFE is used for being virtually inert and having outstanding, high-temperature performance. PTFE is extremely vulnerable to creep and stress relaxation. However the many different filled, grades permit eliminating or improving these, type limitations; its use includes being subjected to severe environments., There is a great range of plastics and elastomers to meet widely varying service requirements and all the types of geometric, shapes and stress relaxation characteristics., Different tests have been set up to develop, industry standards and test evaluations that, should be directly useful in their applications., For example, a gasket relaxometer applies a, compressive stress to a flat annular specimen,, similar to the way many gaskets are stressed, in service (ASTM F 38). This device is simple to operate, inexpensive, and capable of, measuring the effects of such pertinent variables as stress relaxation in regard to time and, environment., The ability of a gasket to seal against leakage resulting from the pressure of a confined, fluid is directly related to retained stress. High, initial stresses often are required to be able, to handle high pressures. In this example,, however, high stresses serve to increase the, tendency of a gasket to creep, thus requiring stronger and more expensive construction. The usefulness of stress relaxation data, to the designer is that they provide a guide, in arriving at the usually required suitable, design compromise, without overdesigning., These data show that the thinner the gasket, the less stress relaxation occurs. In some, material evaluations, stress relaxation can be, correlated with geometric variables by means, of a shape factor, as follows:, Shape factor, = Annular area/total lateral area, = (OD - ID)/4t, (4-1), , 221, , where OD = outside diameter, ID = inside, diameter, and t = thickness., The trend of this factor is generally consistent with plastics' behaviors. However, stressrelaxation information has to be interrelated, with the individual behavior of the plastics, as derived from the relaxation-test data, (Chapter 2)., Grommet and Noise, , To quiet a noise-generating mechanism,, the first impulse is often to enclose it. Sometimes an enclosure is in fact the best solution, but not always. If it can be determined, what is causing the noise, appropriate action, can be taken to be more specific and provide a cost-effective fix. In some cases the, problem is caused by a component such as, a stepper motor or gear set that does not, produce objectionable noise by itself. The, trouble typically develops because a small, noise is transmitted to a metal frame or cabinet that then serves to amplify the sound;, using a plastic cabinet can isolate the noise, problem., Figure 4-3 is an example where in addition to reducing noise, the injection molded, polyurethane (PUR) grommet (right) replaces five individual parts and saves time in, assembling the lever linkage. During assembly it is snapped into a hole in the steel lever,, then a grooved rod is inserted into the grommet. Intended to isolate vibration as well as, connect metal parts, such a PUR grommet, eliminates the hardening and cracking that, use to shorten the life of the old assembly., This design might appear to be mechanically, weaker than the cotter pin assembly, but it, is at least as strong. The 1 in. OD grommets, can withstand a 200 lb. (90 kg) pull on the rod, without undergoing pull-out. In addition, the, assembly can withstand a 100 lb. (45 kg) cyclic, load (about 5,000 cycles at 60 cycles/min.) applied at 60 degrees off the rod axis at 300°F, (149°C)., A cabinet that resonates can be quieted by, damping its large flat areas so that they do not, act like loudspeakers. Different approaches, can be used, such as applying plastic foam

Page 240 : 222, , 4 Designing Plastic Product, , Fig. 4·3, , Grommet designs., , sound insulator or, as reviewed, plastic panels, which have low damping characteristics., Various plastics have helped alleviate problems in all types of noisemakers, including, rotating systems and hammer actions. One, popular approach is to use plastic grommets, where applicable., In the past residential trash compactors, were objectionably noisy. They were reduced, to acceptable noise levels by redesigning, them. Sound-absorbing grommets were used, on the motors' bolt attachments and plastic, gears were employed. Testing and all other, types of equipment can take advantage of, grommets or be redesigned to use plastic., Grommets provide their greatest noise reduction through damping in the octave frequency bands above 500 Hz where the ear is, most sensitive and sound most annoying., , The function that plastics serve in most applications is that of a dielectric or insulator, that separates two conductors with an electrical field between them. The field can be a, steady direct current (DC) field or an alternating current (AC) field and the frequency, range may vary such as from 0 to 10 10 Hz., The fact that plastics are good insulators, does not mean that plastics are inert in an, electrical field. They can in fact conduct electricity using certain plastics but more so by, the addition of fillers such as carbon black, and metallic flake (Fig. 4-4). The type and, , ElectricallElectronic Product, The early development of modern plastic materials (over a century) can be related, to the electrical industry. The electronic and, electrical industry continues to be not only, one of the major areas for plastic applications, they are a necessity in many applications worldwide (2, 190). The main reasons is, that plastic designed products are generally, basically inexpensive, easily shaped, fast production dielectric materials with variable but, controllable electrical properties, and in most, cases the plastics are used because they are, good insulators (Chapter 5, ELECTRICAL, PROPERTY)., , Fig. 4·4 Example of how additives or fillers provide a wide dielectric constant range.

Page 241 : 4 Designing Plastic Product, degree of interaction depends on the polarity of the basic plastic material and the ability, of an electrical field to produce ions that will, cause current flows. In most applications for, plastics, the intrinsic properties of the plastics, are related to the performance under specific, test conditions. The properties of interest are, the dielectric strength, the dielectric constant, at a range of frequencies (Fig. 4-4), the dielectric loss factor at a range of frequencies, the, volume resistivity, the surface resistivity, and, the arc resistance. The last three are sensitive, to moisture content that may exist in certain, materials. These properties are determined, by the use of standardized tests such as those, described by ASTM or UL. The properties of, the plastics are temperature and/or moisture, dependent as are many of their other properties. Temperature and/or moisture dependence must be recognized to avoid problems, in electrical products made of plastics., Examples of ASTM plastics insulation for, wire and cable specifications are presented, that relate to type plastic and specific field of, application., D 1047: Polyvinyl Chloride Jacket for, Wire & Cable., D 1351: Polyethylene Insulated Wire &, Cable., D 2219: Vinyl Chloride Plastic Insulation, for Wire & Cable; 60 C Operation., D 2220: Vinyl Chloride Plastic Insulation, for Wire & Cable, 75 C Operation., D 2308: Polyethylene Jacket for Electrical, Insulated Wire & Cable., D 2633: Thermoplastic Insulated and Jacketed Wire & Cable., D 2770: Ozone-Resist Ethylene-Propylene, Rubber Integral Insulation & Jacket for, Wire & Cable., D 2802: Ozone-Resistant Ethylene-Propylene Rubber Insulation for Wire &, Cable., , Property, Electric currents can vary from fractions, of a volt such as in communications signals to, , 223, , millions of volts in power systems. The currents carried by the conductor range from, micro-amperes to millions of amperes. With, this wide range of electrical conditions the, types of plastic that can be used are different;, no one plastic meets the different operating, conditions. The selection of the materials and, the configuration of the dielectric to perform, under the different voltage, current, and frequency stresses are the primary design problem in electrical applications for plastics., The primary function served by the dielectric or insulator is to separate the fieldcarrying conductors. This function can be, served by air or vacuum, but these media do, not offer any mechanical sup- port to the conductors. From this, the second function of the, plastic insulator is derived. Since it is a mechanical support for the field-carrying conductors, the mechanical properties of the material are important., The dielectric materials interact with the, electrical fields and alter the characteristics, of the electrical field. In some cases this is desirable and in others it is deleterious to the, operation of the system and must be minimized. This is done by both the selection of, the material and the configuration of the dielectric. To see how these concepts are applied, an example is presented of one of the, major applications of plastics materials, i.e.,, to insulate wires, and show how a dielectric, is designed to meet the service requirements., The specific requirements on a standard wire, are:, 1. The voltage between the conductors., 2. The current-carrying capacity., 3. The maximum operating temperature., 4. The frequency of the electric field., 5. The mechanical requirements on bending, etc., 6. Flame retardance., The simplest wire configuration is a solid, conductor with a sheath of insulation that, might be flexible PVC or PE. If the wire, is rated for 600 volts power frequency AC,, the wall thickness would be about 0.020 to, 0.030 in. (0.051 to 0.076 cm). The dielectric

Page 242 : 224, , 4 Designing Plastic Product, , strength of the PVC would be about 300 volts, per mil and the PE about 600 volts per mil so, that the insulation would be more than adequate at room temperature., Insulation Since the insulation value, drops sharply with temperature, the wire, would be limited in service temperature to, 140 P (60°C), where both of these materials, soften. The additional wall thickness above, the theoretical minimum is used to give some, mechanical strength to the insulation as well, as to improve the resistance to cut through, and bending. Since each of the conductors, can handle 600 volts, it is possible to use two, of the wires to handle 1200 volts. This is usually not done because of the possibility of, grounding one of the conductors that would, expose the other one to the full field., The current-carrying capacity of the wire, is not directly related to the dielectric. This, is determined by the conductor resistance, and the heating effect that it produces in the, wire. The required current-carrying capacity, determines the size of the wire and thus, the size of the insulator. The temperature, rise caused by the current flow determines, the type of insulation to be used. If the, wire is limited to 140 P (60°C) service, the, insulation can be one of those discussed, above. If the wire is to operate at 300 P, (150°C), another specification for plastic, wire with better heat resistance such as TP, polyester or PTPE is used., If the wire is to be used to carry much, higher frequency currents, the design problem in geometry and plastic selection becomes more complicated. The dielectric, constant and dielectric loss values for the, plastics become important in the design. At, a frequency of one megahertz the effect of, the dielectric on the power transmission behavior of the wire is substantial and, even at, frequencies of 10 to 100 kilohertz, the insulation on the wire must be considered in the, design as a major electrical element in the circuit. More on the subject of insulation will be, following this section., 0, , 0, , the insulation is also a major problem in the, application of the wire. Such wire is used primarily in communications applications. The, leakage of current from the wire is related to, the volume resistivity of the dielectric material. In most plastics, the volume resistivity is, high and in the case of the plastic most used, in commercial communications wire, PE, the, leakage is so low it causes no problems. When, there is appreciable current leakage, the signal strength in the wire is reduced and noise, from the environment is conducted into the, wire to add to the loss of signal content (signal, to noise ratio)., Dielectric constant/loss The value of the, dielectric constant is important in the wire, because of the effect that it has in coupling, currents in one set of wires into another set of, wires. The higher the dielectric constant, the, higher the value capacitor that is formed between two wires. The capacitor thus formed, is a signal carrying device at the frequencies, used in communications and a signal can be, capacitively coupled from one circuit to another. PE is the preferred choice for insulation of communication wire because of its low, dielectric constant that minimizes the intercircuit coupling effect usually referred to as, cross-talk., , 0, , Leakage resistance When dealing with, low value currents, the leakage resistance of, , Dielectric loss The dielectric loss factor, represents energy that is lost to the insulator, as a result of its being SUbjected to alternating current (AC) fields. The effect is caused, by the rotation of dipoles in the plastic structure and by the displacement effects in the, plastic chain caused by the electrical fields., The frictional effects cause energy absorption, and the effect is analogous to the mechanical, hysteresis effects except that the motion of, the material is field induced instead of mechanically induced., Materials that have highly polar structures,, permitting the field to have strong coupling, to the plastic structure, have high loss factors, particularly if they exhibit large viscoelastic, behavior (Chapter 2). Materials with low polarity structures have a minor effect; combining a crystalline or crosslinked rigid molecular structure, show a low dielectric loss.

Page 243 : 4 Designing Plastic Product, In signal processing applications the dielectric loss represents an attenuation of the signal. Where there are large amounts of power, generated, such as in a radio transmitter, the, dielectric loss represents a sufficient power, drain that it will heat the material of the insulator and possibly destroy it. In both cases, it is, important to minimize the amount of power, dissipated into the dielectric material. This is, done primarily by the use of plastics that have, low dielectric loss factors and generally low, dielectric constants. There is a relationship, of dielectric loss factor as a function of frequency at two temperatures. The higher the, temperature the higher the loss factor at all, frequencies. This is due to the greater mobility of the plastic structure at higher temperatures permitting increased movement by the, electrical fields., The greater amount of frictional energy, generated by the greater excursions possible, at the higher temperature increases the dielectric loss. It should be pointed out that in, the case of high power applications, this tendency produces an effect similar to that in, the dynamic mechanical loading (Chapter 2), in that the heating produces an increase in, the ability to be heated so that, if the heat is, not dissipated, the material proceeds to catastrophic destruction., The other approach to the reduction of, the power loss to the dielectric material is, by reducing the amount used. This is done, by replacing part of the dielectric by air, an, inert gas, or by vacuum. As examples there, are three cable constructions in common use, which employ these approaches to minimize, dielectric loss. The first is the use of a foamed, dielectric PS plastic that is commonly used, in either twin lead transmission lines or in, coaxial cables used for antenna lead-in wires, in the UHF-TV antenna applications. The, second system, which is illustrative of several, sectional spacers, is used widely in communications cables of the coaxial type to minimize losses to the dielectric by reducing the, amount of dielectric material in the cable., Regarding the third system, the cable design must be modified to take into account, the lower dielectric constant of the air that, tends to increase the diameter of the cable so, , 225, , that it is not a simple replacement situation., The additional diameter will tend to increase, the amount of plastic required so that an optimum must be reached in terms of the geometry to reduce the material to a minimum and, still have a mechanically stable cable structure. The third scheme uses bead-like spacers, at intervals along the cable (3). This type of, cable is frequently evacuated to improve the, dielectric performance of the cable., , Connector, The second major area for the use of plastics in electrical applications is at the terminations of the conductors. The connectors that, are used to tie the wires into the equipment, using the power, or used to connect the wires, to the power source, are rigid members with, spaced contacts. These are designed to connect with a mating unit and to the extension, wires. The other type of wire termination is, terminal boards where there are means to secure the ends of the wire leading to the equipment and the internal wiring in the equipment. These termination units require:, 1. Adequate dielectric strength to resist, the electric field between the conductors., 2. Good surface resistivity to prevent leakage of current across the surface of the material of the connector., 3. Good arc resistance to prevent permanent damage to the surface of the unit in case, of an accidental arc over., 4. Good mechanical properties to permit, accurate alignment of the connector elements, so that the connectors can be mated properly., If the connectors are to be used in high, frequency applications, they must be made, of plastics with low dielectric loss to avoid, either damage to the part or signal loss in the, circuit., The design of a connector is a fairly, straightforward process. It is easily illustrated, with the example of a two-element connector of the type that may be used for, either a power connection or to plug in, an audio system. However multiple-element, (32 and over) are extensively used. The

Page 244 : 226, , 4 Designing Plastic Product, , plastic selected will be one that has the required dielectric strength at the maximum, operating temperatures and at the frequency, of intended use. For a power connector TP, polyester, semi-rigid PVC, or phenolic are, examples of what might be used. The anticipated voltage is used to calculate the probable leakage current which should be less that, 0.1 % of the magnitude of the current in the, conductor., The arc resistance of the plastic would, not be critical for an appliance plug, since, this condition rarely occurs in this application. For connectors used for industrial, power connections, the plastic should have, good arc resistance because of the possibility, of flashover. The remainder of the problem, would be to make sure that the connector is, stiff enough to hold the contact members in, alignment when the connector is inserted into, the mating receptacle. The receptacle design, is essentially the same as the plug except that, it has the opposite set of contacting elements., When the connector is used to make connection in an audio circuit, the configuration, can be essentially the same. The additional, consideration is that the material have low, loss dielectric at the frequencies to be transmitted and that the spacing of the contact elements be determined by the transmission line, characteristics required. Spacing is an electrical design function and its determination requires knowledge of the desired transmission, line characteristics of the circuit. This part of, the design is usually done by the electrical, engineer and is an operating parameter for, the plastic designer. The voltage resistance, and other design factors are based on the, data usually supplied for the material by the, manufacturer., In many electronic and electrical applications the internal wiring of the systems is done, by high mechanical strength printed circuit, methods. The substrates on which the printed, wiring is done are usually plastics. Commonly, used materials are epoxy-glass fiber RP laminates; chopped glass fiber-TS polyester injection molded boards, also to a lesser degree paper-based phenolic laminates. These, internal wiring assemblies introduce a special, design area in this application because of, , basically good electrical properties and generally good chemical resistance to the chemicals and solvents used in processing the, printed circuitry. They cannot be used in, applications for high frequency circuitry because of the dielectric loss of the two materials. The phenolic is poor even at low RF frequencies and the epoxy has high loss factors, at higher RF frequencies., For these applications the printed circuit board materials used have included, TS polyester-glass fiber, silicone-glass fiber,, PTFE-glass fiber, different polyolefin-glass, fiber, and glass-bonded mica. Materials such, as glass-filled TS polyester plastic have good, electrical and mechanical properties and with, the contemporary wave soldering techniques, it is possible to solder the boards without, distortion., The past introduction of TP materials into, the area of printed circuit substrates has led to, a broader type of application for the circuits., The products can be injection molded and the, circuit applied to a molded part which will, have a molded-in connector structure used, to interconnect the device to the rest of the, system. By combining the connector and substrate functions, it is possible to make very, compact printed circuit units., Such units are used in the watches with, electronic drives instead of the traditional, mechanical spring driven drives. Another, area where the combination function is, being used is in large-scale integrated circuit unit supports where the complex interconnection requirements make a combination circuit support and printed circuit, unit an attractive way to achieve high packing efficiency such as computer hardware, systems., When using molded plastics parts such as, the connectors and the circuit supports, it is, important to make sure that the moldings, in, addition to being made to close tolerances,, be made under molding conditions that make, for stable products. Electrical products are, subjected to strong electrical fields in addition to the usual environmental abuse. Distortion of the product can lead to serious, electrical malfunction by changing spacings, that will alter electrical characteristics and if

Page 245 : 4 Designing Plastic Product, extreme enough, result in short circuits with, serious results., Designs for electrical products made of, plastics should take into account the effect, of the processing on the performance. In addition to possible distortion from heat, improper molding conditions can lead to premature failure from the effect of chemical agents, if the product is used in an etched circuit application or from the effect of corona degradation if any product is used in a high voltage, application. Conductor-to-insulator must be, tight to eliminate corona., , Insulation, There are two areas of application for electrical insulation where the effects oflong time, exposure to electrical fields produces a fatigue effect that can be compared to the creep, that occurs under static stress or the fatigue, effects that occur under sustained dynamic, loading (Chapter 2). The first effect is encountered in high voltage DC cables such as, are used in X-ray equipment, some industrial, and research equipment, and in the new high, voltage DC distribution systems., , Dielectric break down and mechanical, creep Under sustained DC fields the plastic moves internally so that the dipoles align, themselves in the field in response to the continuing voltage stress. As this continues, the, dielectric constant of the material increases, and the dipoles begin to break loose and migrate through the material. In doing so they, disrupt the structure of the material, reducing the dielectric strength. After an extended, period of time, usually several years, the dielectric will spontaneously break down and, the system will arc over. This effect is similar to mechanical creep (Chapter 2) since the, same sort of field based diffusion effects are, at work to produce structural changes that, take place., The second effect is caused by the operation of alternating electrical fields on the, dielectric in the system. This can happen to, insulation at power frequencies as well as, higher frequencies. This is not the dielectric, , 227, , heating effect mentioned earlier, but an actual disruption of the plastic structure caused, by the alternating stresses imposed by the alternating field. Some regions of the structure, develop higher than average stresses and the, plastic structure is broken at these points., , Dielectric break down and S-N analysis, As the number of defects grow with time,, the structure becomes electrically less resistant to the imposed fields and the dielectric, strength decreases to the point where the field, arcs over. These effects occur after a period, of years, usually in electrical insulation that, is operating near the limit of its dielectric, strength. The same type of S-N analysis that is, used in mechanical fatigue is used in predicting this type of electrical fatigue (Chapter 2)., It is essential that any materials used for this, type of service be carefully evaluated for fatigue and are resistant to this effect., Environment, In terms of environmental exposure, water, and humidity must be carefully evaluated in, electrical applications. In general, if a plastic absorbs a significant amount of water, the, electrical resistivity drops. As examples this, is the case for nylons and phenolic. Care must, be used in selecting a dielectric to insure that, the electrical properties such as the insulation, resistance and dielectric strength, as well as, other electrical properties are adequate under the conditions of field use, particularly, if this involves exposure to high humidity, conditions. Temperature also causes changes, in most electrical products., There is another type of condition that results from exposure to high humidity. The, alteration in electrical properties caused by, moisture absorption in nylon and phenolics, is reversible. When the moisture content is, decreased, the properties of the materials recover to close to the original values. In some, instances the exposure to moisture and electrical fields can cause irreversible damage, that can lead to failure., One case is that of the TS polyester materials such as the alkyd molding compounds.

Page 246 : 228, , 4 Designing Plastic Product, , These materials, when exposed to continuous high humidity, especially in the presence, of an electrical field, hydrolyze into the acid, and alcohol precursors from which they are, made. The acid plus water present make a, conductive material that will cause the material to short the electrical circuit. The process by which the decomposition of the TS, polyester takes place is very gradual at first, and then accelerates so that extended testing, of the material is necessary to be sure that, the particular polyester composition used is, resistant to hydrolytic degradation., One other long-term condition that takes, place with relatively low level DC fields in, the presence of moisture is the migration of, the metal of the conductor into the plastic., This was discovered to be a common thing, in the past with silver conductors and phenolic insulators. The first instance of field, failures were discovered in telephone equipment. The problem can occur with other metals with phenolic and also conceivably with, other plastics that are moisture sensitive and, can have a solvating action on the conductor, metals that they contact. Most of these type, plastics should be avoided inside hermetically sealed containers with movable contacts. Vapors released from the organic plastic, deposit on the contacts to produce an insulation layer leading to contact failure., Other peculiarities have occurred. As an, example of a potential problem that can occur, is when a silicone release agent is used when, injection molding electrical connectors, etc., It can behave like the metal migration just, reviewed., Different Behavior, Capacitor There are several applications, for plastics in electrical devices that use the, intrinsic characteristics of the plastics for the, effect on the electrical circuit. The most obvious of these is the use of plastics particularly, in the form of thin films as the dielectric in, capacitors. TP polyester films such as Mylar, are especially useful for this type of application because of the high dielectric strength in, conjunction with a good dielectric constant., , Mylar has the additional desirable feature, that it is available in very thin films down to, at least 2.5 microns., Since the value of a capacitor is directly, proportional to the area and inversely proportional to the spacing of the conductive, plates, the thinner materials permit high values of capacitance in small size units. There, are other materials that make good capacitors such as polyvinylidene fluoride that has, a very high dielectric constant and good dielectric strength, oriented PS which makes a, good capacitor for high frequencies because, of its low dielectric loss constant, and others., Electret Another application for plastics, which uses the intrinsic properties is in electrets (a dielectric body in which a permanent, state of electric polarization has been set up)., Some materials such as highly polar plastics, can be cooled from the melt under an intense, electrical field and develop a permanent electrical field that is constantly on or constantly, renewable., These electret materials find a wide range, of applications that vary from uses in electrostatic printing processes, to supplying static, fields for electronic devices, to some specialized medical applications where it has been, found that the field inhibits clotting in vivo., One application for the electret material is in, a microphone that has a high degree of sensitivity and the electrical waves are produced, by the field variations caused by the change, in spacing of an electrode to an electret., Structural binder A wide range of applications in electronics makes use of the plastics, as a structural binder to hold active materials., For example, a plastic such as polyvinylidene, fluoride is filled with an electroluminescent, phosphor to form the dielectric element in, electroluminescent lamps. Plastics are loaded, with barium titanate and other high dielectric powders to make slugs for high K capacitors. The cores in high frequency transformers are made using iron and iron oxide, powders bonded with a plastic and molded to, form the magnetic core., Magnetic recording tape, in addition to using plastic films as a support for the recording

Page 247 : 4 Designing Plastic Product, surface, also use polyvinyl alcohol and urethane plastics as binders for the magnetic oxides that form the recording medium. The, range of special behavior materials that can, be made from plastics is broad., Electro-optic The liquid crystal plastics, exhibit some of the properties of crystalline solids and still flow easily as liquids, (Chapter 6). One group of these materials is, based on low polymers with strong field interacting side chains. Using these materials,, there has developed a field of electro-optic, devices whose characteristics can be changed, sharply by the application of an electric field., Summary, A number of areas in which plastics are, used in electrical and electronic design have, been covered; there are many more. Examples include fiber optics, computer hardware, and software, radomes for radar transmitters, sound transmitters, and appliances. Reviewed were the basic use and behavior for, plastics as an insulator or as a dielectric material and applying design parameters. The, effect of field intensity, frequency, environmental effects, temperature, and time were, reviewed as part of the design process. Several special applications for plastics based on, intrinsic properties of plastics materials were, also reviewed., Other areas such as static electricity and, its use and control were not discussed since, they represent a different type of application, (2). As new materials became available and, the electrical art continued to develop, the, uses for plastics in electrical applications has, increase both in the basic application as a dielectric and in special applications using the, special intrinsic properties of the plastics., Toy and Game, , Extensive use is made in using different, flexible to rigid plastics and processes to produce all kinds of toys and games. We see them, all around us particularly through the adver-, , 229, , tising media (stores, TV, Internet, etc.). Extensive use is made in using different flexible, to rigid plastics. They are designed to take, a "beating" and survive within certain time, periods., Toys- Electronic, For the electronic component industry, different types of plastics and processes are extensively used. Not too evident is the high, powered action of electronics in the plastic toy industry. The digital revolution has, opened up a variety of new applications, in "smart" microprocessor-based toys that, use technology in innovative ways. Foremost, player is the MIT Media Laboratory's Toys, of Tomorrow (TOT) consortium that was organized in April 1998., Members include Acer, Bandai America,, Deutsche Telekom, Energizer, Intel, Disney,, LEGO, MatteI, Motorola, Polar Electro Oy,, TOMY, and the International Olympic Committee. This action is being taken since toys, of the future may give birth to technologies, that eventually end up in the workplace. They, will be the first devices that carry new forms, of networking into the home. They report, that toys will lead the way to bring a home, networking technology infrastructure faster, than anything else., Transparent and Optical Product, , Overview, The use of plastics in certain transparent, or optical applications is marked by selective but significant advantages of plastics over, glass. Plastics weigh less and in many cases, cost less, yet provide higher performance,, such as impact strength and safety. They also, have many more configuration possibilities, to simplify assembly. There are the more expensive plastics with added performance features related to chemical resistance, heat resistance, high tensile and flexural strengths,, and others that are used in specialty products, (Chapter 5, OPTICAL PROPERTY).

Page 248 : 230, , 4 Designing Plastic Product, , The factor of configuration flexibility is particularly useful in systems that use aspheric, or curved surfaces to simplify design and reducing the product count, weight, and cost., Moreover, there are light-transmission abilities of plastic optics that are comparable to, those of high-grade crown glass. And from a, safety standpoint, when plastics break they, do not splinter, like glass, and thus are not, hazardous or less hazardous., Plastic's main disadvantages are its lower, scratch resistance and, in some systems, comparative intolerance to severe temperature, fluctuations. Even if plastic does have less, temperature tolerance than glass, most optical systems do not operate in ambient temperatures beyond the thermal limits of plastics or the human body., The processing advantages of plastics that, exist, such as injection molding with multicavity molds, allows low-cost manufacturing, to be combined with comparatively inexpensive materials resulting in low cost products, used in automobiles, cameras, etc. By carefully sizing a mold for the required production volume, plastics' breakeven cost, compared to glass, will be very low. Another, advantage of plastics fabrication is that in the, mounting and assembly features like brackets, holes, and flanges, they can be molded, integrally with the optical element to result, in a single-piece design eliminating mounting, hardware and simplifying alignment. Multiple elements can thus easily be combined and, molded in unique optical configurations., , Property, Performance, and Product, There are plastics that are transparent and, translucent in the unpiginented state. They, have a range of optical properties that make, them interesting for a wide spectrum of optical applications that extends from windows, to lens systems to sophisticated applications, involving action via polarized light. Used, for over a half century are aircraft canopies, (thermoformed) and windows in many different structures., The application for plastics most widely, known, based on the transparency and clarity of plastics, is their use as a window or, , cover. There are a number of relatively inexpensive plastics in the families of acrylics,, polystyrene, cellulosics, and vinyls that have, been widely used to make boxes for displaying merchandise, for windows in instruments,, for glazing applications for buildings, outdoor, signs, and so on. The primary optical property, used in these applications is the transparency, and lack of haze or light scatter., A primary requisite for these materials is, their mechanical, physical, and aging properties. Design of a box, a light, or a display, unit will involve the requirements for static, and/or dynamic loading that may be encountered in the end-use application. The only, change is that the product is designed with, a clear transparent material. (Recognize that, one can say that glass has the highest compression strength of any material. However, any other load, including a very minor load, other than direct compression, will basically, destroy it.), One of the applications for plastics in optics is in refracting and reflecting elements, where they are used as glass in lenses, prisms,, mirror supports, and other refracting and reflecting units. The range of refractive index, for plastics is generally in the same range as, that for optical glasses. As a result, lenses having the same general properties as glass can, be made from plastics such as the acrylics and, polystyrene., The ophthalmic applications for plastics, lenses include contact lenses which are now, made of acrylic plastics. Another material, for this application is a special hydrophillic, acrylic polymer used in soft contact lenses., These lenses are much more comfortable, than rigid contact lenses., Important applicable definitions that concern this subject follows:, 1. Refractive index is the ratio of the velocity of light in free space to the velocity of, light in the medium., 2. Light scattering is the ratio of the velocity of light in free space to the velocity of light, in the medium., 3. Birefringence is the property of an, anisotropic optical media that causes polarized light with one orientation to travel with

Page 249 : 4 Designing Plastic Product, a different velocity than polarized light with, another orientation., 4. Polarized light is light that has the electric field vector of all of the energy vibrating, in the same plane. Looking into the end of, a beam of polarized light one would see the, electric field vectors as parallel or coincident, lines., 5. Dichroism is a property of an optical material that causes light of some wave lengths, to be absorbed when the incident light has, its electric field vector in a particular orientation and not absorbed when the electric field, vector has other orientations., 6. Light transmissability is the ratio of the, light exiting from an optical material to the, light entering the material., 7. Haze is the cloudy appearance in a plastic caused by inclusions that produce light, scattering., 8. Color is the sum effect of the wavelengths of light transmitted by or reflected, from a material., 9. Dispersion is a property of an optical, material which causes some wavelengths of, light to be transmitted through the material, at different velocities and the velocity is a, function of the wavelength. This causes each, wavelength of light to have a different refractive index., , Lens, There are differences between plastic and, glass lenses that the designer must considered. The first is that the plastics have a much, greater change of dimension with temperature and a much greater change of optical, constants with temperature. The other major difference is that, while the plastics are, much more resistant to impact than glass,, their resistance to scratching and to deformation is much lower than that of glass. However there are coatings and surface treatments that have been used for over a half, century that significantly improves scratch resistance. In fact on the automotive design, drawing boards, future cars are targeting to, replace windows with these type plastics. As, , 231, , a result of these limitations, most of the, applications for plastics in optical elements, are for low precision optics. Those products, happen to be the major market for optical, products., In addition to the differences reviewed,, plastics are different in another optical property from optical glass or crystalline optical, materials. The degree of dispersion of light is, much greater for plastics than for glass. Dispersion is the difference in refractive index, for the different wavelengths of light and it, is greater for plastics. As a result, a plastic, prism will separate the different colors of the, spectrum much more than a glass prism. This, characteristic makes it more difficult to make, lenses of plastics without fringing colors. Despite this limitation, good camera lenses corrected enough to use for color photography, have been made out of plastics for low cost, cameras. It is possible to design around the, limitations of the plastic materials when the, cost advantage justifies the additional design, effort., Plastics are the preferred optical materials used in lenses for controlling the light, in warning lamps such as emergency lights,, stop lights on cars, and retro-reflective lenses, used on cars, on high way signs to show the, presence of an obstacle, etc. These lenses are, usually made with a large number of specially shaped lenticulations that are used to, direct the incident or transmitted light in a, direction where it can be readily seen. The, lenticulations may be pyramidal or they may, be spherical sections. Both can be designed, as excellent light directors. The taillight lens, on automobiles probably represents one of, the largest applications of optical plastics and, the retro-reflector element used both on cars., Highway posts is another major use of optical, plastics., , Fresnel Lens, There are other groups of optical elements, that use plastics in very fine patterns to make, special optical elements. One of these is the, Fresnel lens that is a collapsed lens structure that has the effect of a strong magnifier

Page 250 : 232, , 4 Designing Plastic Product, , but is essentially a flat sheet. The lens is made, by a special molding technique from a carefully machined master. It is used as a focusing lens for light sources, as an intensityleveling unit in reflex camera viewers, and, as a coarse view magnifier of simple objects., (Compact discs molding of polycarbonates, are another example of precision molding of, grooves.), Large Fresnel lenses are used in solar furnaces to gather large areas of sunlight and, to focus it at a point to achieve high temperatures. The other fine pattern application, for plastics is in replica diffraction gratings., When a pattern of lines is made with a count, of 50 to 500 lines per millimeter it acts as, a diffraction grating which can break light, into its components by selective interference., Diffraction gratings are made by ruling lines, on a metal or glass plate by means of a ruling engine that is a tedious and expensive, process., The gratings can be replicated by using a, plastic material applied to the surface of the, grating that takes the pattern of the grating, and reproduces it in the plastic. This is usually, done with a curable plastic solution and at low, temperature to avoid damage to the grating., Using this technique, it is possible to make, low cost gratings that can be used for light, analysis or for displays, or even to make an, interesting form of iridescent jewelry., , Lenticular, A lenticular is a tiny lens or a groove on a, screen. The term lenticular image refers to a, specially constructed graphic viewed through, a plastic sheet extruded with a series of mathematically calculated grooves or lenticules,, that give the image depth, movement, or, both. To achieve a 3-D effect, for example,, several angles of one image are recorded., This is usually done by a digital camera or, created right on a computer., Interlacing then takes place, a precise digital merging by computer of the angles into, a master image. When printed on a lenticular sheet such as Eastman Chemical's Spectar PETG, the grooves of the sheet force the, , eye to view different sections of the images, at the same time, thus rendering a 3-D effect, (235)., To get high resolution the sheets are extruded with a precalculated number of lenticules per inch, or LPI. This varies by format., A hand held graphic needs high resolution, and is usually extruded with 75 LPI. A large, display such as 4 x 8 ft (1.2 x 2.4 cm) viewed, from a distance will require as few as 15 LPI., The extruded lenticular formats are predetermined and designed for various imaging and, viewing applications. To create the sheet, different pattern-roll cylinders are mounted on, the extrusion line, each capable of engraving, the precise LPI required for an application., The extrusion line must be capable of running the sheet in a highly controlled and precise environment, to make sure the lenticules, are accurately placed (6). Extrusion must also, be a clean process in order to prevent imagealtering contamination. Sheets are usually, extruded in a thickness range of 0.015 to, 0.100 in. (0.038 to 0.254 cm)., , Piping Light, The high degree of clarity and low haze, of some plastics, particularly acrylics, makes, possible the use of these materials in applications using the light piping effect. Any, light that enters the end of a long rod of a, clear transparent refractive medium at angles, less than the critical angle (defined as the angle at which light is refracted parallel to the, surface) is trapped in the rod and transmitted, down the length of the rod by multiple internal reflection. The trapped light is reemitted, at the end of the rod or plate, or at any place, along the length of the "light pipe," where, the surface is changed in angle or where the, surface is roughened to form a light diffusing, area., Use is made of materials such as acrylic, that are very clear. They have very little light, absorption in the visible spectrum, and have, a very low haze level to scatter the light and, change direction. The light can be piped over, distances of the order of three to four meters, with a minimum of light attenuation.

Page 251 : 4 Designing Plastic Product, This effect has been used in several areas of, plastics product design. One application is in, the illumination of instrument dials and similar indicia where it is impractical to use lamps, close to the indicia. The lamps can be placed, in a convenient location and the light piped, to the indicia where the surfaces are shaped, to release the light. Another application is, for lights that must be inserted in confined, spaces where suitable bright light sources either do not fit or are too hot to use. An example of such an application is the light used in, medical devices for examination of a patient's, throat, etc., The effect is widely used in signs and display devices to make them self illuminated., Edge lighted signs and panels are widely used, in offices, automobiles, aircraft, etc. A sheet, of acrylic material has light introduced into, one edge from suitable lamps. The light is carried across the sheet. The indicia that are to, be displayed are cut into the surface opposite, the side from which the sign is to be viewed., The indicia can be either polished angle cuts, or an area that is roughened to be a diffusing, surface. In either case, the light piped through, the sheet is altered in direction, emitted from, the sheet toward the viewer, and appears as, a self-illuminated sign., Fiber Optic, These devices are also used in the transmission of light to form images as well as to transmit small areas oflight. An optic fiber consists, of a small diameter monofilament of a clear, plastic such as acrylic that has a thin coaxial, layer of another clear material of lower refractive index. The monofilaments are in the, order of 10 to 50 microns in diameter and the, coating is usually 5 to 10% of the diameter., These fibers are very efficient light piping elements as a result of the coatings. A bundle of, optic fibers can transmit light over distances, of at least 10 to 20 meters with a low degree, of attenuation., Random bundles of fiber optics make a, good medium for bringing light to a specific, region for illumination. A coherent bundle, of fibers (one in which the fibers are aligned, , 233, , so that they occupy the same position everywhere along the length of the bundle) can be, used to transmit images over long distances,, around corners, and past other obstacles. The, image can be viewed directly by looking into, the end of the bundle. When the object is, properly illuminated it can be seen directly., In other cases the object is imaged on one end, of the fiber optic bundle and observed at the, other end as a clear image as if it were the, focal plane of the lens., This feature of the fiber optics is used, in a number of optical systems for remote, viewing. One major application has been, for cyctoscopes in medical diagnosis and, for borescopes used to examine inaccessible, areas in machinery such as plasticator barrels., Coherent bundles of fibers, properly transposed, are used as an encoding and decoding, device to handle confidential image information. Short bundles of the fibers are used in, conjunction with cathode ray tubes and other, self-illuminated displays to improve visual, contrast by minimizing the effect of ambient, light on the display. Other applications for, fiber optics are for decorative effects and for, optical and photographic applications where, the ability to transmit an image or to alter it in, a predescribed manner simplifies the system., In using fiber optics the designer is mainly, concerned with a standardized material, which has specific characteristics in terms, of optical performance. Fiber optics made, of plastics can be affected by exposure to, the environment with deterioration of performance. Heat is an important environmental, factor and the most likely cause of damage in, optical applications. The heat can be generated by the light sources used. Some of the, infrared generated by light sources can be removed with the use of appropriate filters., Polarized Lighting, There are a number of applications for, plastics in optics which involve the interaction with polarized light. Polarized light is distinguished from ordinary light that is called, incoherent light. Incoherent light has wavelengths varying over a range of values, the

Page 252 : 234, , 4 Designing Plastic Product, , phase of the individual wave trains do not, have any phase relationship with each other,, and the plane of the electric and magnetic, vectors of the individual wave trains have random orientation with respect to each other., Looking into a beam of incoherent light, the, electric vector can have any angle., When the light is plane polarized, all of, the light which passes through the polarizing, device has the electric vectors parallel and, the magnetic vectors parallel to each other., The effect of the polarizer can be likened to a, picket fence through which you can attempt, to make wave trains with a rope or string., The only waves that will come through are, those with the plane of vibration parallel to, the fence pickets., There are several ways in which light can, be plane polarized. In some light sources, because of the effect of strong electric and/or, magnetic field present when the light is, generated, it is polarized (A). When light, is reflected at low angles from a dielectric, medium which is transparent, the reflected, light is polarized parallel to the surface, and the transmitted light is polarized perpendicular to the surface (C). Naturally, birefringent (double refracting) materials, can be made into prisms which pass light, polarized in one plane and reflect out of, the prism light polarized in the plane at, right angles (D). The method most generally, used for generating polarized light is by, passing incoherent light through a polarizing, filter having the property of absorbing light, which is polarized in the principal absorbing, plane of the material and passing through, polarized light whose electric vector plane is, perpendicular to the absorbing plane (B)., The dichroic polarizer widely utilized to, produce polarized light employs plastics in, the dichroic materials with the polarizing, capability. It consists of a plastic with the, molecules oriented strongly in the direction, desired for polarization (Chapter 8, PROCESSING AND PROPERTIES, Orientation). The plastic has attached color absorbing structures along its length. When light, passes across the plastic molecules perpendicular to the length of the molecule, there is, a minimum of interaction with the color ab-, , sorbing centers. When the light passes across, the plastic chain parallel to the chain, there is, a high degree of light absorption. With a substantial thickness of the oriented material, the, light that passes through is plane polarized, in the plane perpendicular to the orientation, direction., Examples of such dichroic polarizers are, polyvinyl alcohol that is oriented. It is oriented with iodine absorbed on the alcohol, side groups and polyvinylene which is made, from oriented polyvinyl alcohol by heating, to a temperature which causes splitting off of, water to form unsaturation along the plastic, chain. There is also multiple conjugate unsaturation in an organic molecule produces a, light absorbing structure. In addition to the, two examples given, it is possible to make, absorption type dichroic polarizers by other, techniques such as attaching dichroic dyes on, to oriented plastic chains which have an affinity for the dye. Most dichroic polarizers pass, about 45% of the incident energy through as, plane polarized light., , Application One of the simplest and most, interesting applications for polarizers in optical applications is the use of two polarizers to, control the amount of light passing through, the pair. If two polarizers are used serially on, a light beam, the orientation of the second polarizer to the first will determine the amount, of light passed. If the planes of polarization, are parallel, then all of the light passed by, the first polarizer will be passed by the second polarizer. If the planes of polarization, are at right angles for the two polarizers then, no light is passed. At angles between, differing amounts of light are passed based on the, angular relation of the two polarizers to each, other., Two crossed polarizers are frequently used, to inspect transparent materials placed between them for optical activity, either for, birefringence or for optical rotary effects., Birefringence effects are produced by materials with a regular ordered structure that, allows light to pass through at one orientation at a higher velocity than at another orientation. As a result of this, the two wave, trains generated by the different velocities

Page 253 : 4 Designing Plastic Product, cause the phase angle of the light beam to, change so that the light exits from the birefringent material with a different optical, orientation than the entering light. Usually, this is at an angle where part of the light can, pass through the second polarizer. In many, cases the emerging light is elliptically or circularly polarized instead of plane polarized, so that part of the beam is absorbed in the, second polarizer. Light which is elliptically, or circularly polarized has the electric vector varying in value and angle along the wave, train and it behaves similarly to incoherent, light on passage through a plane polarizer, (Chapter 5, STRESS ANALYSIS)., Optical rotary effects are also referred to, as optical activity and are caused by optically, assymetric groups in the structure of the material. A typical optically active group would, be a carbon atom which has a different organic group attached at each position on the, molecule. Cellulose and sugar have this type, of structure. In this case the beam of polarized, light has its plane rotated as it passes through, the structure and the light emerges as plane, polarized light with a different plane of polarization. By rotating the second polarizer's, plane of polarization it is possible to find the, exit angle and pass all of the light., The crossed polarizer effects of both types, are used in analysis work. The concentration, of optically active organic materials is determined by the degree of rotation. In plastic, processing the residual strains in molded materials as well as the degree of orientation of, polymers is determined by the effect on polarized light. Crossed polarizers are used with, special wave plates to control the amount of, light that passes through an optical system., Another application for the crossed polarizers is in electrically modulating the strength, of a light beam. Electric fields have the effect of making certain substances variably, birefringent. The most important of these, materials are the liquid crystal materials, (Chapter 6). Many liquid crystals are low, polymers with highly polar side chains. By, varying the field on the material the birefringence is varied and the light transmission is, controlled. This effect is used in optical devices and has application in communications, , 235, , systems, especially those using lasers as a signal source., Laser Lighting, Plastics such as acrylic are used to make, one type of laser material. When the appropriate luminescent dyes are incorporated, into the material, the acrylics can be made, into large laser units. One advantage of using, acrylics is that very large clear castings can, be made. As a result, large amounts of laser, light can be produced at low volume densities of light. Consequently, heating effects are, at a minimum. Optical systems can be used, to concentrate the light from the large laser, elements., Color Filter, Plastics are suitable for most optical applications that utilize transparent materials,, including color carriers. Color filters have all, types of standard transmission characteristics, that can be made and, because of the uniqueness of the plastic structure, a large number of, dichroic and trichroic materials are possible, that have different colors when viewed from, different angles. One application for this is in, polarizing filters., An interesting application is in sunglasses, where the tinting effect is combined with the, polarizing effect to get sunglasses that are, particularly effective against low angle glare., The lens materials are polarized in the vertical plane and the low angle ground reflections are polarized in the horizontal plane so, that the glare light is strongly absorbed in the, lenses. An antifogging coating on a plastic, lens soaks up condensed moisture., Processing, One ofthe major advantages of plastics optical elements is that they can me made by, different processes such as injection molding, casting, or extrusion to good accuracy, at low cost. Some glass lenses are pressed, from hot glass but the majority of the lenses

Page 254 : 236, , 4 Designing Plastic Product, , by far are ground and polished from rough, blanks. Glass lenses are not molded because, it is difficult to get good surfaces and because, the residual stress left in the glass as a result, of the pressing operation affect the optical, properties of the lenses. In the case of plastics, it is possible to get excellent surface quality, with no stress using precision molds and appropriate molding methods and fabricating, procedures., The plastics may have stresses generated, (less than glass) in the materials as well as flow, orientation caused by the molding process. In, the case of plastics the effect on these conditions are easily corrected by process controls (Chapter 8). When required fabricating processes such as injection-compression, or injection molding a blank followed with, a separate compression molding into the final lens (Chapter 8). Consequently, there, are a large number of magnifiers, lenses,, prisms, opthalmic, and others that are injection molded or cast from plastics., Lenses for safety glasses are made from, highly impact resistant plastics such as modified acrylics and polycarbonate. They will resist puncture from flying objects and offer, the exceptional eye protection. They can be, molded to prescription requirements., Allyl diglycol carbonate (CR-39) is the, most highly scratch resistant of the transparent plastics. Unlike most of the other transparent plastics that are TP, CR-39 is a TS plastic that has been in use for over a half century, in applications such as bullet-proof shields,, high temperature steel blast furnace eye and, face guards, aircraft window side panels, etc., Processing methods include injection molding and casting., To be successful, molded optical elements, of plastics must be produced with careful control of the fabricating process. In the case of, these optical products it is particularly important that the molding conditions be carefully controlled to minimize molded-in stress., In addition to these stresses reducing the dimensional stability of the products leading to, distorted images, the stresses themselves affect the quality of the image. This is a result of, the fact that the stresses/strained areas have, a different refractive index from that of the, , unstrained areas with resultant distortion of, the image., Most optical products are injection molded, in special molds in a dry atmosphere (including dried plastic material) that sustain packing pressure on the product as it cools to give, good surface quality. In addition, the process, controls on the molding machines are of the, best type to insure close control over the melt, temperature and pressure. Static mixers at, the end of the IMM plasticator can be employed to eliminate thermal gradients in the, material (3). Schemes for quality control use, the optical image quality as a test, and use, polarized light inspection methods to check, for residual molding stress and orientation, (Chapter 8, INJECTION MOLDING)., , Designing, The following is a summary to the design, information presented. The design of optical, elements from plastics follows conventional, optical design procedures that are covered, in many texts on lens and prism design. The, basic principles of design are based on ray, tracing to determine the focal point of a lens, or the image distance for a lens system. For, the geometry of a suitable optical element it, is necessary to use a text on optical design, literature such as handbook of optics (101), and/or the services of an optical designer. The, aspects of the design are first the selection of, the appropriate plastic and then the design of, the product and process to make an accurate, stress free product., Within the limitations on the physical properties which generally restrict plastics to low, precision optics, plastics materials have found, wide applications in optical products that, range from lights to binders for electroluminescent phosphors to fiber optics and, lasers. They represent an easily worked material with a wide range of desirable optical, properties in simple to complex shapes. In, this review the discussion has been limited, to the differences between plastics and optical glass materials and to some of the unique, design possibilities that are especially important for plastics. Using the optical arts and the

Page 255 : 4 Designing Plastic Product, , 237, , special properties of plastics, unique products are attainable. The breakage resistance, of the plastics has placed them into many, common functional applications such as instrument windows and street lighting globes., , plastic or wood, etc. The BIBs offer space and, cost efficiencies. The empty BIBs in a warehouse may occupy as little as 20% of the space, required for the equivalent volume in glass or, rigid plastic, reduce shipping weight, etc., , Packaging, , Beverage Can, , The packaging industry and its technology is the major outlet for plastics where, it consumes about 30 wt% of all plastics, with sales at about $40 billion. Saleswise, about 30% is HDPE, 16% LLDPE, 14% TP, polyester, 13% PP, 11 % LDPE, and 16% others. Different products and processing techniques are used to produce many different, packaging designed products. These different, products show how innovative designs have, created different packages based on plastic, behaviors and they're processing capabilities., Most of these products are extruded film and, sheet. Other processes are used with thermoforming, injection molding and blow molding being the other principal types used, (Chapter 8). The following information is, examples of different designing packaging, products with performance requirements., , While aluminum cans dominate the USA, market for soft drink containers with about, 70% of the market, PET and glass are in, second place. Note that most aluminum cans, have an inside coating, usually epoxy, to protect its contents from the aluminum., , Aseptic, In food processing, it is a process condition that renders a processed food product, essentially free of microorganisms capable of, growing in the food in un-refrigerated distribution and storage conditions. The aseptic, food packaging include film pouches and presterilized molded containers that are filled, with aseptic foods, then hermetically sealed, in a commercially sterile atmosphere., , Biological Substance, Many of these substances are classified, as hazardous requiring specialty packaging, where plastics play an important role to meet, strict requirements., , Blister, Also called blister carded packaging. It is a, package in which thin plastics film or sheet is, formed so that a product is placed in the blister, backed up by a material (plastic, paper,, aluminum, etc.), and sealed., , Bubble Pack, Very popular is plastic cushioning material, used in packaging, usually laminated thermoplastic films that incorporate air bubble, pockets., , Clasp, Bag-in-Box, BIB refers to a sealed, sprouted (small, too large, with or without dispensing valves), plastic film bag inside a molded rigid container, generally for packaging liquid products. Outer box may be made of disposable, corrugated cardboard, disposable or reusable, , Plastic molded clasps are commonly used, to secure tops and lids on different type packages. Their holding power can be obtained, from simple friction between the joint surfaces or from positive mechanical engagement. Plastic flexing capability is important, because the products must flex in order to

Page 256 : 238, , 4 Designing Plastic Product, , release the clasp and spring back to their original position., Contour, Contour packaging is also called skin packaging. It is package in which thin plastic film, or sheet is formed over a product and usually simultaneously sealed to a paperboard, or plastic backing. The product serves as a, mold., Dual-Ovenable Tray, DOT is used for frozen foods. They have, been a major outlet for plastics. In the past, thermoset plastic materials were used but it, practically all went to thermoplastics such as, CPET., Electronic, Plastic ease of processing with low cost, have given them a wide application in solving, problems in electronic packaging. They range, from inexpensive consumer devices to sophisticated expensive computer systems and, cellular phones., The demand for antistatic plastics in electronics is of major importance. The size reduction of components and the higher density, packing of components on computer chips, make the devices more susceptible to static, damage. In many cases the environment can, be adjusted through increased humidity, antistatic mats, or ionizing sprays to control the, problem. During transportation and storage, static protection is critical. Components must, be protected from stray electric fields such, as electric motors and discharges that can, destroy r.nicrocircuits. Method of protection, is to pack them in antistatic plastic film, bags, etc., Film Breathable, A major factor contributing to the growth, of this category is refinements of breath-, , able films that are identified as controlledatmospheric packaging (CAP). They substantially extend the shelf life of perishables, by regulating oxygen, CO2 , and moisture permeability. This type packaging has extended, the global food trade. There are different, types for use in food, horticulture, medicine,, etc. It was introduced in 1994 by researchers, in BruneI University, Oxbridge, UK. It has, basically a two-plastic layer structure containing small holes that open and close as the, temperature changes., The principle is the same as that used in, bimetallic strips (thermocouples, etc.) taking, advantage of differences in coefficients of linear thermal expansion. As the temperature, rises, the edges of the holes peel away. Typically PE laminated to TP polyester with an, acrylic adhesive is ideal for packaging vegetables and fruits. Structure can be modified, to meet a wide range of respiratory rates., Other applications include medical dressings, for burns, drug controlled release-delivery, systems, variable vapor barriers for shoes and, clothing, temperature sensitive warning labels, etc., Food, If plastic packaging were not used, the, amount of packaging contents (food, etc.), discarded from USA households would more, than double. Plastics are the most efficient, packaging materials due to their higher, product-to-package ratio as compared to, other materials. One ounce of plastic packaging can hold about 34 ounces of product. A, comparison of product delivered per ounce, of packaging material shows 34.0 plastics,, 21.7 aluminum, 6.9 paper, 5.6 steel, and 1.8, glass. USA food container (annual $14 billion, business) consumption by major materials is, 38wt% paperboard, 28% plastic, 26% metal,, and 8 % glass., Most packaged foods require a barrier, against gases, flavors, or odors to maintain, product quality and provide acceptable shelf, life. Baked foods usually need moisture protection, while fresh meats and vegetables require low or controlled exposure to oxygen

Page 257 : 4 Designing Plastic Product, to maximize shelf life and consumer appeal., Polyethylene films, both single and multilayer, are widely used to package such products. Certain key properties and processing, conditions affect the permeability of PE. As, an example with blown film factors such as, the blow-up ratio, frost line height, and die, gap width can be used to control permeability (Chapter 8)., , Food, Oxygen Scavenger, It is impregnated plastics with chemically, reactive additives that absorb oxygen, ethyl,, and other agents of spoilage inside the package once it has been sealed. Food package, types include flexible pouches, PET bottles,, microwave trays, and cartons (coat plastic, and paper). When such films are combined, with conventional rigid or flexible barrier systems, they can allow food packagers to greatly, retard spoilage and prolong shelf life., , Grocery Bag, Polyethylene sack or T-shirt bags are, stronger than paper bags, take up 30% less, storage space, provide water and puncture resistance, recyclable, etc., , 239, , Modified-Atmosphere, Modified atmosphere packaging (MAT) is, a packaging method that uses special mixtures of gases (carbon dioxide, nitrogen,, oxygen, or their combinations) and polyolefin blown or cast film barrier films to, change the ambient atmosphere influencing, its food content. Film construction includes, polyolefin plastomers (POP, EVOH/PVDC,, ULDPE, LLDPE, Pp, SB, LDPE/PA/EVOH,, and PVDC/coated PET/LDPE). The hermetically sealed MAT extends the shelf life of red, meat, skinless turkey breast, chicken, halfbaked bread, pizza's crust, bagels, etc. and allows them to be presented in a more palatable, manner., As an example, microbial growth of red, meat is retarded maintaining a deoxygenated, blue or gray coloring until the meat is placed, on display. Ground beef normally may last, 3 to 4 days but with MAT can go to 14, days before the sell-by date. This gas-flushed, MAT permits grocers to sell uncooked fresh, meats, marinated varieties, and ready-made, meals for quick preparation for round-theclock sales. This more expensive (but with, reduced costs in service) and sophisticated, packaging concept of using a gas flushed barrier film is not new compared to the basic, traditional method., Peelable Film, , Hot Fill, Thin wall plastics are used to hot fill (injection and blow molded bottles, thermoformed, containers, etc.) without sagging during filling, and maintaining mechanical properties such, as impact strength and stiffness in temperatures from at least -40°F to 250°F ( -40°C to, 120°C). Plastic used includes special grades, of PEN, PET, Pp, PS, and PVc., , Peelable film in case-ready ground beef, package add color and shelf life. As an example Cryovac Div. of W. R. GRACE & CO, uses a peelable barrier lid and foam tray system. It is two packages in one; there is an, oxygen barrier structure, which is peeled off,, leaving an oxygen-permeable film over the, meat., Pouch Heat-Sealed, Wrap,, and Reusable Container, , Loose Fill, They use principally polyethylene and, polystyrene foam in different shapes such as, peanuts and pretzels., , These packaging systems help keep food, fresh and free of contamination. Thus the resources that went into producing the food was, not wasted.

Page 258 : 240, , 4 Designing Plastic Product, , Retortable Pouch, Also called retort able container or flexible packaging. It has superior flavor retention and longer shelf life are principal advantages of single or laminated plastic (such, as PP, PC, PEl, CPET, and EVOH), with or, without aluminum foil, paper, etc. They are, made impervious to light, air, and most other, gases, microbial organisms, water, and most, other liquids, etc. Many applications require, them to be capable of withstanding temperatures of at least 250°F (121 DC) for at least, 20 minutes. Different processing methods are, used such as blow molding and thermoforming. The USA converted flexible packaging, industry consumes about 7 billion lb (900 kg), of which 75% is plastics, 22% is paper, and, 3 % is aluminum foil., , Shrink Wrap Tunnel, An oven in the form of a tunnel mounted, over or containing a continuous conveyor, belt is used to shrink oriented films in the, shrink packaging process. Also use a hot air, blower on the film to provide the heat required in specific areas., , Container Content Misrepresentation, When you use metric, such as in USA, be, sure they are correct. Unwitting errors with, upper and lower case letters can be dramatically misrepresenting package contents. As, an example, there is a drastic difference between 100 ML and 100 ml or 100 million liters, and 100 milliliters. Some designers prefer using capital letters for content designations on, the label. Thus, with metric usage fluid ounces, are replaced by milliliters; quarts are replaced, by liters; pounds by dry ounces are replaced, by grams or kilograms, and so on. Metric, unit short forms are called symbols, not abbreviations; therefore they never should be, followed by a period unless the symbol is, the last word in a sentence. There must always be a space between digits and symbols. Metric symbols are always used in sin-, , gular form, without adding an "s" to indicate, quantity., , Permeability, The ability of a plastic to protect and, preserve products in storage and distribution depends in part upon the diffusion (i.e.,, transport) of gases, vapors, and other lowmolecular-weight species through the materials. A substance's tendency to diffuse through, the plastic bulk phase is its diffusivity or diffusion coefficient. The rate of diffusion is related to the resistance, within the plastic wall,, to the movement of gases and vapors. Two, important aspects of the transport process, are permeability and the migration of additives. Possible migrants from plastics can, include residual monomers, low molecularweight polymers, catalyst residues, plasticizers, antioxidants, antistatic agents, chain, transfer agents, light stabilizers, FR (fire resistant) agents, polymerization inhibitors, reaction products, decomposition products, lubricants and slip agents, colorants, blowing, agents, residual solvents, and others., An important selection of materials to, packaging, particularly food, is based on the, permeability of the materials to oxygen, water vapor, and, in the case of packaging, bananas, to ethylene gas that is used to artificially ripen the bananas. Selective permeability provides chemical separations, one of the, most interesting of which is the use of PTFE, materials to separate the hexafluorides of the, different isotopes of uranium., There are a number of industrial gas separation systems that use the selective permeability of plastics to separate the constituents., In design problems relating to such applications, the designer must consider the environmental conditions to determine whether, the materials having the desired properties, will withstand the temperatures and physical and chemical stresses of the application., Frequently the application will call for elevated temperatures and pressures. In the case, of uranium separation, the extreme corrosivity of the fluorine compounds precluded the, use of any material but PTFE. The PTFE

Page 259 : 4 Designing Plastic Product, , material, however, requires careful design, to make a sturdy membrane because of the, poor mechanical properties of the PTFE, plastics., Basics The driving force for gases and, vapors penetrating or diffusing through, for, example, permeable packages is the concentration difference between environments inside and outside the package. A diffusing, substance's transmission rate is expressed, by mathematical equations commonly called, Fick's First and Second Laws of Diffusion:, F, , = -D(dC/dX), , dC/dt = D(d2C/dX2), , (4-2), (4-3), , where F = flux (the rate of transfer of a diffusing substance per unit area), D = diffusion, coefficient, C = concentration of diffusing, substance, t = time, and X = space coordinate measured normal to the section., To measure gas and water vapor permeability, a film sample is mounted between, two chambers of a permeability cell. One, chamber holds the gas or vapor to be used, as the permeant. The permeant then diffuses through the film into a second chamber,, where a detection method such as infrared, spectroscopy, a manometric, gravimetric, or, coulometric method; isotopic counting; or, gas-liquid chromatography provides a quantitative measurement (2). The measurement, depends on the specific permeant and the sensitivity required., Three general test procedures used to measure the permeability of plastic films are, the absolute pressure method, the isostatic, method, and the quasi-isostatic method. The, absolute pressure method (ASTM D 1434,, Gas Transmission Rate of Plastic Film and, Sheeting) is used when no gas other than the, permeant in question is present. Between the, two chambers a pressure differential provides, the driving force for permeation. Here the, change in pressure on the volume of the lowpressure chamber measures the permeation, rate., With the isostatic method, the pressure in, each chamber is held constant by keeping, both chambers at atmospheric pressure. In, , 241, , the case of gas permeability measurement,, there must again be a difference in permeant partial pressure or a concentration gradient between the two cell chambers. The, gas that has permeated through the film into, the lower-concentration chamber is then conveyed to a gas-specific sensor or detector by, a carrier gas, for quantitation. Commercially, available isostatic testing equipment has been, used extensively for measuring the oxygen, and carbon dioxide permeability of both plastic films and complete packages., The quasi-isostatic method is a variation of, the isostatic method. In this case at least one, chamber is completely closed, and there is no, connection with atmospheric pressure. However, there must be a difference in penetrant, partial pressure or a concentration gradient, between the two cell chambers. The concentration of permeant gas or vapor that has permeated through into the lower-concentration, chamber can be quantified by a technique, such as gas chromatography (2)., Three related methods based on the quasiisostatic method are used to measure permeability. The most commonly used technique, allows the permeant gas or vapor to flow continuously through one chamber of the permeability cell. The gas or vapor permeates, through the sample and is accumulated in the, lower-concentration chamber. At predetermined time intervals, aliquots are withdrawn, from the lower cell chamber for analysis. The, total quantity of accumulated permeant is, then determined and plotted as a function, of time. The slope of the linear portion of, the transmission-rate profile is related to the, sample's permeability., Permeability and barrier resistance In the, past, the usual materials used to contain, food, gasoline, chemicals, perfumes, medication, and many other items that keep them, from permeating or being contaminated were, metal and glass. For over a century, however, plastic containers have been entering, the arena of packaging. At first only certain, plastics could be used, which were usually, rather thick or heavy compared with what is, used today. There have been various plastics, that could provide permeability protection.

Page 260 : 242, , 4 Designing Plastic Product, , With the growth of plastic use in containers and packages, requirements to make them, more compatible or useful resulted in new, developments occuring and continue to occur. The two major approaches for providing permeability resistance in plastic containers involve chemically modifying the plastics', surfaces and, more important from a marketing standpoint, the use of barrier plastics with nonbarrier types to meet cost-toperformance requirements. This is achieved, through coextrusion, coinjection, corotation,, and other such processes (Chapter 8)., Chemically modifying a plastic's surface, during or after fabrication permits controlling the permeation behavior of such products as diaphragms, film, and containers., These techniques are becoming increasingly, important. There is an endless search for better barrier materials for packaging applications. As an example in blow-molded gasoline containers/tanks, the amount of gasoline, permeation through HDPE even though it is, very low, is still excessive, thus has required, some type of barrier. Including a barrier in a, multilayer construction can create such a barrier. Another approach is functionalized PE, formed on the inside of the container wall, by a chemical reaction, mostly sulfonation or, fluorination., There is also oxifluorination that is a process in which fluorine gas is thinned with, nitrogen to which several percent of oxygen by volume have been added. Subjecting, PE to fluorine and oxygen at the same time, leads to functionalization of the PE, making it, impermeable. This technique permits substantially reducing the required amount of, fluorine, resulting in a cost-to-performance, improvement., Barrier plastics using oxifluorination are, widely used for foods. With these, barriers are, needed to protect them against spoilage from, oxidation, moisture loss or gain, and changes, or losses in favor, aroma, or color. Most plastics can be considered barrier types to some, degree, but as barrier properties are maximized in one area (as the gases such as O 2 ,, N2 , or CO 2 ), such other properties as permeability and moisture resistance diminish., , Product, Practically all markets use some type of, packaging. Examples include the following:, 1. Packaging (food, medical devices, egg, cartons, dairy containers, meat and produce, trays, electronic devices, tools, dinnerware,, picnic dishes, drinking cups, lids, etc.), 2. Refrigeration (inner door liners, food, compartments, crisper trays, etc.), 3. Appliances (housings for electrical, mechanical, chemical, etc.), 4. Signs and displays (point of purchase,, interior and external, etc.), 5. Automotive (interior and exterior parts,, air ducts, crash pads, arm rests, etc.), 6. Industrial (tote boxes, many different, shaped machine and other device housings,, etc.), 7. Military (aircraft canopies, contour, maps, etc.), Others include building and construction, cosmetics, dental, drugs, electrical and, electronics, furniture, aerospace, agriculture,, horticulture, industrial, mechanical, medical, public transportation, recreation, toys,, and so on., , Building, , Overview, The usually reported second largest market for plastics is building and construction consuming about 20 wt%. However, the, amount of plastics is only about 5% of all, materials consumed in building and construction so that a large growth area exists for, plastics when the price is right since their, properties provide durability, performances,, insulation, cosmetics, etc. (Fig. 4-5). Different plastics are used that include PVCs, PEs,, PMMA, PSs, phenolics, TS polyesters, and, many more. Examples of products are listed, in Table 4-1.

Page 262 : 244, Table 4·1, , 4 Designing Plastic Product, Applications of plastics in buildings, , Exterior, Adhesives, Air support, structures, Air vents, Cables, Caulkings, Coating-metal, wood, Concrete forms, Concrete mixes, Curtain walls, Doors (prime and, storm), Expansion joints, Facings, Flashings, Gaskets, Glazings, Grilles, Hardwares, Illuminating panels, Lighting fixtures, Louvers, Moisture barriers, Mortar mixes, Paints, Panels, Pipes, Railings, Rain system-gutters,, downspout, etc., Roof edging, panels, Safety and thermal, glasses, Screens, Sealants, Sheathings, Shingles, Shutters, Sidings, Signs, Skylights, Stuccos, Sun shields, Swimming pools, Tapes, Tool sheds, , Topping-walk,, driveways, Vent stacks, Water proofings, Weather strippings, Window panes, Window sash (prime, and storm), Wire insulations, Interior, Acoustical panels, Adhesives, Baseboards, Cabinets, Ceilings, Conduits, Counter tops, Coverings, Decorative panels, Drawers, Ducts, Electrical fixtures, Floorings, Gaskets, Graphic arts, Grilles, Hardwares, Insulations, Light diffusers, Molding, trims, Paints, Panelings, Partitions, Pipe fittings, Plaster backings, Plumbing fixtures, Railings, Sealants, Shower stalls, Stair treads, Tanks, Tile-floor, wall,, ceilings, Vapor barriers, Wall coverings, Wire insulations, , Application and the Environment, The present and growing large market for, plastics in building construction is principally, due to its suitability in different environ-, , ments. The versatility of different plastics to, exist in different environments perhaps may, be related to another characteristic; namely,, ability to be maintenance-free when compared to the more conventional and older, materials. This section will review the different parameters that are important in building construction and are related to different, environments., From a practical review, perhaps it can be, stated that buildings and construction materials are exposed to the most severe environments on earth, particularity when the long, time factor is included. The environments include such conditions as temperature, ultraviolet, wind, snow, corrosion, hail, wear and, tear, etc. Basically the following inherent potentials continue to be realized in different, plastics: ease of maintenance, light weight,, flexibility of component design, combine with, other materials, corrosion/abrasion/weather, resistance, variety of colors and decorative, appearance, multiplicity of form, ease of fabrication by mass production techniques, and, total cost advantages (combinations of base, materials, manufacture and installation)., Success in applying plastics has been, based on a combination of factors; such as,, adequate testing, keeping up-to-date on, customer problems, product identifications,, quality control establishment of engineering standards, approval of regulatory agencies, supervise installations, accurate cost and, time estimations, organizational responsibilities defined, meeting delivery schedules, development of proper marketing and sales approaches, resolution of profit potential based, on careful selection of applications, and acknowledge competition exists., The functional attributes that permits its, growth at an accelerated rate are reliability, acceptability, feasibility and economics., Field installations of the new products are, now providing more of the necessary reliable long time data. The field tests continue, to be the best approach in demonstrating, acceptance., The obstacles, limitations or disadvantages, confronting acceptance of plastics are:, 1. Service life versus legal risk: The architect and builder can appreciate the limited

Page 263 : 4 Designing Plastic Product, 10 to 20 year service test results but rarely, can appreciate the more abundant zero to, two year or accelerated weathering test results. Their thinking is that plastic companies inherit their portion of risk (latter in, this Chapter review RISK and DESIGNING, AND LEGAL MATTER)., 2. Properties: Fire safety continues to be a, major performance requirement. Creep and, heat distortion are other important properties to be considered. A major deterrent for, the architect and builder is lack of common, knowledge about plastics physical properties., 3. Cost: In no business is there more resistance to increase cost even if it represents, true increase value., 4. Codes: The code problems are usually, over emphasized. lt is a recognized fact that, obstacles do exist and many "heated" debates, are already on the books and will continue, to be on the books. The codes are important, to society and must be recognized in plans, and development programs for plastic building products. There are many examples of, approvals such as pipe since 1965 as well as, previous acceptance of paneling in 1959 by, FHA on Sinclair-Koppers Company expandable polystyrene beads (EPSs) faced with asbestos cement or plywood. Recognize that, practically the rest of the world accepted and, used plastic pipe and other plastic building, materials since the late 1940s., In USA the major obstacle to using plastics in the past has been to convert standards and codes to include the use of plastics., There were standards and codes where plastic would meet all their requirements with, "flying" colors except when they specifically, stated that the material to be used had to be, iron, steel, or other material (not plastics)., Eventually (years passed) and plastics were, included. So plastics could not be used until other materials such as plastics would be, included or no specific material was specified. Outside USA the changes in most cases, were immediately particularly immediately, after 1945., 5. Competition: In line with the so-called, sportsmanship approach or competitive business behavior, the entrenched steel, wood,, , 245, , concrete and other industries would logically, continue to resist plastics acceptance and use, all humanly available resources to fight (restrict or eliminate) plastics. This situation existed for almost a century when plastics were, entering into a competitive product. Eventually things changed including where the competing (old time) companies usually enter the, plastics industry to make the products., 6. Aesthetics: The trend is to resist change, in appearance so that plastic originally had to, look like something else. With time passing, the beauty of plastic was accepted and at the, same time usually at lower costs and more, benefits developed., 7. Identification: To the nonplastic user, and even certain plastic users, identification, of over 35,000 plastics tends to be either misleading or confusing even though this situation should never exist. As explained in this, book, certain specific plastics meet certain, product requirements., 8. Standards: Most buildings have never, been subjected to thorough engineering analyses. Traditional precedent and judgment as, reviewed under Codes have (logically) controlled the standards. In fact if wood had, never been used, it would be difficult to, approve (burns, rots, etc.); of course it is, ridiculous to assume that wood would not be, approved., 9. Performance data: Rather than make, available principally sales type of data, the, architect should review realistic and understandable technical data. They should learn, that the behavior of certain plastics provide, for more cost-efficient products rather than, just be contented with only past history on, the materials of construction., 10. Consumer: General demands for traditional materials continue to exist but it is, gradually changing since more plastic products are all around them., 11. Labor: They generally sets-up problems but education on use of new plastics, has been helpful. An example is when plastic pipes were approved for use in buildings, where labor initially was against their use because it interfered by reducing labor hours,, etc.

Page 264 : 246, , 4 Designing Plastic Product, , In the meantime ideas for using plastic, in building continues to vary in all proportions (Table 4-1). Designers produced sprayfoamed homes that were reviewed during, the October 1965 annual National Decorative and Design Show in New York City. It, was described that entire rooms and furnishings molded-in-place would be both practical, appealing, and survive the environment. During the 1950s different military, groups built different foam structures, etc., During this time period all structures (wall,, roof, etc.) of buildings were successfully, built from extruded PVC hollowed sandwichribbed panel structures that were unfilled and, filled with insulation material (PUR foam,, etc.), concrete, or other materials (34--37,, 151). Also building structures were made, from extruded PS foam logs that were heatbonded wrapped in dome shaped structures, (14), RP filament wound room structures, and, so on., , The Architect Approach, Breakdown in communications between, the building industry and plastic manufacturer probably accounts for a large amount, of lost motion and dollars. Perhaps another, major cause is the pure sales approach within, any industry that, in many cases, can delay, technical progress., Architects and builders desire factual data, on products. However, their standards or, codes in many cases only identify the composition of the end item, with no performance data. In most cases, the plastics were, never subjected to engineering analysis but, approved based on past performances. This, situation is not new to the engineering community, where patience, time and/or money, resolve the problem., It has been stated that architecture as a, profession has often stood in the way of, progress. Being a learned profession, it generally looked to the past for knowledge and, inspiration. Although most people have an, inherent resistance to change, there are always enlightened architects, builders, and, consumers who have the courage to over-, , come traditional beliefs and the foresight to, anticipate new developmental trends (14)., Architects and builders do exist who foresee plastics as a major building material and, represent a means to provide extending the, building block or modular construction concept. The versatility of plastics permits developing single units containing water piping, electrical conduit, heating elements and, other services. This building block approach, has been used successfully in other industries, but, in most cases, developed due to, government or military requirements. Many, architects also see that plastics make possible the housewife's dream of a dust-proof, construction., The architect continues to look for products that can he multifunctional. As an example in roofing, the product could perform, a part or all of the functions. The roof has to, provide structural integrity, temperature and, sound insulation, vapor and moisture control, weather resistance, elastic qualities for, change in weather, fire protection, aesthetic, appeal, and so on., What the architect looks for in any new, material has been expressed. The first interest concerns the continuing search for practical, aesthetically pleasing, and economically, priced buildings with long service life. The, materials or products are to provide new, or better solutions to the myriad problems, plaguing the construction industry. The second is that a complete and accurate account, of each new material exists. The material is to, fit within the manufacturing and installation, practices of the present construction industry., The third is the assurance that architects are, not left holding the bag when new materials, do not perform satisfactorily. The economic, situation as to who should be responsible represents a major problem area since legal suits, can occur and architects lose prestige., , House o/the Future, One of the first all plastic house was the, Monsanto House of the Future erected in, Disneyland, CA, USA in 1957 (Fig. 4-6)., The key structural components were four

Page 265 : 4 Designing Plastic Product, , 247, , (a), , Curved steel, , Reinforced concrete, foundation, , (b), , Fig. 4·6 House of the future structure: (a) view of one section, (b) design layout, and (c) cantilever, support beam.

Page 266 : 248, , 4 Designing Plastic Product, , (c), , Fig. 4-6, , 16 ft (4.9 m) V-shaped cantilever (monocoque box girders) reinforced plastic designs, by MIT. Different plastics were used throughout the house including different plastic sandwich panels., When this house was to be removed to, provide a different scene (a main attraction, for two decades), it had suffered almost no, change in deflection. It was estimated to have, been subjected to winds, earthquakes, subjected to families using it to the equivalent of, centuries based on all the people that passed, through it, etc. Destruction by conventional, techniques (wrecking ball, etc.) was impossible without first cutting sections, etc., , Designing a Structure, The following example provides information on designing of plastic structural products to take static loads. It is a structural, problem common to a number of different, structures to show how the different structural requirements will affect the choice architectural designers has to make. The design problem will be a roof section which, may be used for anything from a work shed,, , (Continued), , to a house, to a vehicle, or even to a simple, weather shelter (190)., The analysis begins with a definition of the, function that a roof performs. A roof is the, overhead product of a structure intended to, protect the occupants and/or contents of the, structure from the outside environment. It involves rain, snow, wind, sun, falling objects,, hurricanes, and the other elements that make, up the outside or surrounding environment., In order to perform this function the roof, must be capable of supporting its own weight, and the weight of snow or any other possible accumulations on the roof. It must be, resistant to wind loads that are quite severe, in some regions. The roof must also support, loads imposed by people walking on it, usually for maintenance. In some instances the, roof may double as a deck and the traffic may, be constant., The roof must be able to shed water that, falls on it, although it need not be waterproof, in the sense of being a waterproof membrane, structure. The roof surface is exposed to sun,, wind and driven debris and must be resistant to erosion by the action of sunlight and, the abrasive action of wind driven debris. In, most cases the roof is insulated thermally to

Page 267 : 4 Designing Plastic Product, prevent heat loss in cold weather and heat input during warm weather. Obviously, not all, these roof requirements apply to all roof situations, but most of them do so you can set, up your own requirements., The major load applied to a roof is the static, load of the roof structure itself. Since roofs, come in a wide variety of types the self load, will depend on the basic roof design. The simplest is the corrugated RP panel structure., This type of structural element is widely used, for roofs on industrial buildings to admit daylight, porch and patio roofs, shelter roofs such, as those used at bus stops, and a variety of, similar applications. Variations of this simple roof are used for roof sections on transportation vehicles such as buses and trains., Since this section is one of the easier ones on, which to describe loading conditions, it will, be used to illustrate the design procedure., Other roof sections such as the domes, arches,, geodesics, and paraboloids involve complicated stress analysis and the results would not, be particularly useful in a general analysis of, a static structure., The corrugated materials are available in, sheets which vary from 4 ft x 8 ft to as, large as 10 ft x 20 ft. A typical material is, 0.100 in. thick with 2 in. corrugations, and a, corrugation depth of 1 in. The RP material, from which they are made is glass fiber mat, as the reinforcement and a weather-resistant, TS polyester plastic. In general, the sheet material is nailed or screwed to wooden supports, (could be pultruded RP supports if the price, was right) at proper intervals (Chapter 8)., In some cases the roof section is made in, one piece with spars of TS polyester-glass, material molded into the product to provide, the stiffening support needed. In this case, the only requirement for installation involves, anchoring the edge of the section to the, structure., This type of design problem is somewhat, different from others in that the unit is made, from standardized sections that have specific, physical properties and are available in only, a limited number of thicknesses and configurations. The design problem now consists of, trying the available materials in the structure, , 249, , with the supports that can be used and then, determining if the material will perform. The, self load is easily determined from the weight, of the materials. The snow load is a design, value available from experience obtained in, the area where the structure is to be used., Similarly, the maximum wind load and people load can be determined from experience, factors that are generally known., The problem is worked out using several, different sheet types and different support, spacings in an environment that would be, typical of a city in the Midwestern part of, the USA. The indicated solution is that the, material selected will take the required loads, without severe sagging for a 15 year period, with no danger that the structure will collapse, due to excessive stress on the material. If a, standard material had not been suitable, it, would have been possible to use one specifically molded for the application, or by the use, of several layers of the material. One typical, way in which excessive loading for a single, section is handled is to bond two layers of, the corrugated panel together with the corrugations crossed. This results in a very stiff, section capable of substantially greater, weight bearing than a single sheet and it will, meet the necessary requirements. The double sheet material also provides significant, thermal insulation because of the trapped air, space between the sheets particularly if they, are edged sealed., The roof section was designed to meet the, static load requirements. However, it is necessary to consider transient loads such as, people walking on the roof and fluctuating, wind loads. The localized loads represented, by people walking on the roof can be solved, by assuming concentrated loads at various locations and by doing a short time solution to, the bending problem and the extreme fiber, stress condition. The local bearing loads and, the localized shear should also be examined, since they may cause possible local damage, to the structure., Stresses from varying winds are general, alternating stress loads and occur over wide, areas of the structure. When the wind changes, direction, the stress frequently changes

Page 268 : 250, , 4 Designing Plastic Product, , direction, and the tendency is for the roof to, lift away from the structure. The main point, of stress caused by the wind is at the anchorage points of the roof to the rest of the structure. They should be designed to take lifting forces as well as bearing forces; the lower, the angle of roof, the less wind lifting force., Proper anchorage of the support structure, to the ground is also essential. Certain local, fire and building codes impose additional, restrictions., A large area of plastics, such as described, here, has a change in dimension with temperature. Surprisingly, very few of the traditional building materials, including wood,, have significant expansion under normal temperature shifts. The RP materials generally, are not a problem since they have low linear, thermal coefficients of expansion and the corrugated shape tends to flex and accommodate, the changes caused by heating and cooling. In, the case of materials such as vinyl siding, the, expansion factor becomes significant and is, an important consideration in the fastening, system., The effects of the environment on the performance of the material must be considered., U sing the initial physical properties of the, materials, the structure is sound. Exposure to, weather, which includes water and sunlight,, has a significant effect on the physical properties of the materials and this must be taken, into account in the design. This type data is, available from the reliable panel producers., Let us assume that there is a 50% or more, drop in the physical properties in 5 years;, actually far less. This can be due to surface, damage and to changes in the bulk of the material. In general, this type of loss of physical, properties levels off to a low rate of deterioration in suitable materials so that any potential, failure can be anticipated. This loss of properties can be compensated for by increasing, the strength requirements by a suitable safety, factor (Chapter 2), probably about three in, this case, and by using a protective coating, on the sheet material to minimize the effects, of weathering. The preferred type of coating, would be a fluorocarbon material that has the, best resistance to sunlight and other weathering factors of all of the plastics. If this type, , of surfacing is used, the material will retain, its surface integrity for at least 20 years., The example of the roof structure represents the simplest type of problem in static, loading in that the loads are clearly long term, and well defined. Creep effects can be easily, predicted and the structure can be designed, with a sufficiently large safety factor to avoid, the probability of failure., Chair, , A seating application is a more complicated static load problem than the building, example just reviewed because of the loading situation. The self load on a chair seat is a, small fraction of the normal load and can be, neglected in the design. The loads are applied, for relatively short periods of time of the order of 1 to 5 hours, and the economics of the, application requires that the product be carefully designed with a small safety factor., A different design approach is used in, this case. Instead of assuming an apparent, modulus of elasticity using a constant creep, situation covering the life of the chair, it is, better to determine the actual creep deflection over a typical stress cycle, the creep recovery over a non-use cycle, and so on until, the creep is determined after a series of what, might be considered typical hard usage cycles, for the chair. The accumulated creep after a, period of two weeks can be assumed to represent the base line for an apparent modulus of, elasticity to determine the design life of the, chair., , Load Requirement, With this basic approach in mind, let us do, a design on a typical molded chair seat. The, load will be assumed to be a 250 lb person and, the load cycle which includes loading times, of 4 to 6 hours two or three times in 24 hours, and a relaxation period of 1 to 2 hours during the day and of 10 hours during the night., The curve of loading is a random collection, of these cycles over a 2 week period. The first, step in the design is to select a section for the, chair seat that will have the required strength

Page 269 : 4 Designing Plastic Product, to prevent breakage with the stress calculated, from the extreme fiber formula., The next step is to see that the seat does, not deflect more than a given amount to be, able to continue to function as a seat. An arbitrary deflection of 2 in. in the length of a, seat 16 in. long will be assumed since consumer comfort testing usually arrives at such, values. It might be noted that in some chair, designs where the creep did not result in failure of the chair, the fact that the seat was too, resilient and gave a feeling of insecurity led, to poor consumer acceptance. In many cases, the "feet" of a product is important to its success and the feeling of solidity is important in, furniture applications., Within the limits set above the design can, vary widely. The seat can be attached to the, rest of the chair frame by leg supports at the, four corners, or it can be cantilevered from, the back with a floor pad support, or, in another version, from the front. The seat construction can range from a formed sheet in, two or three dimensions to one with rolled, edges for reinforcement. It can have structural ribs molded in or it can be a sandwich, panel construction made up of two molded, parts bonded together. It can also be a structural foam molding. In each of the configurations there are tradeoffs of stiffness and, strength that may make one more effective, then the others in meeting the seating requirements., , Form and Dimension, In this case the designer has freedom of, choice of both form and dimension as well, as in the selection of the materials. Given, this freedom, it would be desirable to examine several of the alternatives to see which, would provide the best seating at the lowest, cost. Obviously, there is no point in doing all, of the possibilities so a selection should be, made on the basis of anticipated use as well, as style requirements. Three types will be analyzed. They are the single curve sheet cantilever mounted from the back, the molded, pan supported on four legs, and the structural foam molding which is front supported., , 251, , In order to simplify the analytical exercise, a, particular material was selected for each. The, single curved sheet is made of TS polyester, fiber glass molded to the shape. The corner, supported pan is molded from ABS plastics., The structural foam unit is molded from PP, with glass fiber filler., From inspection of the three designs it is, apparent that the main stress of the loading, will be at the support point for the seat. This, will be assumed to be sufficiently strengthened to prevent failure, either by excessive, stress or bending at the support point. The, analysis will be concerned with the fact that, the seat itself will not break as a result of, the load and will not sag excessively after, continued use. For this example the impulse, load caused by dropping into a chair will be, ignored., In each case the section is designed to, keep the deflection to less than 2 in. in 16 in., for a design life of 5 years and the extreme, fiber stress is kept to a value less than the, yield strength of the material. The first step, in the analysis is to determine the necessary, section to resist the bending load using the, short-term tensile and compressive strength, and modulus values. The extreme fiber stress, is calculated for these sections to determine, that the chair will not break when deflected., A time dependent modulus is then calculated using the extreme fiber stress level for, each of the materials at the initial stress value, level using the loading-time curve developed., If the deflection at the desired life is excessive,, the section is increased in size and the deflection recalculated. By iteration the second can, be made such that the creep and load deflection is equal to the maximum allowed at the, design life of the chair. This calculation can, be programmed for a computer solution., , Stiffness, The selection from the possible designs is, made on a cost effectiveness basis. The least, costly construction would be the best unless there is an inherently more useful construction for aesthetic or other reasons. In, most design cases this will be an aesthetic

Page 270 : 252, , 4 Designing Plastic Product, , consideration or, in this case, it may be a, user consideration such as initial stiffness, which leads to a better feeling of security., This may lead to the selection of something, other than the lowest cost design. This value, can be added to the consideration by examining the products' stiffness (EI) for each of the, constructions at the initial short-term loading, (Chapter 3, Geometrical Shape, EI theory)., The higher the El product, the less the seat, will flex under load, and the more secure it, will feel. With the materials and constructions, examined, the initially stiffest construction, may have a higher creep level and require a, heavier and more costly construction to meet, the creep criteria. This may be justified by the, better feel of the seat., As always, the designer must be concerned, with the utility of the product because this is, justification for designing it in the first place., The most important part of the design is that, it satisfy the need for which it is made. The, technical qualities must be such that they result in good acceptance. A technical success, that leaves the user unsatisfied is not a product design success., , Environment, As with any design, the environmental and, end-use requirements must be considered., The chair will be exposed to cleaning agents,, children and dogs climbing on it, possible, abuse in storage and shipment, etc. Such conditions should be considered as part of the, material selection and design procedure. Of, the three materials suggested, PP has the best, chemical resistance, ABS has the best abrasion resistance, and the RP normally would, have medium properties in both areas. All, three are tough materials that would take, rough handling, and the ABS would be best in, terms of exposure to sunlight. In this particular design there would generally be no reason, to choose anyone of the materials over the, other unless it is anticipated that the chair will, have substantial exposure to conditions other, than those typical of the home environment., In the other design procedures we would, tend to follow a minimum test sequence for, , acceptance testing in use to see that the, design is functional, and set a reasonable, quality testing procedure to insure that the, processing is under control. While the use of, plastics in a chair represents a situation where, there is substantial personal injury risk it is, one that is anticipatible and the normal design procedure would anticipate and eliminate the possibility of premature failure., Deterioration of the chair with age should, be examined to see if environmental exposure would lead to a shortened life. The indoor environment where a chair is normally, used does not produce severe damage. Indoor sunlight is much less severe than outdoor exposure and room temperatures do not, vary excessively. The only source of possible damage is in the use of cleaning and debugging agents that may attack the plastics., This can be controlled by following proper, instructions. If difficulty is expected, a chemical resistant material is indicated. Abuse by, dropping and impact should also be considered. This may cause surface or structural, damage. Public seating is subject to much, abuse., As examples we have examined different, types of common statically loaded structural, units. In all case they represent long-life expectancy units which will carry substantial, loads. Since the failure of the product would, involve substantial risk of personal injury, the, designs must be done with caution. In one, case, strong considerations are present and, in the other traditional performance requirements must be considered. The loadings and, the basis for making the design judgments are, different. These examples do not exhaust the, possible combinations of conditions the designer will face, but they indicate what might, be expected., The approach to the problem is to make the, best analysis of the product requirements, including what at first appear to be intangible, requirements, and then to determine what are, the important elements in the design. Using, these as the guide, several types of structural, possibilities are examined with different materials to see if they meet the performance, requirements of the application. The loads,, the duration of the loads, the environment,

Page 271 : 4 Designing Plastic Product, and the intangible use factors will favor one, design over the other, particularly if the economics are made the final basis for choice., The final design is made and tested for performance and sent to production with suitable quality control tests indicated., The process of design for static loads involves a great deal more than the mechanical operation of the stress-strain data to, determine the performance of a section., The results obtained from the stress analysis are used to determine the functionality, of the product and then, combined with the, other factors involved to decide on a suitable, design., Prototype, Different tests are used on prototypes. As, an example industry has a test where a load, may be double that of a heavy person. Its, two rear legs are positioned in front of an, anchored board. The top of the chair has, a rope or chain extending backwards to an, oscillating device. The top of the chair will, be pulled back to the point of almost failing backward and then released. The loaded, chair will bounce on its two front legs. This, cycle is repeated thousands of times. The industry test has requirements so if the chair, is to be used in commercial environment its, number of cycles will be many more than a, noncommercial chair., Using the approach suggested, designers, can be guided in the design of static structure, for performance in any environment from, space, to aircraft, to land applications, to subsea use. Defining the requirements and using, the data available or generated for the application, the end result can be made predictable, to a sufficient extent that successful products, result with minimum cost., Automobile, , For today's and tomorrow's transportation, vehicles (automobiles, trucks, motorcycles,, boats, airplanes, etc.) plastics offer a wide, variety of benefits. Plastics play a very im-, , 253, , portant role in these vital areas of transportation technology by providing special design considerations, process freedom, novel, opportunities, economy, aesthetics, durability, corrosion resistance, lightweight, fuel savings, recyclability, safety, and so on (14,, 153, 179, 234). Designs include lightweight, and low cost principally injection molded, thermoplastic car body to totally eliminate, metal structure to support the body panels, (Figs. 1-13 and 4-7). Example include pick-up, trucks that use 100 lb thermoformed cargobed liners or RP boxes, RP bus interiors, and bodies, injection molded TP fenders, etc., With more fuel-efficiency regulation new developments in lightweight vehicles is occurring with plastics. Plastics used include ABS,, TPO, PC, PC/ABS, PP, PA, PVC, PVC/ABS,, PUR, and RPs., Different cars have and are being designed worldwide to produces low cost purchases, light weights, reduce fuel costs, reduce contaminating emissions, etc. Extensive, use has been made by using unreinforced, or reinforced TPs and/or TS plastics. A few, of the many plastic products used follows., (1) Chrysler Corp.'s light-weight Composite, Concept Vehicle (CCV) includes TP structural body panels with only a limited amount, of metal underneath; it is an all-plastic body, requiring a very large mold. (2) Ford Motor, Co. has an all-aluminum body with plastic, in some of the other parts. (3) GM focusing some plastics in their electric vehicle., (4) Asha/Taisun of Singapore producing taxi, cabs for China with thermoformed body panels mounted on a tubular stainless steel space, frame. (5) NA Bus Industries of Phoenix is, delivering buses in USA and Europe with, all RP bodies. (6) Brunswick Tech. Inc. of, Brunswick, ME produces 30 it RP buses except for the metallic engine (209)., There is Europe's plastic skin, 2-seat coupe,, called the Smart car with molded-in color that, virtually eliminates painting. The idea was to, eliminate the need for three coats of paint, and reducing both cost and emission problems, Project started in 1994 via a joint venture of Daimler-Benz in Stuttgart, Germany,, then known as Mercedes-Benz, and the Swiss, watchmaker SMH AG in Biel. They created a

Page 272 : 254, , 4 Designing Plastic Product, , PRODUCTION OUARTER, PANEL EXTENSIONS, , SMC, PRODUCTION GRILLE, OPE ING PANEl -, , \ G.fRP REAR SUSPENSION, ARMS - UPR. & LWR ., , 2 JL I. ENGINE, C· l AUTO TRANS, , \, , DOWNGAGED UPPER, , & LOWER CONTROL ARMS, TIllES FR 18· '4 ", (UNIOUE LIGHTWEIGHT), , o, , GRAPHITE COMPOSITES, , Fig.4-7 Ford's lightweight concept vehicle made extensive use of high performance graphite fiber, RPs., , new company called Micro Compact Car AG,, or MCC. The first of the cars had plastic injection molded outer body panels using GE's, PC/TP polyester blend (Xenoy). Its unitized, TP body that tied together the front fender,, outer door panels, front panels, rear valence, panels, and wheel arch in one wrap-around, package. The entire car weighs 1,440 lb, (650 kg), about 600 lb (270 kg) less than most, steel-body compacts., , World's First All-Plastic Car Body, From Sichuan Huatong Motors Group,, Chengdu, China is the all-plastic car called, Paradigm, a 4-door/5-passenger midsize vehicle. Its features include glass fiber-TS, polyester RP sandwich chassis, thermoformed coextruded ABS body panels with, molded-in color, adhesively bonded body,, and, for the high-end model, a coextruded, acrylic (ASA) cap cover providing high gloss., Automotive Design & Composites Ltd., San, Antonio, TX, USA has served as the primary contractor for developing the concept., Chassis features a single thermoformed lower, , tub and an upper skeleton X-brace roof. It, employs a monocoque structure where body, panels are stitched-bonded to the chassis,, forming a unitized structure., Thermoformed chassis and body panels, are featured on the car. The products were, made initially in the USA for assembly in, China. The car will weigh less than 2000 1b, (900 kg). Automotive Design & Composites,, Inc of San Antonio, TX, designed the vehicle, to have body panels and trunk formed from, coextruded sheet of ABS with an ASA cap, layer that will hang on a pultruded composite, frame. Ceramic tooling is used to thermoform, plastic products., The chassis is made from a 1/4 in. sheet, of either ABS or TPO vacuum formed into, a tub and reinforced with reinforced pultruded glass fiber-TS polyester plastic tubing., The hood and other products are being made, from a 20 mm thick sandwich of thermoformed PPO-alloy skins, glass fabric infused, with thermosetting vinyl ester, and a urethane foam core. The bumper and front fascia is thermoformed from a poly olefin elastomer sheet with an UV-resistant cap layer, of DuPont's Tediar PVF film. The dash and

Page 273 : 4 Designing Plastic Product, inner console is thermoformed from soft, vinyl over ABS., Quadraxially oriented (four directional, layer) glass fabric-TS vinyl ester polyester RP, sheet panels with a foam core and gel coating are used. Most of the panels are 3 mm, thick with molded-in rib structure supports., Body skins are bonded to the chassis with a, double-stick acrylic tape developed by 3M, Co. as well as mechanical fasteners. Unlike, most steel designs, no B-pillar structural component between the front and rear doors is, required thus providing more interior space, and easy entry since doors open in opposite, directions., The bumper to bumper measures 4.6 m, (15.18 ft); weighs 815 kg (1793 lb) that includes 1200 lb (550 kg) of plastics; has a, gas/electric hybrid power system, air bags,, neon tube tail-lamps, etc.; and gets 132 km, (60 miles) per gallon of fuel. Huatong, and the Chinese government have funded, $100 million in this global project., Evaluation was made on four prototype, cars, and China's Huatong Motors expects, to assemble 5000 units at its Sichuan plant, in the first year. Once on the market, the, , 255, , product will be a moving example of the capability of plastics engineering that includes, using principally thermoforming technology., The all-plastic car will be using joining techniques that have been used for more than, a half of a century. Many examples where, adhesives are used exist. A prime example, where adhesive joints have been used since, the 1950s is on military aircraft where joints, are subjected to all types of environments as, well as static and dynamic loads, fatigue loads,, weather changes, and so on., Aircraft, Since the 1940s extensive use is made externally and internally of light weight, durable,, and high performance plastic in commercial and military aircraft. Included are unreinforced and reinforced plastics as well as, specialty plastics such as anti-icing coating, (Figs. 4-8 and 4-9). Different RP parts, (wing fairings, floor beams, rudder, elevators, engine cowl, etc.) are used on the Boeing 777 (Fig. 4-10) (Appendix A: PLASTICS, DESIGN TOOLBOX)., , Main lan~ln~tdoor8, Seal deprQSSO ')<eel ~m, , talrlng '8ljotfr~bul$t panel$, , G Graphite, Keviaf, F- F\bofglass, , k, , Fig.4-8 Extensive use is made of TP and TS plastics on the Boeing 767.

Page 275 : 4 Designing Plastic Product, During 1944 at U.S. Air Force, WrightPatterson AFB, Dayton, OH the first successful all plastic airplane (primary and, secondary structures) was designed, fabricated, and flight tested (Fig. 4-11). It used, , 257, , glass fiber-TS polyester hand lay-up RP that, included the use of the lost-wax process sandwich constructions for the monocoque fuselage, wings, vertical stabilizer, etc. (Chapter 8,, REINFORCED PLASTIC)., , (a), , (b), , Fig. 4-11 (a) BT-15 in flight, (b) sandwich wing section using RP skins and cellular cellulose acetate, foam, and (c) section of the monocoque fuselage, and (d) example of a design flexibility in RP construction.

Page 276 : 258, , 4 Designing Plastic Product, , (c), , • Modulus. strength, and thickness can be varied, through design and material choices, , (d), , Fig.4-11, , Over the years innovations in aircraft have, given rise to more new plastic developments, and have kept the plastics industry profits at, a higher level than any other major market, principally since they can meet different environmental and load conditions. Virtually all, plastics have received the benefit of the aircraft industry's uplifting influence. Practically, all conceivable top quality plastics are used to, provide cost advantages and improvements, , (Continued), , on flight system performance. At least 5%, of commercial plane's weight is plastics. This, percentage is expected to double or perhaps, triple in the future. Military aircraft include, those with up to at least 50 wt% of primary, and secondary structures., The chief challenge to the plastics industry is not in pounds of plastics needed, but rather in the translation of plastic development technology into production line

Page 277 : 4 Designing Plastic Product, know-how. The aircraft industry is geared to, pay high prices for plastics with exceptional, properties; as high as hundreds of dollars per, pound with up to ten-fold cost increases for, fabricated products plus additional dollars to, conduct continual testing and evaluation to, insure safety of aircraft operation., Medical Product, , Plastics continue to make inroads regarding medical applications. Certain plastics, have been found to exist in the environment, of living tissues. In addition to being of direct aid in medicine, they are also important, in medical devices and packaging medical, items., In effect doctors are designers. They are, constantly helping design, test and evolve, new materials and equipment to augment, new and proposed methods of treatment and, surgery. Their long, intensive training as basic, scientists uniquely suits them to the designer, capacity., , Bioplastic, New plastic applications and plastics are, continually in use to help in the field of, medicine (also biological systems, etc.). They, include both mechanical and chemical applications and show the makeup of the field, that could be called bioplastics (186). The, heart valve that is often used in surgery to, correct heart deficiencies was a spectacular contribution to medicine. In order for, it to be successful it required first, ingenuity in designing a product that would function as a replacement for the mitral valve, and to perform as well as the one replaced, long enough to justify the risk involved in, the operation. Second, it also required using a material that would function in the, highly complex environment of the human, circulatory system without being degraded, and without causing harm to the circulatory, system., The use of special elastomer plastics, (polyurethanes, silicones, etc.) designed ex-, , 259, , pressly for the purpose and tested for years, to determine possible adverse in-vivo effects, combined with good design resulted in a mechanical device that has been a major lifesaver (29). The role of the plastic designer in, an area such as this is one of knowing material limitations, processing problems and of, devising test procedures to monitor the performance of the product in the patient as well, as in continuous laboratory testing., Other surgical implants are essentially, plastic repair products for worn out parts of, the body. It is possible to conceive of major replacements of an entire organ such as, a kidney or a heart by combining the plastic skills with tissue regeneration efforts that, may extend life. This is used to time the heart, action. Extensively used are plastic corrugated, fiber (silicone or TP polyester) braided, aortas (24)., While it would be difficult to enumerate all, of the efforts in the area of implants where, plastics are involved, some of the significant ones are: (1) the implanted pacemaker,, (2) the surgical prosthesis devices to replace, lost limbs, (3) the use of plastic tubing to, support damaged blood vessels, and (4) the, work with the portable artificial kidney. The, kidney application illustrates an area where, more than the mechanical characteristics of, the plastics are used. The kidney machine, consists of large areas of a semi-permeable, membrane, a cellulosic material in some machines, where the kidney toxins are removed, from the body fluids by dialysis based on the, semi-permeable characteristics of the plastic, membrane. A number of other plastics are, continually under study for use in this area,, but the basic unit is a device to circulate the, body fluid through the dialysis device to separate toxic substances from the blood. The, mechanical aspects of the problem are minor, but do involve supports for the large amount, of membrane required., , Bioscience, There are two major areas of application for plastics in bioscience. The plastics, make interesting materials to be used for

Page 278 : 4 Designing Plastic Product, , 260, , mechanical implants into all living systems,, including animals and plants where they can, serve as repair parts or as modifications of, the system. The other applications are based, on the membrane qualities of plastics that, can control such things as the chemical constituents that pass from one part of a system, to another, the electrical surface potential in, a system, the surface catalytic effect on a system, and in some cases the reaction to specific, influences such as toxins or strong radiation., Chemically active plastics such as the polyelectrolytes have been used to make artificial muscle materials. This is an unusual type, of mechanical power device that creates motion by the lengthening and shortening of, fibers made from a chemically active plastic, by changing the composition of the surrounding liquid medium, either directly or by the, use of electrolytic chemical action. Obviously, this form of mechanical power generation is, no competitor to thermal energy sources, but, it is potentially valuable in detector equipment that would be sensitive to the changing, Table 4-2, , composition of a water stream or other environmental flow situation., By using direct mechanical action from, the artificial muscle, it would be possible, to produce reliable sensing and control devices without electrical and electronic equipment. Another interesting application would, be to drive prosthetic devices where the action would be similar to the muscle reaction in, the body. This unusual type of chemically induced motion should be an interesting one to, explore for the solution of unusual problems, where conventional approaches do not work., Surgical Product, , The most dramatic use of plastics in, medicine can be summarized as being in, surgery (Table 4-2). Advances in surgery, have enhanced the need for providing plastics that can be utilized in replacing or repairing tissues or organs which have been damaged as a result of trauma or disease. The wide, , Example of plastics used in the medical industry, , Acrylics, Cellulose acetate, Formaldehyde-treated, polyvinyl alcohol, sponge, Fluorocarbons, Polyamide, Polycarbonates, Polyester fiber, Polyethylene, Polypropylene, Polystyrene, Polyurethanes, Polyvinyl chloride, Polyvinyl pyrrolidone, Silicones, , in bone replacement, corneas, adhesives, hemostatic agents,, dentures, contact lens, artificial eyeballs., in nerve regeneration, packaging material., in support and growth stimulator for blood vessels out-side and into, heart muscle, hemostatic agent in repair of liver and kidney wounds,, abdominal aortic grafts, vascular shunts, synthetic skin., in artificial cornea, blood vessels, heart valve coatings,, reconstructive surgery, bone substitution., in vascular implants, syringes, clamps, blood transfusion sets., in syringes, parts of heart-lung machine, baby bottles, containers., in aortic and peripheral artery transplants., in tubing, syringes, oxygen tents, repair of incisional hernias, stomach, wall support, repair tissue damage, heart valves, contraceptive, implants., in syringes, sutures, containers., in syringes., in plastic surgery, vascular adhesive, bone adhesive., in surgical tubing, blood collection and administration sets, repair of, congenital and traumatic facial defects, surgical drapes, ballon type, splints, adhesive bandages., in artificial membranes for filtration of body fluids., in heart valves, tubing, catheters, defoamers in blood oxygenators,, urethral valve, plastic surgery, tendon replacement, lubricants,, tissue substitutes.

Page 279 : 4 Designing Plastic Product, range of forms such film or fiber and mechanical properties available in plastics continues, to make them attractive candidates for such, uses. However, even though a plastic may, possess the desired physical properties, there, is no assurance that it may be successfully utilized in the body. Tissue compatibility is a sine, qua non for the long-term utilization of a surgical repair material., The answers to all questions are not known, with certainty, and research toward the solution of such problems will require the, combined efforts of the plastic chemist and, designer with the physician. It is through the, efforts of such multidiscipline groups that surgical repair materials of outstanding longterm utility are produced, studied, evaluated,, and made available to the patient., Plastic implants provide a forum for the, cross-fertilization of such prepared minds., There is the utilization in tissues of the, postenucleation moveable implant and plastic artificial cornea. Use is made of such, plastics as PMMAs, silicones, PTFEs, and, hydrophilic polymers. This action is related to the implantation of plastic artificial, corneas, retinal detachment surgery, glaucoma drainage tubes, repair of bony defects,, replacing the vitreous of the eye, and substitution for the eye's crystalline lens. The concept, of the incompletely covered foreign body was, evolved in connection with the plastic artificial cornea and postenucleation implant. In, each case, the plastic (or metal) is exposed to, the exterior environment and epithelial cells, do not heal like epithelial cells. The semiexposed implant has been maintained without extrusion for many years. Each of these, applications requires plastics with varying, properties., , Complex Environment, It is important to recognize that human, bodies have extremely complex environments. They could be identified as having the, most horrible environmental situation. Reason for this situation is due to the fact that, the many different human bodies have differ-, , 261, , ent environmental requirements. Thus what, can survive in one body usually does not survive in other bodies. This type of reaction requires extensive "prototyping" to ensure that, a medical product can survive and meet its requirements in all human bodies., , Dental Product, Most of over six million dentures produced, annually in the USA are made of acrylics, (PMMAs) that includes full dentures, partial, dentures, teeth, denture reliners, fillings and, miscellaneous uses. Plastics have been edging, into the dental market for over a half century., Even before the introduction of acrylics to, the dental profession in 1937, nitrocellulose,, phenol-formaldehyde and vinyl plastics were, used as denture base materials. Results, however, were not wholly satisfactory because, these plastics did not have the proper requisites of dental plastics. Since then, PMMAs, have kept their lead as the most useful dental plastics, although many new plastics have, appeared and are still being tested. Predominance of PMMAs is not surprising, for they, are reasonably strong, have exceptional optical properties, low water absorption and solubility, and excellent dimensional stability., Most denture base materials, therefore, contain PMMA as the main ingredient., Plastics have not progressed very far as, filling materials. About 2 wt% of all fillings, are plastics. The low mechanical properties of, plastics in comparison with metals limit their, application to front teeth where stresses are, not so great. It is interesting to note development efforts has taken place in the use of, whiskers for reinforcing dental plastic, metal,, and ceramic fillings. Some preliminary test results on the addition of randomly distributed, chopped, short whiskers to a coating plastic have reversed the previous proportional, less of strength with powder additions. Although this is far from theoretical, it is already quite significant in that it allows the, addition of pigment for coloring purposes, and a restoration of the loss of strength with, whisker additions.

Page 280 : 262, , 4 Designing Plastic Product, , Medical Packaging, Plastics are extensively used in medicine, to package drugs, ointments, and accessories., Plastics serve to protect medicines, surgical!, clinical equipment, medical materials, etc., from contamination and breakage in many, ways, from single-service squeeze packs of, cough syrup to carrying cases used to ship, human eyes between hospital eye banks., The sophistication of TP processing methods that includes sterilization procedures, has, allowed the development of low cost, disposable packages for single-doses of medication,, eliminating need for sterilization, etc. Rigid, blister packs hold capsules and pills in easily, dispensed single servings; semi-rigid and flexible squeeze packs hold single applications, of medicines and ointments, etc. Availability, of medicines in premeasured single-dose disposable units pleases doctors who previously, could only hope that out-patients would dose, themselves properly when not supervised., Biological and Microbial Degradation, , Certain plastics such as TP polyesters,, polyurethanes, cellulosics, and plasticized, PVC can be degraded by microorganisms. It, has been observed that enzymes attack noncrystalline regions preferentially. As a result,, it has been determined that the resistance of, susceptible plastics to microbial degradation, is related directly to the degree of crystallinity, of these plastics. They remain relatively immune to attack as long as their molecular, weight remains high. Most of these plastics, are characteristically durable and inert in the, presence of microbes., This stability is important to plastics' longterm performance. However, for some applications only short-term performance is desired before the product is discarded, as in, the fast-food and packaging markets. In such, cases it is considered advantageous for discarded plastic to degrade when exposed to, microbes. There thus exists a requirement, to develop or modify plastics possessing the, properties required for their service life, but, with the capability of degrading in a timely, , and safe manner, particularly to handle the, worldwide waste situation., The amount of degradation of plastics under the action of bacteria and fungi is of interest because of land-shortage problems in, solid-waste management and litter accumulation and other environmental problems on, land and sea. The agricultural use of plastics in mulch, films, seeding pots, and binding twines has increased significantly, making, biodegradation a desirable feature in plastics, to minimize disposal and soil-pollution, problems. With plastics designed to include, de grad ability, the designer could have a monumental problem in ensuring that degradation will occur only after a product's useful, life is over., , Other Form of Degradation, Basically degradation is a deleterious, change in characteristics such as the chemical, structure, physical and mechanical properties, and/or appearance of plastic. A degraded, appearance usually means discoloration., Degradation can occur during heat processing. Factors that determine the rate of degradation are: (1) residence time, (2) stock, (melt) temperature and distribution of stock, temperature, (3) deformation rate and deformation rate distribution, (4) presence of, oxygen or other degradation-promoting additive, and (5) presence of antioxidants and, other stabilizers., The deterioration of plastics by biological, agents should be distinguished from other, forms of plastic degradation. Many other, types of plastic degradation may be classified, clearly as chemical in nature. In them a deteriorative agent causes a chemical degradative reaction to occur. Chemical bonds are, broken or new ones established. Different, molecular species of a molecular size smaller, or larger than the original desirable species, are formed, and these species no longer, have the properties for which the original, plastic was chosen. Other forms of degradation include landfill, overheating, photochemistry, photodegradable, photooxidation, radiation induced reaction; ultrasonic

Page 281 : 4 Designing Plastic Product, degradation, fusion, zymoplastic degradation, (substance which, not themselves enzymes,, are believed to participate in the formation, of enzymes), etc., This generalization is also true for the, degradation caused by heat, electromagnetic radiation, oxygen and ozone, and highenergy nuclear radiation. It is also true for, the chemical degradation caused by acids,, bases, or other strongly reactive chemical, agents. The reaction types include oxidation,, ozonization, radical formation, cross-linking,, chain scission, and others. The symptoms are, described as hardening, embrittlement, softening, cracking, crazing, discoloration, or alteration of specialized properties such as dielectric strength., The situation with some forms of biological, deterioration is somewhat different. Where, the agent is macro biological, as in the case, of rodents, insects, and marine borers, the attack is physical in nature, such as by gnawing, or boring. The attack is not at the atomic or, molecular level. Any breaking of molecular, bonds such as in polymer chain shortening, is thus accidental. The attack may be said to, be at the material's structural level, not the, polymer molecule level., An important item to note is that most, commercially used plastics are not single, component pure substances. Practically always, the basic polymer itself, rarely if ever, a single molecular species, is compounded, with other components such as plasticizers,, pigments, antioxidants, and other additives., More often than not, then, biological susceptibility is due to the nonpolymer component., Plastics' deterioration can be classified as, either by a microorganism, a macroorganism, or a marine organism (both micro and, macro). In the case of microbiological agents,, as in fungal and bacterial deterioration, the, plastic alterations are caused by chemical attack. This has been demonstrated for the attack on the natural polymer cellulose by fungi, through the cellulose enzymes, for many, esters, and for many hydrocarbons. It is not, yet so clearly proven for the many synthetic, polymers, but there is sufficient evidence that, may be ascribed to enzyme action as being probably the chief mechanism. Thus, al-, , 263, , though the medium of attack is biological, the, destructive agents are chemical., Fungal and bacterial deterioration are, identified as microbiological and have always, caused problems to materials. Fungal attack, on plastics has received a great deal of attention beginning with the early days of World, War II, when the tropical theaters served to, focus attention on the overall problem of materials deterioration., Microbial deterioration of plastics is intimately involved with the moisture problem,, especially with regard to plastics in electronic, equipment. For this reason much of the literature treats the two problems together. Furthermore, there is often confusion between, the deterioration of the electrical properties, of plastics, more often than not a moisture, phenomenon, and actual deterioration of the, substance of the polymer., Most investigators agree that in the electronics field moisture accounts for the greater, effect. Often, if the moisture problem is, solved the fungal aspect is also overcome because of the dependence of organisms on water. Yet not all of this twin problem may be, ascribed to moisture, for there are instances, where microorganisms are able to destroy the, substance of a polymer or attack the nonpolymer constituents of a plastic formulation. Furthermore, as one shifts attention from plastics, in electronic equipment to other items where, plastics are used, there are clear-cut cases of, destruction by fungi. Examples may be found, in films, fibers, and coatings., Dynamic Load Isolator, , Thermoplastic elastomer (TPE) components are frequently subjected successfully, to dynamic loads where energy and motion, controls are required. The products involved, range from sporting goods to home appliances to automobiles to buildings to bridges, to boats to aircraft to spacecraft. The uses, of bonded elastomers for energy and motion control in construction, vehicles, instruments, etc. are extensively used (Chapter 2,, THERMAL EXPANSION AND CONTRACTION, Energy and Motion Control).

Page 282 : 4 Designing Plastic Product, , 264, , Cover Elastomer, , F, I, , Maximum Lateral, Reaction Force, , I, I, , I, I, , I, I, I, , 1--I, , ,,,, , Steel Reinforcing Plates, , - t l - - - Energy Absorbed, I, , Internal Elastomers Layers, , Fig.4·12(a), isolator., , Lateral Deflection, , I, , Energy and motion control building, , L....l.'---._.o, Fig.4·12(b) Typical load deflection that is characteristic of a marine structure., , An example of this type of energy and mo·, tion control device is shown in Fig. 4-12(a)., It shows a section through a high-load elastomeric building isolator where the elastomer, layers are used to ensure horizontal flexibility. Steel reinforcing plates give rigidity, for vertical loads. This isolator resists wind, loads elastically without perceptible movement, yields under earthquake loads, and deforms plastically dampening side-to-side vibrations (14, 55)., Anyone in a building, on the highway, on, a rapid transit vehicle, or on a ship has a, bonded elastomer working for them. In a, building, it controls vibration and noise from, motors and engines. For rapid transit it supports the rail and the vehicle, thus reducing noise and vibration to adjacent buildings., For ships, bonded elastomers absorb their, berthing energies, with single units being as, large as 3 m (10ft.) high and weighing 19 tons., For all these applications, elastomers are used, either in shear, compression, tension, torsion,, buckling, or a combination of two or more, uses, depending on the needs of the specific, application (Chapters 6 and 7)., Consider, for example, a berthing vessel, that is a structure that has to be designed to, withstand the energy developed by the vessel. The more rigid the system, the higher the, reactive forces must be to absorb the vessel's, kinetic energy. The area under the structure's, load as against its deflection response curve, (that is, of the energy absorbed) is typical to, that shown in Fig. 4-12(b)., , For economic reasons, designers typically, reduce the mass of a structure, but doing, so reduces the lateral reaction forces that, the structure can withstand. This happens as, the structure is allowed to deflect more or, an energy-absorbing device is applied. An, elastomer is ideal in such an environment, because it will not corrode. Metal components can thus be totally encapsulated and, protected against corrosion in an elastomer, and then bonded to all-metal surfaces. The, elastomer can be used in conditions of shear,, compression, or buckling. In examining the, load deflection characteristics of these three, systems, note that the one that results in the, lowest reaction force generally also produces, the lowest-cost structure. Figures 4-12(c) to, 4-12( e) shows six results that could be obtained, compared to an ideal hydraulic system with 100% energy efficiency., Filter, , Water, One of the major problems facing our civilization is the availability of pure water. The, largest source of water located near many, cities is the ocean, but the ocean is filled with, large amounts of dissolved salts. To recover, water from the sea by any of the conventional, distillation processes is to date extremely, wasteful of energy and costly. However in

Page 283 : 265, , 4 Designing Plastic Product, F, , I, I, I, , F, , 1, cl, , .gl, , Force, , F, , F, , Energy, , Same, Energy, , ' - - - - - - - - t - l - li, , ~I, "I, EI, , Energy, , ti1l1, , 100% Higher Force, , F, , I iii, , gt, , Same, Energy, , 0,~I"'I, , 1°, I'", I ~, IUl, , ,, , Ii, , Ii, , I, , L - - - - - - / - - - l _ li, , I~, , I, cl, , 1;l1, , :;:::1, , c, , Ig, , Force, , 20% Higher Force, , F, Same Force, , Same Energy, , L - - - - - - - -.......___ Ii, ~------------+~o, , 100% Higher Dellection, , Fig. 4-12(c) Elastomeric shear energy capacity, as compared to a 100% efficient curve., , areas such as the Middle East where fresh water is very scarce, ocean salt water has been, filtered by different techniques for many, decades., Plastic membranes are being used in systems that could well pave the way to large-, , F, , 25% High Deflection, , Fig.4-12(e) Elastomeric buckling energy capacity as compared to a 100% efficient curve., , scale water recovery from the sea. The, process is reverse osmosis. When water is separated from a concentrated solution of a salt, by a semi-permeable membrane, there is a, pressure that drives the pure water into the, solution for dilution. The driving force is the, concentration gradient and it is in the form of, a pressure that is related to the difference in, the vapor pressure of the water and the vapor, pressure of the solution at the temperature at, which the process takes place. By applying a, pressure greater than the osmotic pressure to, a solution, the direction of flow of the water, is reversed and pure water is removed from, the solution., , F, , Force, , cl, , Energy, , :81, , 1;l1, , :;:::1, ~I, , '------...l.....J-li, , " ' - - - - -........- li, 350% Higher Load, , F, , Same Force, , 300% Higher Dellection, , Fig.4-12(d) Elastomeric compression energy capacity as compared to a 100% efficient curve., , Plastic membrane This is done by the use, of a water permeable plastic membrane held, deep enough under the sea so that the hydrostatic pressure is greater than the osmotic, pressure of the seawater. The water distills, out of the solution through the membrane, and is pumped to the surface. Large areas of, the membranes, mechanically supported to, withstand the very high pressures are essential to make the process perform rapidly for, the most economical production., Cellulosic plastics are usually used for, the membrane, but any water vapor permeable material is a good possibility, provided, the film has good mechanical properties.

Page 284 : 266, , 4 Designing Plastic Product, , Designing the membrane structure for a reverse osmosis plant is a difficult project, particularly in view of the fact that in addition to, the pressure exposure, the presence of strong, concentrations of dissolved minerals is a hostile environment for plastics., There have been several very ingenious designs for membrane structures using naturally, strong shapes such as arches and tubes reduced to a scale where the amount of surface area for diffusion per unit volume is very, high. Other innovations in design and fabrication of these large area membrane structures could easily lead to a significant breakthrough in the availability of an unlimited, supply of pure water., Plastics have had a long history of use in, water problems using a special type of plastic material. Ion exchange plastics have been, used for many years to remove dissolved materials from water and to make high purity, water. The quality of ion exchange treated, water is probably better than water purified, by any other means. The ion exchange plastics, are polyelectrolytes. These plastics are polymers that contain either acid or alkaline side, groups capable of reacting with dissolved ions, in the water. A standard system used is an, acid substituent that forms an insoluble salt, with ions such as calcium and strontium and, removes them from the water and replaces, the mineral ion with hydrogen. The ion exchange plastics can be regenerated by passing another solution through the bed such as, a mild mineral acid which removes the attached ions and replaces them with hydrogen, again so that the resin can be reused., , Gas, Plastics have a unique contribution to, make in exploring new environments. Their, applications in space vehicles are well known, and are generally of a mechanical nature., Plastics are used extensively in equipment for, exploring under the sea. One unique application for plastics used in the sea environment, and which is important in other areas that, range from packaging to space is in filtering, , gases. This specific application involves the, use of membranes made from special plastics, such as silicone compounds that permit dissolved oxygen in seawater to permeate the, membrane in one direction and to allow carbon dioxide and carbon monoxide to pass, through in the opposite direction., A large membrane pack of this type will act, like an artificial gill, permitting a swimmer to, breathe like a fish and remain submerged for, much longer periods of time than are possible with scuba equipment. Speculative fiction has man returning to live in the seas, and, this type of application may make it possible., Their application in spacecraft is obvious as, a part of a continuously recycled air support, system. The oxygen permeability of silicone, materials is just one example of the selective, permeability of plastics., Liner, , Plastics provide different performance requirement in providing protective liners in, many different applications such as building foundations, pipe and tank liners containing corrosive liquids, etc. As an example, Fig. 4-13 shows an RP stack liner being inspected prior to installation in a 682 ft. high, reinforced concrete chimney (background), of the 1,500-megawatt Intermountain Power, Project near Delta, Utah (1985)., The liner, of PPG glass fiber, protects the, concrete shell from the corrosive gases that, occur when sulfur dioxide is produced during coal-fired power generation. Fiber glassTS polyester RPs provided years of service, under these operating conditions. Such liners have been used in this type of application since at least the 1970s. They rapidly became a viable construction material against, steel and brick liners. The liners in this Utah, project are in canlike sections 45 ft. long and, 28 ft. in diameter. The sections were filament wound using 46 to 50 wt% TS polyesterimpregnated fiber glass rovings. The completed liner contained about 100 thousand, miles, or 11 million pounds of fiber glass roving strands.

Page 285 : 4 Designing Plastic Product, , Fig. 4·13, , 267, , RP stack liner., , Paper and Plastic, , One of the problems that face our civiliza·, tion is the fact that the pressure on natural, resources is reported to be hindering progress. Periodically an energy crisis exists that, has led to a so-called materials crisis in plastics and even other materials such as cellulose papers. Petroleum is currently the major, source of raw materials for most high volume, plastics., Oil and substitute resources such as coal, are supposedly in limited supply (although, our government reports we have enough coal, for the next 250 years that includes its growth, in use during that period), and it may well, be that another approach to the problem is, required. An example is different raw mate-, , rial sources to produce plastics that involve, biotechnology (186), more vegetation, etc., Ingenuity in the applications of materials, the, province of the designer, and the use of materials that seem to be uniquely modifiable,, such as plastics, are needed. Thus the plastics, material suppliers are developing renewable, resources for the plastics., We can take as an example worldwide papermaking that now consumes forests at a, rate that is supposedly difficult to replace., Unlike the uses for wood, which are generally, long-term use goods, most wood pulp paper, is used for newspapers, business world, and, periodicals or publications that are read and, usually discarded, loading our solid waste disposal system and adding mountains to our, trash.

Page 286 : 268, , 4 Designing Plastic Product, , Save the Tree Myth, Plastic papers have been developed as substitutes for these cellulose papers, but the economics are poor since the plastics are more, costly. Also plastics weigh tend to be more, than the cellulose paper. So it is possible to, save the forests (does it really need it since it is, easy to replenish as the past century proved)., Did you know when America was discovered and up until the end of the 19th century there were literally no trees when compared to those in USA now and any depletion, can be replaced and even expanded (as one, knows who is learned in this field). Another, factor related to this tree myth is that when, the world started its Computerized World it, was said by many that much less paper would, be required. Of course much more is used and, required., Synthetic paper now targets high-priced, specialty applications that include beverage, labels, restaurant menus, drivers' licenses,, recipe books, instruction manuals, maps, and, book jackets., The justification to go to a higher cost paper material would be part of a system where, the paper is continuously reused. By using, a material which has erasable printing generated by the remote printing terminal, the, newspaper or periodical could be printed at, its destination., Plastics can be used to make erasable printing media by a number of different techniques. Photo changing dyes could be incorporated into the structure of the plastics., The printer could change the dye to the colored form to read, and the material can be, bleached with another unit that would reverse the photo coloring process. An ionic, type plastic can be incorporated into the plastics and used to color the printed area by the, use of an indicator type reaction with an organic acid or base. Another method would, be to use a thermal printer in conjunction, with liquid crystal type materials that would, alter the state of the liquid crystals in the, printed areas. Applying heat and electrical, fields to the printed sheet would erase the, printing., , Other schemes involving dichroic dyes, with heat and electrical fields are also possible. Each of the possibilities could use the, plastic structure of the substrates, its durability, or both. This approach would recycle the, material for carrying the printed messages at, the point of use, eliminating handling and distribution costs, and would require a fraction, of the enormous amount of paper now consumed in delivering news and other literary, material. The newspaper or periodical would, have the familiar size and appearance and, would present little change to the reader. The, convenience of real on time home delivery, and other built in aspects of the system would, make it a useful successor to the present one., (This is just a point to discuss and amuse oneself but it could happen.), Union Carbide Corp produced the first of, the synthetic papers in the late 1960s. Since, that time other examples of synthetic papers include DuPont's Tyvek nonwoven paper and Van Leer's Valeron cross-laminated, film. This market is now dominated by a few, large, worldwide ventures with proprietary, processing techniques that extend the use of, single and multilayer extruded blown film or, cast film., Developing Idea, , Polyelectrolytes such as the ion exchange, plastics form an interesting group of materials because of their ability to interact with water solutions. They have been used in medical, applications involving the removal of heavy, metal ions from the human body. They can be, used to interact with external electric fields, and change their physical properties drastically as is illustrated by the fact that some, electrically active liquid crystals are polyelectrolytes of low molecular weight., Another application for polyelectrolyte, materials is in the forming plastics with unusual physical properties with regard to adhesion. The incorporation of small amounts of, organic acid materials into poly olefin structures results in materials that have excellent, adhesion to metals, paper, glass, and a variety

Page 287 : 4 Designing Plastic Product, of other materials. In addition, the materials, with electrolytic structures can have a metal, ion incorporated into the structure resulting, in the formation of the ionomer type of resin, that has much better mechanical properties, than the basic polymer material., Several other interesting material developments that may be useful to the designer in, the future will be mentioned. Since one key, step in any design is the material selection, an, important aspect of the designer's responsibility is to be familiar with the range of material possibilities. Plastics interact with high, energy radiation by giving bursts of visible, light. This can be made selective for particular types of radiation and the effect has been, used to make materials for scintillation counters to measure gamma radiation and particle streams such as alpha particles and beta, rays., The ability of some plastic systems to do, this may be useful in schemes for handling the, radiation output of nuclear devices, including, the radiation from the fusion power machines, under development. Obviously the application is not for shielding, which the heavy metals do much better, but rather for an energy, level reduction system that would convert the, high energy radiation to forms which would, be more useful in power distribution., There has been a great deal of interesting, work done recently in attaching active enzyme materials to plastics substrates to convert simple organic molecules into the more, complex forms used in biological processes., This technique makes available a catalyst bed, capable of doing large-scale synthesis of materials such as proteins and carbohydrates, that are essential to life processes. With a major food crisis always looming as a result of the, rapidly increasing population of the world,, it may be necessary to revive the possibility of synthetic food production even though, this subject is very controversial. Since farm, land is being depleted and recurring drought, conditions reduce food supplies, it is likely, that synthetic food will be a necessary, supplement. The selective action of enzyme, membranes may be a way to approach the, food synthesis problem., , 269, , Joining and Assembling, Joining of a plastic product to another, product composed of the same or a different plastic material, as well as other materials such as metal, is often necessary when:, (1) the finished assembly is too complex or, large to fabricate in one piece or (2) disassembly and re-assembly is necessary., The success of a specific technique will, depend on whether, as a by-product of the, technique, sizable stress levels in the plastic product may result. Guarding against, potential stresses in the assembly is a very, important aspect of complete product design., There are many techniques that provide assembling all kinds of products. Each have, technical and/or cost advantages and limitations. Examples of a few are reviewed in, this section with more information in Chapter 3, BASIC FEATURE and FEATURE, INFLUENCING PERFORMANCE., , Molded-In Insert, Plastics perform satisfactorily with metalmolded inserts and expansion-type inserts. To, minimize the stresses created at the metalplastic interface by the differences in thermal expansion rates for molded-in inserts, observe the following safeguards: (1) the design, permitting, use plain, smooth inserts; (2) use, simple pull-out and torque-retention grooves, when high torque and pull-out retention are, required; (3) if a knurled insert is used, keep, the size of the knurls to a minimum, remove, all sharp comers, and round the hidden end of, the insert and keep the knurled section away, from products' edges (Fig. 4-14), (4) keep the, inserts clean, removing chemicals such as oil, from them; (5) use high side of mold temperatures to reduce thermal stresses, such as, for commodity plastics at 82 to 105°C (180, to 220°F); and (6) provide sufficient material, around the insert., Use the following guidelines for material, thicknesses around inserts: with aluminum, use 0.8 times the outer radius of the insert, with brass use 0.9 times it, and in steel

Page 288 : 270, , 4 Designing Plastic Product, , Fig. 4·14 Example of an insert with special features., , use a thickness equal to the outer radius., To ensure a proper interface, prototyping, is recommended (Chapter 3, FEATURE, INFLUENCING PERFORMANCES, Injection Molding, Molded-in insert)., When metal inserts require hermetic sealing, consider coating them with a flexible elastomer such as an RTV rubber, polyurethane,, or epoxy system. A second method is to design an annular space or reservoir at one end, of the insert from which to dispense the flexible elastomers to effectively create a hermetic seal. Flexible sealants are also used, to compensate for differences in the thermal, coefficient of expansion between metal and, plastic., , Holding with Formed Head, A holding head is similar to the head, formed during riveting except that in the plastic product there is a protruding stud that fits, through a hole in the product to be joined and, the head is shaped over it. It is an economical method of joining. Spinning or ultrasonic, forming can shape the head., The spinning operation consists of highspeed rotating and suitably shaped tool that, creates frictional heat that will permit the, stud to conform to the configuration in, the tool. Pressure exerted on the tool and, , the time of rotation are accurately controlled., The spinning device can produce joints, at, high speed, of good quality., Ultrasonic head forming and welding is a, fast assembly technique. It is a very rapid operation of about 2 seconds or less and lends, itself to full automation. In this process highfrequency vibrations and pressure are applied to the products to be joined, heat is generated at the plastic causing it to flow, and,, when the vibrations cease, the melt solidifies. The heart of the ultrasonic system is the, horn, which is made of a metal that can be, carefully tuned to the frequency of the system. The manufacture of the horn and its, shape is normally developed by the manufacturer of the equipment. The results from, this operation are not only economical, but, also most satisfactory from a quality control, standpoint., , Snap Fit, Snap fits are widely used for both temporary and permanent assemblies, principally in, injection and blow molded products. Besides, being simple and inexpensive, snap fits have, superior qualities. Snap fits can be applied to, any combination of materials, such as plastic, and plastic, metal and plastics, glass and plastics, and others. All types of plastics can be, used (Chapter 3, DESIGN CONCEPT, Snap, Joint)., The strength of a snap fit comes from its, mechanical interlocking, as well as from friction. Pullout strength in a snap fit can be made, hundreds of times larger than its snap in force., In the assembly process, a snap fit undergoes, an energy exchange, with a clicking sound., Once assembled, the components in a snap fit, are not under load, unlike the press fit, where, the component is constantly under the stress, resulting from the assembly process. Therefore, stress relaxation and creep over a long, period may cause a press fit to fail, but the, strength of a snap fit will not decrease with, time (84)., When used as demountable assemblies,, snap fits can compete very well with screw, joints. The loss of friction under vibration can

Page 289 : 4 Designing Plastic Product, loosen bolts and screws. A snap fit is vibration, proof, however, because its assembled products are in a low state of potential energy., There are also fewer parts in a snap fit that, means a saving in component and inventory, costs., Successfully designing snap fits depends on, observing a set of rules governing the shape,, dimensions, materials, and interaction of the, mating parts. The interference in a snap fit is, the total deflection in the two mating members during the assembly process. Too much, interference will create difficulty in assembly,, but too little will cause low pullout strength., A snap fit can also fail from permanent deformation or the breakage of its spring components. A drastic change in the amount of, friction, created by abrasion or oil contamination, may ruin the snap., A snap can be characterized by the geometry of its spring component. The most common snaps are the cantilever type, the hollowcylinder type (as in the lids of pill bottles) and, the distortion type (Fig. 4-15). These snaps, include those in any shape that is deformed, or deflected to pass over interference. The, shapes of the mating parts in a hollow cylinder snap is the same, but the shapes of the, mating parts in a distortion snap are different,, by definition. These classifications are rather, nominal, because the cantilever category is, used loosely to include any leaf-spring components, and the cylinder type is used also to, include non circular section tubes., For high-volume production, snap fit designs provide economic, rapid assembly. In, , Straight u.ss·secti.n, , Sire» conce~rolion -........, , Toper diuribvtei t.tr8u, , Tapered uoss-sedion, , Fig.4-15 Example of cantilever beam stresses in, a snap fit., , 271, , many products, such as inexpensive housewares or hand-held appliances, they are designed for one assembly only, with no nondestructive means for disassembling them., Where servicing them is anticipated, provision is made for the release of the assembly with a tool. Other designs, such as those, used in the battery compartment covers for, calculators and radios, are designed for easy, release and reassembly many hundreds of, times., There is always some part of a snap fit, that must flex like a spring, usually past a, designed-in interference, and quickly return,, or at least nearly return to its unflexed position, to create the assembly of two or more, parts. The key to successful design is to, provide sufficient holding power, without, exceeding the elastic limits of the plastic., Fig. 4-16 shows a typical design. Using, the beam equations, calculate the maximum, stress during assembly. If it stays below the, yield point of the plastic, the flexing finger, will return to its original position. However,, for certain designs there will not be enough, holding power, because of the low forces or, small deflections., It has been found that with many plastics, the calculated flexing stress can far exceed, the yield point stress, if the assembly occurs, too rapidly. In other words, the flexing finger, will just momentarily pass through its condition of maximum deflection or strain, and the, material will not respond as if the yield stress, had been greatly exceeded., A common way to evaluate snap fits is to, calculate their strain rather than their stress., Then compare this value with the allowable, dynamic strain limit for the particular plastic. In designing the finger it is important to, avoid having sharp comers or structural discontinuities that can cause stress risers. A tapered finger provides a more uniform stress, distribution, which makes it advisable to use, where possible. Snap fits usually require undercuts, so a mold with a side action can be, used. Another approach when an opening at, the base of the flexing finger is permitted permits no use of a side action (3). There are, times when all that has to be done is just pop it, off the mold, taking advantage of the plastic's

Page 290 : 4 Designing Plastic Product, , 272, , PROPORTIONALITY CONSTANT. K., FOR TAPERED BEAM, , 2.3, 2.2, 2.1, , 2.0, 1.9, 1.8, 1.7, , K, , 1.6, 1.5, 1.4, , 1.3, 1.2, 1.1, , 1.0, 0.3, , 0.4, , 0.5, , 0.6, , 0.7, , 0.8, , 0.9, , 1.0, , TAPERED BEAM, STRAIGHT BEAM, , -~, , .1, , T, , Y (MAX DEFLECTION), , h., , DYNAMIC STRAIN, £, , = ..3yh., 2L2, , r, , Y (MAX DEFLECTION), , h,, , h., , DYNAMIC STRAIN, !., , _ 3yho, , -, , --_._._-, , 2L2K, , Fig.4-16 Basic snap fit design for a cantilever beam with a rectangular cross-section., , flexibility. Another type of system is the snap, on or snap-in kind, used primarily in round, products., A snap fit can be rectangular or of a geometrically more complex cross-section. The, design approach for the finger is that either its, thickness or width tapers from the root to the, , hook. Thus, the load- bearing cross-section at, any location relates more to the local load., The result is that the maximum strain on the, plastic can be reduced and less material will, be needed (Table 4-3). With this design approach, the vulnerable cross-section is always, at the root (100).

Page 291 : 4 Designing Plastic Product, Table 4-3, , Examples of different cross section types of snap fit designs, , ~•, , B, , A, , Ty p e of d esign, 't', , I~, , Y, , "", , 2, , 0;, , ~ty, All dimensions In, , :is, , direction y, e. g. h or, Ar, decrease to, one·half., , 'iii, , ·s, ..'", , .., , ~, , 3, , ~!, b, , ",,'E, , decrease to one-quorter, , c, , "1S, , ~, , 0, c" ..., , Q, , b, , T ra p ezoid, , 0.67, , {·t·, 11, , 1.09, , 11 Y~ 1.64 2;~~', , - rb,S", a+, , Y, , ~C,, h, r', , c,, , b -, , Irregul a r, CrOSs section, , R ing segment, , £.)2, , 11, , Y, , Cl, , (., , r,, , r., , - C .. ~, , 1, , Y, , =""3', , E·,2, , ~, , Y, , ~, , E .(2, , .-it- y, , = 1. 64 .C,., , .!.:!:.., r2, , y, , z, , 0 .55 .~, , =, , 0.43, , G3,, , Z, , All dimensions on direc·, tlon 2., e. g. b and a,, , 0, , r2 'P, , c,, , over the length, , <J, , .,, , ~, , ~, , h, , c,, , Cross section constant, , 0, , '".,, , <::, , ~, , D, , C,, , Rectang le, , IY, , c, , 273, , Y, , = O. 6, , -, , E· ,2, y, 1 1 Y=1.282;~~·4 y = 1.28,C2. ~, r2, , Z, , bh', p - "'""!r, . J;.!..., 1, , ,, , P, , =, , Welding, It is the joining TP parts by one of several heat-softening processes (2). Not all of, them will be equally suited to a shape, size,, or joining certain different material or even, certain types of the same material. Different, type fixtures or jigs are used during welding, based on the method used. The different techniques are used to make permanent bonds, between materials that can meet different requirements such as shapes, thickness, appearance, bond strength, capability of different, being bonded, hermetic seal, or effect of additives or fillers used in the plastics (2)., Once a process is being used, recognize, that if the compound additives or fillers are, changed or added, bond performance can, change or even not exist. As an example an, unreinforced plastic can be welded to itself;, however with a certain amount of glass fiber, fillers (they do not melt) added to the plastic, action in weld strength can be reduced or, even eliminated., An example of welding is frictional spinning that can be applied to two plastic prod-, , z, , . .!.:.L, C,:II, , .., , h' .a 2 + 4a~ ~ + b2, "'T2, 2a+, .~, 1, , p - Z"'· ~, 1, , P, , = 2, ..., , ~, 1, , ucts with circular joints. It is especially suitable for large parts where ultrasonic welding, may be impractical or equipment cost prohibitive. In this operation the faces to be, joined are pressed together while one part, is rotated and the other is held in a fixed, position. Frictional heat produces a molten, zone that becomes a weld when rotation, stops. When alignment is precise and centering means are incorporated in the parts,, the result is a good joint in terms of strength, and appearance. The approximate parameters are 40 to 50 feet per minute peripheral, speed and 300 to 400 psi pressure., Ultrasonic welding's principle of operation, requires that the design of the joining surfaces meet special requirements. The important feature in ultrasonic welding is the energy director that consists of an initial small, contact area through which the flow of energy is started. Variations of this design can, be adopted readily to larger parts without the, need of resorting to proportionately larger, welding facilities. The cycle times are fast, (less than 2 seconds) and energy consumption is low due to the fact that only a thin layer

Page 292 : 274, , 4 Designing Plastic Product, , of material on both components is softened,, from which a good welding joint is obtained., , Summary, The joining and assembling of plastics is, only limited by the ingenuity and skill of, the designer. The only precaution that has to, be exerted is that no stresses are generated, during the operation. Basically the preferred, method is to have the material softened so, that it can flow and adjust to the new condition. The softening need be only a few mils, thick to have a favorable result. The plastic, does not care as long as the temperature is, within its melt limits. Not all plastic permit, a melting action so they may be difficult to, bond. Some of these plastics require special, surface treatment to obtain a bond., Predicting Pedormance, Avoiding structural failure can depend in, part on the ability to predict performance for, all types of materials (plastics, metals, glass,, and so on). When required designers have developed sophisticated computer methods for, calculating stresses in complex structures using different materials. These computational, methods have replaced the oversimplified, models of materials behavior relied in the, past. The result is early comprehensive analysis of the effects of temperature, loading rate,, environment, and material defects on structural reliability., This information is supported by stressstrain behavior data collected in actual materials evaluations. With computers the finite, element method (FEA) has greatly enhanced, the capability of the structural analyst to calculate displacement, strain, and stress values, in complicated plastic structures subjected, to arbitrary loading conditions (Chapter 2)., FEA techniques have made analyses much, more precise, resulting in better and more optimum designs., Nondestructive testing (NDT) is used to, assess a component or structure during its operational lifetime. Radiography, ultrasonics,, eddy currents, acoustic emissions, and other, , methods are used to detect and monitor flaws, that develop during operation (Chapter 5)., The selection of the evaluation methodes), depends on various factors such as the specific type of plastic, the type of flaw to be, detected, the environment of the evaluation,, the effectiveness of the evaluation method,, the size of the structure, and the economic, consequences of structural failure. Conventional evaluation methods are often adequate for baseline and acceptance inspections. However, there are increasing demands, for more accurate characterization of the size, and shape of defects that may require advanced techniques and procedures and involve the use of several methods., Designing a good product requires a, knowledge of plastics that includes their, advantages and disadvantages (limitations), with some familiarity of the processing methods. Until the designer becomes familiar with, processing, a reliable fabricator Or fabricators) must be taken into the designer's confidence early in the development stage and, consulted frequently during those early days., The fabricator and the mold or die designer, should advise the product designer on plastic materials behavior and how to simplify, the design to permit easier process ability, (Chapter 3, FEATURES INFLUENCING, PERFORMANCE)., There are material and processing limitations that can influence the fabrication, and performances of products. These subjects are reviewed in Chapter 6, MATERIAL, VARIABLE and Chapter 8, EQUIPMENTI, PROCESSING VARIABLE., , Design Verification, DV refers to the series of procedures used, by the product development group to ensure, that a product design output meets its design, input. It focuses primarily on the end of the, product development cycle. It is routinely understood to mean a thorough prototype testing of the final product to ensure that it is, acceptable for shipment to the customers., In the context of design control, however,, DV starts when a product's specification or

Page 293 : 4 Designing Plastic Product, standard has been established and is an ongoing process. The net result of DV is to, conform with a high degree of accuracy that, the final product meets performance requirements and is safe and effective. According, to standards established by ISO-9000, DV, should include at least two of the following, measures: (a) holding and recording design, reviews, (b) undertaking qualification tests, and demonstrations, (c) carrying out alternative calculations, and (d) comparing a new, design with a similar, proven design., Design and Safety, The ultimate requirement of any product, is that it performs the function for which it is, designed. With many materials the design life, of the product is usually not as important as it, is with plastics because of the behaviors such, as creep of plastics (Chapter 2). In all cases, the useful life is an important consideration, whether the item is a pan for the kitchen or a, bridge to handle traffic in a city., The people who use the designed product, expect it to be properly designed to perform, satisfactorily in the intended environment for, the indicated life, without endangering any, person or becoming functionally useless before the end of the predicted life. This, of, course, implies that the user does not abuse, the product and maintains it properly. It, is the responsibility of the designer to provide the user with sufficient information so, that one can intelligently use the product and, properly maintain it. No product can be guaranteed to perform properly if it is abused., The responsibility is always reviewed by, different organizations. This has become a, matter of legal as well as moral responsibility. Improper design or inadequate safety instructions can lead to litigation in civil and, criminal action. It is important for the designer to keep the ultimate user in mind, when one designs a product. One must also, make adequate allowance for human error, and poor judgment to prevent malfunction, and possible hazards to the user or to other, property (such as a car that can be a real life, threatening hazard)., , 275, , Plastic products are used most everywhere, and it would be difficult to describe a typical use situation. One environment familiar, to most people is the home and this environment has enough hazardous elements to, serve as a useful starting point for this discussion. The kitchen is a particularly difficult environment. The list of hazards includes, a surprising range of physical and chemical, environments that make the kitchen a torture chamber for plastics (or other materials) used in this area. lithe stresses that the, plastics encounter in use are included, it is, apparent that kitchen items require careful, designing to resist the environment. For example, an egg beater has plastics gears that, are exposed to chemical attack from food oils,, acetic acid (vinegar), fruit juices, cleaning detergents, etc., Environmental factors for kitchen appliances are many. Examples are as follows:, heat, cold, water, water erosion effects, impact, high humidity at elevated temperature,, chemicals (soaps and detergents, oils, fats,, and greases, fruit juices, phosphates in dishwasher cleaners), fruit acids, caustic bleach,, etc.), biological exposures, fungus garbage,, microorganisms, enzymes, vermin, mechanical loading (static and/or dynamic), and, so on., This type of caution approach is essential, in high risk applications since only certain, plastics can be used as the basis for such applications. This chapter has been concerned, with the problems of the product in use, under the types of environments and potential abuse that may be encountered, and, how the designer can prevent premature, product failure which is one of their major, responsibilities., Determination of the hazard potential and, designing to eliminate the hazard is one element of the solution. The use of carefully designed accelerated and continuous prototype, testing is another element. The instruction, in use and proper maintenance procedure is, the third element. By exercising judgment as, to the appropriate combination of these elements consistent with the economic factors, involved, the designer can have a product that, will perform for its projected design life with

Page 294 : 276, , 4 Designing Plastic Product, , a minimum of hazard to the user and with a, high degree of satisfaction in use., The application area is so large that no, cookbook advice would be useful. Each type, of application must have the potential failure, evaluated, the economics calculated, the degree of assurance of performance set, the extent of required testing determined, and the, product designed and evaluated to meet the, criteria established. There are sources of data, available on which to base the approaches, to the requirements, but the final combination of factors must be determined by the, designer., Product evaluations must be done more, carefully and the testing must be more sophisticated and extensive. A systematic approach, is essential for the evaluation of a plastic, (or any material) and this must be backed up, by a quality control system to insure that the, actual products are made to perform properly. A guide to the steps involved follow:, 1. Material selection to meet the requirements of the application, followed by materials testing to indicate the performance over, the range of operating conditions expected., 2. Construction of test samples that can be, subjected to actual exposure to the end-use, environments which are tested to destruction, to determine the possible modes of failure, and the conditions that cause the failure., 3. Design of the product to meet the anticipated environmental stresses as well as the, functional requirements. The product must, have a designed-in means for reducing the, possibility of failure plus either a fail-safe, mode or an indication of incipient failure that, can be monitored., 4. Extensive testing of the product in simulated service as well as accelerated testing. The testing program should include a, method of evaluating the effects of fabrication procedures on the product performance, and methods to inspect for compliance with, the proper procedures. This may include destructive testing, x-ray inspection, ultrasonic, testing, and a wide range of other rather sophisticated testing procedures., 5. Introduction of the product into limited, service with constant monitoring of its per-, , formance. As the experience factor on the, product performance increases its use can be, extended. The continuing testing of the products under the procedure in step 4 is essential, so that if degradation in the product performance is seen, it will show up in the tests before it becomes a serious problem in the end, use., 6. Continuous monitoring in use over a period of several years to insure continued performance and a replacement program that, will take products out of service after a conservative use-life to preclude possible failure., Risk, , As reviewed designers in the plastics and, other industry have the responsibility to ensure that all products produced will be safe, and not contaminate the environment, etc., Recognize that when you encounter a potential problem, you are guilty until proven innocent (or is it supposed to be the reverse)., So keep the records you need to survive the, legal actions that can develop., There are many risks people are subjected, to in the plant, at home, and elsewhere that, can cause harm, health problems, and/or, death with plastic products representing very, few. Precautions should be taken and enforced based on what is practical, logical, and, useful. However, those involved in laws and, regulations, as well as the public and, particularly the news media should recognize there, is acceptable risk., , Acceptable Risk, This is the concept that has developed, decades ago in connection with toxic substances, food additives, air and water pollution, fire and related environmental concerns,, and so on. It can be defined as a level of risk, at which a seriously adverse result is highly, unlikely to occur but it cannot be proven, whether or not there is 100% safety. In these, cases, it means living with reasonable assurance of safety and acceptable uncertainty., Examples of this concept exists all around, us such as the use of automobiles, aircraft,

Page 295 : 4 Designing Plastic Product, boats, lawnmowers, foods, medical devices, (231), water, air we breathe, news reports, and, so on. Practically all elements around us encompass some level of uncertainty and risk., Otherwise as we know it would not exist., Interesting that about 1995 a young intern, at FDA made some interesting calculations. If, they permitted the packaging of Coca Cola in, acrylic barrier plastic bottles, and if you drank, 37,000 gallons of coke per day for a lifetime,, you would have a 10% risk of getting cancer. Since normal people have a 25% risk of, getting cancer, reducing it by 10% was a real, plus for coke and the acrylic barrier plastic, bottles. So perhaps a law should be enacted, requiring that the public should drink "lots", of coke., People are exposed to many risks. Some, pose a greater threat than others. The following data concerns the probability over a, lifetime of premature death per 100,000 people. In USA 290 hit by a car while being a, pedestrian, 200 tobacco smoke, 75 diagnostic X-ray, 75 bicycling, 16 passengers in a car,, 7 Miami/New Orleans drinking water, 3 lightning, 3 hurricane, and 2 fire., Perfection, The target is to approach perfection in, a zero-risk society. Basically, no product is, without risk; failure to recognize this factor, may put excessive emphasis on achieving an, important goal while drawing precious resources away from product design development and approval. The target or goal should, be to attain a proper balance between risk, and benefit using realistic factors and not the, "public-political panic" approach., Achievable program plans begin with the, recognition that smooth does not mean perfect. Perfection is an unrealistic idea. It is a, fact of life that the further someone is removed from a task, the more they are apt, to expect so called perfection from those, performing it. The expectation of perfection blocks genuine communication between, designers, workers, departments, management, customers, vendors, and laws (lawyers)., Therefore one can define a smoothly run program as one that designs or creates a product, , 277, , that meets requirements (safety, etc.), is delivered on time, falls within the price guidelines, and stays close to budget., Perfection is never reached; there is always, room for improvements as summarized in the, FALLO approach (Fig. 1-3) and throughout, history. As it has been stated, to live is to, change and to reach perfection is to have, changed often (in the right direction)., In addition to the product, the designer,, equipment installer, user, and all others involved in production should all consider, performing a risk assessment and target in, the direction of perfection. The production, is reviewed for hazards created by each, part of the line when operating as well as, when equipment fails to perform or complete its task. This action includes startups, and shutdowns, preventative maintenance,, QC/inspection, repair, etc., PlasticJProcess Interaction, , Material and process interaction and, their effects on the performance of plastic, products are important factors for the designer to understand. It can result in design, limitations such as a selected material meeting performance requirements but not processible by the desired method of fabrication., Most of the limitations that are reviewed in, this book can be corrected and do not effect the product performances when qualified, people handle the limitations. However they, are presented to reduce or eliminate potential problems., When a product is made from a plastic, in, most cases the fabricating process could subject the material to rather severe conditions, such as excess elevated temperatures, high, pressures, high shear rate flow, and/or chemical changes. These interactions can place limitations on the design approach. Recognizing, the limitations or problems that can develop,, the successful design will be a compromise, between the requirements of function, productibility, and cost. Examples of these limitations or problems are presented. Only the, major limitations or problems are presented, even though there are usually exceptions. If, exceptions are important, they are included.

Page 296 : 278, , 4 Designing Plastic Product, , Even though this review pertains to certain, fabricating processes, they can be related to, other processes (1, 3, 6, 8, 9, 11, 50, 62, 64,, 190)., , Molding, Molding can be classified as high or low, pressure processing systems. High pressure, identifies processes such as injection molding, compression molding, and transfer molding. Low pressure identifies reaction injection molding, rotational molding, and form, molding; also identifies processes such as extrusion, thermoforming, blow molding, and, casting. Each process has its advantages and, limitations as reviewed in Chapter 8. Since, more interacting problems exist with the, high pressure systems the following review, highlights this system. Even though these, limitations or problems can be related to, low pressure systems, the low pressure systems are usually much easier to eliminate or, control., , Injection Molding, In high pressure molding, such as injection molding, the walls and other sections, of a TP product represent to the designer, the structures required to make the product functional for its intended use. To the, mold designer and molder they represent, the flow path for the plastics material. This, flow takes place at high rates and under, the (controllable) complicating conditions of, flow in a passage much cooler than the plastic, through a gate (orifice) whose dimensions are severely restricted to reduce the effect on the appearance of the product. With, these complications in mind, it is apparent, that it may not be possible, or it may be, very difficult, to mold certain shapes. Large, area products with thin walls represent one, class of products that can present difficulties, to certain molders, however it is routinely, done in qualified operations (Chapter 8,, INJECTION MOLDING)., , Freezing action Because of the heat exchange between the flowing TP melt and the, mold walls, the flow may freeze (solidify) before the product is completely filled. Products, that have alternate sections with thick and, then thin walls can cause problems in flow, and cooling that make them difficult to fill., In some cases the plastics that have been selected for the end use requirement are too, viscous to flow properly in a mold cavity, and, this makes the manufacture difficult., TS plastic products that are injection,, transfer, or compression molded combine, thick and thin sections relatively easily since, the hardening process is a chemical reaction, (Chapter 6). Annular shapes are best made, by compression to gain best dimensional control and freedom from distortion. In the compression process, the molding compound is, compressed and reduced to the plastic state, in the mold. During this process, portions of, the material may lie in hard forms in the mold, while other portions are flowing rapidly with, great force., Without proper preheating or mechanical, plasticizing of the charge, portions of the, product may be uncured and low in density., Transfer (compression) molding insures better properties under average conditions. Impact materials that include long fibers can, easily be compression or plunger molded., Screw injection will usually break up the, long fibers and produce weaker products thus, short fibers are usually used., Thin to large wall Designing around TP, problems is the joint responsibility of the, product and mold designers. For example,, one way to handle the problem of thin to, large area walls is by the inclusion of long, ribs into the product in the direction of plastic, flow. These ribs are not a functional requirement of the product but they act as auxiliary, runners attached to the product to facilitate, plastic flow in difficult to fill areas. In some, instances the ribs may be used as a surface, decoration like a corrugation or they may, be on the concealed side of the product where, they are stiffeners., Another problem in molding is the existence of contiguous areas of thick and thin

Page 297 : 4 Designing Plastic Product, sections in the flow direction. In some cases, placing the gate in the thinner section can, control this problem. However the usual approach is to gate the thicker section to ensure, the complete fill in both sections. Where there, are several thick sections multiple gates are, used. There could be a limitation on this approach because the weld lines produced by, the joining of the several plastic flows are a, weak point on the molded product., In some cases the use of a section that spans, the thick and thin regions can be used to act as, a built-in runner. This may be across the product or it may be a thickened edge or frame, around the product. Still another approach, would be to redesign the product for a more, uniform wall thickness. The additional wall, thickness required can be supplied on a mating part., Melt flow restriction This preliminary discussion of the flow restriction problem was, concerned with the simple and obvious necessity of filling the mold with plastic. There, are a number of other consequences of restricted flow in molding which are less obvious and, generally, more significant to the, performance of the product. Restricted flow, cause high shear rates in the material as it, fills the mold. This necessitates the use of, higher injection pressures and usually the use, of higher melt temperatures and higher melt, index materials to fill the mold cavity can result in lower product performance., Higher melt index materials generally have, lower impact and lower strength properties., The use of higher temperatures usually results in degradation of the plastic properties. Monomer or other low molecular weight, breakdown products can be produced which, drastically reduce the properties of the plastic, material. The high shear rates encountered, in molding also result in degradation of the, molecular weight of the material just from, the shearing action. The shear rate is directly, dependent on the pressure drop in a channel, and the pressure drop is a cubic function of, the channel height., The high shear rate produces two other, effects that significantly affect product performance. The plastics molecules become, , 279, , aligned as a result of the high shear flow so, that the material in the walls is highly oriented in the flow direction. This may be a, desirable effect. For example, a restrictor bar, is used in molding polypropylene products, to generate a living hinge effect by orienting the material. In some materials such as, polyamides (nylons), the unidirectional orientation results in improved strength in both, the flow direction and perpendicular to the, flow direction. In most cases the effect is undesirable since the strength in the direction, perpendicular to the flow direction is reduced, and the product has a tendency to split along a, flow line. In addition, the oriented materials, have reduced elevated temperature properties in that the orientation tends to be relieved, at a fairly low temperature and the product, will distort as a result of the de orientation, process., Residual stress There is a condition that, develops, particularly in products with thin, walls. This is a frozen-in stress, a condition, that results from the filling process. The TP, flowing along the walls of the mold is chilled, by heat transferring to the cold mold walls, and the material is essentially set (approaching solidification). The material between the, two chilled skins formed continues to flow, and, as a result, it will stretch the chilled skins, of plastics and subject them to tensile stresses., When the flow ceases, the skins of the product are in tension and the core material is in, compression that results in a frozen-in stress, condition. This stress level is added to any externally applied load so that a product with, the frozen-in stress condition is subject to failure at reduced load levels., There are other conditions that result from, the frozen-in stresses. In materials such as, crystal polystyrene, which have low elongation to fracture and are in the glassy state at, room temperature, a frequent result is crazing; it is the appearance of many fine microcracks across the material in a direction, perpendicular to the stress direction. This result may not appear immediately and may, occur by exposure to either a mildly solvent, liquid or vapor. Styrene products dipped in, kerosene will craze quickly in stressed areas.

Page 298 : 280, , 4 Designing Plastic Product, , In any event, the crazing effect can lead to, premature product failure. An annealing operation may minimize these stresses., There is another result of frozen-in residual stresses that can be equally damaging to, the product function and which affects materials that are not in the glassy state. This, may affect an impact grade of material or a, crystalline plastic even more drastically than, a glassy material. The frozen-in stresses are, real loads applied to the material and when, even slightly elevated temperatures are applied stresses can cause the product to deform, severely., What has been reviewed are interactions, between the molding process and the product design. Poor process control during molding can produce these severe orientation and, frozen strains. However, there are designs, used particularly with certain plastics where, it is impossible to avoid the frozen strain and, orientation problems. For transparent products these difficult-to-mold products the condition can be observed by the means of the, photo-stress effect. Examination of a transparent molded product by polarized light will, show the combined effect of the orientation, and the frozen stresses (Fig. 5-2). It is difficult, to determine which effect is being observed, since both have the same birefringence effect on the polarized light. The use of reflected polarized light from the surface gives, a somewhat different reading of the effect., This may be a way to separate the two effects, that would be desirable since the result on the, performance is different for each condition., It would be desirable to make sample prototype tooling and analyze the flow effects, on a product that is likely to present a flow, problem. In addition to the usual physical, testing of the product, the use of photo-stress, analysis techniques plus the exposure to selected solvents to check for stress crack characteristics would lead to changes in the product to minimize the effects of the molding, on the product performance. As an example there have been cases in the past where, piano keys with frozen-in stresses have been, released from perspiration, leaving open flow, lines (Chapter 5, STRESS ANALYSIS)., , Gate area The gate area on a molded, product represents another processing problem in molded products. The gate causes severe restriction to particularly TP melt flow, since it is always desirable to have it as small, as possible to reduce its visibility on the product. Because of the especially high shear rate, on the material as it passes through the gate,, the material is heated because a substantial, part of the potential energy represented by, the pressure on the material is converted to, heat by friction., The effect on the material can be drastic and, in the case of shear sensitive materials, there is substantial degradation in the, molecular weight of the material as it passes, through the gate. If the material is a filled, one, such as a fiber glass material, the severe, flow patterns generated at the gate will break, up the reinforcing materials and can convert, fiber to powder with a substantial loss in the, reinforcing properties of the filler. (The same, action can occur when a screw plasticizer is, used.) These type problems can be reduced or, basically eliminated with proper mold design, and process control during fabrication., There is not too much orientation that is, permanently added to material as it passes, through the gate since the continued flow in, the cavity basically tends to produce turbulence that destroys the orientation. The last, material to pass through, however, does retain its orientation and the gate area in a, molded product is usually highly oriented and, could be weak. In the case of jetting, the result, is a patch of highly oriented material somewhere on the molded product near where the, first material entered the mold., Jetting Jetting is a condition that results, when the mold design has no immediate impediment to flow and the plastics is ejected, into a relatively large open volume. This jetted material becomes a weak point on the, product and a surface blemish that is difficult, to conceal., It is controlled by changing the gate to direct the material to a nearby wall to slow the, initial flow, by changing the size of the gate, to reduce flow rate, by changing the shape

Page 299 : 4 Designing Plastic Product, of the gate, and/or by making adjustments, in the fill rate on the product during molding. The design's involvement in these areas, is achieved by consultation with the mold designer and molder to indicate which options, are available on the product that will not interfere with its function., , Weld line Weld or knit lines where two, parts of a melt join while flowing into the, mold cavity can result in problems. The quality of the weld depends on the temperature, of the material at the weld point and the pressure present in the melt after flowing from the, gate. The higher the temperature and pressure, the more complete the weld and the, better the product performance and appearance. Bringing the material to the weld point, at a higher temperature and pressure requires, rapid filling of the mold cavity (Chapter 3,, BASIC FEATURE, Weld Line)., This action tends to produce flow orientation of the material and the possibility of induced frozen-in stresses that will also detract, from product performance. In order to reach, a reasonable compromise on these problems,, the molder can operate the mold at a higher, temperature. However it will increase machine cycle time due to longer cooling time, resulting in higher production costs. The, product designer can minimize the problem, by increasing the wall thickness to permit easier flow, by the use of ribs to act as built in, runners to improve and redirect the flow of, material in the cavity, and/or by modification, of the design to shift and/or eliminate obstructions to flow. In some cases holes may be, molded partially through the section to eliminate weld lines so the melt flows through it., Mold makers will suggest mold designs that, minimize weld lines., These are the primary process interactions, that the designer must be aware of in order, to determine process interference in product performance and design. Specific materials may introduce other problem areas as,, for example, air entrapment, differential expansion, and the problem of a level of crystallinity in a crystalline plastic that exceeds, the allowed level for stability of a product., , 281, , Venting Proper venting of the mold cavity is essential for the successful molding of, plastic products. Since venting may influence, the product design, it is desirable to consider the different venting techniques used, in a mold cavity (1, 3, 9). Included for certain plastics is "breathing" or "bumping", the mold halves to eliminate entrapped, air (3)., Molded TSs, whether molded by injection,, transfer or compression, also have design, restrictions imposed because of the chemical curing action that takes place during the, molding and curing. Certain specific problems occur with specific TSs. For example, there are phenolic materials and others that, evolve gaseous products during the cure., They can have porosity problems caused by, insufficient pressure applied to a particular, area of the product. This lack of pressure in, an injection or transfer molded is caused by, filling at too slow a rate so that the pressure, is not transferred from the gate to the remote portion of the cavity before the reaction, causes the material to set up and block pressure transfer. In some cases this is a result of, the product design that has complex paths for, the material to fill. It can be overcome by redesigning the product to increase the flow as, suggested for TP products. Part of the problem can be corrected by changes in the grade, of material. Here, as in the other cases, determining which factors are best changed in cooperation with the mold designer and molder, will produce the quality result., Extrusion, For several basic reasons, the extrusion, process does not have the large number of, possible process product interactions that, the preceding molding methods presented., Due to this situation it can not fabricate the, complex shapes and tighter tolerances obtained from molding. The process is a steadystate continuous production operation that, can be brought to a condition of control., However it has its share of potential problems (Chapter 8, EXTRUSION).

Page 300 : 282, , 4 Designing Plastic Product, , The operating pressures and shear rates in, the extrusion process are considerably lower, than they are in molding. As it exits the die,, but not necessarily when it leaves the process,, the material is in an essentially stress-free, condition. Depending on the wall thickness, of the material and the particular material,, there is orientation of the plastic to a greater, or lesser controllable degree. Thin walls produce higher orientation in materials such as, Pp, that is a highly crystalline polyolefin, and, which orients much more than materials such, as PVc., Melt flow After the material (extrudate), leaves the die, it is usually drawn in size and, passed through a set of auxiliary equipment, that basically can form the final desired shape, (6). The material is also cooled either by subjecting it to air flows, by immersing it in a water tank, by subjecting the extrudate to a water spray, and/or these combinations. There, are other techniques such as having the material drawn through a chilled metal mandrel, by the use of vacuum applied into the mandrel. These draw-down, forming, and cooling, procedures can and do introduce stresses in, the product which can affect the performance, of the extruded materials if they are not properly controlled., Memory One commonly encountered, problem with extruded products as a result, of processing interaction, particularly with, materials such as acrylics and vinyls which, have an extensive type of "memory" characteristics, is that the product will shorten, in the machine direction and thicken in the, cross machine direction with the application of even low heat. This effect is analogous to the molding melt flow orientation, reviewed and results from the orientation, produced by the draw-down process and, frozen-in stresses produced because the, draw-down was done at too Iowa temperature. Generally the die-induced orientation is, not a major factor in this effect since it can be, corrected usually by changes in the process, operating conditions and/or modification of, the material. Any orientation can cause this, effect at high enough temperature, generally, , near the glass transition or crystalline melting, point., The designer should be aware of the fact, that this is to be considered in designing with, extruded products. The designer can exercise, little control over this pull back condition except to be guided by the experience of the extrusion processor to indicate which materials, are particularly susceptible to this problem, and what the recommended wall thicknesses, are to minimize the effect. In general, one of, the best ways to improve the condition is to, slow down the rate of extrusion. As a result,, products have a tendency to pull back. They, also will be more costly to produce., Distortion Another problem with extrusions is caused by distortion of the section, by the effect of heat and other environmental conditions such as exposure to water or, chemical agents that tend to soften the plastic. These distortions are generally reversals, of the profile back to the shape that it had, exiting in the die. This action indicates that, the post die forming operations were done, at a lower than desirable temperature which, results in a molded-in stress. When the stress, is relieved the product distorts. In some instances these stresses cannot be eliminated, by process changes so that the product is inherently deficient in performance., One way the designer can cope with this situation is to indicate to the die designer and, extrusion processor what the anticipated operating conditions for the product are, so that, the design of the tooling will minimize the potential for distortion. This action provides the, processor to: (1) better control of the shape, leaving the die achieved by more careful die, design and correction so that a minimum of, post die shaping is required, (2) operating the, line at a higher temperature when shaping jigs, are used, (3) careful cooling of the extrudate,, and (4) finally by generally operating the process at lower rates to insure better process, control., Dimension One general problem that exists with extruded shapes could be the control of dimensions. Because the production, rate can affect the relative dimensions in an

Page 301 : 4 Designing Plastic Product, extrusion as well as the overall size, dimension control becomes an important economic, factor. For economical production of extruded products it is advisable for the product, designer to indicate which dimensions, if any,, are really critical to the function of the product so that these are controlled, and to indicate the widest acceptable variance on other, less critical dimensions. In this way the extrusion operator can adjust the process to the, maximum speed consistent with the production of a usable product., Insistence on all dimensions as critical will, result in the process being restricted to one, narrow set of operating conditions, usually, at a low production rate, with a high scrap, rate and high product costs. In cases where, the dimensions are critical, it may be that the, extrusion process should be discarded in favor of molding or machining of the product., However controlling all dimensions can be, accomplished at a cost., Subject to the limitations indicated, control, over extrusion process products is consistent, enough to make a uniform repeatable product once the limitations are accommodated., Here, as in other processing, good communication between the processor and the designer will help make for a successful economical product., Thermoforming, Sheet forming processes, such as vacuum, forming, do have effects on the product. The, designer should be aware that these will affect the performance of one's product and, one should learn how to modify the design, to minimize any deleterious effects. Probably the most serious problem encountered in, formed film or sheet products results from, the fact that the materials are made from film, or sheet at temperatures well below the melt, softening point of the plastic, usually near, the heat distortion temperature for the material. Forming under these condition when, the draw down ratio is exceeded for a specific plastic can result in over stretched orientation of the material, the production of, frozen-in stresses, poor product reproducibil-, , 283, , ity, and/or immediate or in service failure by, the product cracking (Chapter 8, THERMOFORMING)., Stress These conditions are unavoidable, by the very nature of the sheet forming processes. The designer must accept the fact that, the heat resistance of a sheet formed product and its resistance to other environmental, stress factors even though lower than for a, molded or extruded products do exist. The, objective of the designer should be to minimize the amount of stretching needed to, make the product so that the over-all performance will be as close to the molded product, as possible. Also by using tighter film or sheet, thickness dimensional controls, thermoforming permits more accurate reproduction followed with reduced product costs (1, 6)., There is a variation or degree of stretching that occurs as a film or sheet is drawn, down over several different male or female, shapes. The variation in stretching can occur, in different portions of the film or sheet as, the corners become sharper. There is a good, correlation between the extent of stretching, and the susceptibility of the product to damage; the degree to which it will occur will, vary widely from one material to another. A, material such as rigid PVC or cellulose acetate propionate will be much less likely to, show damage when subjected to thermal or, environmental stress than a polystyrene or, polyethylene., Memory The nature of the damage due, to "memory" to the TP product varies from, one material to another. One temperature effect common to all materials results in products where it tends to revert to the original, shape. The extent of this and the temperature at which it will occur will depend on, the material, the forming process operating, conditions, and the product design. With regard to the design, the most stable TP products are those with generous corner radii and, smoothly blended surfaces with a minimum, of sharp corners and reentrant curves that will, stretch the material excessively., TP materials are stable when properly, molded. The best processing conditions will

Page 302 : 284, , 4 Designing Plastic Product, , preheat the material to the highest possible, uniform temperature of the material particularly thicknesswise and then form the sheet as, rapidly as possible. There are limitations on, the process temperature because some materials such as PE have a narrow range of forming temperatures while others such as PVC, may be susceptible to thermal degradation., The speed of closure to the form is a function of machine condition and sheet thickness, with the thicker sheets being more difficult to move rapidly. The designer should, indicate this to the sheet former when form, stability at elevated temperatures is critical, and the process must be tailored to improve, this condition. One should also select a material which is intrinsically more stable and, easily formed to minimize the possibility of, unmolding. These factors must be considered, in conjunction with the design of the product, to minimize sheet stretching differentials in, the part., , Orientation In addition to where the, product tends to revert to the original shape,, the effects of the stretching of the sheet materials result in two other impairments of the, product. Highly stretched sections are usually thin and highly oriented. It has a decided, tendency to split in these areas in a direction, parallel to the stretching that took place. The, designer should consider this potential situation and consider thicker material so that the, product will perform adequately in use., The other effect of having a stretched area, is a reduction in resistance to stress cracking. Crazing is a possibility in such areas such, as in polystyrenes, and environmental stress, cracking caused by solvent substances will, occur in the stretched areas. This is a particularly important consideration in vacuum, formed products used for packaging food that, frequently has some solvent action on the, plastics., Blow Molding, With respect to the BM process, the type, of situation where the material is stretched, at temperatures below the melt temperature, , applies in a similar manner to that reviewed, above for thermoformed sheet processing,, only to a lesser degree. It is convenient to, think of extrusion or injection BM as a more, generalized form of a plastics reforming process such as sheet forming. The comments on, designing to minimize points of sharp stretching and excessive draw mentioned in forming apply to blow molded products as well, (Chapter 8, Blow Molding)., By extrusion parison control it is possible, to minimize the wall thickness variation and, the extent of stretching and stretch orientation. These are the province of the processor when the designer is not familiar with, BM. Knowledge is required to provide information on what is possible and to select, the specific BM process that has the capability to mold the product. The designer should, be aware of the possible failure modes and, compensate for them in the design. There, is little else the designer can do but select, the best material and process to make the, product., , Complex design BM has started to full, fill its rather unlimited capability in producing complex shaped products. The reason is, due to designers becoming familiar with the, behavior of BM processes and their exceptional design capabilities and few limitations, (Chapter 8)., Casting, The process interaction in cast plastic products is mainly involved with the curing processes and with mold filling problems. Voids, and porous sections are a frequent problem, with castings because the mold filling is done, at atmospheric pressure, or low pressure, and, if the product has thin sections to fill, the flow, may be a problem., Other than designing to avoid such difficult flow conditions and selecting a material, with good flow characteristics that will perform properly, the designer must rely on the, skills of the fabricator to make good products. Frequently a casting is selected because, of the low tooling requirements and rapidity

Page 303 : 4 Designing Plastic Product, with which the product can be put into, production. After the production level is increased and the requirements for better product quality are imposed, it may be desirable, to change to pressure molded products when, the higher production level justifies the increased tooling costs. However there are high, production casting lines, such as encasing jewelry, emblems, etc., that are more beneficial, costwise., In many cases design modifications can, substantially improve the productibility of, the products and reduce their cost with improved product quality. As an example if, voids exist the problem can usually be corrected by modifying or changing the plastic's, composition and/or the use of a vacuum system during the casting. Understanding the effects of the process on the product is essential, in making successful products., Specific information in this area is usually, available from the processor who has experience with a wide variety of products and, knows the type of problems that have been, encountered in the past., Because of the complexities of the materials and the effects of the processing on the, materials, this is an area where predictability based on scientific data is very limited, and casting experience is desirable. Successful products will result from close cooperation between designer, tool designer, mold, maker, and processor to arrive at design compromises that make the products acceptable, and producible at an economical price., Law and Regulation, , The consuming public must assume that, the producer of a product has shown reasonable consideration for the safety, correct, quantity, proper labeling, and other social aspects of the product. Since the 1960s these, types of important concerns have expanded, and been reinforced by a recognition of the, consumer's right to know as well as by concerns for conservation, ecology, antilittering,, and the like. Numerous safety-related and socially responsible laws have been enacted and, more are on the way., , 285, , A designer's failure to be aware of and, comply with existing regulations can lead to, legal entanglements, fines, restrictions, and, even jail sentences. In addition, there are also, the penalties of costly, damaging publicity,, lawsuits, and the loss of consumer goodwill., In the meantime, as for all other industries,, the goal of reliable companies and associations is to produce products that eliminate, potential problems. Unfortunately, nothing, is perfect, so problems can develop, which is, simply a fact of life. And there is always more, to be done, as in the disposal issue (like eliminating wars and having all people like each, other)., There are many examples of action to, eliminate or reduce problems. As an example there is the Quality System Regulation, (APPENDIX, TERMINOLOGY). FDA requires details on how products made of different materials (steel, glass, plastic, etc.) such, as medical devices be manufactured. The details of the process are documented so that, once a product produced in USA is approved,, the product can only be produced by following what was in the QSR preparation., No change can be made. The exact plastic, composition has to be used, process control, settings remain the same, etc. Literally if a, waste paper basket had been identified and, located in a specific location in the plant,, you can not relocate, change its size, etc. It, has been reported that to make a change, could cost literally over a million dollars., Result of the QSR regulation is too ensure, the safety of a person when the medical device is used. The QSR approach should be, considered/used by plastic fabricators and/or, product customers when rigid requirements, exist., On just the subject of appliance safety, the Underwriters Laboratories (UL) have, published more than four hundred safety, standards to assess the hazards associated, with manufacturing appliances. These standards represent basic design requirements, for various categories of products covered by, the organization. For example, under UL's, Component Plastics Program a material is, tested under standardized, uniform conditions to provide preliminary information as

Page 304 : 286, , 4 Designing Plastic Product, , to a material's strong and potentially weak, characteristics., The UL plastics program is divided into, two phases. The first develops information on, a material's long- and short-term properties., The second phase uses these data to screen, out and indicate a material's strong and weak, characteristics. For example, manufacturers, and safety engineers can analyze the possible, hazardous effects of potentially weak characteristics, using UL standard 746C., Products manufactured using concepts in, UL Standard 746D provide quick verification, of material identification, along with the assurance that acceptable blending or simple, compounding operations are used that would, not increase the risk of fire, electrical shock,, or personal injury., The Standard for Tests for Flammability, of Plastic Materials for Parts in Devices and, Appliances (UL 94) has methods for determining whether a material will extinguish, or, burn and propagate flame. The UL Standard, for Polymeric Materials-Short Term Property, Evaluations is a series of small-scale tests, used as a basis for comparing the mechanical,, electrical, thermal, and resistance-to-ignition, characteristics of materials., It is the general consensus within the, worldwide "fire community" that the only, proper way to evaluate the fire safety of products is to conduct full-scale tests or complete fire-risk assessments. Most of these, tests were extracted from procedures developed by the American Society for Testing and Materials (ASTM) and the International Electrotechnical Commission (IEe)., Because they are time tested, they are generally accepted methods to evaluate a given, property. Where there were no universally accepted methods the UL developed its own., The advisory committees for developing, the test protocol include the following:, American Association of Retired Persons, (AARP), American Furniture Manufacturers Association (AFMA), American Hotel and Motel Association, (AHMA), , American Society for Testing and Materials (ASTM), Carpet and Rug Institute (CRI), Consumer Product Safety Commission, (CPSe), Fire Marshals Association of North, America (FMANA), Fire Retardant Chemicals Association, (FRCA) General Services Administration (GSA), International Association of Fire Chiefs, (IAFe), Man-Made Fiber Producers Association, (MMFPA), National Association of Home Builders, (NAHB), National Institute of Standards & Technology (NIST), National Conference of States on Building, Codes and Standards (NCSBCS), National Electrical Manufacturers Association (NEMA), Underwriters Laboratories (UL), U.S. Fire Administration (USFA), Designing and Legal Matter, In designing a product factors to consider, include protecting your design, product liability, and many more. It is important to recognize what laws and legal matters exist or, actions can occur unfortunately for even the, "good guy." This type of information or action could be considered a competitive situation. It is important to keep up to date on, laws and legal matters that can effect your, product. The following provides some general information guides., , Accident Report, Fabricators/manufacturers do not plan for, their products to fail or to cause harm to people. But if an incident should occur that results in serious injury or death, the problem, must be investigated immediately to prevent

Page 305 : 4 Designing Plastic Product, it from occurring again. U.S. Federal regulations require that a manufacturer report, the event to FDA. However, the customer,, the patient, his or her family, and the manufacturer all need to know what happened,, which makes the investigation of the problem, critical. To eliminate any improper investigation, manufacturers should have a trained crisis management committee in place before a, complaint is received so that a standard operating procedures is followed defining what, actions are to be taken and by whom., , 287, , associated with consumer products; (2) to assist consumers in evaluating the comparative, safety of consumer products; (3) to develop, uniform safety standards for consumer products and to minimize conflicting state and local regulations; and (4) to promote research, and investigation into the causes and prevention of product-related deaths, illnesses,, and injuries. Overall target is to prevent hazardous material and products or defective designed products from reaching the consumer., Copyright, , Acknowledgment, The formal document that accepts a customer order; includes a delivery promise,, method and time for payment, and identifies, any exceptions to the terms and conditions, stated on the customer's purchase order., Chapter 11 Act, US permits legal protection from creditors under Chapter 11 of the US Federal Bankruptcy Act. Interesting, particularly when you study being on both side and, what one can get away with legally. Time the, law changes for the credible operation even, though the change has been discussed for, many decades., Conflict of Interest, They range from personal to legal matters, with the usual main conflict between the private interests and the official responsibilities, of a person in a position of trust such as the, company's top executive officers or a government official or agency., Consumer Product Safety Act, CPSA is a significant consumer safety law., It is part of U.S. legislative law and augments, , the common law and case of product liability. Purpose of the law is: (1) to protect the, public against unreasonable risks of injury, , It is an intangible property such as the ownership of a design or literary property granted, by law., , Defendant, While anyone along the trail of commerce, (manufacturer, wholesaler, or retailer) can, become a defendant in a law suit, it is usually the manufacturer who is held liable to, the injured party. The manufacturer is the one, with the "$ deepest pockets" or the one from, which the largest award can be obtained., Employee Assignment Invention, In assigning an invention, usually the employment contract will govern. However,, some states have Employee Invention Laws., These laws, in effect, retain personal, nonbusiness related inventions for the employee, as long as they are not made on the employer's equipment or time., Expert Witness, Litigation in the plastic and other industries usually involves patent infringement,, theft of trade secret, product liability, or a, specific performance. With the usual patent, law, the expert is expected to report on the, obviousness of an invention. Prior art and, knowledge of the requirements for patentability will often be key parts of the expert's

Page 306 : 288, , 4 Designing Plastic Product, , testimony. Unfortunately judges who have a, weak technical background and little understanding of the patent law hear many of these, cases. The job of the expert is to reduce a complex art or science into easy to understand, testimony for all in the proceedings., An expert witness is to be a person with, substantial training in a specific field who can, look at a set of data and come to a scientific conclusion about the merits of the issues., Target here is that any conflict between objectively and the highly opinionated atmosphere, inherent in legal proceedings has always, been problematic for technical people with, ethics., , Patent, In USA a patent is awarded to the person first producing an invention, not necessarily who first applied for a patent. The opposite policy prevails in the rest of the world, with USA policy probably changing in order, to achieve worldwide patent law harmonization. USA utility patents (machines, equipment, etc.) in the past where good for at least, 17 years after date the patent was issued. As, of 1995, the patent is good for 20 years after, the date the patent is filed (prior to the date, it is issued) that eliminated those who would, file for a patent and let it drag out for many, years prior to being issued when it would be, needed for infringement, etc., , Insurance Risk Retention Act, With IRRA companies in the same industry are permitted to form a specialized insurance company to insure themselves. As an example, one was been established in Vermont, 1992 that was called the Plastics Industry Risk, Retention Group (PIRRG)., Invention, Chief requirement is that (1) it be an unobvious to a person having ordinary skill in the, art to which the claim pertains and (2) knowing everything that has gone wrong before is, not applicable., Mold Contractional Obligation, Custom molders have traditionally assumed no responsibility for the legality of, the design of the customer's product, the design ofthe molded product as a component of, that product, or products produced to the customer's design and specification. In the event, a molded product infringes, or is claimed to, infringe, any letters of patents, or copyright,, the customer has assumed the responsibility involved. Normally most quotation forms, include clauses that explicitly detail the indemnification provisions and mold storage, responsibility., , Patentability, Qualifications for obtaining a patent on an, invention or process (USA) are: (1) the invention must not have been published in any, country or in public use in USA in either case, for more than one year to date of filing application, (2) it must not have been known in, USA before that date of invention by the applicant, (3) it must not be obvious to an expert, in the art/technology, (4) it must be useful for, a purpose not immoral and not injurious to, the public welfare, and (5) it must fall within, five statutory classes on which only patents, may be granted, namely, (a) composition of, material, (b) process of manufacture or treatment, (c) machine, (d) design, and (e) plant, produces asexually., Patent Information, Patents tend to be the literature of technology with full disclosure of its invention details. This legal document confers to its owner, the right to exclude others from using it., Patent Infringement, Generally, ignorance of the patent or, trademark rights of others is no excuse to an

Page 307 : 4 Designing Plastic Product, infringing activity. Moreover, it may give rise, to costs and risks in withdrawal or recall of, products, ads, attorney' fees, etc. These potential costs will probably outweigh the cost, of the initial searches or clearances., , 289, , inate "substitutions") requires time and, money to prepare a foolproof patent. Cost, per patents has been in the millions of, dollars., Plaintiff, , Patent Pooling with Competitor, In the past, USA competing companies, could not cooperate, such as in R&D, without breaching antitrust laws. Patent pooling, such as collecting and cross-licensing, patents, was precluded. Today the antitrust, laws are reviewed, interpreted, and enforced, less stringently, which permits industrial cooperation in selected and specific areas, where poling does exist. This explanation, is a simplistic summation to a very complicated situation., Patent Search, There are three major steps to a patent, search. (1) There is the US Patent Classification System that is a sort of subject index, to all patents, (2) CASSIS is a computerized, software information system provided by the, USA patent office, and (3) review the patent, that takes time; involves the weekly official, worldwide gazettes, magazines, etc. There are, many ways available to search the patent, database in both US and worldwide, but one, web that is particularly useful to the novice, or occasional searcher is one offered by IBM, locate at: http://wwwpatents.IBM.com, Patent Term Extension, The PTE complex law of 1984 (USA) offers an opportunity to extend the effective, life of patents for new medical inventions up, to five years., Patent Terminology, Preparing a patent and ensuring that proper and protective terms are used (to elim-, , A lawsuit is a civil suit seeking compensation by the plaintiff for damages, usually, money, for some type of liability against the, responsible party(s). A product liability may, arise as a result of a defect in design and/or, manufacturer, improper service, breach of, warranty, negligence in marketing, etc. Under the doctrine of strict liability the plaintiff, must prove factual proof of damage. Before, the trial the plaintiff is entitled to certain information by right of discovery. It includes, all records that pertain to the alleged damage and depositions of individuals involved., Oral depositions before a court reporter permit both sides of the litigation to discover the, important facts of the case., Processor Collaborative Venture, PCV provides an innovative approach to, cost containment (55). One method is to, lower the cost of outsourcing parts and components by forming a group-purchasing venture. When legally structured meeting the established guidelines of the Antitrust Div. of, the U.S. Dept. of Justice (DOJ), allow members to aggregate purchases in order to obtain, competitive volume discounts, reducing their, costs, and subsequently the prices charged to, their customers. Such collaborations are often viewed by DOJ as not only benign, but, pro competitive., As explained by R. Branand (55) while, U.S. manufacturers are well aware of the barriers imposed on U.S. collaborations by antitrust considerations. However they are usually not as familiar with the opportunities, that are encouraged. Properly structured the, competitor association can help USA companies achieve goals such as expanding into foreign markets, funding expensive innovations, efforts, and lowering production and other

Page 308 : 290, , 4 Designing Plastic Product, , costs. For over a decade this powerful costcutter has been available to U.S. businesses,, yet misapplied antitrust concerns have prevented many companies from pursuing its, benefits., , patents/protect the ornamental appearance, of a product without regard to how it, functions., , Protection Strategy, Processor Contract, It is usually consider a subgroup to the cus-, , tom processor. They have little involvement, in the business of their customer. They usually just sell machine time., Product Liability Law, , Two types of law are involved; contract and, tort. A contract is an agreement between two, or more parties that is enforceable in a court, of law. A tort is a civil wrong committed by, the invasion of any personal or private right, that each person enjoys by virtue of federal, and state laws. The personal or private right, affected must be one that is determined by, law rather than by contract. In addition to, the tortuous act, there must also be personal, injury and/or property damage. Over half the, USA states have adopted to varying degrees, the doctrine of strict liability tort, that means, that the injured person need only prove that a, product was unreasonably dangerous to win, the case. Various conditions make it easier, to win cases. As an example proof that the, manufacturer of the product is negligent is, no longer required., Protect Design, , Five different methods of protecting your, design exists in USA. Each is weighed according to its advantages and disadvantages based on specific needs. They are:, (1) contracts/other party agrees not to, make, use, etc. without designer's permission;, (2) copyrights/protection exists upon creation of design; (3) trade dresses/protection, when design is either inherently distinctive or has become distinctive; (4) utility, patents/protects the functional and structural features of a product; and (5) design, , For a molder to control secrecy concerning, proprietary information, the first approach is, to keep it as a personal secret. If people have, to be exposed to it, such as present or new employees, visitors, and customers since there, exists a need to know, those people should, sign a nondisclosure agreement. This agreement could set up problems since a person, could already be familiar with the so-called, secret., , Quotation, , Document quote that states the selling, price and other sales conditions of a material,, product, etc. Did you know that by law if, someone reports that verbally the vender, made statements such as "buy this injection, molding machine and all you have to do, is push a button to make good/acceptable, parts" ... the vender is in trouble ... even if, that vendor wins the case (odds are against, winning), it will be very expensive to be in, court., , Right-to-Know, , This law (Fed. Reg. 29 cfr 1910.1200) covers, employees' right to know about the chemical, hazards to which they are exposed if they exist in a working area., , Shop-Right, It is a term referring to a non-exclusive, royalty-fee license given to a employer where, an employee uses the employment's time, and/or equipment to develop an invention., Shop-rights come into play when there is no, assignment agreement.

Page 309 : 4 Designing Plastic Product, Software and Patent, , The Court of Appeals for the USA, Federal Circuit issued (1992) a decision, that could strengthen the legal position that, so-called pure software could be patented, (Arrhythmia Research Technology vs., Corazonix Corp. 22 USPQ2d 103 of CAFC, march 12, 1992)., , 291, , only, and (3) federal registration that offers, registered TM protection across state lines., Trade Name, , TN is the name or style under which a, concern does business. The government concerned alone or with a device such as a surrounding oval may register the TN., , Tariff, , Warranty, , It is basically a schedule of duties or cost, rates imposed by a government on imported, or in some countries exported goods. In certain areas of the world to offset tariff duties,, worldwide free-trade agreements exist., , There are different items that have warranties such as equipment, products, and materials. Fulfillment of warranties tends to be, a two-way situation. As an example when, one buys equipment, you are not just buying, equipment, you are entering into a relationship. This may sound tripe, but it is demonstrably true in the case of capital equipment., The warranty relationship can be defined in, writing by the warranty document. It goes, into detail as to what the OEM (original, equipment manufacturer) seller promises to, do in event of equipment failure due to specific causes. It also details the responsibilities, of the equipment owner. Sometimes the expectations of the processor and OEM are seriously mismatched., The best way to avoid this situation is to, clarify understandings before the equipment, is delivered. It is usually clear who pays for, parts. Make sure you understand, however,, the responsibilities vs. the OEM for shipping,, travel, and other costs. The details can significantly defer from OEM to OEM., , Term, It is important in the workplace and when, legal actions occur that terms have their, proper definition to ensure accuracy of discussions in the plant and/or in the court room., , Tort Liability, , The tort laws have been impeding new biomaterial and medical device developments, by the large companies. It is very difficult for, them to justify the financial risk incurred from, the relatively low level of their sales. Action, is being taken to change the laws., Trademark, , TM is a symbol or insignia designating, one or more proprietary products or the, manufacture of such products, that has been, officially registered and approved by the U.S., Patent and Trademark Office (PTO). The, acceptable designation is a superior capital, R enclosed in a circle, however, quotation, marks may be used. There are three levels, of TM protection namely: (1) common law, covers unregistered TM with limited legal, protection; (2) state registration where you, register the TM and are protected in that state, , Design Detractor and Constrain, , As reviewed throughout this book, designing acceptable products requires knowledge of the behavior of the different, plastics and their processing characteristics, (Chapter 6, MATERIAL VARIABLE and, Chapter 8 EQUIPMENTIPROCESSING, VARIABLE)., Although there is no limit theoretically, to the shapes that can be created, practical, considerations must be met such as available

Page 310 : 292, , 4 Designing Plastic Product, , and size of processing equipment with cost., These relate not only to the product design,, but also the mold or die design, since they, must be considered as one entity in the total creation of a usable, economically feasible, product., Troubleshooting Design ProblemIFailure, , Troubleshooting is the art and science of, remedying product defects after the process, has demonstrated the ability to produce acceptable production products. Most defects, respond to one of a variety of process and/or, material changes. The target is knowing when, a particular solution will work, and correctly, identifying which problem is actually causing the defect. When making adjustments, consider: (1) create a mental image of what, should be happening, (2) look for obvious differences, (3) make only one change at a time, designwise, materialwise, and/or processingwise, and (4) allow the process to stabilize, after any change is made., Studies have determined that probably, 60% of defects result from the machine/, equipment, 20% mold/die, 10% material, and, 10% operator. Available are software programs already installed on the machines processor controller or available as a software, package that can provide some troubleshooting help., Troubleshooting Guide, With all types of equipment, materials, and, products, troubleshooting guides are setup, (usually required) to take fast, corrective, action when products do not meet their, performance requirements such as dimensions, shape, surface appearance, and physical and mechanical properties. This problem solving approach fits into the overall, fabricating-design interface as summarized, in the FALLO approach (Fig. 1-3). Troubleshooting guides are reviewed in throughout this book (1, 3, 6, 7, 20)., Many different guides are provided by, equipment and material suppliers. However,, , the product "problems-to-solutions" are usually developed when setting-up a fabricating, line by the processor. A simplified approach, to troubleshooting is to develop a checklist, that incorporates the rules of a problem-tosolving procedure. (1) Have a plan and keep, updating it based on the experienced gained, in operating the equipment. (2) Watch the, processing conditions. (3) Change only one, condition at a time. (4) Allow sufficient time, for each change and keep some kind of a, log of the action, with results, that are occurring. (5) Check housekeeping, storage areas,, dryers, granulators, personnel clothing, and, personnel behavior. (6) Narrow the range of, areas in which the problem belongs, e.g. material storage and handling, mold/die, specific equipment in the fabrication line (such, robot, cooling tank, and puller), specific control, product design, environment (humidity,, ventilation location and direction of forced, air, dust, etc.), people, and management., The following provides an example as a, guide pertaining to extruded products that, starts with common operating problems and, possible solutions. When possible start with, feeding low bulk density plastic in a starved, fed extruder. To avoid aeration and therefore, increased potential for volumetric feed limitation, minimize the free fall path from the, feeder to the extruder feed throat. If a barrel zone on the barrel constantly overrides, or requires too much cooling to maintain a, set point, it may be that the melting is being, concentrated in that section. This can either, exist because of screw design or an improper, barrel heat profile. A simple and hopeful solution is to increase the melting prior to the, "hot zone" ofthe screw (6)., Troubleshooting by Remote Control, To aid the manufacturing plants, remote, troubleshooting has been available from different equipment manufacturers and service facilities. Users of certain microprocessor equipment need not be concerned about, their plant's personnel's ability to service and, maintain the equipment. Via a communication link from your computer controller to the

Page 311 : 4 Designing Plastic Product, services central computer, a specialist and/or, automatic device can immediately check out, conditions in your controller as well as in the, complete production line. This remote diagnostic link can also be used to set-up preventative maintenance programs., , Defining the Trouble, When setting up troubleshooting guides,, as well as reviewing any problems or even, open discussions on the subject of fabricating, it is important that the terms used to, identify a problem be understandable, clear,, and properly defined. As an example the, word flaw could have different meanings to, different people. Flaw could identify blush,, burn, discoloration, fill-in, flow marks, glossiness, gouge, haze, inconsistency, misalignment, non-adhesion, nonuniform, pit, porosity, protrusion, runs, scratches, sink mark,, smearing, speck, void, and weld line. This is, "stretching" or "far-fetching" the term flaw, but it should highlight the fact that a proper, definition can eliminate problems., , Design Failure Theory, In many cases, a product fails when the material begins to yield "plastically." In a few, cases, one may tolerate a small dimensional, change and permit a static load that exceeds, the yield strength. Actual fracture at the ultimate strength of the material would then constitute failure. The criterion for failure may, be based on normal or shear stress in either, case. Impact, creep and fatigue failures are, the most common mode of failures. Other, modes of failure include excessive elastic deflection or buckling. The actual failure mechanism may be quite complicated; each failure, theory is only an attempt to explain the failure mechanism for a given class of materials., In each case a safety factor is employed to, eliminate failure., An example of a theory is the Griffith theory. It expresses the strength of a material in, terms of crack length and fracture surface energy. Brittle fracture is based on the idea that, the presence of cracks determines the brittle, , 293, , strength and crack propagation occurs. It results in fracture rate of decreased elastically, stored energy that at least equals the rate of, formation of the fracture surface energy due, to the creation of new surfaces., These failures could be due to the variability of the plastic material and/or fabrication, control of equipment. Applying an approach, such as the Troubleshooting Guide reviewed,, can direct you to the solution., , Product Failure, Different techniques or methodologies are, used to analyze premature molded product, failures in order to meet cost requirements., Various methods of auditing and computer, software programs are used or developed by, designers and/or fabricators to provide an, analysis of potential problems. Interesting is, the fact that the actual time and cost to design products may take less than 5% of the total time and cost to fabricate products. Even, though this is a relatively small percentage of, the overall operation, it has a direct and important influence performancewise and costwise on the success or failure of fabricating, molded products., Avoiding product failures can depend, in, part, on the ability to predict the performance, of plastic materials and their shapes. With, available time, the usual approach of product prototype and/or field-testing provides, useful and reliable performance data when, conducted properly. As an example designers, continue to develop sophisticated computer, methods for calculating stresses in complex, structures., The computational methods have replaced, the oversimplified models of material behavior formerly relied on. However, for new and, very complex product structures that are being designed to significantly reduce the volume of materials used and in turn the product cost, computer analysis is conducted on, prototypes already fabricated and undergoing testing. This computer approach can result in early and comprehensive analysis of, the effects of conditions such as temperature, loading rate, environment, and material

Page 312 : 294, , 4 Designing Plastic Product, , defects on nonstructural and/or structural, reliability. The information is supported by, stress-strain behavior collected in actual material evaluations., When required, combined with the use of, computers, the finite element analysis (FEA), method can greatly enhanced the capability, of the structural analyst to calculate displacement and stress-strain values in complicated, structures subjected to arbitrary loading conditions. In its fundamental form, the FEA, technique is limited to static, linear elastic, analysis. However, there are advanced FEA, computer programs that can treat highly nonlinear dynamic problems efficiently., Important features of these programs include their ability to handle sliding interfaces, between contacting bodies and the ability, to model elastic-plastic material properties., These program features have made possible, the analysis of impact problems that in the, past had to be handled with very approximate, techniques. FEAs have made these analyses, much more precise, providing better direction in locating high stress areas. Final verification of load-carrying capability usually requires actual testing of the fabricated product, prototype based on computational analysis., Managing Failure, Effective management of any product, (1M, etc.) is much more than the production of immediate results. As Leonard A., Schlesinger (Harvard Business School) reviews, effective management includes creating the potential for achieving good results, over the long run. There is the manager, who, as president of a company, can produce spectacular results for a 3- to lO-year period., However that person can hardly be considered effective if, concurrently, people allow, plant and equipment to deteriorate, creates, an alienated or militant workforce, lets the, company develop a bad name in the marketplace, and ignores new product development., Dealing with current or impending problems is a key reality of people behavior in almost all-modern organizations. Coping with, complexities associated with today and the, , immediate future absorbs the vast majority, of time and energy for most managers., Most managers will readily admit that their, ability to predict their company's future is, limited. Indeed, with the possible exceptions, of death and taxes, the only thing entirely predictable is that things will change. Even for, the most bureaucratic company in the most, mature and stable environment, change is, inevitable., Over a period of 20 years, it is possible, for a company, even one that is not growing, to experience numerous changes in its, business, product markets, competition, government regulations, available technologies,, business strategy, labor markets, and so on., These changes are the inevitable products of, its interaction with a world that is not static., Business and change Growing organizations tend to experience even more businessrelated changes over a long period of time., Studies will show that growing businesses not, only increase the volume of the products or, services they provide, but also tend to increase the complexity of their products or services, their forward or backward integration,, their rate of product innovation, the geographic scope of their operations, the number and character of their distribution channels, and the number and diversity of their, customer groups. While all of this growthdriven change is occurring, competitive and, other external pressures also increase. The, more rapid the growth, the more extensive, the changes that are experienced., These types of business changes generally, require organizational adjustments. For example, if a company's labor markets change, over time, it must alter its selection criteria, and make other adjustments to fit the new, type of employee. New competitors might, emerge with new products, thus requiring renewed product development efforts and a, new organizational design to support that effort. In a growing company, business changes, tend to require major shifts periodically in all, aspects of its organization., The inability of an organization to anticipate the need for change and to adjust effectively to changes in its business or in its

Page 313 : 4 Designing Plastic Product, organization causes problems. These problems sometimes take the form of poor collaboration and coordination; they may involve high turnover or low morale. Always,, however, such problems affect the organization's performance goals that are not, achieved and/or resources are wasted. Because change is inevitable and because it, can so easily produce problems for companies, the key characteristic of an effective organization from a long-run viewpoint is its, ability to anticipate needed organizational, changes and to adapt as business conditions, change., Anticipatory skills can help prevent the resource drain caused by organizational problems, while adaptability helps an organization, avoid the problems that change can produce., Over long periods of time, this ability to avoid, an important and recurring resource drain, can mark the difference between success and, failure for an organization., Bureaucratic dry rot It has been emphasized by a number of social scientists, that in the past decades there has been, expressed serious concern over what they, call bureaucratic dry rot. We all pay a heavy, price, they note, for the large, bureaucratic,, nonadaptive organizations that are insensitive to employees' needs, ignore consumers', , 295, , desires, and refuse to accept their social, responsibilities., Existing evidence suggests that although, most contemporary organizations cannot be, described as adaptive, many managers nevertheless appreciate the benefits of adaptability. When polled managers often respond that, "ideally" they would like to have the ideal organization, but they also admit that their current organization does not have all or even, some of these characteristics., Business Failure, There is a formula for business failures, based on Dun & Bradstreet, Inc. annually, published data. The vast majority of the firms, involved are small. Why do failures occur?, D&B has offered the following tabular explanation (apparent cause/percent): inadequate, sales/49.9, competitive weakness/25.3, heavy, operating expenses/13.0, receivables difficulties/8.3, inventory difficultiesl7.7, excessive, fixed assets/3.2, poor location/2.7, neglect/0.8,, disaster/0.8, fraud/O.S, and others/1.1. Numbers do not add up to 100% because some, failures are attributed to a combination of apparent causes. One can include that product, design directly influences competitive weakness and heavy operating expenses.

Page 314 : 5, Testing and Meaning, of Test Data, , Introduction, , This chapter will present examples of testing and their behavior that influence decisions to be made by designers when analyzing, data. Testing methods have been prepared, and used for over 2,000 years with probably, more in the past century that in all the past., Examining and properly applying property, test data of plastics is important to designers., The technology of manufacturing the same, basic type or grade of plastics (as with steel, and other materials) by different suppliers, may not provide the same results. In fact a, supplier furnishing their material under an, initial batch number could differ when the, next batch is delivered and in turn could effect the performance of your product. Taking, into account manufacturing tolerances of the, plastic, plus variables of equipment and procedure, it becomes apparent that checking, several types of materials from the same or, from different sources is an important part of, material selection and in turn their use., Based on past performances it has been, proven that the so-called interchangeable, grades of plastics have to be evaluated carefully by the designer as to their affect on, the performance of a product. An important, consideration to include as far as equivalent, , grade of material is concerned is its processing characteristics. There can be large differences in properties of a product and test data, if the manufacturing features vary from grade, to grade or batch to batch. This situation in, most cases does not effect the product performances but could require changing equipment process controls to maximize the product performances and minimize cost., , Overall Responsibility, Should the designer have this type of responsibility. That person gets the credit for a, successful product. If the product fails in service regardless of the reason the responsibility should be the designer who did not meet, the product's entire requirement. In specifying the specific plastic and/or process to, use, their test requirements should have been, more complete and/or meet closer requirements. This action would include factors such, as the limits on the variabilities of the design configuration (dimensions, etc.), plastic,, and process. As an example, quality control, (QC) on the plastic and fabricated product is, required even if all that is required is limiting (±) the weigh the material and fabricated, product.

Page 315 : 5 Testing and Meaning of Test Data, The problem of acquiring complete knowledge and control of candidate material grades, should be resolved in cooperation with the, raw material suppliers. Having the material, supplier meet specific performance requirements is important. In turn it may be necessary for testing incoming material even if, the supplier provides data you requested. It, should be recognized that selection of the, favorable material is one of the three basic, elements in producing a successful product, namely design, material selection, and conversion into a finished product. How to resolve processing problems uses the same approach as reviewed with material control., So one can say the designer should not, carryall these responsibilities. True but if the, responsibility is not delegated to one person,, you allow for problems to develop. Perhaps, a certain qualified manager (the designer's, boss) should have the responsibility. For a, small operation it is usually its owner who, mayor may not properly delegate specific, responsibilities., Destructive and Nondestructive Testing, Testing yields basic information about any, materials (plastics, steels, etc.), its properties, relative to another material, its quality with, reference to standards or material inspections, and can be applied to designing with, plastics. Examples of static and dynamic tests, are reviewed in Chapter 2., There are destructive and nondestructive, tests (NDTs) (2). Most important, they are, essential for determining the performance of, plastic materials to be processed and of the, finished fabricated products. Testing refers to, the determination by technical means properties and performances. This action, when, possible, should involve application of established scientific principles and procedures., It requires specifying what requirements are, to be met. There are many different tests, (thousands) that can be conducted that relate to practically any material or product, requirement. Usually only a few will be applicable to meet your specific application. Examples of these tests will be presented., , 297, , In the familiar form of testing known as, destructive testing, the original configuration, of a test specimen and/or product is changed,, distorted, or usually destroyed. The test provides information such as the amount of force, that the material can withstand before it exceeds its elastic limit and permanently distorts (yield strength) or the amount of force, needed to break it. These data are quantitative and can be used to design structural, products that would withstand a certain load,, heavy traffic usage, etc., NDT examines material without impairing, its ultimate usefulness. It does not distort the, specimen and provides useful data. NDT, allows suppositions about the shape, severity,, extent, distribution, and location of such, internal and subsurface residual stresses;, defects such as voids, shrinkages, and cracks;, and others. Test methods include acoustic, emission, radiography, IR spectroscopy, x-ray, spectroscopy, magnetic resonance spectroscopy, ultrasonic, liquid penetrant, photoelastic stress analysis, vision system, holography, electrical analysis, magnetic flux, field, manual tapping, microwave, and birefringence (Fig. 5-1)., There is usually more than one test method, to determine a performance because each, test has its own behavior and meaning. As, an example there are different tests used to, determine the abrasion resistance of materials. There is the popular Taber abrasion test., It determines the weight loss of a plastic or, other material after it is subjected to abrasion, for a prescribed number of the abrader disk, rotations (usually 1000). The abrader consists, of an idling abrasive speed controlled rotating wheel with the load applied to the wheel., The abrasive action on the circular specimen, is subjected to a rotary motion., Other abrasion tests have other type actions such as back and forth motion, one direction, etc. These different tests provide different results that can have certain relations, to the performance of a product that will be, subjected to abrasion in service., A method of evaluating the adhesive bond, to a plastic coating substrate is a tape test., Pressure-sensitive adhesive tape is applied, to an area of the adhesive coating, which is

Page 316 : 5 Testing and Meaning of Test Data, , 298, , I, , Sample log-in terminal, , Report management terminal, , LIMS/2000, , Printer, , =, 550, , Program, development, terminal, , .-+==I====l, , Program, development, terminal, , Analytical disciplines, data stations, , Gas, chromatography, , 1:15, Liquid, chromatography, , 1:15, , UV IV IS spectroscopy, , 3600, Fluorescence spectroscopy, , 3600, I nfrared spectroscopy, , Atomic spectroscopy, , 3600, , 3600, Elemental analysis, , Thermal analysis, , 3600, , 3600, , Fig.5-1 Examples of plastics evaluation in a computer-aided chemistry laboratory., , sometimes crosshatched with scratch lines., Adhesion is considered to be adequate if the, tape pulls off no coating when it is removed., A bearing strength test method is used for, determining the behavior of materials subjected to edgewise loads such as those applied to mechanical fasteners (plastics, etc.)., For plastics, one of the tests uses a flat rectangular specimen with a bearing hole centrally, located near one end. It is loaded gradually, either in tension or compression. Load and, longitudinal deformation of the hole are measured frequently or continuously to rupture, with resulting data plotted as a stress-strain, curve. For this purpose, strain is calculated by, dividing change in the hole diameter in the, direction of loading by the original hole diameter. Bearing stress is calculated by divid-, , ing the load by the bearing area being equal, to the product of the original hole diameter, and specimen thickness. Test results are influenced by the edge-distance ratio, that is the, ratio between the distance from the center, of the hole to the nearest edge of the specimen in the longitudinal direction and hole, diameter., A different type of evaluation is the potential of a material (plastic, etc.) that comes, in contact with a medical patient to cause or, incite the growth of malignant cells (that is,, its carcinogenicity). It is among the issues addressed in the set of biocompatibility standards and tests developed as part 3 of ISO10993 standard that pertain to genotoxicity,, carcinogenicity, and reproductive toxicity. It, describes carcinogenicity testing as a means

Page 317 : 5 Testing and Meaning of Test Data, to determine the tumorigenic potential of devices, materials, and/or extracts to either a, single or multiple exposures over a period, simulating the total life span of the devices., The circumstance under which such an investigation may be required is given in part 1 of, ISO-10993., Interesting that in this highly scientific, world, there are what appear to be nonscientific test methods. As an example early, during the 1930s, the US navy in Dalgren, VA, developed a very successful and useful aircraft canopy "chicken" impact test called the, Dalgren test. This test continues to be used, providing the required test results to ensure, the proper performance of a canopy in service. Basically a 4 lb (2 kg) chicken is fired, out of a cannon-like device and is used to, evaluate the impact damage on aircraft windows. Your author attempted to develop a, replacement, highly scientific test, to replace, the Dalgren test without success other than, making one more intricate and costly to conduct that provided the same results., In order to determine the strength and endurance of a material under stress, it is necessary to characterize its mechanical behavior., Moduli, strain, strength, toughness, etc. can, be measured microscopically in addition to, conventional testing methods. These parameters are useful for material selection and design. They have to be understood as to applying their mechanisms of deformation and, fracture because of the viscoelastic behavior, of plastics (Chapter 2). The fracture behavior, of materials, especially microscopically brittle materials, is governed by the microscopic, mechanisms operating in a heterogeneous, zone at the crack tip or stress raising flow., In order to supplement micro-mechanical, investigations and advance knowledge of the, fracture process, micro-mechanical measurements in the deformation zone are required, to determine local stresses and strains. In, TPs, craze zones can develop that are important microscopic features around a crack, tip governing strength behavior. For certain, plastics fracture is preceded by the formation of a craze zone that is a wedge shaped, region spanned by oriented micro-fibrils., Methods of craze zone measurements include, optical emission spectroscopy, diffraction, , 299, , techniques, scanning electron microscope,, and transmission electron microscopy., Conditioning procedures of test specimens, and products are important in order to obtain, reliable, comparable, and repeatable data, within the same or different testing laboratories. Procedures are described in various, specifications or standards such as having a, standard laboratory atmosphere [50 ± 2%, relative humidity, 73.4 ± 1.8°F (23 ± 1°C)], with adequate air circulation around all specimens. The reason for this type or other conditioning is due to the fact the temperature, and moisture content of plastics can affect, different properties., Testing and Classification, Properties of plastics such as physical, mechanical, and chemical are governed by their, molecular weight, molecular weight distribution, molecular structure, and other molecular parameters (Chapters 2 and 8); also the, additives, fillers, and reinforcements that enhance certain processing and/or performance, characteristics. Properties are also effected, by their previous history (includes recycled, plastics), since the transformation of plastic, materials into products is through the application of heat and pressure involving many, different fabricating processes. Thus, variations in properties of products can occur even, when the same plastic and processing equipment are used. Conducting tests such as those, related to molecular characteristics provides, a means of classifying them based on test, results (2)., Testing and Quality Control, Testing and QC are discussed but often, the least understood. Usually it involves, the inspection of materials and products as, they complete different phases of processing., Products that are within specifications proceed, while those that are out of specification are either repaired or scrapped. Possibly, the workers who made the out-of-spec products are notified so "they" can correct "their", mistake.

Page 318 : 300, , 5 Testing and Meaning of Test Data, , The approach just outlined is after-the-fact, approach to QC; all defects caught in this, manner are already present in the product, being processed. This type of QC will usually, catch defects and is necessary, but it does little to correct the basic problem(s) in production. One of the problems with add-on QC, of this type is that it constitutes one of the, least cost-effective ways of obtaining quality, products. Quality must be built into a product from the beginning of the design that follows the FALLO approach (Fig. 1-3); it cannot be inspected into the process. The target, is to control quality before a product becomes, defective., , Testing and People, Personnel or operators involved in testing, from raw materials to the end of the fabricating line develop capability via proper training, and experience. Experience and/or developing the proper knowledge are required to ensure that the correct test procedure is being, conducted and test results are accurate and, not interrupted incorrectly. At times, with, new problems developing on-line, different, tests are required that may be available or, have to be developed. Unfortunately a great, deal of "reinventing the wheel" can easily occur so someone should have the responsibility to be up to date on what is available., Another unfortunate or fortunate situation exists that a very viable test was at one, time developed and used within the industry., In time it was changed many times by different companies and organizations (ASTM,, ISO, etc.) to meet new industries needs concerning specific requirements. One studying, the potential of using that particular test may, not have the access to the basic test that probably is all that is required., , Basic vs. Complex Test, Choosing and testing a plastic when only, a few existed that could be used for specific products would prove relatively simple, if the selection were limited, but the variety, , of plastics has proliferated. Today's plastics, are also more complex, complicating not only, the choice but also the necessary tests. Fillers, and additives can drastically change the plastic's basic characteristics, blurring the line between commodity and engineering plastics., Entirely new plastics have been introduced, with esoteric molecular structures. Therefore, plastic suppliers now have many more, sophisticated tests to determine which plastic best suits a product design or fabricating, process., For the product designer, however, a simple basic test, such as a tensile test, will help, determine which plastic is best to meet the, performance requirements of a product. At, times, a complex test may be required. The, test or tests to be used will depend on the, product's performance requirements., To ensure quality control material suppliers and developers routinely measure such, complex properties as molecular weight and, its distribution, crystallinity and crystalline, lattice geometry, and detailed fracture characteristics (Chapter 6). They use complex,, specialized tests such as gel permeation, chromatography (2, 3), wide- and narrowangle X-ray diffraction, scanning electron microscopy, and high-temperature pressurized, solvent reaction tests to develop new polymers and plastics applications., , Specification and Standard, The industry specifications and standards, are regularly updated to aid designers and, processors in controlling quality and to meet, safety requirements, and thus they will prove, useful to anyone who must choose tests and, QC procedures. For example, the ASTM, UL,, ISO, and DIN (see below) tests are among, the most popular and important ones. Organizations involved directly or indirectly in, preparing or coordinating specifications, regulations, and standards include the following:, ASTM. American Society for Testing and, Materials., UL. Underwriters Laboratories., ISO. International Organization for Standardization.

Page 319 : 5, , Testing and Meaning of Test Data, , DIN. Deutsches Instut, Normung., ACS. American Chemical Society., AMS. Aerospace Material Specification., ANSI. American National Standards, Institute., ASCE. American Society of Chemical, Engineers., ASM. American Society of Metals., ASME. American Society of Mechanical, Engineers., AWS. American Welding Society., BMI. Battele Memorial Institute., BSI. British Standards Institute., CPSc. Consumer Product Safety Commission., CSA. Canadian Standards Association., DOD. Department of Defense., DODISS. Department of Defense Index &, Specifications & Standards., DOT. Department of Transportation., EIA. Electronic Industry Association., EPA. Environmental Protection Agency., FMRC. Factory Mutual Research Corporation., FDA. Food and Drug Administration., FMVSS. Federal Motor Vehicle Safety, Standards., FTC. Federal Trade Commission., JAPMo. International Association of, Plumbing & Mechanical Officials., IEC. International Electrotechnical Commission., IEEE. Institute of Electrical and Electronic Engineers., IFI. Industrial Fasteners Institute., IPC. Institute of Printed Circuits., ISA. Instrument Society of America., ns. Japanese Industrial Standards., MIL-HDBK. Military Handbook., NADC. Naval Air Development., NACE. National Association of Corrosion, Engineers., NAHB. National Association of Home, Builders., , 301, , NEMA. National Electrical Manufacturers' Association., NFPA. National Fire Protection Association., NIST. National Institute of Standards &, Technology (previously the National, Bureau of Standards)., NIOSH. National Institute for Occupational Safety & Health., OSHA. Occupational Safety & Health, Administration., PLASTEC. Plastics Technical Evaluation, Center., PPI. Plastics Pipe Institute., QPL. Qualified Products List., SAE. Society of Automotive Engineers., SPE. Society of Plastics Engineers., SPI. Society of the Plastics Industry., STP. Special Technical Publications of the, ASTM., TAPPI. Technical Association of the Pulp, and Paper Industry., These test procedures and standards are, subject to change, so it is essential to keep, up to date if one has to comply with them., It may be possible to obtain the latest issue, on a specific test (such as a simple tensile, test or a molecular weight test) by contacting the organization that issued it. For example, the ASTM issues new annual standards, that include all changes. Their Annual Books, of ASTM Standards contain more than seven, thousand standards published in sixty-six volumes that include different materials and, products. There are four volumes specifically, on plastics: 08.01-Plastics 1; OS.02-Plastics 11;, OS.03-Plastics III, and OS.04-Plastic Pipe and, Building Products. Other volumes include information on plastics and RPs. The complete, ASTM index are listed under different categories for the different products, types of tests, (by environment, chemical resistance, etc.),, statistical analyses of different test data, and, so on (56, 12S, 129)., The ASTM issues other useful information for the designer that are included in its, Special Technical Publications (STPs). Some, examples of STPs are STP 701, Wear Tests

Page 320 : 302, , 5 Testing and Meaning of Test Data, , for Plastics: Selection and Use, R. Bayer, ed.,, 1980,106 pages; STP 736, Physical Testing of, Plastics, R. Evans, ed., 1981, 142 pages; STP, 816, Behavior of Polymeric Materials in Fire,, E. L. Schaffer, ed., 1983, 121 pages; STP 846,, Quality Assurance of Polymer Materials and, Products, Green, Miller and Turner, ed., 1985,, 142 pages; and STP 936, Instrumental Impact, Testing of Plastics and Composite Materials,, S. L. Kessler, ed. 376 pages., Stress Analysis, , There are different techniques to evaluate, the quantitative stress level in prototype and, production products. They can predict potential problems. Included is the use of electrical resistance strain gauges bonded on the, surface of the product. This popular method, identifies external and internal stresses. Their, various configurations are made to identify, stresses in different directions. This technique, has been extensively used for over a half, century on very small to very large products, such as toys to airplanes. There is the optical, strain measurement system that is based on, the principles of optical interference. It uses, Moire, laser, or holographic interferometry, (2,3,20)., Another very popular method is using solvents that actually attack the product. It, , works only with those plastics that can be attacked by a specific solvent. Immersed products in a temperature controlled solvent for, a specific time period identifies external and, internal stresses. After longer time period's, products could self-destruct. Stress and crack, formations can be calibrated using different, samples subjected to different loads., There is the brittle coating system applied, on the surface of a product that identifies conditions such as stressed levels, cracks, etc. A, lacquer coating is applied, usually sprayed,, on the surface of the product. It provides, experimental quantitative stress-strain measurement data. As the product is loaded in, proportion to loads that would be encountered in service, cracks begin to appear in the, coating. The extent of cracks is noted for each, increment of load. Prior to this action, the, coating is calibrated by spraying it on a simple, beam and observing the strain at which cracks, appear. This nondestructive test method can, be used to aid in placing strain gauges for further measurements., Photoelastic measurement is a very useful, method for identifying stress in transparent, plastics. Quantitative stress measurement is, possible with a polarimeter equipped with a, calibrated compensator. It makes stresses visible (Fig. 5-2). The optical property of the index of refraction will change with the level, of stress (or strain). When the photoelastic, , Fig. 5-2 Photoelastic stress patterns for these two molded products during the same production run, shows that the processing conditions have changed; right view relates to why the product fails in service.

Page 321 : 5, , Testing and Meaning of Test Data, , material is stressed, the plastic becomes birefringent identifying the different levels of, stress via color patterns (2, 3, 216)., This photo elastic stress analysis is a technique for the nondestructive determination, of stress and strain components at any point, in a stressed product by viewing a transparent, plastic product. If not transparent, a plastic, coating is used such as certain epoxy, polycarbonate, or acrylic plastics. This test method, measures residual strains using an automated, electro-optical system., This concept has been known for over a, century. Expressed as Brewster's Constant, law, it states that the index of refraction in, a strained material becomes directional, and, the change of the index is proportional to the, magnitude of the stress (or strain) present., Therefore, a polarized beam in the clear plastic splits into two wave fronts in the X and, Y directions that contain vibrations oriented, along the directions of principal stresses. An, analyzing filter passes only vibrations parallel to its own transmitting plane (Chapter 4, TRANSPARENT AND OPTICAL, PRODUCT, Polarized Lighting)., The constructive and destructive interference creates the well known colorful patterns seen when stressed plastic are placed, between two polarized filters. Some information about the stress gradients comes from, observations of the patterns that provide, qualitative analysis. The index of refraction, in these directions is different and the difference (or birefringence) is proportional to the, stress level., When light that has experienced such retardation is viewed by a polarizer oriented, at 90° to the original plane of light polarization, the two components of the original light, beam interfere with one another. This results, in a change in color and intensity of the observed light. Observed colors correspond to, different levels of retardation at that point,, which in turn correspond to stress levels., To solve the measurement problem and obtain quantitative results (retardation, magnitude of the residual strain, etc.), various techniques are used. An example is using a very, simple device known as a wedge compensator, (ASTM D 4093). It is placed between the, , 303, , light coming through the sample and the analyzing filter. The compensator reverses the, retarding action of the induced strains in the, plastic. Strain is calculated in the compensator by multiplying the birefringence (retardation per unit thickness) by a strain-optic response of the plastic being tested. Equal but, opposite retardation is established and when, superimposed on the retardation caused by, the induced strain that restores a null. The intensity of the transmitted light becomes zero;, revealed by a visible black fringe. A scale on, the compensator supplies a quantitative reading of retardation., Flat surfaces that are not readily conducive, to stress evaluation by other means can be, tested by the nondestructive Moire fringe, analysis. Measurements of strains both elastic and plastic as well as evaluation of high, temperature effects on the part are possible., A transparent film with a grid of equidistant lines is initially deposed on the product., Deformation in the product due to stresses, changes the spacing between the grid lines., When a test grid is superimposed on a nondeformed grid the superposition produces an, optical effect known as Moire fringes. If the, test product is not strained and the grids, are precisely aligned, no fringes will be observed. Visible fringes can be precisely measured to determine the degree of strain in a, product., , Flaw Detection, Test methods are used to detect flaws. As, an example when flaws or cracks "grow" in, plastic, minute amounts of elastic energy are, released and propagated in the material as, an acoustic wave. A nondestructive acoustic emission test has sensors placed on the, surface that can detect these waves providing information about location and rate of, flaw growth. These principles form the basis, for nondestructive test methods such as sonic, testing., The nondestructive electrical eddy current, test is a method in which eddy current flow, is induced in the test object. Changes in, the flow by variations in the test specimen

Page 322 : 304, , 5 Testing and Meaning of Test Data, , are reflected into a nearby coil or coils for, subsequent analysis by suitable instrumentation and techniques. With the nondestructive electromagnetic test methods, different, wavelength regions of electromagnetic energy having frequencies less than those of, visible light yields information regarding the, quality of materials., A frequently used test has x-rays or gamma, rays passing through a structure that absorbs, distinctive flaws or inconsistencies in the material so that cracks, voids, porosity, dimensional changes, and inclusions can be viewed, on the resulting radiograph., The nondestructive temperature differential test by infrared is used. In this method,, heat is applied to a product and the surface is, scanned to determine the amount of infrared, radiation is emitted. Heat may be applied, continuously from a controlled source, or the, product may be heated prior to inspection., The rate at which radiant energy is diffused, or transmitted to the surface reveals defects, within the product. Delaminations, unbonds,, and voids are detected in this manner. This, test is particularly useful with RPs., With nondestructive ultrasonic test back, and forth scanning of a specimen is accomplished with ultrasonics. This NDT can be, used to find voids, delaminations, defects in, fiber distribution, etc. In ultrasonic testing, the sound waves from a high frequency ultrasonic transducer are beamed into a material. Discontinuities in the material interrupt, the sound beam and reflect the energy back, to the transducer, providing data that can be, used to detect and characterize flaws. It can, locate internal flaws or structural discontinuities by the use of high frequency reflection, or attenuation (ultrasonic beam)., Of historical interest may be the use of a, half dollar coin (the lighter weight 25¢not as, efficient). During the early 1940s the coin tap, test was used very successfully in evaluating, the performances of plastics, particularly RP, primary aircraft structures. With a good ear, (human hearing ear) there was (and is) a definite different sound between a satisfactory, and unsatisfactory RP product. The unsatisfactory product would contain voids, delaminations, defects in fiber distribution, etc. In, , the mean time the more elaborate and accurate sonic testing equipment were developed, and used., There is the microtoming optical analysis test. In this procedure thin slices (under, 30 JLm) of the plastics are cut from the product at any level and microscopically examined, under polarized light transmitted through the, sample. Rapid quality and failure analysis, examination occurs by this technique. This, technique has been used for many years in, biological studies and by metallurgists to determine flaws, physical and mechanical properties. Examination can be related to stress, patterns, mechanical properties, etc., Limitation of Test, , When working with tests it becomes, (logically) obvious in most cases that options, exist as to how the test is to be conducted., This is true for the different materials or, products (plastics, steels, etc.). Different sizes, (thicknesses, widths, and/or lengths) and/or, shapes of test specimens are usually required, with plastics such as those rigid to flexible to, brittle. Different speed of testing are used,, and so on. The explanation in the test provides a guideline as to what specific test conditions and specimen are used for the different, types of materials. Another potential variable, relates to specimen shrinkage, which results, from the preparation of specimens. After being processed or upon cooling, specimens, can develop nonuniform shrinkage (sink, marks)., These test methods and the number and, complexity of the variables present is related, to the level of sophistication of the test. The, combination that can influence test data defines the test limitations. Variables are found, not only in test methods, but also in other, non-test-related areas affecting data generation. Examples include misinterpretation,, misuse, or misapplication of the test or any of, its integral parts (test setup, test procedure,, reporting, etc.) contribute to their limitations, (2 to 11, 64, 208)., Test variables are a primary contributor, to test limitations. These limitations are

Page 323 : 5, , Testing and Meaning of Test Data, , determined by the variables within a standard, test method (STMs from ASTM) and within, statistical analysis. Variables are also associated with materials (Chapter 6), and processability (Chapter 8). Adding to test limitations, is a general lack of understanding regarding, the language of testing. As usually reported,, some people do not know the definition of, a test, nor do they know the difference between physical properties (length, temperature, density, etc.) and mechanical properties (tensile, flex, impact, etc.). Also, the term, sample and specimen are sometimes used, interchangeably that is not correct., Let it be known that one can say the tests, are essential and all provide useful functions., However like design, material and process, variables that exist, there are also testing variables. In order to apply them to a design, the, designer should understand their meanings, and purpose for existing. The result will be, the proper use of tests., Meaning of Data, , It is evident that in order to use the data, from those you perform to those from material suppliers data sheets, it is imperative to, have a thorough understanding of how the, data are evolved and what caution is to be, exercised when applying the data to product, designs or other evaluations. They can easily be interpreted incorrectly to mean something one desire's in their design approach., Interpretations are always made and provide excellent logical approaches to developing a design however they require dedicated, concentrations and relationships to the basic, meaning of the test., In reality tests have only certain meanings., The following information provides examples of guides as to the meaning to a test. Tests, reviewed are based on ASTM standards., Very limited reviews are provided in each, of the following examples regarding size of, specimens, speed of testing, and so forth that, are provided in the specific standards or specifications. Information in the standards or, specifications generally provide much more, details on what they mean. When reviewing, , 305, , a test that is to be used in a purchase order,, etc. make sure you have proper identification, of the test including where required specimen, configuration with test's date of issue. What is, important to the designer is if the test relates, to the product performance requirements., Physical Property, , Specific Gravity/Density, , Specific gravity and density are frequently, used interchangeably; however, there is a, very slight difference in their meaning. Specific gravity is the ratio of the weight of a given, volume of material at 73.4°F (23°C) to that of, an equal volume of water at the same temperature. Density is the weight per unit volume, of material at 73.4°F (23°C) (Table 5-1). Water is the standard where it has a specific gravity of 1. The density of water is at 62.4 Ib/ft3 ., The discrepancy enters because water at, 73.4°F (23°C) has a specific gravity slightly, less than one. To convert density to specific gravity, the following factor can be used, (ASTM D 792):, Density, g per cm3 = specific gravity, x 0.99756, (5-1), To the designer, the specific gravity is useful in calculating strength-to-weight and costto-weight ratios, and as a means of identifying, a material., Specific volume is a conversion of specific, gravity into cubic inches per pound. Since the, volume of material in a product is the first bit, of information established after its shape is, formulated, the specific volume is a convenient conversion factor for weight:, Specific volume (in3 lib), = 27.7/specific gravity, , (5-2), , Many different additives, fillers, andlor reinforcements are used in plastic materials., The weight ofthe compounds change according to the amount included. Figure 5-3 provides a guide to determining their specific, gravities.

Page 324 : 5 Testing and Meaning of Test Data, , 306, , Table 5-1 Specific gravity and density, comparisons of different materials, , Materials, , Specific, Gravity, , Density,, lb./cubic in., , Thermoplastics, ABS, Acetal, Acrylic, Cellulose Acetate, Cellulose Acetate, Butyrate, Cellulose Propionate, Ethyl Cellulose, Methyl Methacrylate, Nylon, Glass-Filled, Nylon, Polycarbonate, Polyethylene, Polypropylene, Polybutylene, Polystyrene, Polyimides, PVC-Rigid, Polyester, , 1.06, 1.43, 1.19, 1.27, 1.19, , 0.0383, 0.0516, 0.0430, 0.0458, 0.0430, , 1.21, 1.10, 1.20, 1.40, 1.12, 1.20, 0.94, 0.90, 0.91, 1.07, 1.43, 1.20, 1.31, , 0.0437, 0.0397, 0.0433, 0.0505, 0.0404, 0.0433, 0.0339, 0.0325, 0.0329, 0.0386, 0.0516, 0.0433, 0.0473, , Thermosets, Alkyds, Glass-Filled, Phenolic-G.P', Polyester, Glass-Filled, , 2.10, 1.40, 2.00, , 0.0758, 0.0505, 0.0722, , Rubber, , 1.25, , 0.0451, , 2.64, 8.50, , 0.0953, 0.3070, , 7.85, 7.92, 1.81, 7.10, 6.60, , 0.2830, 0.2860, 0.0653, 0.2560, 0.2380, , Metals, Aluminum, SAE-309 (360), Brass-Yellow (#403), Steel-CR Alloy, (Strip & Bar), Steel-Stainless 304, Magnesium AZ-91B, Iron-Pig, Basic, Zinc-SAE-903, , The number of grams per cubic centimeter is the same, as the specific gravity. For example, if the specific gravity, is 1.47, that substance has a density of 1.47 gms/em3 ., , Water Absorption, The data should indicate the temperature, and time of immersion and the percentage of, weight gain of a test specimen. The same applies to data at the saturation point of 73.4°F, (23°C), and, if the material is usable at 212°F, (l00°C), also to saturation at this temperature., , Moisture or water absorption is an important design property. It is particularly significant for a product that is used in conjunction with other materials that call for fits and, clearances along with other close tolerance, dimensions., The moisture content of a plastic affects, such conditions as electrical insulation resistance, dielectric losses, mechanical properties, dimensions, and appearances. The effect, on the properties due to moisture content depends largely on the type of exposure (by, immersion in water or by exposure to high, humidity), the shape of the product, and the, inherent behavior properties of the plastic, material. The ultimate proof for tolerance, of moisture in a product has to be a product test under extreme conditions of usage in, which critical dimensions and needed properties are verified. Plastics with very low watermoisture absorption rates tend to have better, dimensional stability., Water Vapor Transmission, There are substantial differences in the, rates at which water vapor and other gases, can permeate different plastics. For instance,, PE is a good barrier for moisture or water, vapor, but other gases can permeate it rather, readily. Nylon, on the other hand, is a poor, barrier to water vapor but a good one to other, vapors. The permeability of plastic films is reported in various units, often in grams or cubic centimeters of gas per 100 in.2 per mil of, thickness (0.001 in.) of film per twenty-four, hours. The transmission rates are influenced, by such different factors, as pressure and temperature differentials on opposite sides of the, film., The effectiveness of a vapor barrier can be, rated in a term such as perms. An effective, vapor barrier in buildings should have a rating no greater than, say, 0.2 perm. A rating of, one perm means that one ft 2 of the barrier is, penetrated by one gram of water vapor per, hour under a pressure differential of one in., of mercury. One in. of mercury equals virtuallyO.S psi; one gram is one seven-thousandth, of a pound.

Page 325 : 307, , 5 Testing and Meaning of Test Data, C, Reference line, , o, , Specific gravity, compound, , 4.0, , 4.0, , 3.0, , 3.0, , 2.5, , 2.5, , 2.0, , 2.0, , A, Specific gravity resin or filler, 5.0, 4.0, 3.0, , B, Weight fractio,}/, 1.0/, 0.8, 0.6, 0.5, 0.4, , 0.70, 0.60, 0.50, 0.40, 0.35, 0.30, , 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, , 0.25, 0.20, 0.15, , 0.6, 0.5, , 0.10, 0.09, 0.08, 0.07, 0.06, 0.05, , 0.3, 0.2, , Fig. 5-3, , 0.04, , Nomograph for determining specific gravity., , A similar problem is presented by vehicle tires and certain blow molded bottles,, which must be virtually impermeable to air, and other gases. An example of the use of a, very impermeable elastomers is butyl rubber., Because of its impermeability to gases, butyl, rubber is used as a roof coating. With plastic bottles, different layers of both coinjected, and coextruded plastics (Chapter 8) can be, used to fabricate the bottle to make it impermeable to different vapors and gases depending on the barrier plastic included., , Water Vapor Permeability, The material to be tested is fastened over, the mouth of a dish that contains either water or a desiccant. This assembly is placed, in an environment of constant humidity and, temperature. The gain or loss in weight of, , the assembly is used to calculate the rate of, water vapor movement through the specimen under prescribed conditions of humidity inside and outside of the dish. The results are reported in grams per 100 square, inches during 24 hours, or equivalent metric, units., It should be recognized that all plastic materials over a time period allow a certain, amount of water vapor, organic gas, or liquid to permeate the thickness of the material., It is only a matter of degree of permeation, between various materials used as barriers, against vapors and gases. It has been found, that the permeability coefficient is a function of the solubility coefficient and diffusion, coefficient. The process of permeation is explained as the solution of the vapor into the, incoming surface of the barrier, followed by, diffusion through the barrier thickness, and, evaporation on the exit side.

Page 326 : 308, , 5 Testing and Meaning of Test Data, , The problem of permeability exists whenever a plastic material is exposed to vapor, moisture, or liquids. Typical cases are, electrical batteries, instruments, components, installed underground, encapsulated electrical components, food packaging, and various fluid-material containers. In these cases,, a plastic material is called upon to form a barrier either to minimize loss of vapor or fluid or, to prevent the entrance of vapor or fluid into, a product. From the designers' viewpoint, the, tolerable amount of permeation established, by test under conditions of usage with a prototype product of correct shape and material, is the only direct answer., Different factors influencing permeation., (1) The composition of the barrier, including, additives, fillers, colorants, plasticizers, etc., Even when data on permeability are available for a specific industry grade of a plastic,, they cannot be used for evaluation because, different commercial grades can contain ingredients that can change the values. (2) Crystalline plastics are better vapor barriers than, amorphous plastics. Also, TSs have better, barrier properties than TPs, especially when, the fillers are nonmoisture absorbing. (3) An, increase in temperature brings about an increase in permeability. Additionally, an increase in vapor pressure of the permeating, agent also causes acceleration of transmission. (4) Product thickness is inversely proportional to permeation, i.e., with double the, thickness, there is one-half of the evaporation. (5) Coatings such as epoxy-based finishes will improve resistance to permeation., (6) In the case of organic vapors, the permeation will depend not only on the composition, of the barrier, but also on the molecular configuration of both the barrier material and the, permeating agent., , Shrinkage, The use of correct shrinkage information, is very important, not only for having the, desired proportions of a product, but also, for functional purposes. The shrinkage data, can be shown in a range of two values. The, lower figure is intended to apply to thin parts,, , whereas the higher figure would involve, thicker parts. Your interest is in your specific thicknesses). Determining the shrinkage, to occur when products (plastics, steels, etc.), are fabricated is not an easy task even when, similar products are to be manufactured., The choice of shrinkage for a selected material and a specific product is the responsibility initially of the designer but also involves, the mold or die designers and the fabricators. When the product designer has limited, knowledge on how shrinkage is effected by, the mold or die during fabrication, these people have to be included in the design. If experience with the selected grade of plastic is, limited, the design should be submitted to, the material supplier for recommendations, or someone how is knowledgeable, and the, data coordinated with the interested parties., , Tolerance Where very close tolerances, are involved, preparing a prototype of the, full size product may be necessary to establish, critical dimensions. If this step is not practical, it may be necessary to test a mold or die, during various stages of cavity or die opening manufacture with allowances for correction in order to determine the exact shrinkage, needed., Considering the factors that can contribute, to variations in shrinkage during the fabrication of the products, it will be fully appreciated how significant it is to select the appropriate numbers. The data on shrinkage have, to be approached with much care if one is, to avoid dimensional problems with the plastic product. Examples of how shrinkage is influenced by different processes will provide, some insights on how critical it is to ensure, a degree of repeatability in the materials behavior and the process. Chapters 6 and 7 provide more information., As an example the shrinkage and in turn, its tolerance of injection molded TPs will be, affected as follows. (1) Higher cavity pressures will cause lower shrinkages. (2) Thick, sections will shrink more than thin ones. (3) A, cooler at the time ofthe product being ejected, from the mold cavity will bring about a lower, shrinkage. (4) A melt temperature of the material at the lower end of the recommended

Page 327 : 5 Testing and Meaning of Test Data, , 309, , Mechanical, Properties, , Rigidity, Tensile, Yield, Compression, Flexural, Shear, Creep, Stress ru plure, , % elongation, % reduction in, area, Bend radius, , Modulus of, elasticity, Flexural modulus, , I mpact strength, Notch sensitivity, Critical stress, intensity factor, , Hardness, Wear resistance, Fatigue strength, , Fig. 5-4 General guides to mechanical property tests., , range will produce a lower shrinkage. (5) A, longer cycle time, above the required solidification point, will partially conform the product closer to the mold dimensions, thereby, bringing about lower shrinkage. (6) Openings in a product (holes and core shapes) will, somewhat interfere with shrinkage in the cavity and thus will bring about lower and varying shrinkages than would be the case in a, product without openings. (7) Larger feeding, gates to the product will cause lower shrinkage permitting higher pressure buildup in the, cavity. (8) Materials that are crystalline have, dual shrinkage so they are higher in the direction of material flow and lower perpendicular to it. In a symmetrical part; when center gated, the shrinkage will average out and, be reasonably uniform. (9) Most TPs attain, their full shrinkage after 24 hours, but there, are some which may take weeks to stabilize, their dimensions fully (manufacturer of the, material usually indicates whether there is a, delayed shrinkage effect present). (10) Glass, fiber-reinforced or otherwise filled TPs have, considerably lower shrinkages than the basic, plastic., The TS plastic compression-molded products will have a higher shrinkage when:, (1) cavity pressure is on the low side,, (2) when mold temperature is on the high, side, (3) when cures are shorter, (4) when, products are thicker, (5) when a material is, soft flowing (highly plasticized), (6) when a, material is preheated at relatively low heat,, and/or (7) when a high moisture content is, present in the raw material., , Mechanical Property, , As summarized in Fig. 5-4 mechanical properties encompass different behaviors., , Tensile Property, It should be recognized that tensile properties would most likely vary with a change, of speed of the pulling jaws and with variation in the atmospheric conditions. Figure, 2-14 shows the variation in a stress-strain, curve when the speed of testing is altered; also, shown are the effects of temperature changes, on the stress-strain curves. When the speed of, pulling force is increased, the material reacts, like brittle material; when the temperature, is increased, the material reacts like ductile, material., The tensile data show the stress necessary, to pull the specimen apart and the elongation prior to breaking. A moderate elongation (about 6 % ) of a test specimen generally, implies that the material is capable of absorbing rapid impact and shock. The area under, the stress-strain curve is indicative of overall toughness except for reinforced plastics, (Fig. 2-9). A material of very high strength,, high rigidity, and little elongation would, tend to be brittle in service. For applications, where almost rubbery elasticity is desirable,, a high ultimate (over 100%) elongation is an, asset., The tensile test and the calculated property, data from it provide a most valuable source of

Page 328 : 310, , 5 Testing and Meaning of Test Data, , information for the designer in determining, product dimensions. The important consideration is that use conditions compare reasonably closely to the test conditions as far, as speed of load, temperature, and moisture, are concerned. Should use conditions differ appreciably, a test should be requested, for data that are comparable to service requirements, which would thereby ensure that, applicational needs will be based on more, exacting data. The test is relatively inexpensive, and, where critical uses are encountered,, it will eliminate interpolation and guessing., The tensile data are also useful for comparing various materials in this property. It is to, be noted that tensile data should only be applied to short-term stress conditions, such as, operating a switch or shifting a clutch gear,, etc., The yield point is the first point on the, stress-strain curve at which an increase in, strain occurs without an increase in stress., The stress at which a material exhibits a speciallimiting deviation from the proportionality of stress-to-strain is the yield strength., A material whose stress-strain curve exhibits points of zero slope may be considered, to have a yield point such as described in, Fig. 2-11. The data sheets usually omit the, yield strength when there is a zero slope point, on the stress-strain curve in the yield region., In reinforced plastic materials, the values of, the yield strength and the tensile strength are, very close to each other., The important tensile modulus (modulus, of elasticity) is another property derived from, the stress-strain curve. The speed of testing,, unless otherwise indicated is 0.2 in.!min, with, the exception of molded or laminated TS, materials in which the speed is 0.05 in.!min., The tensile modulus is the ratio of stress to, corresponding strain below the proportional, limit of a material and is expressed in psi, (pounds per square inch) or MPa (megaPascal) (Fig. 2-7)., The proportional limit is the greatest stress, that a material is capable of sustaining without any deviation of the proportionality law., It is located on the stress-strain curve below, the elastic limit. The elastic limit is the great-, , est stress that a material is capable of sustaining without any permanent strain remaining, upon complete release of the stress., For materials that deviate from the proportionality law even well below the elastic, limit, the slope of the tangent to the stressstrain curve at a low stress level is taken as, the tensile modulus. When the stress-strain, curve displays no proportionality at any stress, level, the secant modulus is employed instead, of the tensile modulus (Fig. 2-2). The secant, modulus is the ratio of stress to corresponding strain, usually at 1 % strain or 85 % from, the initial tangent modulus., The tensile modulus is an important property that provides the designer with information for a comparative evaluation of plastic, material and also provides a basis for predicting the short-term behavior of a loaded product. Care must be used in applying the tensile, modulus data to short-term loads to be sure, that the conditions of the test are comparable, to those in use. The longer-term modulus is, treated under the creep test (Chapter 2)., The tensile data can be applied to the design of short-term (such as 1 or 2 hour duration) or intermittent loads in a product provided the use temperature, the humidity, and, the speed of the load are within 10% of the, test conditions outlined under the procedure., The intermittent specification merely indicates that there be sufficient time for strain, recovery after the load has been removed., The next step is to determine an allowable working stress. This is done by using, a safety factor usually of 1 t;z to 21/2 on the, yield strength or tensile strength. If the type, of stress is clearly defined, the 1 t;z factor is, adequate; otherwise, it should be higher, (Chapter 2, Safety Factor)., The final step is to calculate the elongation that the product would experience under the selected allowable working stress to, see if such an elongation would permit the, proper functioning of the product. The elongation could conceivably become the limiting component, and the working stress can, be calculated from:, Modulus, , = stress/strain = E, , (5-3)

Page 329 : 5 Testing and Meaning of Test Data, If product use conditions vary appreciably, from those of the standard test, a stress-strain, curve, derived using the procedure of anticipated requirement, should be requested and, appropriate data developed., , Flexural Property, , These properties apply to products subjected to bending, and, since many plastic, products are involved in uses where bending, stresses are generated, this deserves close attention, especially in view of the viscoelastic, nature of the materials., It should be noted that test information, would vary with specimen thickness, temperature, atmospheric conditions, and different, speed of straining force. This test is made at, 73.4°F (23°C) and 50% relative humidity. For, brittle materials (those that will break below, a 5% strain) the thickness, span, and width, of the specimen and the speed of crosshead, movement are varied to bring about a rate, of strain of 0.01 in.lin.lmin. The appropriate, specimen size are provided in the test specification., The flexural strength is the maximum stress, that a material sustains at the moment of, break. For materials that do not fail, the, stress that corresponds to a strain of 5% is, frequently reported as the flexural strength, (Fig. 2-15)., As a matter of interest it should be stated, that in this test the force of bending and associated amount of deflection is recorded. A, formula gives the relationship between deflection and strain:, The flexural yield strength is determined, from the calculated data of load-deflection, curves that show a point where the load does, not increase with an increase in deflection., The flexural modulus is the ratio, within, the elastic limit, of stress to corresponding, strain. It is calculated by drawing a tangent, to the steepest initial straight-line portion of, the load-deflection curve and using an appropriate formula., In many plastic materials, as is the case, with metals, when performing the flexural, , 311, , tests, increasing the speed of deflecting force, makes the specimen appear more brittle and, increasing the temperature makes it appear, more ductile. This is the same relationship as, in tensile testing., When materials are evaluated against each, other, the flexural data of those that break in, the test cannot be compared unless the conditions of the test and the specimen dimensions, are identical. For those materials (most TPs), whose flexural properties are calculated at, 5% strain, the test conditions and the specimen are standardized, and the data can be, analyzed for relative preference. For design, purposes, the flexural properties are used in, the same way as the tensile properties. Thus,, the allowable working stress, limits of elongation, etc. are treated in the same manner as, are the tensile properties., Compressive Property, , The compressive data are of limited design, value. They can be used for comparative material evaluation and design purposes if the, conditions of the test approximate those of, the application. The data are of definite value, for materials that fail in the compressive test, by a shattering fracture. On the other hand,, for those that do not fail in this manner, the, compressive information is arbitrary and is, determined by selecting a point of compressive deformation at which it is considered that, a complete failure of the material has taken, place. About 10% of deformation are viewed, in most cases as maximum., The test can provide compressive stress,, compressive yield, and modulus. Many plastics do not show a true compressive modulus of elasticity. When loaded in compression, they display a deformation, but show, almost no elastic portion on a stress-strain, curve; those types of materials should be, compressed with light loads. The data are derived in the same manner as in the tensile test., Compression test specimen usually requires, careful edge loading of the test specimens, otherwise the edges tend to flour/spread out, resulting in inacturate test result readings, (2-19).

Page 330 : 312, , 5 Testing and Meaning of Test Data, , Shear Strength, The specimen is mounted in a punch-type, shear fixture, and the punch (1 in. diameter), is pushed down at a rate of 0.05 in.lmin until the moving portion of the sample clears, the stationary portion. Shear strength is calculated as the force per area sheared. Shear, strength is particularly important in film and, sheet products where failures from this type, of load may occur (Fig. 2-21). This property, can be used for comparison with other materials and for determination of the forces, needed for punching openings (holes, etc.)., Izod Impact, The popular Izod impact tester can use, different size specimens depending on the, type of plastic and their method of fabrication. The specimen is usually 1/8 in. x 1/2 in., x 2 in.; other sizes are also used. Specimens, can be notched or unnotched. A notch is cut, in a specified manner on the narrow face of, the specimen. The sample is clamped in the, base of a pendulum testing machine so that it, is cantilevered upward with the notch facing, the direction of impact. The pendulum is, released, and the force expended in breaking, the sample is calculated from the height the, pendulum reaches on the follow-through., The speed of the pendulum at impact is, controlled., The impact test, with its usual notch, indicates the energy required to break notched, specimens under standard conditions. It is, calculated as foot-pounds per inch (JIm) of, notch and is usually calculated on the basis of, 1 in. wide specimen, although the specimen, may be thinner in the lateral direction., The Izod value is useful in comparing various types of grades of a plastic within the, same material family. In comparing one plastic with another, however, the Izod impact, test should not be considered a reliable indicator of overall toughness or impact strength., Some materials are notch-sensitive and develop greater concentrations of stress from, the notching operation. It should be noted, that the notch serves not only to concentrate, the stress, but also to present plastic deformation during impact., , The lzod impact test may indicate the need, to avoid inside sharp corners on parts made, of such materials. For example, nylon and, acetal-type plastics, which in molded products are among the toughest materials, are, notch-sensitive and register relatively low, values on the notched Izod impact test., Tensile Impact, Small and long specimens of tensile bar, shape specimens have their major change in, dimensions in the necked-down section. The, specimen is mounted between a pendulum, head and crosshead clamp on the pendulum, of an impact tester. The pendulum is released, and it swings past a fixed anvil that halts the, crosshead clamp. The pendulum head continues forward, carrying the forward portion, of the ruptured specimen. The energy loss, (tensile impact energy) is recorded, as well, as whether the failure appeared to be of a, brittle or ductile type., This test has possible advantages over the, notched Izod test. The notch sensitivity factor is eliminated, and energy is not used in, pushing aside the broken portion of the specimen. The test results are recorded in ft-Ib/in. 2, (kJ/m 2 ). This allows for minor variations in, dimensions of the minimum in cross-section, area., Two specimens are used, Sand L (short, and long), so that the effect of elongation on, the result can be observed. A ductile failure, (best observed on the L specimen) results in, a higher elongation and, consequently, in a, higher total energy absorption than a brittle, failure (best observed on the S specimen) in, any specific material. The energy for specimen fracture is a function of the force times, the distance it travels. Thus two materials, showing the same energy values in the tensile impact test (all elements of the test being, the same) could consist of two different factors, such as a small force and a large elongation compared to a large force and a small, elongation., If one is to consider the application of these, data to a design, the size of the force and its, rate of application would have to be obtained, and compared with the design requirement., The breakdown of energy into components

Page 331 : 5 Testing and Meaning of Test Data, of force and speed becomes possible by the, addition of electronic instrumentation to the, testing apparatus, thus enabling the supplier, of the material to furnish additional information for material selection., Impact Strength, The data from the lzod and tensile impact tests can be comparatively evaluated especially when experience has been acquired, with anyone type of material (Table 5-2)., One should keep in mind their individual, limitations. Impact resistance is a significant, characteristic of a material in many product, designs. Associated with impact resistance is, the term material toughness. Neither one can, be measured in a way that is meaningful to, the designer. Per ASTM test procedures test, specimens can be of different thicknesses., With certain plastics from different manufacturers the impact strength test result for one, thickness can be higher than the other using, a different thickness. However in actual service, products from these materials can show, the tougher material to have the lower impact strength result; this is a rare situation, (Chapter 7, SELECTING PLASTIC, Property Category, Impact)., The term impact implies a very high speed, of the acting force, whereas toughness is not, related to any specific speed. Since the two, terms are used in conjunction with each other, in describing resistance to impact, it appears, desirable to correlate those readily obtainable properties that would reflect on speed, of impact and toughness., At a 73.4°F (23°C) test temperature and a, (ASTM) speed of acting force listed in each, test category, the following results prevail:, (1) a high modulus and high lzod points to a, very tough material, (2) a high modulus and, low Izod points to a brittle material, and (3) a, low modulus and high Izod points to a flexible, and ductile material., When use conditions differ from those applied to data sheet tests, certain comparative, evaluation can be made. Selecting an established high impact plastic such as polycarbonate as the standard, a tensile test would be, made on this material at use speeds of strik-, , 313, , ing force and end use environmental conditions. This provides a modulus and stressstrain curve. The same kind of test would be, made on the materials being evaluated., The area under a tensile stress-strain curve, is a measure of toughness. It thus becomes, possible to compare the modulus and areas, under the curve and thereby estimate impact strength as a percentage ofthe standard., The notch sensitivity factor is eliminated and, a judgment element is introduced that can, prove accurate if the information is diligently, analyzed. Where critical design areas involving safety to humans or protecting valuable, devices are concerned, the simulation of end, use with full size prototype products (including extremes of conditions) is the most desirable way to test selected materials., There are other types of impact tests for, shock loading where energy is required to, cause complete failure is reported. Each has, their specific behaviors that can be related to, specific product performance requirements., Tests include ball burst, ball or falling dart using different weights and heights, bag drop,, bullet-type instantaneous impact, Charpy,, dart drop, Mullen burst, tear resistance, and, tub (2)., Hardness, Hardness basically is the resistance to indentation as measured under specific conditions such as depth of indentation, load, applied, and time period. Different tests relate to different hardness behaviors of plastics. They include Barcol, Brinell, durometer, Knoop, Mohs, Rockwell, Shore, and, Vicat (2)., Hardness is closely related to strength,, stiffness, scratch resistance, wear resistance,, and brittleness. The opposite characteristic,, softness, is associated with ductility. There, are different kinds of hardness that measure, a number of different properties (Fig. 5-5)., The usual hardness tests are listed in three, categories: (a) to measure the resistance of a, material to indentation by an indentor; some, measure indentation with the load applied,, some the residual indentation after it is removed, such as tests using Brinell hardness,

Page 332 : 314, Table 5-2, , 5 Testing and Meaning of Test Data, Room temperature impact resistance data for several plastics, , Generic Material, Type, , Trademark, , ABS, , Cycolac, , Acetal copolymer, , Celcon, , Acetal, homopolymer, , Delrin, , Acrylic, , Plexiglas, , Nylon (DAM), (0.2% moisture), , Zytel, , Nylon (50% RH), (2.5% moisture), , Zytel, , Phenolic, , Durez, , Polycarbonate, , Lexan, , Polyethylene, , Dow, , Phenylene ether, copolymer, Polypropylene, , Pre vex, , Polystyrene, , Fostarene, Hostyren, , Polysulfone, , Udel, , Pro-fax, , Izod Impact Energy, for 0.318 cm (0.125 in.), thick, Notched, Specimens,, , Tensile-impact, Short, Specimens,, , Energy, Long, Specimens,, , Grade, , Jim, , kJ/m 2, , kJ/m 2, , DH, GSM, KJB, L, M25, M90, 100, 500, 900, V052/045, MI-7, DR, 101, ST801, 158L, 211, 101, ST801, 158 L, 2905Y, 152d, 18441 d, 141, 940, 08064N, 10062N, 04052N, 08035N, PQA, VKA, 6523, 7523, 8523, 50, 360, 760, 840, P-1700, P-1710, P-1270, , 235, 374, 214, 400, 85, 75, 123, 74.7, 69.4, 21b, 32c, 64b, 53, 907, 53, 80, 112, 1068, 75, 19, , 99-131 a, 102-115", 95, 100--120", , aO.159 cm (ft, in.) thick specimens., bMolded notch., , cO.635 cm (0.250 in.) thick specimen with molded notch., dlnjection-molded specimens., , 190, 150, 350, 200, 150, , 157, 153, 231, 218, , 504, 588, 611, 525, 1470, 1155, 945, , 17, , 14, 640--850, 640, 53, 48, 80, 130, 267, 293, 42.7, 133.5, 379, 21, 54, 97, 161, 69, 69, 69, , 473--631, 526, 88, 105, 140, 81, 113a, 86a, , 341, 421, 336

Page 333 : 5 Testing and Meaning of Test Data, , 315, , Hardness Scales, , Rubber, band, , Fig. 5-5, , Inner, , tube, , Auto tire, tread, , Hardness of different materials using different test methods., , Vickers and Knoop indentors, Barcol, hardness, and Shore durometers (2); (b) to, measure the resistance of a material to, scratching by another material or by a sharp, point, such as the Bierbaum hardness or, scratch-resistance test and the Moh one, for hardness; and (c) to measure rebound, efficiency or resilience, such as the various, Rockwell hardness tests. The various tests, provide different behavior characteristics, for plastics, as described by different ASTM, standards such as D 785. The ASTM and, other sources provide different degrees of, comparison for some of these tests., Some ductile plastics, such as PC and ABS,, can be fabricated like metals with punching, and cold-forming techniques. These processing techniques are analogous to the hardness, tests in that a rigid "indentor" is pressed into, a sheet of a less-rigid plastic., Durometer hardness An arbitrary numerical value that measures the resistance to, intention of a blunt indenter point of the, duro meter. The higher the number, the, greater indention hardness., Barcol hardness Also called Barcol impresser. It is a measure of the hardness, of a plastic, that includes laminate or reinforced plastic, using a Barber Coleman spring, loaded indenter. Gives a direct reading on a 0, to 100 scale; higher number indicates greater, hardness. This test is often used to measure, the degree of cure for plastics, particularly TS, plastics., , Brinell hardness A common test used to, determine the hardness of a material by indentation of a specimen. Pressing a hardened, steel ball generally 10 mm diameter down on, a specimen carries out the test, and the diameter of the subsequent impression formed, provides a basis for calculating hardness., Knoop hardness It is a measure of hardness is measured by a calibrated machine that, forces a rhomb-shape, pyramidal diamond indenter having specified edge angles under, specific small loading conditions into the surface of the test material; the long diagonal in, the material is measured after removal of the, load., Mohs hardness It is a measure of the, scratch resistance of a material. The higher, the number, the greater scratch resistance, with number 10 being termed diamond., Rockwell hardness Sheets or plaques at, least 0.25 in. thick are used. This thickness, may be built up of thinner pieces, if necessary., A steel ball under a minor load is applied to, the surface of the specimen. This indents the, specimen slightly and assures good contact., The gauge is then set at zero. Basically the, major (higher) load is applied for 15 seconds, and removed, leaving the minor load still applied. The indentation remaining after 15 seconds is read directly off the testing equipment, dial., The size of the balls used and loadings, vary, and values obtained with one set cannot

Page 334 : 316, , 5 Testing and Meaning of Test Data, , be correlated with values from another set., Rockwell hardness can differentiate the relative hardness of different types of a given, plastic; but, since elastic recovery is involved, as well as hardness, it is not valid to compare, the hardness of various types of plastic entirely on the basis of this test., Hardness usually implies resistance to, abrasion, wear, or indentation (penetration)., In plastics it only means resistance to indentation. The scales range from; (1) "R" with a, majorload of 60 kg; indenter of 0.5 in., (2) "L", with a major load of 60 kg; indenter of 0.25 in.,, (3) "M" with a major load of 100 kg; indenter, of 0.25 in., (4) "E" with a major load of, 100 kg; indenter of 0.125 in., and (5) "K" with, a major load of 150 kg; indenter of 0.125 in., The hardness is of limited value to the designer, but can be of some value when comparing these data between materials., Scleroscope hardness It is a dynamic indentation hardness test using a calibrated instrument that drops a diamond-tipped hammer from a fixed height onto the surface of, the material being tested., Shore hardness It is the indentation hardness of a material as determined by the, depth of an indentation made with an indenter of the Shore type durometer. The, scale reading on this durometer is from zero, (corresponding to 0.100 in. depth) to 100 for, zero depth. The Shore A indenter has a sharp, point, is spring-loaded, and is used for the, softer plastics. The Shore B indenter has a, blunt point, is spring-loaded at a higher value,, and is used for harder plastics., Vicat hardness It is a determination of the, softening point for TPs that have no definite, melting point. The softening point is taken, the temperature at which the specimen is, usually penetrated to a depth of 1 mm2, (0.0015 in2 ) circular or square cross section,, under a 1,000 g load., Deformation Under Load, , The specimen is a small cube, either solid, or composite. It is placed between the anvils, , of the testing machine, and loaded at 1000,, 2000, or 4000 psi. The gauge is read 10 s after, loading, and again 24 h later. The deflection, is recorded in mils. Calculation is made after, the specimen is removed from the testing machine. By dividing the change in height by the, original height and multiplying by 100, the, percentage deformation is calculated. This, test may be run at different temperatures., This test on rigid plastics indicates their, ability to withstand continuous short-term, compression without yielding and loosening, when fastened as in insulators or other assemblies by bolts, rivets, etc. It does not indicate, the creep resistance of a particular plastic for, long periods of time. It is also a measure of, rigidity at service temperatures and can be, used as identification for procurement. Data, should indicate stress level and the temperature of the test., Fatigue Strength, , The fatigue strength is defined as that stress, level at which the test specimen will sustain, "N" cycles prior to failure. The data are generated on a machine that runs at 1800 cycles, per minute. This test is of value to material, manufacturers in determining consistency of, their product (Chapter 2)., Long- Term Stress Relaxation/Creep, , This review concerns the long-term behavior of plastics when exposed to conditions, that include continuous stresses, environment, excessive heat, abrasion, and continuous contact with liquids. This subject has, been reviewed in Chapter 2 (LONG-TERM, LOAD BEHAVIOR) but since itisa veryimportant subject the review is continuing. Tests, such as those outlined by ASTM D 2990 that, describe in detail the specimen preparations, and testing procedure are intended to produce consistency in observations and records, by various manufacturers, so that they can, be correlated to provide meaningful information to product designers., The procedure under this heading is intended as a recommendation for uniformity

Page 335 : 5 Testing and Meaning of Test Data, of making setup conditions for the test, as, well as recording the resulting data. The reason for this action is the time consuming nature of the test (many years duration), which, does not lend itself to routine testing. The test, specimen can be round, square, or rectangular and manufactured in any suitable manner, meeting certain dimensions. The test is conducted under controlled temperature and atmospheric conditions., The requirements for consistent results, are outlined in detail as far as accuracy of, time interval, of readings, etc., in the procedure. Each report of test results should indicate the exact grade of material and its supplier, the specimen's method of manufacture,, its original dimensions, type of test (tension,, compression, or flexure), temperature of test,, stress level, and interval of readings., When a load is initially applied to a specimen, there is an instantaneous strain or elongation. Subsequent to this, there is the timedependent part of the strain (creep), which, results from the continuation of the constant, stress at a constant temperature. In terms, of design, creep means changing dimensions, and deterioration of product strength when, the product is subjected to a steady load over, a prolonged period of time., All the mechanical properties described in, tests for the conventional data sheet properties represented values of short-term application of forces. and, in most cases, the data, obtained from such tests are used for comparative evaluation or as controlling specifications for quality determination of materials, along with short-duration and intermittentuse design requirements., The visualization of the reaction to a load, by the dual component interpretation of a, material is valuable to the understanding of, the creep process, but meaningless for design, purposes. For this reason, the designer is interested in actual deformation or part failure, over a specific time span. This means making, observations of the amount of strain at certain time intervals which will make it possible, to construct curves that could be extrapolated, to longer time periods. The initial readings, are 1,2,3,5,7,10, and 20 h, followed by readings every 24 h up to 500 h and then readings, every 48 h up to 1000 h (Chapter 2)., , 317, , The time segment of the creep test is common to all materials, i.e., strains are recorded, until the specimen ruptures or the specimen is, no longer useful because of yielding. In either, case, a point of failure of the test specimen has, been reached., The stress levels and the temperature of, the test for a material is determined by the, manufacturer. The guiding determinants are, the continuous allowable working stress at, room temperature and the continuous allowable working stress at temperatures of potential applications., The strain readings of a creep test can be, more convenient to a designer if they are presented as a creep modulus. In a viscoelastic material, strain continues to increase with, time while the stress level remains constant., Since the modulus equals stress divided by, strain, we have the appearance of a changing, modulus., The creep modulus, also known as apparent modulus or viscous modulus when, graphed on log-log paper, is normally a, straight line and lends itself to extrapolation, for longer periods of time. The apparent modulus should be differentiated from the modulus given in the data sheets, because the latter is an instantaneous value derived from the, testing machine., The method of obtaining creep data and, their presentation have been described; however, their application is limited to the exact same material, temperature use, stress, level, atmospheric conditions, and type of test, (tensile, compression, flexure) with a tolerance of ±10%. Only rarely do product requirement conditions coincide with those of, the test or, for that matter, are creep data, available for all grades of material that may, be selected by a designer. In those 'Cases a, creep test of relatively short duration such as, 1000 h can be instigated, and the information, can be extrapolated to the long-term needs., It should be noted that reinforced thermoplastics and thermosets display much higher, resistance to creep (Chapter 2)., Creep information is not as readily available as short-term property data sheets, are. From a designer's viewpoint, it is important to have creep data available for, products subjected to a constant load for

Page 336 : 318, , 5 Testing and Meaning of Test Data, , prolonged periods of time. The cost of performing or obtaining the test in comparison, with other expenditures related to product, design would be insignificant when considering the element of safety and confidence, it would provide. Furthermore, the proving, of product performance could be carried out, with a higher degree of favorable expectations as far as a plastic material is concerned., Progressive material manufacturers can be, expected to supply the needed creep and, stress-strain data under specified use conditions when requested by designer; but, if that, is not the case, other means should be utilized, to obtain required information., In conclusion regarding creep testing, it, can be stated that creep data and a stressstrain diagram indicate whether plain plastic, properties can lead to practical product dimensions or whether a RP has to be substituted to keep the design within the desired, proportions. For long-term product use under continuous load, plastic materials have to, consider creep with much greater care than, would be the case with metals., Summation, Throughout this book all the different, types of mechanical properties are presented, and reviewed. These mechanical properties, include a tremendous range of different types, that can usually be characterized by their, stiffness, strength, and toughness., Stiffness The same factors that influence, thermal expansion dictate the stiffness of, plastics. Thus in a TS the degree of crosslinking and amount of overall flexibility are, important. As an example, in a TP its crystallinity and secondary bond's strength control its stiffness., Strength The subject of strength is much, more complex than stiffness, since so many, different types exist such as short or long, term, static or dynamic, and torsion or impact, strengths. Some strength aspects are interrelated with those of toughness. This section reviews certain simplified concepts of strength, that are important influences on strength, based on long and short term exposure., , The crystallinity of TPs is important for, their short term yield strength. Unless the, crystallinity is impeded, increased molecular weight generally also increases the yield, strength. However, the cross-linking of TSs, increases their yield strength substantially, but has an adverse effect upon toughness., Long term rupture strengths in TPs are increased much more readily by increasing the, secondary bonds' strength and crystallinity, than by increasing the primary bond strength., Fatigue strength is similarly influenced, and, all factors that influence thermal dimensional, stability also affect fatigue strength. This is a, result of the substantial heating that is often, encountered with fatigue, particularly in TPs., Toughness The subject of toughness is, usually the most complex factor to define, and understand. Tough plastics are usually, described as ones having a high elongation, to failure or ones in which a lot of energy, must be expended to produce failure. For, high toughness a plastic needs both the ability, to withstand load and the ability to elongate, substantially without failing except in the, case of reinforced TSs that are tough, which, may have high strengths with low elongation., It may appear that factors contributing to, high stiffness are required, but this is not, true, because there is an inverse relationship, between flaw sensitivity and toughness: the, higher the stiffness and the yield strength of a, TP, the more flaw sensitive it becomes. However, because some load bearing capacity is, required for toughness, high toughness can, be achieved by a high trade off of certain, factors., Crystallinity increases both stiffness and, yield strength, resulting usually in decreased, toughness. This is true below 18 in most amorphous plastics, and below or above the 18 in, a substantially crystalline plastic. However,, above the 18 in a plastic having only moderate, crystallinity increased crystallinity improves, its toughness. Furthermore, an increase in, molecular weight from low values increases, toughness, but with continued increases, the, toughness begins to drop., Cross-linking produces some dimensional, stability and improves toughness in a noncrystalline type of plastic above the 18, but

Page 337 : 319, , 5 Testing and Meaning atTest Data, high levels of cross-linking lead to embrittlement and loss of toughness. This is one of the, problems with TSs for which an increase in Tg, is desired. Increased cross-linking or stiffening of the chain segments increases the Tg, but, it also decreases toughness. A popular way, to increase toughness is to blend, compound,, or copolymerize a brittle plastic with a tough, one. Although some loss in stiffness is usually encountered, the result is a satisfactory, combination of properties., , Thermal Property, , Figure 5-6 and Tables 5-3 to 5-5 provide an, introductory guide to the different thermal, properties of plastics. Heat resistance properties of plastics retaining 50% of properties, obtainable at room temperature with plastic exposure and testing at elevated temperatures are shown in Fig. 5-6 for the general, family or group type., Zone 1: acrylic, cellulose esters, crystallizable block copolymers, LDPE, PS,, vinyl polymers, SAN, SBR, and ureaformaldehyde., Zone 2: acetal, ABS, chlorinated polyether, ethyl cellulose, ethylene-vinyl acetate copolymer, furan, ionomer, phe-, , noxy, polyamides, PC, RDPE, PET, PP,, PVC, and urethane., Zone 3: polychlorotrifluoroethylene, and, vinylidene fluoride., Zone 4: alkyd, fluorinated· ethylenepropylene,, melamine-formaldehyde,, phenol-furfural, and polysulfone., Zone 5: acrylic, diallyl phthalate, epoxy,, phenol-formaldehyde, TP polyester, and, polytetrafluoroethylene., Zone 6: parylene, polybenzimidazole,, polyphenylene, and silicone., Zone 7: polyamide-imide, and polyimide;, Zone 8: plastics now being developed using rigid linear macromolecules rather, than crystallization and cross-linking,, etc., Specific family or group of plastics, (polyethylene, polyvinyl chlorides, etc.) are, compounded or alloyed to provide different, properties and/or processing behaviors. Thus, a plastic listed in Fig. 5-6 could have different, heat resistance properties., Deflection Temperature Under Load, The DTUL, also called the heat distortion, temperature (HDT) of a plastic is a method, to guide or assess its load-bearing capacity at an elevated temperature. Details on, the method of testing are given in ASTM, D648. Basically a 1.27 cm, in.) deep plastic test bar is mounted on supports 10.16 cm, (4 in.) apart and loaded as a beam. A bending, stress of either 66 psi or 264 psi (455 gPa or, 1,820 gPa) is applied at the center ofthe span., The test is conducted in a bath of oil, with, the temperature increased at a constant rate, of 2°C per minute. The DTUL is the temperature at which the sample attains a deflection of 0.0254 cm (0.010 in.). This test is only, a guide. It represents a method that could, be correlated to product designs, but as with, most other tests conducted on test specimens, and not on a finished product, it is just a guide, (Fig. 5-7)., In this test, if the specimen contains internal stresses the value will be lower than a, specimen with no stresses. In fact, the test can, , eh, , Time.h, , Fig. 5·6 Guide to heat resistance with 50% retention of properties.

Page 338 : 320, , 5 Testing and Meaning of Test Data, Examples of plastics in elevated temperature applications, , Table 5-3, , Polymer, Polyphenyls, Polyphenylene oxide, Polyphenylene sulfide, Polybenzyls; polyphenethyls, Parylenes (poly-p-xylylene), Polyterephthalamides, Polysulfanyldibenzamides, Polyhydrazides, Polyoxamides, Phenolphthalein polymers, Hydroquinone polyesters, Polyhydroxybenzoic acids, Polyimides, Polyarylsiloxanes, Carboranes, Polybenzimidazoles, Polybenzothiazoles, Polyquinoxalines, Polyphenylenetriazoles, Polydithiazoles, Polyoxadiazoles, Polyamidines, Pyrolyzed polyacrylonitrile, Polyvinyl isocyanate, ladder polymer, Polyamide-imide, Polysulfone, Polybenzaylene, benzimidazoles, (pyrrones), Polybenzoxazoles, Ionomer, , Comments, Decompose at 530°C (986°F); infusible, insoluble polymers., Decomposes close to 500°C (932°F); heat cures above 150°C, (302°F) to elastomer; usable heat range -135-185°C, ( -211-365°F)., Melts at 270-315°C (578-599°F); crosslinked polymer stable to, 450°C (842°F) in air: adhesive and laminating applications., Fusible, soluble, and stable at 400°C (752°F); low molecular weight., Melt above 520°C (968°F); insoluble; capable of forming films;, poor thermal stability in air; stable to 400-525°C (752-977°F), in inert atmosphere., Melting points up to 455°C (851°F); fibers have good tenacity,, elongation, modulus., Melting points up to 330°C (626°F); soluble; good fiber properties., Dehydrate at 200°C (392°F) to over 400°C (752°F) to form, polyoxadiazoles; good fiber properties., Some melting points above 400°C (752°F); give clear, flexible films., Melting points of 300°C (572°F) to over 400°C (752°F); formable, into fiber and film., Soluble polymers with melting points of 335°C (635°F) to over, 400°C (752°F)., Films melt at 380-450°C (716-842°F); stable to oxidation but not, to hydrolysis; tough, flexible films; good thermal stability., Commercial film, coating, and resin stable up to 600°C (1112°F);, continuous use up to 300°C (572°F)., Good thermal stability 400-500°C (752-932°F); coatings, adhesives., Stable in air and nitrogen at 400-450°C (752-842°F); elastomeric, properties for silane derivatives up to 538°C (lOOO°F); adhesives., Developmental laminating resin, fiber, film; stable 24 hours, at 300°C (572°F) in air., Stable in air at 600°C (1112°F); cured polymer soluble in, concentrated sulfuric acid., Stable in air at 500°C (932°F); tough, somewhat flexible resins;, make film, adhesive., Thermally stable to 400-500°C (752-932°F); make film, fiber,, coatings., Decompose at 525°C (977°F); soluble in concentrated sulfuric acid., Decompose at 450-500°C (842-932°F); can be made into fiber or film., Stable to oxidation up to 500°C (932°F); can make flexible elastomer., Stable above 900°C (1625°F); fiber resists abrasion with low tenacity., Soluble polymer that decomposes at 385°C (725°F); prepolymer, melts above 405°C (761°F)., Service temperatures up to 288°C (550°F); amenable to fabrication., Thermoplastic; use temperature -102°C (-152°F) to greater than, 150°C (302°F); acid and base resistant., Thermally stable to 600°C (1112°F); insoluble in common solvents;, good mechanical properties., Stable in air to 500°C (932°F); insoluble in common solvents except, sulfuric acid; nonflammable; chemical resistant; film., High melt and tensile strength; tough; resilient; oil and solvent, resistant; adhesives, coatings., ( Continues)

Page 339 : 321, , 5 Testing and Meaning of Test Data, Table 5-3, , (Continued), , Polymer, , Comments, , Diazadiphosphetidine, Phosphorous amide epoxy, Phosphonitrilic, Metal polyphosphinates, Phenylsilesesquioxanes, (phenyl-T ladder polymers), , Thermoplastic up to 350°C (662°F); thermosetting at 357°C (707°F);, cured material has good thermal stability to 500°C (932°F);, amenable to fabrication., Soluhle B-staged material; amenable to fabrication; good thermal, stability., Retention of properties in air up to 399°C (750°F)., Polymers stable to better than 400°C (752°F)., Soluble; high molecular weight; infusible; improved tensile strength;, high thermal stability to 525°C (977°F) in air; film forming., , be used to determine the degree of internal, stress. Since a stress and the deflection for a, certain depth of test bar are specified, this test, may be thought of as establishing the temperature at which the flexural modulus decreases, to particular values: 35,000 psi (240 MPa) at, 66 psi load stress, and 140,800 psi (971 MPa), at 264 psi., Coefficient of Linear Thermal Expansion, The specimen can be square or round to fit, a dilatometer test tube in a free sliding manner. The length is governed by the sensitivity, of dial gauge, the expected expansion, and the, , Table 5-4, , accuracy desired. The specimen is mounted, in the dilatometer and placed in a bath of, either -22°F (-30°C) or 87°F (+30°C) until the temperature of the bath is reached., When this takes place, the indicator dial is, read showing the expansion or contraction of, the specimen. These readings are compared, with measurement of specimen length prior, to placing it in the dilatometer., With the application of plastics in combination with other materials, the coefficient of, expansion plays an important role in making design allowances for expansions (also, contractions) of various materials at different, temperatures so that satisfactory functions of, products are ensured., , Examples of ignition and flash temperatures, Self Ignition, , Polyethylene, Polypropylene, Polytetrafluoroethylene, Polyvinyl chloride, Polyvinyl fluoride, Polystyrene, SBR (Styrene Butadiene Rubber), ABS (Acrylonitrile Butadiene Styrene, Polymethyl methacrylate, PAN (Poly acrylonitrile ), Cellulose (paper), Cellulose acetate, 66 Nylon cast, 66 Nylon spun and drawn, Polyester, , Flash Ignition, , OF, , °C, , OF, , °C, , 662, 1022, 1076, 842, 896, 914, 842, 896, 806, 1040, 446, 878, 842, 986, 896, , 350, 550, 580, 450, 480, 490, 450, 480, 430, 560, 230, 470, 450, 530, 480, , 644, 968, 1040, 734, 788, 662, 680, 734, 572, 896, 410, 644, 788, 914, 824, , 340, 520, 560, 390, 420, 350, 360, 390, 300, 480, 210, 340, 420, 490, 440

Page 340 : 322, , 5 Testing and Meaning of Test Data, , Table 5-5 Effects of elevated temperature and chemical agents on stability of plastics, Environment, , .., 5, , id, , I], Plastic Material, Acetuls, , Acrylics, Acryltmitrile·Butadiene·, Sly.. n", (ABS), Aramids (aromatic, polyamide), Cellulose DCclalCS (CA), Cellulose acetate butyrates, (CAB), Cellulose acetate, , propionate., (CAP), Oiallyl pblhalalcs (OAP,, filled), Epoxie., Elhylene copolymers (EVAI, (ethylene-vinyl, acetates), , n, , m, , 200, , 17, , 200, , n, , 200, , 77, , 200, , n, , 200, , n, , 2-4, , 2, , 4, , 5, , 3, 3-5, , 1-2, 5, 3-5, , 1-3, I, I, , 2-5, 3, 2-4, , 1-5, 2, , 2-5, 5, 2-4, , 5, 4, 1-4, , 5, 4-S, 5, , 5, 5, 1-5, , 4, , 2, , (25'C), , (93.3'C), , 1-4, 5, , 5, , n, , 5, 5, , 4, 4, 4, , 3, , 4, , 4, , 5, , 3, , 4, , 1-2, , 2-4, , 2, , 4, , 2, , 2, 1-2 3-4, 555, , 5, , 2, , 4, , 3, , 5, S, , 5, 5, , 5, , 5, , 1-2, 2, , 1-2, , 5, , 2-3, , 2, , 2, 2-3 3-4, SIS, , 4, , 4, , 200, , 4-5, 5, , I, , g, , Ii:, , by Weight, , 200, , I, 5, 3-5, , 2-3, 5, 5, , 0.22-0.25, 0.2-0.4, 0.1-0.4, , 2, , 0.6, , 5, 5, , 2-7, 0.9-2.0, , 5, , 1.3-2.8, , 3-4, , 4-5, , 0.2-0.7, , 2, 2, , 3-4, 5, , 0.01-0.10, 0.05-0.13, , Ethylenellerralluoroethylent copolymers, , ~S, , %~, , 77, , <0.03, , (ETFE), , fluoriDated ethylene, propylene. (PEP), PerftuOlOlIlkoJtles, (PPA), Polychlorotrifluoroethylene. (CTPE), Polyterraftuoroethylenes ®(TFE), , Fursns, , lonomers, Molamines (filled), Nilriles (high barrior .IIoys, of ABS or SAN), Nylons, Phenolics (filled), Polyallomers, , <0.01, I., , <0.03, , ·1, , 3, , 4, , 0.01-0.10, , o, , 4, , 4, 1, 2-4, , I, 4, I, 1-4, , 4, I, 2-5, , I, 4, , 1, I, 4, , I, 4, , 2, I, S, , I, 2, I, , I, 4, , I, , I, , 2, , I, , 2, I, 2, I, , 2, , 2, , 4, 3, 2-4, , I, 2, I, , I, 2, , 3, , 2, , 2, , 3, , 2, 4, 3, 2-4, , I, 2, 2, 2-5, , 3, , 2, , S, , 3-S, , 3, S, , S, , 5, , 5, , I, 3, , 4, I, , I, , 4, , I, , I, 4, , 1, 1-5, , 2, S, , 0.01-0.20, 0.01-1.4, 0.01-1.30, 0.2-0.5, , I, , I, 2, 3, , 0.2-1.9, 0.1-2.0, <0.01, , 5, , 1, , 3, 5, , 5, , 5, , 5, 4, , I, , 2, , A rating of 1 indicates greatest stability., , The difference in thermal expansion between the usual commodity plastics and steel, is very large. It is to be noted that some plastic material changes in length rather abruptly, at some temperatures, beyond the limits of, the test condition. In such cases, a special, investigation should be instigated, and the, coefficient of expansion established under, temperatures of usage. However there are, plastics that can be compounded to match or, even have less thermal expansion than steel,, etc., This test shows the reversible linear thermal expansion. The accuracy of these results, , may be affected by factors in certain plastics, such as loss of plasticizer, solvent, relieving of, stresses, etc. When a product demands most, precise data, the factors mentioned should be, considered for their possible influence on the, information., Brittleness Temperature, The conditioned specimens are cantilevered from the sample holder in the, test apparatus, which has been brought to, a low temperature (that at which the specimens would be expected to fail). When the

Page 341 : 323, , 5 Testing and Meaning of Test Data, Table 5-5, , ( Continued), Environment, , .5::!, ~, , .g, , In, , ~, , ~, , ~l, , ~~, , <Jl, , :;, , ], .~ ~, , !1, c, , ~~, , <'", , ,n, , ~, , II c, , .", , §i!, , 'll'", , e3i, o, , r~, , '", , ~, "'c:>, , :i, , g~~, .;<, , "'..:, , ~l, , j, , ",0, , ;I; ~, '.0, , ;1;..:, , Temperature (oF), , 77, Plastic Material, , Polyamide-imides, PolyllIJ'lsulfones (PAS), Polyburyle.es (PB), Poly.arbons.es (PC), Polyesters (thermoplastic), , Polyesters (thennoset-glass, fiber fiUed), Polyethylenes (LOPE·, HOPE-low density to, high density), Polyethylenes, (UHMWPE-ultrahigh, , (25"C), , 200, (93,3"C), , I, 4, 3, S, 2, I-J, , 5, 5, 5, 5, 3-5, , 4, , 5, , 77, , 200, , 77, , 200, , 5, 1, 3-5, 3, , 4, 4, 5, 3, 2, , 5, 5, S, S, 4, , 5, , 4, , 5, , 77, , 200, , 77, , 200, , 77, , I, , 3, 2, , 4, 2, 3, , I, , I, I, 2, , 2, 2, S, 3-4, 3, , I, , 4, , 4, , 4, , 2, J, , S, 5, 5, , 200, , 77, , 200, , 77, , 3, I, 5, , 3, , 200, , I, , I, I, 3, 2, , I, 4-5, 3, , I, 2, 2, , 4, 4, I, 3-5, 4, , 1-2, , 1-2, , 1-3, , 3-5, , 2, 3-4, , % Change, by Weighr, 0.22~.28, , 4, 3, 5, 3-4, 4-5, , 1.2-1.8, <O.OI~.J, , 0.15~.JS, , 0.06--0.09, 0.01-2.50, 0.00~.01, , 4, , <0.01, , molecular weigh£), Polyimides, , PoIyphenylene oxides, , I, 4, , (PPO) (modified), Polyphenylene sulfides, (PPS), Polyphenylsulfones, Polypropylenes (PP), Polystyrenes (PS), , Polysulfones, Polyurethanes (PUR), Polyvinyl chlorides (PVC), Polyvinyl chlorideschlorinated (CPVC), Polyvinylidene fluorides, (PVDF), Silicones, , Styrene acrylonitriles, , I, , 2, , I, , 5, , 4, , 5, , 4, 2, , 4, , I, , 0.3--0.4, 0.06--0.07, , 2, , 2, 4, 2, 4, 4, 3, 4, 4, , 4, 4, 5, 4, 4, 5, 4, , <0.05, , 4, , 4, I, 2, , 5, I, 3, 5, Z, , 5, 2-J, 5, , 5, 4-5, I, , I, 2-3, , 4, 5, 5, , 3-4, 5, 2, , I, 2-3, , 3-4, 5, 2, , 4, I, 2-3, , 1, 2-3, 5, I, , 3-4, 5, 2, , I, 2-3, 4, I, 4, 2, 2, , 1, 4-5, 1, 4, , 3, 2, 4, 3, 4, 4, 4, , 0.5, O.OI--O.OJ, 0.OJ~.60, 0.2~.J, , 0.02-1.50, 0.04-1.00, 0.04~.45, , 2, 4, 4, , (SAN), Ure., (filled), Vinyl esters (glass. fiber, filled), , 4, 5, , 2, 3, , 3, 4, , 4, 3, , I, , 3, , 1-2, , 3, 2-4, , 1-2, , I, , 2, 3, 3, 4, , 4, 2, , 4, 3, 4, , 5, 2, , 5, 4, , 0.04, , 2, 4, 3-4, , 4, , 0.1~.2, , 5, , 0.20-0.35, , 2, 4-5, , 0.01-2.50, , 0.4~.8, , A rating of 1 indicates greatest stability., , specimens have been in the test medium for, 3 minutes, a single impact is administered,, and the samples are examined for failure., Failures are total breaks, partial breaks, or, any visible cracks. The test is conducted at, a range of temperatures producing varying, percentages of breaks. From these data, the, temperature at which 50% failure would occur is calculated or plotted and reported as, the brittleness temperature of the material, according to this test, This test is of some use in judging the, relative merits of various materials for lowtemperature flexing or impact However, it, is specifically relevant only for materials and, conditions specified in the test, and the values cannot be directly applied to other shapes, and conditions., , The brittleness temperature does not put, any lower limit on service temperature for, end use products. The brittleness temperature is sometimes used in specifications., Thermal Aging, Section UL 746B provides a basis for selecting high-temperature plastics and provides a long-term thermal-aging index, the, RTI or relative thermal index. The testing, procedure calls for test specimens in selected, thicknesses to be oven aged at certain elevated temperatures (usually higher than the, expected operating temperature, to accelerate the test), then be removed at various intervals and tested at room temperature.

Page 342 : 324, , 5 Testing and Meaning of Test Data, F, 1000, 950, , 900, 850, Polyimide/Graphite, , 800, 750, , Polyimlde{Glass, Silicone, Fluoroplastics/Glass, Polyetherketoneketone (PEEK)/Graphite, Liquid Crystal/Polymer, Polyester TS!Glass, Epoxy/Glass, Nylon/Glass, Allyl/Glass, Cyanates, TS polyester!Glass, Polyetherimlde/Glass, Polybutadiene/Glass, Silicone, Melamine-Formaldehyde, , 700, 650, , 600, 550, 500, , Silicones!Glass, Polybenzimidazole (PBI), Bismaleimide, (BMI)/Carbon, Polyimide{Glass, Polyetherketone/Glass, Bismaleimide (BMI)!Glass, Polyketone{Glass, Polyetheretherketone (PEEK)/Glass, Polyphenylene Sulfide/Glass, Polyimide, Pol amide-Imide/Glass, Phenol-Formaldehyde, Cyanate Ester!Glass, , Polyethylene{Glass, , 300, , Polysulfone/Glass, PolyaromaticTP-EpoxyTS/Glass, Polyethylene Terephthalate/Glass, Si Iicon -Po lycarbonate{G lass, Polyethersu Ifone!Glass, Polyarylsulfone!Glass, Polyurea!Glass, Polysulfone, Polyester TP/Glass, Polymethylpentene, Polycarbonate Copolymer, Polypropylene/Glass, , Epoxy, PBT, Polyester TS, Polyester TP, , 250, , Polycarbonate, ABS!Glass, Polyurethane{Glass, , 200, , ABS, SAN, , 450, 400, , 350, , Vinyl/Glass, Polyurethane, , Fig. 5-7 Guide to heat resistance based on the, heat-distortion temperature per ASTM D 648 at, 264 psi., , Another reason for using higher temperatures is that for an application requiring, long-term exposure a candidate plastic is often required to have an RTI value higher, than the maximum application temperature., The properties tested can include mechanical strength, impact resistance, and electrical, characteristics. A plastic's position in a test's, RTI is based on the temperature at which it, still retains 50% of its original properties., The time required to produce a 50% reduction in properties is selected as an arbitrary failure point. These times can be gathered and used to make a linear Arrhenius plot, of log time versus the reciprocal of the absolute exposure temperature. An Arrhenius, relationship is a rate equation followed by, many chemical reactions. A linear Arrhenius, plot is extrapolated from this equation to predict the temperature at which failure is to be, expected at an arbitrary time that depends, on the plastic's heat-aging behavior, which, , are usually 11,000 hours, with a minimum of, 5,000 hours. This value is the RTI., As practiced by the UL, the procedure for, selecting an RTI from Arrhenius plots usually involves making comparisons to a control, standard material and other such steps to correct for random variations, oven temperature, variations, condition of the specimens, and, others. The stress-strain and impact and electrical properties frequently do not degrade at, the same rate, each having their own separate, RTIs. Also, since thicker specimens usually, take longer to fail, each thickness will require, a separate RTI., The UL uses RTIs as a guideline to qualify materials for many of the standard appliances and other electrical products it regulates. This testing is done in a conservative, manner qualified by judgments based on long, experience with such devices; UL does not, apply indexes automatically. In general, these, RTIs are very conservative and can be used, as safe continuous-use temperatures for lowload mechanical products., Other Heat Test, There are different heat tests, some being specific to a product environment. There, are those for temperature and also humidity., With certain materials, humidity combined, with elevated temperatures has a significant, effect on the material's behavior. This effect, would not be evident in the conventional heat, distortion test (HDT)., Test specimens can also be used to simulate, some degree of warpage. Figure 5-8 compares, unreinforced and reinforced glass fiber-TS, polyester flexural-type specimens at different temperatures in a droop test (with a center support), sag test (end supports), and an, expansion test (bolted at three points). The, study for this particular test is conducted at, various temperatures., Thus by analyzing the thermal limits of, the various materials available, starting with, the maximum and minimum environmental, temperatures under which a product must, operate and adding any thermal increase

Page 343 : 325, , 5 Testing and Meaning of Test Data, , with glass, , 260·, without glass, , with glass, , 220·, without glass, , with glass, , 160·, without glass, , with glass, Ambient, without glass, Droop Test, , Fig. 5·8, , Sag Test, , Expansion Test, , Example of droop, sag, and expansion tests using RP samples., , from hysteresis heat that develops from, flex or vibration and so on will at least, tell the designer which materials cannot be, used., The ratings given the designer will also provide some idea of the short-term stiffness to, be expected of various materials at elevated, temperatures, as well as their thermal aging, resistance with regard to certain properties., Establishing two parameters, ASTM D 648, and UL 746B, for a variety of materials provides the designer with a reasonable starting point for initially assessing materials for, high-temperature applications. Most highperformance plastics are filled compounds,, since fillers and reinforcements (Fig. 5-9) generally enhance high temperature strength and, stiffness., A general definition for a high-temperature plastic is one having a thermal value in, terms of ASTM D 648 and UL 746B higher, than 149°C (300°F). There are numerous, plastics that are both processable and have, , useful mechanical properties in the 149 to, 260°C (300 to 500°F) range (Fig. 5-10). Their, costs are usually high, but so is their performance., High-temperature plastics fall into the, usual categories of TSs and TPs. The TSs are, used principally by the aircraft and aerospace, markets but also for automotive, industrial,, medical, and electronic products. Epoxies are, principally used, with other plastics being TS, polyesters, phenolics, and urethanes. These, plastics are usually reinforced with the high, strength fibers seen in Fig. 5-9, individually or, in combination with S-glass, graphite, aramid,, and others. About 85wt% of all RPs used, in conventional-temperature environments, only require E-glass (14)., High-temperature TPs are available to, compete with TSs, metals, ceramics, and other, nonplastic materials. The heat-resistant TPs, include polyetheretherketone (PEEK) and, polyethersulfone (PES), polyamideimide,, liquid crystal polymer (LCP) and others.

Page 344 : 5 Testing and Meaning of Test Data, , 326, , GRAPHITE, , :i, , t;, , :z, , 300,000 -, , -, , 200'000~, , -, , w, , :;:;, "", , ~STEEL, , 100,000 I-, , TITANIUM, , ~LUMINUM, o ~~I--~--_I~~I--_~I~I~~I--_~I~I--~--~I~~I--~--~I~, , °, , 400, , 800, , 1200, 1600, TEMPERATURE, 'F, , 2000, , 2400, , 2800, , Fig. 5-9 Examples of tensile strengths vs. temperature in high performance materials., , These TPs have high inherent heat resistance, and offer such other advantages over TSs, as higher toughness and ease of processing., Some of these plastics are amorphous with a, high Tg such as PES, and some like PEEK and, Temperature, , CO, , 60, , PS, CA, ABS, PVC, , I:, , .g, , PUR, , C, , Red Oak, , .!:!', ..c:, , ;:;:, "''", , PC, PP, PMMA, Nylon, PTFE, , PVC 4111, , =, , ~, , 'c, , ~, , 0;, en, , PE, , Fig. 5-10 Basic guide to flash ignition and selfignition temperatures (per ASTM D 1929) for, plastics and red wood., , the liquid crystal polymer (LCP) are highly, crystalline. Some high-temperature plastics, are commercially available in neat form, with, most being available only in the filled or, reinforced form for such high-performance, products. Many of these plastics can be processed on standard or modified TP processing, equipment, which requires melting at higher, temperatures than commodity or engineering plastics, but others, like the polyimides,, may require machining into shape., The direction of high-temperature TSs appears to be toward more toughness using new, processing techniques for the aviation and, aerospace markets. The high-temperature, TPs have been receiving considerable attention as possible replacements for TSs in advanced RPs because of their higher toughness, faster processing, and ease of repair., The TPs are being promoted in both unreinforced and reinforced forms as molding and, extrusion materials. Their high continuous, use temperatures, combined with their good, chemical, water, and flame resistance and low, smoke generation, are finding new applications, particularly as their price is reduced, through higher volume usage. The growth, of TP-TS hybrids, offering TPs' ready processing combined with TSs' long-term dimensional stability, are also positive.

Page 345 : 5 Testing and Meaning of Test Data, Electrical Property, , The resistance of most plastics to the flow, of direct current is very high. Both surface, and volume electrical resistivities are important properties for applications of plastics insulating materials. The volume resistivity is, the electrical resistance of the material measured in ohms as though the material was a, conductor. Insulators will not sustain an indefinitely high voltage; as the applied voltage, is increased, a point is reached where a drastic, decrease in resistance takes place accompanied by a physical breakdown of the insulator. This is known as the dielectric strength,, which is the electric potential in volts, which, would be necessary to cause the failure of, a l/8-in. thick insulator (Chapter 4, ELECTRICALIELECTRONICS PRODUCT)., , Electrical Resistance, Specimens for these tests may be any practical form, such as flat plates, sheets, or tubes., These tests describe methods for determining the several properties defined below. Two, electrodes are placed on or embedded in the, surface of a test specimen. Different properties are obtained., Insulation resistance is the ratio of direct, voltage applied to the electrodes to the total, current between them; dependent upon both, volume and surface resistance of the specimen. In materials used to insulate and support components of an electrical network, it, is generally desirable to have insulation resistance as high as possible., Volume resistivity is the ratio of the potential gradient parallel to the current density., Surface resistivity is the ratio of the potential gradient parallel to the current along, its surface to the current per unit width of, the surface. Knowing the volume and surface, resistivity of an insulating material makes it, possible to design an insulator for a specific, application., Volume resistance is the ratio of direct voltage applied to the electrodes to that portion, of current between them that is distributed, through the volume of the specimen., , 327, , Surface resistance is the ratio of the direct, voltage applied to the electrodes to that portion of the current between them that is in, a thin layer of moisture or other semiconducting material which may be deposited on, the surface. High volume and surface resistance are desirable in order to limit the current leakage of the conductor that is being, insulated., , Arc Resistance, This test shows the ability of a material to, resist the action of an arc of high voltage and, low current close to the surface of the insulation in tending to form a conducting path, therein. The arc resistance data are of relative value only for distinguishing materials of, nearly identical composition, such as for quality control, development, or identification., , Dielectric Strength, Specimens are thin sheets or plates having parallel plane surfaces and are of a size, sufficient to prevent flashing over. Dielectric strength varies with thickness and, therefore, specimen thickness must be reported., The dielectric strength varies inversely with, the thickness of the specimen. The dielectric, strength of plastics will drop sharply if holes,, bubbles, or contaminants are present in the, specimen being tested., Since temperature and humidity affect results, it is necessary to condition each type of, material as directed in the specification for, that material. The test for dielectric strength, must be run in the conditioning chamber, or immediately after removing the specimen, from the chamber., The specimen is placed between heavy, cylindrical brass electrodes, which carry electrical current during the test. There are, two ways of running this test for dielectric, strength. In the short-time test the voltage is, increased from zero to breakdown at a uniform rate. The precise rate of voltage rise, is specified in the governing material specifications. In the step-by-step test the initial

Page 346 : 328, , 5 Testing and Meaning of Test Data, , voltage applied is 50% of breakdown voltage, shown by the short-time test. It is increased at, rates specified for each type of material, and, the breakdown level is noted. Breakdown by, these tests means passage of sudden excessive, current through the specimen and can be verified by instruments and by visible damage to, the specimen., This test is an indication of the electrical, strength of a material as an insulator. The, dielectric strength of an insulating material, is the voltage gradient at which electric failure or breakdown occurs as a continuous arc, (the electrical property analogous to tensile, strength in mechanical properties). The dielectric strength of materials varies greatly, with several conditions such as humidity and, geometry, and it is not possible to directly, apply the standard test values to field use, unless all conditions, including specimen dimensions, are the same. Because of this, the, dielectric strength test results are of relative, rather than absolute value as a specification, guide., Dielectric Constant and Dissipation Factor, The specimen may be a sheet of any size, convenient to test, but should have uniform, thickness. The test may be run at standard, room temperature and humidity, or in special, sets of conditions as desired. In any case, the, specimens should be preconditioned to the, set of conditions used. Electrodes are applied, to opposite faces of the test specimen. The, capacitance and dielectric loss are then measured by comparison or substitution methods, in an electric bridge circuit. From these measurements and the dimensions of the specimen, dielectric constant and loss factor are, computed., The dissipation factor is a ratio of the real, power (in-phase power) to the reactive power, (power 90° out of phase ).It is also defined as:, (1) IT is the ratio of conductance of a capacitor in which the material is the dielectric to, its susceptance, (2) IT is the ratio of its parallel reactance to its parallel resistance; it is the, tangent of the loss angle and the cotangent, , of the phase angle, and (3) IT is a measure of, the conversion of the reactive power to real, power, showing as heat., The dielectric constant is the ratio of the, capacity of a condenser made with a particular dielectric to the capacity of the same condenser with air as the dielectric. For a material used to support and insulate components, of an electrical network from each other and, ground, it is generally desirable to have a low, level of dielectric constant. For a material to, function as the dielectric of a capacitor, on, the other hand, it is desirable to have a high, value of dielectric constant, so that the capacitor may be physically as small as possible., The loss factor is the product of the dielectric constant and the power factor, and, is a measure of total losses in the dielectric, material., Optical Property, , Examples of plastics' transparent properties are shown in Table 5-6. A basic behavior of the appearance of a transparent material, that is one that transmits light, is its, transmittance: the ratios of the intensities of, light passing through and the light incident on, the specimen. Similarly, the appearance of an, opaque material (one which may reflect light, but does not transmit it) is characterized by, its reflectance, the ratio of the intensities of, the reflected and incident light. A translucent, substance is one that transmits part and reflects part of the light incident on it. Gloss is, the geometrically selective reflection of a surface responsible for its shiny or lustrous appearance. This property may be measured by, the use of various photoelectric instruments, or simply by observation., Haze and Huminous Transmittance, In this test, haze of a specimen is defined, as the percentage of transmitted light that, in, passing through the specimen, deviates more, than 2.5° from the incident beam by forward, scattering. Basically it is defined as the ratio, of transmitted to incident light.

Page 347 : 5 Testing and Meaning of Test Data, Table 5-6, , 329, , Examples of plastics' transparent properties, , Properties, Refractive, index (nD), Abbe. value (v), dnldt x 1O- 5 rC, Haze (%), Luminous, transmittance, (0.125-in., thickness), Critical angle (ic), Deflection, temperature, 3.6F/min.,, 264 psi, 3.6F/min.,, 66 psi, Coefficient of, linear thermal, expansion, Recommended, max. cont., service temp., Water absorption, (immersed, 24 hrs. at 73°F), Specific gravity, (density), Hardness, (0.25-in. sample), Impact strength, (Izod Notch), Dielectric, strength, Dielectric, constant, 60HZ, 106 Hz, Power factor, 60Hz, 106 Hz, Volume resistivity, , ASTM, Method, , Units, , Methyl, Methacrylate, (Acrylic), , Polystyrene, (Styrene) Polycarbonate, , Methyl, Methacrylate, Styrene, Copolymer, , D542, , 1.491, , 1.590, , 1.586, , 1.562, , D542, , 57.2, 8.5, <2, 92, , 30.9, 12.0, <3, 88, , 34.7, 14.3, <3, 89, , 35, 14.0, <3, 90, , 42.2, , 39.0, , 39.1, , 39.6, , 198, , 180, , 280, , 214, , 230, , 270, , 212, , in'/in./°F, x 10-6, , 3.6, , 3.5, , 3.8, , 3.6, , OF, , 198, , 180, , 255, , 200, , %, , 0.3, , 0.2, , 0.15, , 0.15, , D792, , 1.19, , 1.06, , 1.20, , 1.09, , D785-62, , M97, , M90, , M70, , M75, , D 1003, D 1003, , %, %, , D 648-56, , degree, OF, , D 696-44, , D 570-63, , D256, , ft.-lb'/in., , 0.3-0.5, , 0.35, , 12-17, , D 149-64, , V/mil, , 500, , 500, , 400, , 450, , D 150, , 3.7, 22.2, , 2.6, 2.45, , 2.90, 2.88, , 3.40, 2.90, , D 150, , 0.05, 0.03, 1018, , 0.0002, 0.0002-0.0004, >10 16, , 0.0007, 0.0075, 8 x 1016, , 0.006, 0.013, 1015, , D257, , ohm-cm, , These qualities are considered in most applications for transparent plastics, forming a, basis for directly comparing the transparency, of various grades and types of plastic. The, data are of value when a material is considered for optical purposes. Many transparent, plastics do not have water clarity, and, for, this reason, the data should indicate whether, , the material was natural or tinted when, tested., Luminous Reflectance, Opaque specimens should have at least one, plane surface. Translucent and transparent

Page 348 : 330, , 5 Testing and Meaning of Test Data, , specimens must have two surfaces that are, plane and parallel. This test is the primary, method for obtaining colormetric data. The, property determined that is of design interest, is luminous transmittance., , in Chapter 4, TRANSPARENT AND, OPTICAL PRODUCTS, Properties, Performances, and Products., Abrasion and Mar Resistance, , Opacity and Transparency, , Opacity or transparency is important when, the amount of light to be transmitted is a consideration. These properties are usually measured as haze and luminous transmittance. As, reviewed haze is defined as the percentage of, transmitted light through a test specimen that, is scattered more than 2S from the incident, beam. Luminous transmittance is the ratio of, transmitted light to incident light. Table 5-7, provides the optical and various other properties of different transparent plastics., Some definitions of key terms used in, identifying optical conditions are reviewed, , In this test for transparent plastics, the, loss of optical effects is measured when, a specimen is exposed to the action of a, special abrading wheel. In one type of test, the amount of material lost by a specimen is, determined when the specimen is exposed to, falling abrasive particles or to the action of, an abrasive belt. In another test, the loss of, gloss due to the dropping of loose abrasive, on the specimen is measured. The results, produced by the different tests may be of, value for research and development work, when it is desired to improve a material, with respect to one of the test methods. The, variables that enter into tests of this type are, , Table 5-7 Notable behaviors of some transparent plastics, Generic Family, Transparent ABS, Acrylic (PMMA), Allyl diglycol carbonate, Cellulosics, Nylon, amorphous, PET,PETG, Polyarylate, Polycarbonate, Polyetherimide, Polyphthalate carbonate, Polyethersulfone, Poly-4-methylpentene-l, Polyphenylsulfone, Polystyrene, Polysulfone, PVC, rigid, Styrene acrylonitrile, Styrene butadiene, Styrene maleic anhydride, Styrene methyl methacrylate, Thermoplastic urethane, rigid, , Notable Characteristics, Good impact properties, good processibility, Excellent resistance to outdoor exposure, crystal clarity, Good abrasion/chemical resistance, thermoset, Heat sensitive, limited chemical resistance, good toughness, Excellent abrasion resistance, moisture sensitive, Good barrier properties, not weatherable, clarity dependent, on processing, orientation greatly increases physical properties, Excellent UV resistance, high heat distortion, Excellent toughness, good thermal/flammability characteristics, Good chemical/solvent resistance, good thermallflammability, properties, inherent high color, Good thermal properties, autoclavable, Excellent thermal stability, resists creep, UV/moisture sensitive, high crystalline melting point,, lowest density of all thermoplastics, Excellent thermal stability, resists creep, inherent high color, Excellent processibility, poor UV resistance, brittle, Excellent thermal/hydrolytic stability, poor weatherability/, impact strength, Excellent chemical resistance/electrical properties, weatherable,, decomposition evolves HCI gas, Good stress-crack and craze resistance, brittle, Good processibility, no stress whitening, Higher-heat styrenic, brittle, Good processibility, slightly improved weatherability, Excellent chemical/solvent resistance, good toughness

Page 349 : 5 Testing and Meaning of Test Data, so numerous that it is questionable how the, information from such tests could be used., Some of the factors are type of abrasive,, shape of abrading particle, nature of plastic, material, speed of action on the plastic,, shape of the part and its temperature, the, manner in which the abrasive is attached to, the backing, and the bonding agent., Currently, these tests are of no practical, value to the designer and the only approach, to the problem of scratch, mar, and abrasion, resistance is to simulate actual performance, needs. For optical purposes, a cast sheet in, the allyl family of plastics known as CR39, has been used as a standard of comparison, in evaluating scratch and mar resistance of a, material. The CR39 is used for eye lenses and, other optical products where the advantages, of plastics are a consideration. Coatings have, been developed for polycarbonate, acrylics,, and other plastics that dramatically improve, the scratch and mar resistance of these, materials., , Weathering, , Outdoor Weathering, The specimen has no specified size. Specimens for this test may consist of any standard fabricated test specimen or cut/punch, pieces of sheet or machined sample. Specimens are mounted outdoors on racks slanted, at 45° and facing south. It is recommended, that concurrent exposure be carried out in, many varied climates to obtain the broadest,, most representative total body of data. Sample specimens are kept indoors as controls, and for comparison. Reports of weathering, describe all changes noted, areas of exposure,, and period of time., Outdoor testing is the most accurate, method of obtaining a true picture of other, resistance. The only drawback of this test is, the time required for several years' exposure, that are usually located in different climatic, zones around the world. A large number of, specimens are usually required to allow periodic removal and to run representative laboratory tests after exposure., , 331, , Accelerated Weathering, The specimen may be any shape. Artificial weathering has been defined by ASTM, as "The exposure of plastics to cyclic laboratory conditions involving changes in temperature, relative humidity, and ultraviolet (UV), radiant energy, with or without direct water, spray, in an attempt to produce changes in, the material similar to those observed after, long-term continuous outdoor exposure.", Three types of light sources for artificial, weathering are in common use: (1) enclosed, UV carbon arc [7.5 UV energy output, approx. (x sunlight)], (2) open-flame sunshine, carbon, and (3) water-cooled xenon arc. Selection of the light source involves many conditions and circumstances, such as the type of, material being tested, product service conditions, previous testing experience, or the type, of information desired., Since weather varies from day to day, year, to year, and place to place, no precise correlation exists between artificial laboratory, weathering and natural outdoor weathering., However, standard laboratory test conditions, produce results with acceptable reproducibility and in general agreement with data obtained from long-time outdoor exposures., Fairly rapid indications of weatherability are therefore obtainable on samples of, known materials that through testing experience over a period of time have general, correlations established. There is no artificial substitute for precisely predicting outdoor weatherability on materials with no, previous weathering history. Weatherometers produce conditions to accelerate effects, that would be observed in specimens exposed, outdoors., , Accelerated Exposure to Sunlight, The Atlas Type FDA-IR Fadeometer is, used primarily to check and compare color, stability. Besides determining the stability, of various pigments needed to provide both, standard and custom colors, the Fadeometer, is helpful in preliminary studies of various, stabilizers, dyes, and pigments compounded, in plastics to prolong their useful life.

Page 350 : 332, , 5 Testing and Meaning of Test Data, , It is primarily for testing materials to be, used in products subject to indoor exposure, and to sunlight. Exposure in the Fadeometer, cannot be related directly to exposure in direct sunlight, partially because other weather, factors are always present outdoors., , Conditioning Procedure, , These specimens are inspected periodically, and any visible crack is considered a failure., The duration of the test is reported along, with the percentage of failures. The cracking obtained in this test is indicative of what, may be expected from a wide variety of, stress-cracking agents. The information cannot be translated directly into end-use service, prediction, but serves to rank various types, and grades of polyethylene categories of resistance to environmental stress cracking., Though restricted to type 1 polyethylene, this, test can be used on high and medium density, PE materials as well as other plastics, in which, case it would be considered a modified test., , As reviewed it is important that test specimens or products be properly prepared based, on available specifications and/or standards, that provide controlled conditioning procedures when conducting weathering as well as, all other tests. The following is one example., There are other conditions set forth to provide for testing at higher or lower levels of, temperature and humidity., Procedure for conditioning test specimens, can call for the following periods in a standard, laboratory atmosphere [50 ± 2% relative humidity, 73.4 ± 1.8°F (23 ± 1°e): Adequate air, circulation around all specimens must be provided. The reason for this test is due to the, fact the temperature and moisture content, of plastics affects different properties such as, the physical and electrical properties. In order to get comparable test results at different, times and in different laboratories a standard, has been established., , Underwriters' Laboratories (UL) Test 94, can be used. The placement of the specimen, the size of the flame, and its position, and location with respect to the specimen, are described in detail in this important UL, specifications. Depending on their nonburning to burning capabilities, results of tests are, reported as being materials classed 94V-0,, 94V-l, 94V-2, 94-5V, etc. (Chapter 2, HIGH, TEMPERATURE, Flammability)., , Harmful Component, , Oxygen Index, , Review in Chapter 2, WEATHERINGI, ENVIRONMENT, Weather Resistance., , The test method describes a procedure, for measuring the minimum concentration of, oxygen in a flowing mixture of oxygen and, nitrogen that will support glowing combustion of plastics. The oxygen index is the minimum concentration of oxygen expressed as, a volume percent in a mixture of oxygen and, nitrogen that will just support glowing combustion of a material initially at room temperature under the conditions of this method., From this description, it is apparent that the, lower the oxygen index the more the plastic, contributes to the support of combustion., Many of the basic plastics require additives, that will improve their resistance to supporting combustion. These improvements vary in, degree, and the designer must be cautioned, not to over specify the requirement for, , Environmental Stress Cracking, This test was prepared and is limited to type, 1 (low-density) polyethylenes. Specimens are, annealed in water or steam at 212°F (l00°e), for 1 h and then equilibrated at room temperature for 5-24 h. After conditioning the, specimens are nicked according to directions, given. The specimens are bent into a U shape, in a brass channel and inserted into a test tube, that is then filled with fresh reagent (Igepal)., The tube is stoppered with an aluminumcovered cork and placed in a constant temperature bath at 122°F (50°e)., , Fire, , Flammability

Page 351 : 5 Testing and Meaning of Test Data, flammability. It should be recognized that, the highest protection against burning can, be costly, can contribute to higher specific, gravity, and can adversely affect mechanical, properties., Analyzing Testing and Quality Control, , Designers and processors should keep, quality under control and demand consistent, materials that can be used with minimum of, uncertainty. Basically involves inspection and, testing of raw materials to the finished products. Plant QC is as important to the end, result as selecting the best processing and, control conditions with the correct grade, of plastic, in terms of both properties and, appearance. After the correct plastic has, been chosen, any blending, reprocessing, and, storage stages of operation need to be frequently or continuously updated. The processor should set up specific measurements, of quality to prevent substandard products, reaching the customer. QC involve those, quality assurance actions which provide a, means to control, measure, and establish requirements of the characteristics of plastic, materials, processes, and products., From a practical aspect, when the expression "quality control" is use, we tend to think, in terms of a good or excellent product. In, industry, it is one that fulfills customer's expectations. These expectations or standards, of performance are based on the intended, use and selling price of the product. Control is the process of regulating or directing an activity to verify its conformance to, a standard/specification and to take corrective action if required. Therefore QC is the, regulatory testing process for those activities that measure a product's performance,, compare that performance with established, standards/specifications, and pursue corrective action regardless of where those activities occur., There are three phases in the evolution of, most QC systems; (1) defect detection where, an "army" of inspectors tries to identify defects; (2) defect prevention where the process, is monitored, and statistical methods are used, to control process variation, enabling adjust-, , 333, , ments to the process to be made before defects are produced; and (3) total quality control where it is finally recognized that quality, must extend throughout all functions and it is, management's responsibility to integrate and, lead the various functions towards the goals, of commitment to quality and customer-first, orientation (3)., When using the defect-detection approach, to quality control certain problems develop., Inspection does nothing to improve the process and is not very good at sorting goodfrom-bad. Also, sampling plans developed to, support an acceptable quality level (AQL) of, 5%, for example, say that a company is content to deliver or reject 5% defects., There are different methods to apply QC, on-line. An example is with infrared measurement. The ability to record IR spectra, of plastic melts provides for process monitoring and control in the manufacture process. Precise information on quality can be, obtained rapidly. Furthermore, it is also possible to make measurements on unstable intermediates of importance. Although spectroscopy on melts is considerably different, from that on solid materials, this does not, limit the information content. IR has for, many years been an important aid to investigating the chemical and physical properties, of molecules. It gives qualitative and quantitative information on chemical constituents,, functional groups, impurities, etc. As well as, its use in studying low molecular weight compounds, it is used with equal success for characterizing plastics. It is a highly informative, method of applying testing., To ensure that QC and testing procedures are followed a quality control manual should be implemented. It is a document usually setup in a computer's software, program that states and provides the details of the plant's quality objectives and how, they will be implemented, documented, and, followed., Statistical Process Control, and Quality Control, , The term statistics basically is a summary, value calculated from the observed values in

Page 352 : 334, , 5 Testing and Meaning of Test Data, , a sample or product. It is a branch of mathematics dealing with the collection, analysis,, interpretation, and presentation of masses of, numerical data. The word statistic has two, generally accepted meanings: (1) a collection, of quantitative analysis data (data collection), pertaining to any subject or group, especially, when the data are systematically gathered, and collated and (2) the science that deals, with the collection, tabulation, analysis, interpretation, and presentation of quantitative, data., Statistical process control (SPC) is an important on-line method in real time by which, a production process can be monitored and, control plans can be initiated to keep quality, standards within acceptable limits. Statistical, quality control (SQC) provides off-line, analysis of the big picture such as what was, the impact of previous improvements. It is, important to understand how SPC and SQC, operate., There are basically two possible approaches for real-time SPC. The first, done, on-line, involves the rapid dimensional measurement of a part or a non-dimensional bulk, , parameter such as weight that is the more, practical method. In the second approach,, contrast to weight, other dimensional measurements of the precision needed for SPC, are generally done off-line. Obtaining the final dimensional stability needed to measure, a part may take time. As an example, amorphous injection molded plastic parts usually, require at least a half-hour to stabilize., The SPC system starts with the premise, that the specifications for a product can be, defined in terms of the product's (customer's), requirements, or that a product is or has been, produced that will satisfy those needs. Generally a computer communicates with a series, of process sensors and/or controllers that operate in individual data loops., The computer sends set points (built on, which performance characteristics of the, product must have) to the process controller, that constantly feeds back to the computer, to signal whether or not the set of points, are in fact maintained. The systems are, programmed to act when key variables affecting product quality deviate beyond set, limits (3).

Page 353 : ________ 6 ________, Plastic Material Formation, and Variation, , Introduction, , Plastics are the most used materials on a, volume basis when compared to steel and, aluminum. They are broadly integrated into, today's lifestyle and make a major, irreplaceable contribution to virtually all market areas. They are one of a large and varied group, of materials totaling over 35,000 worldwide., They usually consist of, or contain as an essential ingredient, an organic substance. Most, are produced synthetically; very few occur in, nature. There are also plastics that contain inorganic material. Table 6-1 and Fig. 6-1 show, their manufacturing stages from raw materials to products., Practically all plastics at some stage in their, manufacture or fabrication can be formed, into various simple to extremely complex, shapes that can range from being extremely, flexible (rubbery/elastomeric) to extremely, hard (high performance properties). The use, of a virtually endless array of additives, fillers,, reinforcements, etc. permits compounding, from the raw material suppliers to the fabricators imparting specific qualities to the basic raw materials (polymers) and expanding, opportunities for plastics. Compounding relies on the polymerization chemistry to mechanical mixing to combine a base polymer, , with modifiers, additives, and other plastics, to develop new plastics. Clearly these many, combinations are endless so that new materials are always on the horizon to meet new, industry requirements., The usefulness of plastics materials is due, to the fact that they provide many different, environment resistant properties, are light in, weight, and have a higher strength per pound, than most metals and other material of construction. They can be changed into end products by the relatively simple and relatively, inexpensive means of fabricating the material in a liquid or semisolid form and then, cooling it to a solid. They usually have good, appearance and surface characteristics. The, advantages of plastics as compared to competing materials include corrosion resistance,, wide range of color and appearance properties, and, in many cases, excellent chemical, and weather resistance. Plastics are usually, well adapted to mass production methods., Their use often reduces overall manufacturing costs., Plastics are important for three main, reasons., 1. They can be manufactured with a, wide variety of properties and may very, often be "tailored" for a specific set meeting

Page 354 : New and larger, manufacturing, facilities which, will lower, prices through, economies of, sale, , Mostly, liquids, , Gases and, liquids, Monomer, manufacturers, , New manufacturing, processes which, will lower prices, through greater, efficiency and use, of lower cost raw, materials, , Polymerizers, , Monomers, , Petrochemicals plus, other chemicals are, converted into, monomers such as:, ethylene, vinyl, chloride,, acrylonitrile,, styrene, propylene, , Basic Chemical, , Petroleum is, converted to, petrochemicals, such as:, ethylene,, benzene,, propylene,, acetylene, , Chemical, , Stages in plastics manufacturing, , Important trends, and, improvements, , Customers, , State, , Stages, , Process:, , Table 6-1, , New techniques of, copolymerization, and stereospecific, polymerization, which allow, producers to, create polymers, with specific sets, of processing and, end use, characteristics, New and more effective, additives which, expand the range of, usefulness of plastics, , Processors, , Solids and, slurries, , Solids and, slurries, , New processing, equipment and, techniques which can, produce very large, and/or stress-free, parts, , Solids, Fabricators and, end users, , Processing, The plastics compounds, are formed into a, variety of solid shapes, such as sheets, tubes,, rods, film, and other, shapes, by the heat, and/or pressure of, casting, molding,, extrusion, or other, means of processing., This step may provide a, finished product such as, plastic pipe, etc., , Compounding, Plasticizers, stabilizers,, color pigments,, anti-exidants,, inhibitors, and other, chemicals are, sometimes added to, the base polymers to, form compounds, suitable for use by, processors or as, coatings for paper,, wood, etc. or in paints, and adhesives, , Polymerization, One or more, monomers are, polymerized to form, polymers or, copolymers such as:, polyethylene, poly, (vinyl chloride),, styrene-acrylonitrile,, butadiene,, copolymer (ABS),, polystyrene, polypropylene, , Fabricating, , Use of butt, welding of, large plastics, parts is, extending, the range of, shapes which, maybe, made out of, plastics, , Solids, Finishers and, end users, , These solid shapes, maybe, fabricated by, thermoforming,, machining, etc.,, to create usable, plastics articles, such as toys or, appliances, , Physical and Mechanical, Finishing, , New plating, methods which, increase the, environmental, resistance and, eye appeal of, plastics. New, graphic finishing, techniques such, as woodgraining, which will allow, plastics to, compete as, decorative items, , End users, , Solids, , In some cases, there is a, finishing step, such as the, printing of, surface designs, on vinyl film, , ~, , <:::l, , l::), , ...., , -., , ;::::., , ~, , $::)..., , ~, l::), ~, , <:::l, , l::), , -., , ~, ...., , ~, , is', -.., , ."., , ~, , ~, , ('), , -., , ~, ...., , 0\, , ~

Page 355 : 6 Plastic Material Formation and Variation, , 337, , PLASTICS SIMPLIFIED FLOW CHART GUIDE FROM RAW MATERIALS TO PRODUCTS, , I, , ENERGY, , I I, , NATURAL GAS, , PETROLEUM, , COAL, , I, , AGRICULTURE, , ~R~ "----------------------------~--------------------------~, --------------------------~--------------------------, , ~, , ~T~ "-, , ETHANE, , PROPANE, , BENZENE, , NAPHTHA, , BUTENE, , """", , ----.....-----------------------~, , / --------------------------~-------------------------ETHYLENE, STYRENE, FORMALDEHYDE, POLYOL, ADIPATE, ~, , ~~ "--, , PROPYLENE, , VINYL CHLORIDE, , CUMENE, , ACRYLIC, , ------, , ../, , "", , -------------------------~--------------------------, , ~, , ~S~ "-/, , ~C~ "-, , EXTRUSION, , INJECTION, , CALENDER, , COATING, , /", , PRODUCTS, , Fig.6-1 Plastics simplified flow chart guide from raw materials to products., , environmental and end use conditions. This, may be done by adjusting the operating conditions during manufacture, by adding fillers,, reinforcements, and/or other additives, by, copolymerization, by compounding, etc., 2. They may be processed in a wide variety, of ways, some of which are adapted to highspeed manufacturing to making very small to, very large products., 3. The wide variety of formulations and, manufacturing processes available allows the, designer to achieve the lowest possible cost, for a product, often the lowest cost of any, available construction material., It is unfortunate that plastics do not have, all the advantages and none of the disadvantages of other materials but often overlooked, is the fact that there are no materials that do, not suffer from some disadvantages or limitations. The faults of materials known and, utilized for hundreds of years are often overlooked; the faults of the new materials are, often overemphasized., , As examples, iron and steel are attacked, by the elements of weather but the common, practice of coating these with protective, plastic paints and then forgetting their, susceptibility to attack is all too prevalent., Wood and concrete are useful materials, yet, who has not seen a rotted board and cracked, concrete. Does this lack of perfection mean, that no steel, wood, or concrete should be, used? Of course not. The same reasoning, should apply to plastics. In many respects,, the gains made with plastics in a short span, of time far outdistance the advances made, in other technologies., , Definition, The term plastic comes from the Greek, word "to form." It identifies many different, plastic materials. Polymers, the basic ingredients used in practically all plastics, can be, defined as high molecular weight organic, compounds, synthetic or natural substance

Page 356 : 338, , 6 Plastic Material Formation and Variation, , consisting of molecules characterized by the, repetition (neglecting ends, branch junctions,, and other minor irregularities) of one or, more types of monomeric units. A repeated, small unit, the mer, such as ethylene, rubber, or cellulose, can represent its structure., Practically all of these polymers (base materials) use certain types of ingredients to perform properly during fabrication and meet, performance/cost requirements of products, in service., Petroleum is currently the major source of, raw materials for most high volume polymers., Also used are gas and substitute resources, such as coal that are supposedly in limited, supply (although our government reports we, have enough coal for the next 250 years, that includes its growth expansion in use, during that period), and it may well be, that another approach to the problem is, required. An example is different raw material sources to produce plastics that involve, biotechnology (186)., The term's plastic, polymer, resin, elastomer, and reinforced plastic (RP) are somewhat synonymous. However, polymer and, resin usually denote the basic material., Whereas plastic pertains to polymers or, resins containing additives, fillers, and/or reinforcements. Recognize that practically all, materials worldwide contain some type of, additive or ingredient. An elastomer is a, rubberlike material (natural or synthetic)., Reinforced plastics (also called composites, although to be more accurate called plastic, composites) are plastics with reinforcing additives, such as fibers and whiskers, added, principally to increase the product's mechanical properties., Worldwide the term preferred is plastics., The fact is that: (1) this industry identifies, itself as a plastics industry, (2) practically, all people worldwide use the term plastics,, (3) practically all materials, products, exhibition shows, technical meetings, advertising, etc. use the term plastics, and (4) as it, is repeatedly said, this is a World of Plastics. As shown in this book there are terms, that overlap and also interfere with each, other. A major example is stating that thermoplastics (TPs) are cured during processing; cure occurs only with thermoset plas-, , tics (TSs) or when a TP is converted to a, TS plastic., Plastic also refers to a material that has a, physical characteristic such as plasticity and, toughness. The general term commodity plastic, engineering plastic, advanced plastic, advanced reinforced plastic, or advanced plastic, composite is used to indicate different performance materials. These terms and others will, be reviewed latter in this chapter. Plastics are, made into specialty products that have developed into major markets. An example is, plastic foams that can provide flexibility to, rigidity as well as other desired properties, (heat and electrical insulation, toughness, filtration, etc.)., The term plastic is not a definitive one., Metals, for instance, are also permanently deformable and are therefore plastic. How else, could roll aluminum be made into foil for, kitchen use, or tungsten wire be drawn into, a filament for an incandescent, light bulb, or, a 100 ton ingot of steel be forged into a rotor for a generator. Likewise the different, glasses, which contain compounds of metals, and nonmetals, can be permanently shaped, at high temperatures. These cousins to polymers and plastics are not considered plastics, within the plastic industry or context of this, book., To better understand the properties of, plastics it is important to know about the transitions that occur, such as those that have a, glass transition temperature (Tg) (Chapter 7,, THERMAL PROPERTY, Glass Transition, Temperature). Nearly all the mechanical, properties of plastics are determined primarily by these transitions and the temperatures at which they occur. With a change, in temperature different plastics can have either quick or gradual changes in viscosity, and as temperatures increase certain materials can change from basically rigid solids, to liquids either quickly or gradually, depending on their chemical structure and, composition., , Thermoplastic and Thermoset Plastic, Thermoplastics (TPs) are plastics that repeatedly soften when heated and harden

Page 357 : 339, , 6 Plastic Material Formation and Variation, Table 6·2 Examples of melt-processing, temperatures for TPs, Thermoplastic:, , Processing Temperature Rate, , These plastics become soli when exposed, to sufficient heat and harden when cooled,, no mailer how olten the process is repeated., , "'."; ~"', ~""", ", , ;~::, , , ,,',...•...............".'.".' ....•.., , ', , "';"'-',,., , ............., ",",:',"<;:'~", '...•..... •.........••., , ....., , Thermosetting:, , ~o, . . . . . . .0. . . . ., If.., , :',"',, , The plastics materials belon9ing to this group, are set into permanent shape when heat and, pressure are applied to them during 10r'TIing., Reheating will not soHen these materials., , Ii,!, , E, . •.9, •..9. .•. . .•. . •, , Fig. 6·2 Characteristic of thermoplastics and, thermosets., , when cooled (Figs. 6-2 and 6-3 and Table 6-2)., There are those soluble in specific solvents, and burn to some degree. Their softening temperatures vary. Care must be taken, to avoid degrading, decomposing, or igniting these materials. Generally, no chemical, changes take place during processing. An, analogy would be a block of ice that can be, softened (turned back to a liquid), poured, into any shape mold or die, then cooled to, Example of a Thermoplastic, Processing Heat·Time Profile Cycle, !~, , JI-=A==--=, !l/a, ~, , low - - Time -+ liigh, , a. Start of process, b. Plastic melted, c. Plastic hard but can, be resoftened, , Example of a Thermoset, Processing Heat·Time Profile Cycle, , a. Start of process, b. Plastic melted, d. Plastic permanently hard, , Fig. 6·3 Melting characteristics of TPs and TSs, based on their heat-time processing profiles., , Material, , °C, , OF, , ABS, Acetal, Acrylic, Nylon, Polycarbonate, LDPE, HDPE, Polypropylene, Polystyrene, PVC, rigid, , 180-240, 185-225, 180-250, 260-290, 280-310, 160-240, 200-280, 200-300, 180-260, 160-180, , 356--464, 365-437, 356--482, 500-554, 536-590, 320-464, 392-536, 392-572, 356-500, 320-365, , Note: Values are typical for injection molding and most, extrusion operations. Extrusion coating is done at higher, temperatures (i.e., about 600°F for LDPE)., , become a solid again. This cycle repeats. TPs, generally offer easier processing, and better, adaptability to complex designs than do thermosets (TSs)., Most TP molecular chains can be thought, of as independent, intertwined strings resembling spaghetti. When heated, the individual chains slip, causing a plastic flow. Upon, cooling, the chains of atoms and molecules, are once again held firmly. With subsequent, heating the slippage again takes place. There, are practical limitations to the number of, heating and cooling cycles before appearance or mechanical properties are drastically affected. Initially this recycling practically does not effect certain TPs. However, there are those that are effected after just one, cycle., Thermosets (TSs) are plastics that undergo, chemical change (cross-linking) during processing to become permanently insoluble and, infusible (Figs. 6-2 and 6-3). This cross-linking, is a curing reaction. Such natural and synthetic elastomers as latex, nitrile, mill able, polyurethanes, silicone butyl, and neoprene,, which attain their properties through the process of vulcanization, are also in this crosslinking behavior pattern. The best analogy of, all TSs is that of a hard-boiled egg that has, turned from a liquid to a solid and cannot be, converted back to a liquid. In general, with, their tightly cross-linked structure TSs resist higher temperatures and provide greater

Page 358 : 340, , 6 Plastic Material Formation and Variation, , >I-, , en, o, (), , CIl, , :;, , MELTING, X-LINKING, COMPOUNDING, ("S" STAGING) (MOLDING), , TIME, , Fig. 6-4 Viscosity changes during the processing, ofTS_ The B-stage represents the start ofthe heating cycle followed by a chemical reaction (crosslinking) and solidification of the plastic_, , dimensional stability and strength than do, most TPs_, The structure of TSs, as of TPs, is also, chainlike_ Prior to fabricating, TSs are similar, to TPs_ Chemical cross-linking is the principal difference between TSs and TPs_ In TSs,, during curing or hardening the cross-links, are formed between adjacent molecules, resulting in a complex, interconnected network, that can be related to its viscosity and performance (Figs_ 6-4 and 6-5)_ These cross-bonds, prevent the slippage of individual chains,, thus preventing plastic flow under the addition of heat. If excessive heat is added after cross-linking has been completed, degradation rather than melting will occur_ TSs, generally are not used alone in load bearing, products_ They must be filled or reinforced, with materials such as calcium carbonate, talc, or glass fiber_ The most common, , tt, <1l, , "o, Q., , _ _ _ _ _ _ Elastic modulus, , ~Strength, , c:, , '", , .!:, , U, <1l, , ~, , Distance between cross-links_, , Fig. 6-5 Effect of distance between TS crosslinked sites on compression properties_, , reinforcement is glass fiber, but others are, also used (16, 25, 227)_, Each plastic has its own distinct or special properties and advantages_ See Tables 6-3, and 6-4, also Fig_ 1-8, for the typical names, and properties of plastics_ The dividing line, between a TP and a TS is not always distinct., For instance, cross-linked TSs are TPs during their initial heat cycle and prior to chemical cross-linking_ Plastics, such as a crosslinked polyethylene (XLPE), normally are, TPs that have been cross-linked either by, high-energy radiation or chemically during, processing_, In addition to the broad categories of TPs, and TSs, TPs can be further classified in terms, of their structure, as either crystalline, amorphous, or liquid crystalline_ Other classes, (terms) include elastomers, copolymers, compounds, commodity resins, engineering plastics, or neat plastics_ Additives, fillers, and, reinforcements are other classifications that, relate directly to plastics' properties and, performance_, Structure and Morphology, , In addition to the size of the molecules and, their distribution, the shapes or structures of, individual polymer molecules also play an, important role in determining the properties and process ability of plastics_ There are, those that are formed by aligning themselves, into long chains of molecules and others with, branches or lateral connections to form complex structures_ All these forms exist in either, two or three dimensions_, Because of the geometry, or morphology,, of these molecules some can come closer together and more orderly than others_ These, are identified as crystalline and all others that, behave like spagetti as amorphous_ Morphology influences such properties as mechanical, and thermal, swelling and solubility, specific, gravity, and other properties (mechanical,, physical, chemical, electric, etc_)_, This behavior of morphology basically occurs with TP, not TS plastics_ When TSs are, processed, their individual chain segments, are strongly bonded together during a chemical reaction that is irreversible_

Page 360 : 342, Table 6·4, , 6 Plastic Material Formation and Variation, Examples of a few properties of a few plastics, Property, , Low Temperature, Low Cost, Low Gravity, Thermal Expansion, Volume Resistivity, Dielectric Strength, Elasticity, Moisture Absorption, Steam Resistance, Flame Resistance, Water Immersion, Stress Craze Resistance, High Temperature, Gasoline Resistance, Impact, Cold Flow, Chemical Resistance, Scratch Resistance, Abrasive Wear, Colors, , Thermoplastics, , Thermosets, , TFE, PP, PE, PVC, PS, Polypropylene methylpentene, Phenoxy glass, TFE, PVC, EVA, PVC, TPR, Chlorotrifiuorethylene, Polysulfone, TFE, PI, Chlorinated polyether, Polypropylene, TFE, PPS, PI, PAS, Acetal, UHMWPE, Polysulfone, TFE, FEP, PE, PP, Acrylic, Polyurethane, Acetate, PS, , Crystalline and Amorphous Plastic, Plastic molecules that can be packed closer, together can more easily form crystalline, structures in which the molecules align themselves in some orderly pattern. During processing they tend to develop higher strength, in the direction of the molecules. Since commercially perfect crystalline polymers are not, produced, they are identified technically as, semicrystalline TPs (normally up to 85%, crystalline and the rest amorphous). In this, book and as usually identified by the plastic, industry, they are called crystalline., The amorphous TPs, which have their, molecules going in all different directions,, are normally transparent. Compared to crystalline types, they undergo only small volumetric changes when melting or solidifying, during processing. Tables 6-5 to 6-9 compare the basic performance behaviors of crystalline and amorphous plastics. Exceptions, exist, particularly with respect to certain plastic compounds that include additives and reinforcements., As symmetrical molecules approach within, a critical distance, crystals begin to form in, , DAP, Phenolic, Phenolic/nylon, Epoxy-glass fiber, DAP, DAP, polyester, Silicone, Alkyd-glass fiber, DAP, Melamine, DAP, All, Silicones, Phenolic, Epoxy-glass fiber, Melamine-glass fiberglass, Epoxy, Allyl diglycol carbonate (C-39), Phenolic-canvas, Urea, melamine, , the areas where they are the most densely, packed. A crystallized area is stiffer and, stronger, a noncrystallized (amorphous) area, is tougher and more flexible. With increased, crystallinity, other effects occur. As an example, with polyethylene (crystalline) there, is increased resistance to creep, heat, and, stress cracking as well as increased mold, shrinkage., In general, crystalline types of plastics are, more difficult (but controllable) to process,, requiring more precise control during fabrication, have higher melting temperatures and, Table 6·5, , General morphology of TPs, , Crystalline, No, Excel, No, High, High, Low, Yes, Yes, , Amorphous, Transparent, Chemical resistance, Stress-craze, Shrinkage, Strength, Viscosity, Melt temperature, Critical T / Tt, , *Major exception is Pc., t T / T = Temperature/time., , Yes, Poor, Yes, Low, Low*, High, No, No

Page 361 : 343, , 6 Plastic Material Formation and Variation, Table 6-6 Distinctive characteristics of polymers, Crystalline, , Amorphous, , Sharp melting point, Usually opaque, High shrinkage, Solvent resistant, Fatigue/wear resistant, , Broad softening range, Usually transparent, Low shrinkage, Solvent sensitive, Poor fatigue/wear, , melt viscosities, and tend to shrink and warp, more than amorphous types. They have a relatively sharp melting point. That is, they do, not soften gradually with increasing temperature but remain hard until a given quantity of, heat has been absorbed, then change rapidly, into a low-viscosity liquid. If the amount of, heat is not applied properly during processing, product performance can be drastically, reduced and/or an increase in processing cost, occur. This is not necessarily a problem, because the qualified processor will know how, to process the plastic., Amorphous plastics soften gradually as, they are heated, but they do not flow as easily, during molding as do crystalline materials., Processing conditions influence the performance of plastics. For example, heating a, crystalline material above its melting point,, then quenching it can produce a plastic that, has a far more amorphous structure. Its properties can be significantly different than if it, is cooled properly (slowly) and allowed to, recrystallize; during processing it becomes, amorphous. The effects of time are similar, to those of temperature in the sense that any, Table 6-7 Examples of crystalline and, amorphous TPs, Crystalline, Acetal (POM), Polyester, (PET, PBT), Polyamide, (nylon) (PA), Fluorocarbons, (PTFE, etc.), Polyethylene (PE), Polypropylene (PP), , Amorphous, Acrylonitrile-butadienestyrene (ABS), Acrylic (PMMA), , Table 6-8 Examples of key properties for, engineering TPs, Amorphous, , Crystalline, Acetal, Best property balance, Stiffest unreinforced, thermoplastic, Low friction, , Polycarbonate, Good impact, resistance, Transparent, Good electrical, properties, , Nylon, High melting point, High elongation, Toughest thermoplastic, Absorbs moisture, , Modified PPO, Hydrolytic, stability, Good impact, resistance, , Glass reinforced, High strength, Stiffness at elevated, temperatures, , Good electrical, properties, , Mineral reinforced, Most economical, Low warpage, Polyester (glass reinforced), High stiffness, Lowest creep, Excellent electrical, properties, , given plastic has a preferred or equilibrium, structure in which it would prefer to arrange, itself time wise. However, it is prevented from, doing so instantaneously or at least on "short, notice." If given enough time, the molecules, will rearrange themselves into their preferred, pattern. Heating causes this action to occur sooner. During this action severe shrinkage and property changes could occur in all, directions in the processed plastic products., This characteristic morphology of plastics, can be identified by tests (2, 3). It provides, excellent control as soon as material is received in the plant, during processing, and, after fabrication., , Polycarbonate (PC), Modified polyphenylene, oxide (PPO), Polystyrene (PS), Polyvinyl chloride (PVC), , Liquid Crystalline Polymer, Liquid crystalline polymers (Leps) are, best thought of as being a separate, unique, class of TPs. Their molecules are stiff, rodlike

Page 362 : 344, , 6 Plastic Material Formation and Variation, , Table 6-9, , General properties of TPs during and after processing, Property, , Crystalline', , Amorphous t, , Melting or softening, Density (for the same material), , Fairly sharp melting point, Increases as crystallinity, increases, Greater, Greater, Greater, Greater, Often greater, , Softens over a range of temperature, Lower than for crystalline material, , Heat content, Volume change on heating, After-molding shrinkage, Effect of orientation, Compressibility, , Lower, Lower, Lower, Lower, Sometimes lower, , 'Typical crystalline plastics are polyethylene, polypropylene, nylon, acetals, and thermoplastic polyesters., tTypical amorphous plastics are polystyrene, acrylics, PVC, SAN, and ABS., , structures organized in large parallel arrays, or domains in both the melted and solid, states. These large, ordered domains provide, LCPs with characteristics that are unique, compared to those of the basic crystalline, or amorphous plastics (Table 6-10). They, are called self-reinforcing plastics because, of their densely packed fibrous polymer, chains., These LCPs provide the designer with unparalleled combinations of properties, such, as resisting most solvents and heat. Unlike, many high-temperature plastics, LCPs have, a low melt viscosity and are thus more easily, processed resulting in faster cycle times, than those with a high melt viscosity thus, reducing processing costs. They have the, lowest warpage and shrinkage of all the TPs., When they are injection molded or extruded,, their molecules align into long, rigid chains, that in turn align in the direction of flow and, thus act like reinforcing fibers, giving LCPs, both very high strength and stiffness. As the, Table 6-10, , melt solidifies during cooling, the molecular, orientation "freezes" (solidifies) into place., The volume changes are only minute with, virtually no frozen-in stresses., In service, products experience very little, shrinkage or warpage. They have high resistance to creep. Their fiberlike molecular, chains tend to concentrate near the surface,, resulting in products that are anisotropic,, meaning that they have greater strength and, modulus in the flow direction, typically on, the order of three to six times those of the, transverse direction. However, adding fillers, or reinforcing fibers to LCPs significantly reduces their anisotropy, more evenly distributing strength and modulus and even boosting, them. Most fillers and reinforcements also reduce overall cost and place mold shrinkage, to zero or near zero. Consequently, products, can be molded to tight tolerances. These lowmelt-viscosity LCPs thus permit the design of, products with long or complex flow paths and, thin sections., , General properties of crystalline, amorphous, and liquid crystalline polymers, , Property, , Crystalline, , Amorphous, , Liquid Crystalline, , Specific gravity, Tensile strength, Tensile modulus, Ductility, elongation, Resistance to creep, Max. usage temperature, Shrinkage and warpage, Flow, Chemical resistance, , Higher, Higher, Higher, Lower, Higher, Higher, Higher, Higher, Higher, , Lower, Lower, Lower, Higher, Lower, Lower, Lower, Lower, Lower, , Higher, Highest, Highest, Lowest, High, High, Lowest, Highest, Highest

Page 363 : 6 Plastic Material Formation and Variation, They have outstanding strength at extreme, temperatures, excellent mechanical-property, retention after exposure to weathering and, radiation, good dielectric strength as well, as arc resistance and dimensional stability,, low coefficient of thermal expansion, excellent flame resistance, and easy processability., Their UL continuous-use rating for electrical, properties is as high as 240°C (464°F), and, for mechanical properties it is 220°C (428°F)., LCPs' high heat deflection value permits LCP, molded products to be exposed to intermittent temperatures as high as 315°C (600°F), without affecting their properties. Their resistance to high-temperature flexural creep, is excellent, as are their fracture-toughness, characteristics. This family of different LCPs, resists most chemicals and weathers oxidation and flame, making them excellent replacements for metals, ceramics, and other, plastics., LCPs are exceptionally inert and resist, stress cracking in the presence of most chemicals at elevated temperatures, including the, aromatic and halogenated hydrocarbons as, well as strong acids, bases, ketones, and, other aggressive industrial products. Their, hydrolytic stability in boiling water is excellent, but high-temperature steam, concentrated sulfuric acid, and boiling caustic materials will deteriorate LCPs. In regard to, flammability, LCPs have an oxygen index, ranging from 35 to 50%. When exposed to, open flame they form an intumescent char, that prevents dripping., , of homopolymers, which may be made from, the individual monomers, and sometimes superior or inferior to them. (A polymer such, as polyethylene is formed from its monomer, ethylene, polyvinyl chloride polymer from its, vinyl chloride monomer, and so on.), , Compounded/Alloyed Plastic, Since the first plastic cellulosic was produced in 1868, there has been an evergrowing demand for specially compounded, plastics. Using a post-reactor technique, plastics can be compounded by alloying or blending polymers in addition to using additives, such as colorants, flame retardants, heat or, light stabilizers, lubricants, fillers, and/or reinforcements (Fig. 6-6). With reinforcements, the resulting reinforced compounds are usually referred to as reinforced plastics (RPs)., , Alloy and Blend, Alloys are combinations of polymers that, are mechanically blended. They do not depend on chemical bonds, but do often require, special compatibilizers. Plastic alloys are, usually designed to retain the best characteristics of each constituent. Most often,, property improvements are in such areas, Plastic Composition, , Copolymer, Polymer properties can be varied during, polymerization. The basic chemical process, is carried during their manufacture; the polymer is formed under the influence of heat,, pressure, catalyst, or combination inside vessels or tubular systems called reactors. One, special form of property variation involves, the use of two or more different monomers, as comonomers, copolymerizing them to produce copolymers (two comonomers) or terpolymers (three monomers). Their properties are usually intermediate between those, , 345, , Interplay Between, Composite Constituents, , Fig. 6-6, , Composition of plastics.

Page 364 : 346, , 6 Plastic Material Formation and Variation, , High, , 20, , 1~, , .s::., , g, , ?;, , ...., , 15, , ~, , .c, 0,, c:, , ~, , iii, , ~, , 100, , a., .§, , Fig. 6-7 Strength and elasticity of different, materials., , .§, , 10, Elastic Limit (Percent), , "0, , 5, , "0, , OJ, , .s::., , ~, , Z, , as impact strength, weather resistance, improved low-temperature performance, and, flame retardation (Figs. 6-7 to 6-10 and, Tables 6-11 and 6-13)., The classic objective of alloying and blending is to find two or more polymers whose, mixture will have synergistic property improvements (Fig. 6-8). Among the techniques, used to combine dissimilar polymers are, cross-linking to form what are called interpenetrating networks (IPNs), and grafting, to, improve the compatibility of the plastics., Alloys can be classified as either homogeneous or heterogeneous. The former can, be depicted as a solution with a single phase, or single glass-transition temperature (Tg)., A heterogeneous alloy has both continuous, , 10, , OL-____________________, 100/0, , 50/50, , ~, , 0/100, , PVC/ASS ratio, , Fig. 6-9 Example of how alloying affects plastic, properties; curves reflect four different blends., , and dispersed phases, each retaining its own, distinctive Tg. Until recently, blending and, alloying were either restricted to polymers, that had an inherent physical affinity for, each other or else a third component, called, a compatibilizer, was employed. These, constraints severely limited the types of, polymers that could be blended without, sacrificing their good physical properties., As a rule, incompatible polymers produce a, ACRYlONITRILE, , A, , Synergistic effect, , CHEMICAL RESISTANCE, ABRASION RESISTANCE, HARDNESS, SAN, , STRENGTH, CHEMICAL RESISTANCE, NBR, , LUSTER, MOLDABILITY, STRENGTH, RIGIDITY, , Antisynergistic effect, , 100%A, , 50A/50 B, , 100%B, , Fig. 6-8 Developing synergistic effects is the, most usual objective of compounding plastics to, gain significant performance., , BUTADIENE, , SBR, STRENGTH, , STRYENE, , Fig. 6-10 ABS terpolymer properties are, shown influencing individual constituent plastic, properties.

Page 365 : 347, , 6 Plastic Material Formation and Variation, Table 6-11, , Examples of alloying to provided cost-performance improvements, , o, Plastic, Polypropylene, Polvstyrene, , Impact <tyrene (alloy I, ASS, ASS;PVC (alloy I, ASS/Polycarbonate (alloy), Rigid PVC, PVC/acrylic (alloy), Polyphenyleneo .. de (Noryl), , CoS! index, , p, , t=J, :L:d, , '/ ///1, , ;'~~ t.,., ;' / / -TA:, , V / / /, , 500, , h, , /, , / I If.f! ,., , 100, , 200, , I, , I, /, , I I I, , ,./, , 12j, , II, , I II, , {~, , 1, , 11'11111, , t., , I, , I / 11~0, , I, 1, , heterogeneous alloy with poor physical, properties., The advances in polymer blending and, alloying technology have occurred through, three routes: (1) similar-rheology polymer pairs, (2) miscible polymers such as, polyphenylene oxide and polystyrene, or (3), interpenetrating polymer networks (IPNs)., All these systems were limited to specific, polymer combinations that have an inherent, physical affinity for each other. However with, Table 6-12, , l, , 1, , 1, , 100, , 1, , V.I /77/1, , ////1, 1, //11, "////,,1, , ~, , Impact strength Index, , tJ, , 1, , ~//,I, , '1//1 lIlt, , Alloy, , Yield strength index, , B, ~, , Polvcarbonate, , Poly,ullone, POly,ullono; ASS (alloy I, , ~, , Unmodified resin, , 1, , I I I II~~ I, 100, , LI, , 450.1250, , i, 3000, , R&D developments, there is another overall approach to producing blends via reactive, polymers., Interpenetrating Network, IPNs consist of an interwoven matrix of, two polymers. A typical method for producing these alloys involves cross-linking, one of the monomers in the presence of, , Upgrading PVC by blending, , Upgraded Property, Impact resistance, Tensile strength, Low-temperature, toughness, Dimensional stability, Heat-distortion, temperature, Processability, Moldability, Plasticization, Transparency, Chemical/oil resistance, Toughness, Adhesion, , Blending Polymer, ABS, methacyrylate-butadiene-styrene, acrylics, polycaprolactone,, polyimide, polyurethanes, PVC-ethyl acrylate, ABS, methacyrylate-butadiene-styrene, polyurethanes, ethylene-vinyl, acetate, Styrene-acrylonitrile, polyurethanes, polyethylene, chlorinated, polyethylene, copolyester, Styrene-acrylonitrile, methacrylate-butadiene-styrene, ABS, methacyrylate-butadiene-styrene, polyimide, poly dimethyl, siloxane, Styrene-acrylonitrile, methacrylate-butadiene-styrene, chlorinated, polyethylene, PVC-ethyl acrylate, ethylene-vinyl acetate, chlorinated, polyoxymethylenes (acetals), Acrylics, polycaprolactone, Polycaprolactone, polyurethanes, nitrile rubber, ethylene-vinyl acetate,, copolyester, chlorinated polyoxymethylenes (acetals), Acrylics, polymide, Acrylics, Nitrile rubber, ethylene-vinyl acetate, Ethylene-vinyl acetate

Page 366 : 348, Table 6·13, , 6 Plastic Material Formation and Variation, Outstanding properties of some commercial plastic alloys, Properties, , Alloy, PVC/acrylic, PVC/ABS, Polycarbonate/ABS, ABS/polysulfone, Polypropylene/ethylene-propylene-diene, Polyphenylene oxide/polystyrene, Styrene acrylonitrile/olefin, Nylon/elastomer, Polybutylene terephthalate/polyethylene, terephthalate, Polyphenylene sulfide/nylon, Acrylic/polybutylene rubber, , the other. The need for a chemical similarity between the two types of molecules is, thus reduced, because cross-linking physically traps one with the other. The result is, a structure composed of two different intertwined plastics, each retaining its own physical characteristics., Reactive Polymer, A reactive polymer (RP) is simply a device to alloy different materials by changing, their molecular structure inside a compounding machine. True reactive alloying induces, an interaction between different phases of an, incompatible mixture and assures the stability of the mixture's morphology. The concept, is not new. This technology is now capable of, producing thousands of new compounds to, meet specific design requirements., The relatively low capital investment associated with compounding machinery (usually, less than $1 million for a line, compared with, many millions for a conventional reactor),, coupled with a processing need for small, amounts of tailored materials, allows small, and mid-sized compounding companies, to take advantage of producing reactive, polymers., There are a variety of reactive alloying techniques available to the compounder., They typically involve the use of a reactive, agent or compatibilizer to bring about a, molecular change in one or more of the, , Flame, impact, and chemical resistance, Flame resistance, impact resistance, process ability, Notched impact resistance, hardness, heat-distortion, temperature, Lower cost, Low-temperature impact resistance and flexibility, Processability, lower cost, Weatherability, Notched Izod impact resistance, Lower cost, Lubricity, Clarity, impact resistance, , blended components, thereby facilitating, bonding. They include the grafting process, and copolymerization interactions, whereby, a functional material is built into the polymer, chain of a blend component as a comonomer,, with the resultant copolymer then used as, a compatibilizer in ternary bonds, such as a, PP-acrylic acid copolymer that bonds PP and, AA. Another technique is solvent-based interactions, using materials such as polycaprolactone, which is miscible in many materials, and exhibits strong polarity, as well as hydrogen bonding, using the simple polarity of alloy components., Grafting, Grafting two dissimilar plastics often involves a third plastic whose function is to improve the compatibility of the principal components. This "compatibilizer" material is a, grafted copolymer that consists of one of the, principal components and is similar to the, other component. The mechanism is similar, to that of having soap improve the solubility, of a greasy substance in water. The soap contains components that are compatible with, both the grease and the water., Additive, Filler, and Reinforcement, Compounding to change and improve, the physical and mechanical properties, of plastics makes use of a wide variety of

Page 367 : 349, , 6 Plastic Material Formation and Variation, Table 6-14, , Guide to use of fillers and reinforcements, Properties Improved, ?, , .1, , J, , Ji, ~, , I, , l, , Filler or Reinforcement _, Alumina. tabular, Aluminum powder, Ar.unid, Bronze, Calcium carbonate, Carbon black, Carbon fiber, Cellulose, Alpha cellulose, Coal, powdered, Cotton, Fibrous glass, Graphite, Jute, Kaolin, Mica, Molybdenum disulfide, Nylon, Orion, Rayon, Silica, amorphous, Sisal fibers, Fluorocarbon, Talc, Wood flour, , • • • •, • • • •, • • • •, •, •, •, •, • •, • • • •, •, •, •, •, •, , •, , •, •, , •, •, , •, •, , •, , •, •, , • •, • •, • •, •, •, •, •, , •, • •, •, •, •, •, , •, •, • • •, • •, •, • •, •, •, •, • •, , •, , •, , •, •, , •, •, , •, •, , •, , •, •, •, , • • • •, • • • •, • • • • • • •, •, • • • •, •, • • • •, •, • • •, •, •• •• •• •• •, •, • • • •, •, • • •, •, • • • •, • • • •, •, •, , SIP, S, SIP, S, SIP, SIP, S, SIP, S, S, S, SIP, SIP, S, , •, , •, , SIP, SIP, , P, , •, •, , SIP, SIP, S, , •, , SIP, SIP, SIP, , •, , SIP, S, , .p = lIIennoplaslic. S = !llennosel., , ingredients (Fig. 6-6 and Tables 6-14 to 6-17)., The major and large market for products, such as additives, fillers, colorants, etc. continues to expand as the demand for plastics, to function in wider or more extreme markets and under stricter regulatory regimes, continue to expand. There are ingredients, that are used to improve the processing, capabilities of plastics., In general adding reinforcing fibers significantly increases mechanical properties., Particulate fillers of various types usually, increase the modulus, plasticizers generally, decrease the modulus but enhance flexibility, and so on. These RPs can also be called, composites. However the name composites, litterly identifies thousands of different combinations with very few that include the use of, plastics (Table 6-18). In using the term com-, , posites when plastics are involved the more, appropriate term are plastic composites., Many ingredients, especially those that are, conductive, may affect electrical properties., Most plastics, which are poor conductors of, current, build up a charge of static electricity. Antistatic agents can be added to attractmoisture, reducing the likelihood of a spark, or discharge., In most cases, different additives are, used to provide lower cost and different, characteristics encompassing specific overall, properties. As an example, coupling agents, are added to improve the bonding of a plastic to its inorganic reinforcing materials such, as glass fibers. A variety of silanes and titanates are used for this purpose. Some extenders (that is fillers) permit a large volume of a given plastic to be produced with

Page 368 : 6 Plastic Material Formation and Variation, , 350, Table 6-15, , Trade-off in TPs and RPs, , Desired, Modification, , How, Achieved, , Increased, Tensile, Strength, , Sacrifice (from Base Resin), Amorphous, , Crystalline, , Comments, , Glass fibers, Carbon fibers, Fibrous, minerals, , Ductility, cost, Ductility, cost, , Ductility, cost, Ductility, cost, Ductility, , Increased, Flexural, Modulus, , Glass fibers, Carbon fibers, Rigid minerals, , Ductility, cost, Ductility, cost, Ductility, , Ductility, cost, Ductility, cost, Ductility, , Flame, Resistance, , FR additive, , Ductility, tensile, strength, cost, , Ductility, tensile, strength, cost, , Increased, HeatDeflection, Temperature, (HDT), , Glass fibers, Carbon fibers, Fibrous, minerals, , Ductility, cost, Ductility, cost, , Ductility, cost, Ductility, cost, Ductility, , Warpage, Resistance, , 5 to 10%, glass fibers, 5 to 10%, carbon, fibers, Particulate, fillers, , Glass fibers are the most, cost-effective way of, gaining tensile strength., Carbon fibers are more, expensive; fibrous, minerals are least, expensive but only, slightly reinforcing., Reinforcement makes, brittle resins tougher, and embrittles tough, resins., Fibrous minerals are not, commonly used in, amorphous resins., Any additive more rigid, than the base resin, produces a more rigid, composite. Particulate, fillers severely degrade, impact strength., FR additives interfere, with the mechanical, integrity of the polymer, and often require, reinforcement to, salvage strength. They, also narrow the molding, latitude of the base resin., Some can cause mold, corrosion., When reinforced,, crystalline polymers, yield much greater, increases in HDT than, do amorphous resins., As with tensile strength,, fibrous minerals increase, HDT only slightly., Fillers do not increase, HDT., Amorphous polymers, are inherently, nonwarping molding, resins. Only occasionally, are fillers such as milled, glass or glass beads, added to amorphous, materials, because they, reduce shrinkage, anisotropically., ( Continues), , Cost, Cost, Ductility,, cost,, tensile, strength, , Ductility,, cost,, tensile, strength

Page 369 : 351, , 6 Plastic Material Formation and Variation, Table 6-15, , ( Continued), , Desired, Modification, , Reduced Mold, Shrinkage, (Increased, mold-to-size, capability), , Reduced, Coefficient, of Friction, , Reduced Wear, , Electrical, Conductivity, , How, Achieved, , Sacrifice (from Base Resin), Amorphous, , Crystalline, , Glass fibers, Carbon fibers, Fillers, , Ductility, cost, Ductility, cost, Tensile strength,, ductility, cost, , Ductility, cost, Ductility, cost, Tensile strength,, ductility, cost, , PTFE, Silicone }, , Cost, , Cost, , Ductility, cost, Tensile strength,, d uctility, cos t, , Ductility, cost, Tensile strength,, ductility, cost, , MoSe, Graphite, , Glass fibers, Carbon fibers, Lubricating, additives, Carbon fibers, Carbon, powders, , Comments, Addition of fibers tends to, balance the difference, between inflow and, cross-flow shrinkage, usually found in, crystalline polymers., When a particulate is, used to reduce and, balance shrinkage, some, fiber is needed to offset, degradation., Reinforcement reduces, shrinkage far more than, fillers do. Fillers help, balance shrinkage,, however, because they, replace shrinking, polymer. The sharp, shrinkage reduction in, reinforced crystalline, resins can often lead to, warpage. The best, "mold-to-size", composites are, reinforced amorphous, composites., These fillers are soft and, do not dramatically, affect mechanical, properties. PTFE, loadings commonly, range from 5 to 20%;, the others are usually, 5 % or less. Higher, loadings can cause, mechanical degradation., The subject of plastic wear, is extremely complex and, should be discussed with, a composite supplier., Resistivities of 1 to, 100,000 ohm-cm can be, achieved and are, proportional to cost., Various carbon fibers and, powders are available, with wide variations in, conductivity yields in, composites.

Page 370 : 352, , 6 Plastic Material Formation and Variation, , Table 6-16, , Influence of fillers and reinforcements on TPs, , Resin, , Reinforcements, , Fillers, , Amorphous, ABS, SAN, Amorphous, Nylon, Polycarbonate, Modified PPO, Polystyrene, Polysulfones, , +Can more than double, tensile strength, +Can increase flexural, modulus fourfold, + Raise HDT slightly, ±Toughen brittle resins, embrittle, tough resins, +Can provide 1000ohm-cm, resistivity, + Reduce shrinkage, - Reduce melt flow, -Raise cost, , - Lower tensile strength, +Can more than double flexural, modulus, + Raise HDT slightly, - Embrittle resins, +Can impact special properties such, as lubricity, conductivity, flame, retardance, + Reduce and balance shrinkage, - Reduce melt flow, +Can lower cost, , Crystalline, Aceals, Nylon 6, 6/6, 6/10,6/12, 11, 12, Polypropylene, Polyphenylene sulfide, Thermoplastic, Polyesters, Polyethylene, , +Can more than triple tensile, strength, +Can raise flexural modulus·, sevenfold, +Can nearly triple HDT, ± Toughen brittle resins,, embrittle tough resins, +Can provide 1 ohm-cm, resistivity, + Reduce shrinkage, -Cause distortion, - Reduce melt flow, -Raise cost, , - Lower tensile strength, +Can more than triple flexural, modulus, + Raise HDT slightly, - Embrittle resins, +Can impart special properties such, as lubricity, conductivity, magnetic, properties, flame retardance, + Reduce shrinkage, + Reduce distortion, - Reduce melt flow, +Can lower cost, , relatively little actual plastic. Calcium carbonate, silica, and clay are frequently used, as extenders reducing the cost of the plastic., Many plastics because they are organic are, flammable incorporate flame-retardants. Additives that contain chlorine, bromine, phosphorous, metallic salts, and so forth reduce, the likelihood that. combustion will occur, or spread. Lubricants like wax or calcium, stearate reduce the viscosity of molten plastic, Table 6-17, , Example of carbon black on mechanical properties of an ABS, , Filler, Content c, %, 0, 3, 5, 7.5, 10, 15, 20, , and improve its forming characteristics. Plasticizers are low-molecular-weight materials, that alter the properties and forming characteristics of plastics. An important application, is the production of flexible grades of PVc., Colorants must provide colorfastness under the required exposure conditions of, light, temperature, humidity, chemical exposure, and so on, but without reducing, other desirable properties such as flow during, , Tensile Modulus, E, N/mm2 (kips/in.2), , Breaking Strength aT,, N/mm (kips/in.2), , Elongation at, Break ST, %, , Impact Strength, an kJ/m2, , 2,280 (331), 2,500 (362), 2,720 (394), 2,820 (409), 3,010 (436), 3,540 (513), 4,000 (580), , 30.9 (4.48), 44.2 (6.41), 43.2 (6.26), 37.7 (5.47), 35.1 (5.09), 27.8 (4.03), 24.8 (3.60), , 8.2, 3.4, 3.1, 2.5, 2.2, 1.9, 1.1, , 208, 36, 43, 41, 31, 29, 26

Page 371 : 6 Plastic Material Formation and Variation, Table 6-18, , 353, , Examples of different composite systems, , Matrix Material, , Reinforcement Material, , Properties Modified, , Metal, , Metal, ceramic, carbon, glass fibers, , Elevated temperature strength, Electrical resistance, Thermal stability, , Ceramic, , Metallic and ceramic particles and fibers, , Glass, , Ceramic fibers and particles, , Organics,, Thermosets,, Thermoplastics, , Carbon, glass, organic fibers, glass, beads, flakes, ceramic particles,, metal wires, , Elevated temperature strength, Chemical resistance, Thermal resistance, Mechanical strength, Temperature resistance, Chemical resistance, Thermal stability, Mechanical strength, Elevated temperature strength, Chemical resistance, Antistatic, Electrical resistance, EMF shielding, Flexibility, Wear resistance, Energy absorption, Thermal stability, , processing, resistance to chalking and crazing, and impact strength retention. Colorants, are usually classed as either pigments or dyes., Pigments are insoluble particles large enough, to scatter light but not to provide the high, transparency of dyes that are soluble. But, dyes are usually poorer in lightfastness, heat, stability, and tendency to bleed and migrate in, the plastic system, so that they are much less, used than pigments. The various special colorants include rnetallics, fiuorescents, phosphorescents, and pearlescent colorings., Pigments may be organic or inorganic., Organic ones usually provide stronger,, more transparent colors, are higher priced, (although not necessarily more costly to, process), and more soluble in plastic systems. Important organic pigments include, monochromes and diazos (in yellow, orange,, and red), phthalocyanine (in blues and, greens), quinacridone (in gold, maroon,, violet, and so on), peryiene, and others., Inorganics are denser and usually of a, larger particle size. Common inorganic pigments include iron oxides in buff colors,, titanium dioxide in white, lead and zinc, , chromates (in yellows, oranges, and reds),, and other metal oxides and salts. Carbon, blacks are also widely used, both as a colorant, and to protect polymers from thermal and, UV degradation as well as a reinforcing filler., Reinforced Plastic, , Reinforced plastics (RPs) hold a special, place in the design and manufacturing industry because they are unique materials, (Figs. 6-11 and 6-12). During the 1940s, RPs, (or low-pressure laminates, as they were then, commonly known) was easy to identify. The, basic definition then, as now, is simply that, of a plastic reinforced with either a fibrous, or nonfibrous material. TSs such as polyester, (Table 6-19) and E-glass fiber dominated, and still dominates the field. Also used are, epoxies., What essentially characterizes RPs is their, ability to be molded into extremely small but, also large shapes well beyond the basic capabilities of other processes, at little or no, pressure. Also, there are instances in which

Page 372 : 354, , 6 Plastic Material Formation and Variation, 4, , -, , SP'CIFIC i l l " " C I F I C, STRENGTH, , -, , MODULUS, , ,...-, , r--, , I-, , r--, , rr-, , o, , I, CARSONI, EPOXY, , Fig.6-11, , WOOD, , GLASSI, , .., , VI, , ""8.'", , ..., I, 0, , E, , 8, , )(, , ~30, , ~, , ~, , .., , :£l, .!!!, ~, , !:l, , :;, , 20, , '8, , ::IE, , 10, , 0, , 0, , 4, , Specific gravity, , STEEL, , Comparison of RPs with other materials., , 50r-----~----~----~----~--__,, , 40, , ALUMINUM, , EPOXY, , less heat is required. Consequently, RPs during the 1940s and 1950s went by the name, low-pressure laminates., In the past, the term high-pressure laminates was reserved for melamine and phenolic impregnated papers or fabrics compressed, under high pressures (about 13.8 to 34.5 MPa,, or 2,000 to 5,000 psi). They were heated to, form either decorative laminates (for example Formica and Micarta) or industriallami-, , ..., , -, , -, , 10, , Fig. 6-U Relationship of modulus of elasticity to, specific gravity of materials., , nates for electrical and other industries. The, compression molding process was used., By the early 1960s, the processing of RPs, had begun to involve higher pressures,, and the name "low-pressure laminates" was, dropped in favor of simply reinforced plastics (RPs). But even then, the name referred, primarily to reinforced TSs using principally, glass fibers and encompassed specialized RP, molding processes. By 1970 major changes, had occurred. Reinforcements other than, glass fiber were in use and TPs as well as, TSs were being reinforced. The application, of RTS and RTP methods of processing began to increase, using conventional processing techniques like injection molding and rotational molding., By this time the industry required a more, inclusive term to describe RPs, so composite was added. Thus the name in the plastics industry became Reinforced Plastic Composites. More recently they became known, only as Composites. However composites, identify many other combinations of basic, materials (Table 6-18). The fiber reinforcements included higher modulus glasses, carbon, graphite, boron, aramid (strongest fiber, in the world, five times as strong as steel on, an equal-weight basis), whiskers, and others, (Table 6-20 and Figs. 6-13 and 6-14). In

Page 373 : 355, , 6 Plastic Material Formation and Variation, Table 6·19, , Characteristics of glass fiber-TS polyester RPs, , Polyester Type, , Characteristic, , Typical Uses, , General purpose, , Rigid moldings., , Flexible resins and, semirigid resins, , Tough, good impact resistance,, high flexural strength, low, flexural modulus., , Light-stable and, weather-resistant, Chemical-resistant, , Resistant to weather and, ultraviolet degradation., Highest chemical resistance of, polyester group; excellent, acid resistance, fair in, alkalies., Self-extinguishing, rigid., , Flame-resistant, High heat distortion, Hot strength, Low exotherm, Extended pot life, Air dry, Thixotropic, , Table 6·20, , Service up to 500o P, rigid., Past rate of cure (hot), moldings, easily removed from die., Void-free thick laminates, low, heat generated during cure., Void-free uniform, long flow, time in mold before gel., Cures tack-free at room, temperature., Resists flow or drainage when, applied to vertical surfaces., , Trays, boats, tanks, boxes, luggage,, seating., Vibration damping; machine covers and, guards, safety helmets, electronic part, encapsulation, gel coats, patching, compounds, auto bodies, boats., Structural panels, sky lighting, glazing., Corrosion-resistant applications, such as, pipe, tanks, ducts, fume stacks., Building panels (interior), electrical, components, fuel tanks., Aircraft parts., Containers, trays, housings., Encapsulating electronic components,, electrical premix parts-switch-gear., Large complex moldings., Pools, boats, tanks., Boats, pools, tank linings., , Examples of different fiber reinforcements, , Type of Fiber, Reinforcement, Glass, E Monofilament, 12-end roving, S Monofilament, 12-end roving, Boron (tungsten, substrate), 4 mil or 5.6 mil, Graphite, High strength, High modulus, Intermediate, Organic, Aramid, , Specific, Gravity, , Density, Ib./in. 3, (g/cm3), , Tensile, Strength, 103 psi (GPa), , Specific, Strength, 106 in., , Tensile Elastic, Modulus 106, psi (GPa), , Specific, Elastic, Modulus, 108 in., , 2.54, 2.54, 2.48, 2.48, , 0.092 (2.5), 0.092 (2.5), 0.090 (2.5), 0.090 (2.5), , 500 (3.45), 372 (2.56), 665 (4.58), 550 (3.79), , 5.43, 4.04, 7.39, 6.17, , 10.5 (72.4), 10.5 (72.4), 12.4 (85.5), 12.4 (85.5), , 1.14, 1.14, 1.38, 1.38, , 2.63, , 0.095 (2.6), , 450 (3.10), , 4.74, , 58 (400), , 6.11, , 1.80, 1.94, 1.74, , 0.065 (1.8), 0.070 (1.9), 0.063 (1.7), , 400 (2.76), 300 (2.07), 360 (2.48), , 6.15, 4.29, 5.71, , 38 (262), 27 (190), , 5.85, 7.86, 4.29, , 1.44, , 0.052 (1.4), , 400 (2.76), , 7.69, , 18 (124), , 3.46, , 55 a (380), , a Also, , commercially available up to 100 x 106 psi., Note: The principal reinforcement, with respect to quantity, is glass fibers, but many other types are used (cotton,, , rayon, polyesterlTp, nylon, aluminum, etc.). Of very limited use because of their cost and processing difficulty are, "whishers" (single crystals of alumina, silicon carbide, copper, or others), which have superior mechanical properties.

Page 374 : 356, , 6 Plastic Material Formation and Variation, , Ci~ARAMID, , 600,000, , ~, , uf, I/), w, , --S-GLASS, , 400,000, , a:, , STEEL, , l-, , I/), , 200,000, , a, , 0.05, 0.10, STRAIN,INCHES liNCH, , Fig. 6·13 Stress-strain curves of different fiber, materials., , Fig. 6-14 specific modulus = modulus/density., Plastics include use of the heat-resistant TPs, such as the polimides, polyamide-imide, and, others. Table 6-21 provides data on the thermal properties of RPs. To date at least 80 wt %, are glass fiber and about 60 wt% of those are, polyester (TS) type RPs., A designer can produce RP products, whose mechanical properties in any direction will be both predictable and controllable., This is done by carefully selecting the plastic and the reinforcement in terms of both, their composition and their orientation, and, , following up with the appropriate process, (Chapter 8, REINFORCED PLASTIC). All, types of shapes can be produced: flat and, complex, solid and tubular rods or pipes,, molded shapes and housings and other complex configurations and structures such as angles, channels, box and I -beams, and so on., The RPs can produce the strongest materials, in the world (Fig. 2-6)., The reinforcement type and form chosen, (woven, braided, chopped, etc.) will depend, on the performance requirements and the, method of processing the RP (Fig. 6-15)., Fibers can be oriented in many different, patterns to provide the directional properties, desired. Depending on their packing arrangement, different reinforcement-to-plastic ratios are obtained (Appendix A. PLASTICS, TOOLBOX)., In its simplest presentation, using glass, fiber with plastic, if the fibers were packed, as closely as possible (like stacked pipe), the, glass would occupy 90.6 vol% (volume) or, 95.6 wt%. With a "square" packing (paralleI layered fibers so that each layer has fibers, 90° to each other) the glass would occupy, 78.5 vol% or 88.8 wt%., , ULTIMATE TENSILE ST~ENGTH (lbSlsq In x 1()3), , 88 8, , §, , §, , §'", , ALUMINIUM, ALLOY, __ TITANIUM _, ALLOY, HIGH TENSILE, STEEL, _, SPECIAL _.. . . ._ _, GLASS FIBRE, _, EPOXY_, FIBREGLASS, - SILICA, EPOXY, CARBON FIBRE:, , FIBRE-ellll~---­, , BORON FIBRE CARBON FIBRE-IRON WHISKER, ALUMINA, WHISKER, GRAPHITE, WHISKER, , 5, , 10, , 15, , 20, , 25, , 30, , a M . wga M, , 35, , 40, , 45, , SPECIFIC MODULUS (In- ' x 1()6), , Fig.6·14 Properties of different RPs that includes whiskers, aluminum, titanium, and steel.

Page 375 : 357, , 6 Plastic Material Formation and Variation, Table 6-21 Thermal properties of reinforcing fibers, Property, Mean fiber diameter, J1, (mils), Therm. Cond.,, BTU-in.lhr.-ft. 2 (W/m-K), Specific Heat @ 70°F,, BTU/lb.oF(J/Kg-K), Coefficient of thermal exp.,, , E Glass, , Carbon, , HMCarbon, , Aramid, , 10-17 (0.39--0.67), 7.0, (1.0), 0.192, (803), , 7 (0.27), 60, (8.6), 0.17, (710), , 8 (0.31), 97, (14), 0.17, (710), , 12 (0.47), 3.5, (0.50), 0.34, (1400), , 1.6 (2.9), 4.0 (7.2), 31.0, , -0.55 (-0.99), 9.32 (16.8), 53.0, , -0.28 ( -0.50), - (1.8), , -1.1 (-2.0), 33.0 (59.4), 41.0, , 10- 6 in.linPF, (10- 6 cm/cm 0C), , Longitudinal, Transverse, Surface energy, ergs/cm2, , Note: One micron = 0.001 cm or = 0.00004 in., One grain of salt = 100 microns., , One human hair = 70 microns., The human eye cannot distinguish below 40 microns., Usually the length of short fibers is less than 3.175 mm (0.125 in.), but generally is 0.76 to 0.52 mm (0.030 to, 0.060 in.), and long fibers are longer than 3.175 mm (0.125 in.)., , Glass fibers and most other reinforcements, require special surface treatment to ensure, the bonding and compatibility of the fibers, to the plastic in order to maximize performances. Treatments are also used to protect, individual filaments during handling and processing (7, 14)., Basic Design Theory, , Fiber-reinforced plastics differ from many, other materials because they combine two essentially different materials of fibers and a, plastic into a single composite. In this way, they are somewhat analogous to reinforced, concrete, that combines concrete and steel., However, in the RPs the fibers are generally, much more evenly distributed throughout the, , mass and the ratio of fibers to plastic is much, higher (Fig. 6-16)., In designing fibrous-reinforced plastics it is, necessary to take into account the combined, actions of the fiber and the plastic. At times, the combination can be considered homogeneous, but in most cases homogeneity cannot, be assumed., Thus, it is necessary to allow for the fact, that two widely dissimilar materials have, been combined into a single unit. In the, basic design approach certain fundamental, assumptions are made. The first, and most, important assumption, is that the two materials act together. With a load applied (stretching, compression, twisting, etc.) the fibers and, plastic under load is the same; that is, the, , Continuous strand, 0.., , a:, , 1, , LL, , a, , I, f-, , ('), , Z, , ~, c, , w, , a:, , f-, , 0.1, , 1.0, , 10, , FIBER LENGTHS (mm), , Fig. 6-15, , Chopped strand, , ~, , (f), , 0.01, , Fabric, , Effect of fiber length on RP strength., , Volume of reinforcement, , •, , Fig.6-16 Strength-to-volume relationship for reinforcement used in RPs.

Page 376 : 358, , 6 Plastic Material Formation and Variation, , strains in the fiber and plastic are equal. This, assumption implies that a good bond exists, between the plastic and the fiber to prevent, slippage between them and wrinkling of the, fiber (7,10,14)., The second major assumption is that the, material is elastic, meaning that the strains, are directly proportional to the stresses applied and when the load is removed the deformation will disappear. In engineering terms, the material is assumed to obey Hooke's, Law. This assumption is probably a close, approximation of the material's actual behavior in direct stress below its proportional, limit, particularly in tension, if the fibers are, stiff and elastic in the Hookean sense and, carry essentially all the stress. This assumption is probably less valid in shear, where, the plastic carries a substantial portion of the, stress. The plastic may then undergo plastic flow, leading to creep or relaxation of, the stresses, especially when the stresses are, high., More or less implicit in the theory of materials of this type is the assumption that all, the fibers are straight and unstressed or that, the initial stresses in the individual fibers are, essentially equal. In practice this is quite unlikely to be true. It is expected, therefore, that, as the load is increased some fibers will reach, their breaking points first. As they fail, their, loads will be transferred to other as yet unbroken fibers, so that the successive breaking, of fibers rather than the simultaneous breaking of all of them will cause failure. As reviewed in Chapter 2 (SHORT TERM LOAD, BEHAVIOR, Tensile Stress-Strain, Modulus, of elasticity) the result is usually the development of two or three moduli., The effect is to reduce the material's overall strength and reduce its allowable working, stresses accordingly, but the design theory is, otherwise largely unaffected, as long as basically elastic behavior occurs. The development of higher working stresses is thus largely, a question of devising fabrication techniques, like filament winding to make fibers work, together to obtain their maximum strength, (Chapter 8)., In the following discussion of design theory, the values of a number of elastic constants, , must be known in addition to the strength, properties of the plastic, the fibers, and their, combination. In the examples used, more-orless arbitrary values for the elastic constants, and strength values have been chosen to illustrate the basic theory, but any other values, could have been used just as well., , Theory of combined action Any material, when stressed stretches or is otherwise deformed. If the plastic and the fiber in RPs are, firmly bonded together, the deformation will, be the same in both. For efficient structural, behavior high-strength fibers are employed,, but these must be more unyielding than the, plastic. Therefore for a given deformation, or strain a higher stress is developed in the, fiber than in the plastic. If the stress-strain, relationships of fiber and plastic are known, (e.g., from their stress-strain diagrams), the, stresses developed in each for a given strain, can be computed and their combined action, determined., Figure 6-17 shows stress-strain diagrams, for glass fiber and two plastics. Curve A,, typical of glass, shows that stress and strain, are very nearly directly proportional to each, other to the breaking point. Here stiffness, or, the modulus of elasticity as measured by the, ratio of stress to strain, is high. Curve B represents a hard plastic. Stress here is directly, proportional to strain when both are low, but, the stress gradually levels off as the strain, increases. Its stiffness is much lower than, that of glass. It is measured by the tangent, to the curve, usually at the origin. Curve C, represents a softer plastic intermediate between the hard plastic and the very soft plastics. Stress and strain here are again directly, proportional at low levels, but not when the, strains become large. The modulus of elasticity, as measured by the tangent to the curve,, is lower than for the hard resin., These stress-strain diagrams may be applied, for example, to the investigation of a, rod of which has its total volume is glass fiber, and half plastic. If the glass fibers are laid, parallel to the axis of the rod, at any crosssection, half the total cross-sectional area is, glass and half plastic. If the rod is stretched, 0.5%, reference to the stress-strain diagrams

Page 377 : 6 Plastic Material Formation and Variation, 240, , 60, , 220, , 55, , 200, , 50, , 180, , 45, , 160, , 359, , Glass fiber A, , 40, , .s. 35, , ·it 140, , ~.5 120, , §, , jl00, , .; 25, , 80, , 20, , 60, , 15, , :; 30 en, , 10, , Tangent 10 B, , I, , I, , I, , I, , ,I, , 0~~~~??J., 0.5 1.0 1.5 2.0, % Strain, , % Strain, , Fig.6-17 Stress-strain diagrams for RPs., , in Fig. 6--17 will show that the glass is stressed, at an intensity of 345 MPa (50,000 psi) and, the plastic Bat 52 MPa (7,500 psi) or plastic, C at 17 MPa (2,500 psi)., If, for example, the rod has a total crosssection of one-half square inch, the glass is, one-quarter square inch and the total stress, in the glass is one-quarter times 50,000, or, 12,500 lb (5700 kg). Similarly, the stress in the, plastic B is 1,875Ib (850 kg) and in plastic C is, 625 lb (285 kg). The load required to stretch, the rod made with plastic B is therefore the, sum of the stresses in the glass and plastic, or, 14,375Ibs. Similarly, for a rod utilizing plastic, C the load is 13,125 lbs. The average stress, on the one-half square inch cross-section is, therefore 28,750 psi (198 MPa) or 26,250 psi, (180 MPa), respectively., An analogous line of reasoning shows that, at a strain of 1.25% the stress intensity in the, glass is 125,000 psi (862 MPa) and in plastic B, and C at 12,600 and 4,500 psi (87 and 31 MPa),, respectively. The corresponding loads on, rods made with plastics Band Care 34,400 lb, (15,600 kg) and 32,375 lb (14,700 MPa), respectively. Additional detailed information, is available concerning this analysis as well, as developing data for plain RP plates, composite plates, bending of beams and plates,, etc. (10)., , Property Range, , With RPs different performance capabilities can be obtained. Reason for this capability is because the designer can combine, different materials in different proportions., Examples of properties, including other materials of construction, are shown in Figs. 5-9,, 6-18a to c and Table 6-22., Elastomer, An elastomer is a rubberlike material (natural or synthetic) that is generally identified as a material which at room temperature, stretches under low stress to at least twice its, length and snaps back to approximately its, original length on release of the stress (pull), within a specified time period. The term elastomer is often used interchangeably with the, term plastic or rubber (2, 14)., Although rubber originally meant a natural thermoset material obtained from a rubber tree, with the development of plastics, it identifies a thermoset elastomer (TSE), or thermoplastic elastomer (TPE) material. Different properties identify the elastomers such as strength and stiffness, abrasion resistance, solvent resistance, shock and

Page 378 : 360, , 6 Plastic Material Formation and Variation, eGel·spun, polyethylene fiber, Rigid rod, ordered polymer fiber, (liquid crystal), , 3.5, 3.0, , Thermotropic, liquid crystal, aramid fiber, , I:}:@!:], , ~2.5, , E, , z, , '§, , 2.0, eSglass, , ~, , \\, , ~ 1.5, , .g, , j, , 1::::?:(i)){A, , ':' High strength, carbon fiber, , 1.0, , H, /;;, , E glass, , •, , 5, , ., , e Uftradrawn, polyethylene fiber, , ~~~, , SiC, ;/ (ceramic fiber), , -Steel, Aluminum, , •Liquid•crystal polymer molding, o, , .5, , 1.0, , 1.5, , 2.0, , Specific tensile modulus,, , 2.5, , lOS N· m/kg, , 3.0, , 3.5, , Fig.6-18a Comparison of specific strength vs. specific modulus of RPs. Specific properties are normalized by plastics density (Pa or N/m3 divided by kg/m3)., , vibration control, electrical and thermal insulation, waterproofing, tear resistance, costto-performance, etc., Plastic elastomers are generally lowermodulus flexible materials that can be, stretched repeatedly and will return to, their approximate original length when the, stresses are released. The rubber materials, have been around for over a century. They, will always be required to meet certain desired properties, but thermoplastic TPEs are, replacing traditional TS natural and synthetic rubbers (elastomers). TPEs are also, 100, , :x:, to, Z, w, a:, , 80, , t-, , (f), , w, , t-, , «, , 60, , ~, , i=, ...J, ::>, , u., , 40, , 0, , !zw, U, , a:, , 20, , w, , 0.., , 0, 10', , 10', , 103, , 10', , 105, , 10·, , 101, , CYCLES TO FAILURE, , Fig.6·18b, materials., , Fatigue property curves of different, , widely used to modify the properties of, rigid TPs, usually by improving their impact, strength., TPEs offer a combination of strength and, elasticity as well as exceptional processing, versatility. They present creative designers, with endless new and unusual product opportunities. More than hundreds of major different groups of TPEs are produced worldwide,, with new grades continually being introduced, to meet different electrical, chemical, radiation, wear, swell, and other requirements, (Tables 6-23 and 6-24)., Quite large elastic strains are possible with, minimal stress in TPEs; these are the synthetic rubbers. TPEs have two specific characteristics: their glass transition temperature, (Tg) is below that at which they are commonly used, and their molecules are highly, kinked as in natural TS rubber (isoprene)., When a stress is applied, the molecular chain, uncoils and the end-to-end length can be extended several hundred percent, with minimum stresses. Some TPEs have an initial, modulus of elasticity of less than 10 MPa, (1,500 psi); once the molecules are extended,, the modulus increases., The modulus of metals decreases with, an increase in temperature. However, in, stretched TPEs the opposite is true, because

Page 379 : 361, , 6 Plastic Material Formation and Variation, 100, , :x:, ~, , (!1, , z, , w, a:, ~, en, , (,), , 90, , ITt, 1011, , ~, , 80 f-, , 70 f-, , ~, , 60, , -, , ~, , 50, , -.---, , ~, , en, w, , <, :;, , t=, ...., , ...0, , 40, , ;:), , ~, , Z, , w, a:, w, (,), ~, , 30, , -, , r--, , -, , CYCLES, , t--, , ...-, , .--.--f--, , 20 I--, , .---, , -, , -, , r--, , 10 fSTEEL, , 4130, , ALUMINUM ALUMINUM, , 2024·1'3, , 7075·T6, , TITANIUM, 6AI4V, , l, , GLASS, FIBER!, , GLASS, FIBER!, , EPOXY, , EPOXY, , "E", "S", Fig.6·18c Fatigue bar graph of different materials., , with them at higher temperatures there is increasingly vigorous thermal agitation in their, molecules. Therefore, the molecules resist, more strongly the tension forces attempting to uncoil them. To resist requires greater, stress per unit of strain, so that the modulus, increases with temperature. When stretched, into molecular alignment many rubbers can, form crystals, an impossibility when they are, relaxed and "kinked.", To date, with the exception of vehicle tires,, TPEs have been replacing TS rubbers in, virtually all applications. Unlike natural TS, rubbers, most TPEs can be reground and, reused, thereby reducing overall cost. There, are types where the need to vulcanize them is, eliminated, reducing cycle times, and products can be molded to tighter tolerances. Most, TPEs can be colored, whereas natural rubber, is available only in black. TPEs also weigh 10, to 40% less than natural rubber (166)., TPEs range in hardness from as low as, 25 Shore A up to 82 Shore D (Chapter 5,, MECHANICAL PROPERTY, Hardness)., They span a temperature of -34 to 177°C, (-29 to 350°F), dampen vibration, reduce noise, and absorb shock. However,, , CARBON, FISER!, EPOXY, , designing with TPEs requires care, because, unlike TS rubber that is isotropic, TPEs, tend to be anisotropic during processing as, with injection molding. Tensile strengths in, TPEs can vary as much as 30 to 40% with, direction., Commodity and Engineering Plastic, , About 90 wt% of plastics can be classified, as commodity plastics, the others being engineering plastics. The five families of commodities LDPE, HDPE, Pp, PVC, and PS account for about two thirds of all the plastics, consumed. The engineering plastics such as, nylon, PC, acetal, etc. are characterized by, improved performance in higher mechanical, properties, better heat resistance, higher impact strength, and so forth. Thus, they demand a higher price. About a half century, ago the price per pound difference was about, 20¢; now it is about $1.00. There are commodity plastics with certain reinforcements, and/or alloys with other plastics that put them, into the engineering category. Most TSs and, RPs are engineering plastics.

Page 380 : 362, Table 6-22, , 6 Plastic Material Formation and Variation, RP trade-offs, , Desired, Modification, , Sacrifice (from Base Resin), How Achieved, , Amorphous, , Increased, Tensile, Strength, , Glass fibers, Carbon fibers, Fibrous, minerals, , Ductility,, cost, Ductility,, cost, NA, , Ductility,, cost, Ductility,, cost, Ductility, , Increased, Flexural, Modulus, , Glass fibers, Carbon fibers, Rigid minerals, , Flame, Resistance, , FR additive, , Ductility,, cost, Ductility,, cost, Ductility, Ductility,, tensile, strength,, cost, , Ductility,, cost, Ductility,, cost, Ductility, Ductility,, tensile, strength,, cost, , Increased, HeatDeflection, Temperature, (HDT), , Glass fibers, Carbon fibers, Fibrous, minerals, , Ductility,, cost, Ductility,, cost, NA, , Ductility,, cost, Ductility,, cost, Ductility, , Warpage, Resistance, , 5 to 10%, glass fibers, 5 to 10%, carbon fibers, Particulate, fillers, , Crystalline, , NA, , Cost, , NA, , Cost, , Ductility,, cost,, tensile, strength, , Ductility,, cost,, tensile, strength, , Comments, Glass fibers are the most cost, effective way of gaining tensile, strength. Carbon fibers are, more expensive; fibrous, minerals are least expensive but, only slightly slightly reinforcing., Reinforcement makes brittle, resins tougher and embrittles, tough resins. Fibrous minerals, are not commonly used in, amorphous resins., Any additive more rigid than, the base resin produces a, more rigid composite., Particulate fillers severely, degrade impact strength., FR additives interfere with the, mechanical integrity of the, polymer and often require, reinforcement to salvage, strength. They also narrow, the molding latitude of the, base resin. Some can cause, mold corrosion., When reinforced, crystalline, polymers yield much greater, increases in HDT than do, amorphous resins. As with, tensile strength, fibrous, minerals increase HDT only, slightly. Fillers do not increase, HDT., Amorphous polymers are, inherently nonwarping, molding resins. Only, occasionally are fillers such as, milled glass or glass beads, added to amorphous materials, because they reduce shrinkage, anisotropically. Addition of, fibers tends to balance the, difference between in-flow and, cross-flow shrinkage usually, found in crystalline polymers., When a particulate is used to, reduce and balance shrinkage,, some fiber is needed to offset, degradation., , (Continues)

Page 381 : 363, , 6 Plastic Material Formation and Variation, Table 6-22, , ( Continued), , Desired, Modification, Reduced Mold, Shrinkage, (Increased, mold-to-size, capability), , Reduced, Coefficient, of Friction, , Reduced Wear, , Electrical, Conductivity, , Sacrifice (from Base Resin), How Achieved, , Amorphous, , Glass fibers, Carbon fibers, Fillers, , Ductility,, cost, Ductility,, cost, Tensile, strength,, ductility,, cost, , Ductility,, cost, Ductility,, cost, Tensile, strength,, ductility,, cost, , Cost, , Cost, , Ductility,, cost, Tensile, strength,, ductility,, cost, , Ductility,, cost, Tensile, strength,, ductility,, cost, , ~E, Silicone, , Crystalline, , }, , MoS 2, Graphite, , Glass fibers, Carbon fibers, Lubricating, additives, Carbon fibers, Carbon, powders, , Neat Plastic, , Identifies a plastics with Nothing Else, Added To. It is a true virgin polymer since it, does not contain additives, fillers, etc. These, are very rarely used., Structural Foam, , The following review concerns structural, foams (SFs). Review Chapter 8, FOAMING, regarding the different TP and TS types of, foam available. Most of the foamed plastics, , Comments, Reinforcement reduces, shrinkage far more than, fillers do. Fillers help, balance shrinkage, however, becuase they replace, shrinking polymer. The, sharp shrinkage reduction in, reinforced crystalline resins, can often lead to warpage., The best "mold-to-size", composites are reinforced, amorphous composites., These fillers are soft and do not, dramatically affect mechanical, properties. PTFE loadings, commonly range from, 5 to 20%; the others are, usually 5% or less. Higher, loadings can cause mechanical, degradation., The subject of plastic wear is, extremely complex and, should be discussed with a, composite supplier., Resistivities of 1 to, 100,000 ohm-cm can be, achieved and are proportional, to cost. Various carbon fibers, and powders are available with, wide variations in, conductivity yields in, composites., , are TPs. When compared to solid plastics, a, density reduction of up to at least 40% can, easily be obtained in SF products. The actual density reduction obtained will depend, on the products' thickness, the design's shape,, and the melt flow distance during processing, such as how much plastic occupies the mold, cavity., Low-pressure SF products can have characteristic surface splay patterns. However,, the utilization of increased mold temperatures, increased injection rates, or grained, mold surfaces will serve to minimize or hide, this surface streaking. Finishing systems like

Page 382 : 6 Plastic Material Formation and Variation, , 364, Table 6-23, , Guide to data for elastomers (E = Excellent, G = Good, F = Fair, & P = Poor), , NR, , IR, , SBR, , BR, , IIR, , AST M D2000 designations, , M,, , M,, , M,, , BA, , M,, BA, , M,BA, CA, , Densiry, MglmJ, Glass trlUlsition temp., ·C, Temperarure serviceabiliry, ·C, lower limit, upper limit, continuous, intcrollrrent, Physical properties, , 0.92, , 0.92, , 0.94, -60, , 0.93, -105, , 0 .92, , +70, +100, , -55, +70, +100, , -45, +70, , +100, , -70, +70, , +100, , +100, +l2S, , 30-100, , 35-100, , 40-100, , 45-90, , 35-85, , 24, , 28, , 21, 24, , 3, 24, , 3, 17, , 10, 17, , Resilience, , E, , E, , G, , E, , p, , Resistance to:, tear, abrasion, compression set, creeplsrress relaxation, gas permeation, , E, E, G, E, F, , G-E, E, , F, , G, , G, E, , G, E, , G, , G, F, , G, F, , F, F, F, E, , Electrical rcsisti vi ry, , E, , E, , E, , E, , E, , F, , F, , F, , F, , G-E, , P, P, G, G, , P, , Abbreviation(s), , Hardness range, IRHD, , Tensile strength, MPa, gum, reinforced, , Environmental resistance to:, beat, oxidation, ozone, , fiame, , water, dil u te acids, coneentra tcd acids, alkalis, alipbatic hydrocarbons, aromatic bydrocarbons, halogenated solvents, oxygenated solvents, a.nim3llvegetable oils, , BA, , -70, , -55, , F, , F-G, G, P, P, P, , F-G, P-G, , BA, , -70, , F, , F, , P, G, G, F-G, G, p, p, P, , F-G, , P-G, , E, G, , F, P, , F, , G, , G, , P, , G, , P, , P, , G, , F-G, , F-G, , P, P, P, F-G, , F-G, , G, , P-G, , G, P, P, , P, , P-G, , -65, , -so, , G, G, , p, E, G, , F-G, G, P, P, , P, , G, G, , (Continues), , sanding, filling, and painting for these structural foam areas are used and have proved to, be capable of completely eliminating surface, splay., High-pressure structural foam products, have generally been found to require little, or no postfinishing. Although high-pressure, foam products may exhibit visual splay, their, surface smoothness is maintained and no, sanding or filling is required., For SF, mold pressures of approximately, 4.1 MPa (600 psi) are required compared to, , pressures of 34.5 MPa (5,000 psi) and greater, in injection molding. As a result, large, complicated parts of 23 kg (50 lb.) and higher can, be produced using multi-nozzle equipment,, or up to about 16kg (35 lb.) with single-nozzle, equipment and hot runner systems. Product, size is, in fact, limited only by the size of existing equipment, tool design, and a material's, properties limit product complexity. Product, cost can be kept in line through such advantages as product consolidation, function integration, and assembly labor savings.

Page 383 : 6 Plastic Material Formation and Variation, Table 6-23, , ( Continued), , .J', , ~, , oS', , "§, , t}, f2, , ~, , ~, , ~, , EPM,, EPDM, , ~, , §<, , CR, , ~, .§, if, , "§, , ~, , §, ;i§, U, , ?, , ~, , .J', , ~, , ~, , ~, oS', , 365, , .~, , $, , .::, , NBR, , .§, .§., , Q.,0, , AU,, EU, , §.,, -s:/j, ,s~, ?l'~, o if, , -#.§., , (J~, CSM, , ~~, ~, , ~, , .8, ~, Q, , §, , #, , C;;, , Note, , FKM, , AA,BA, CA,DA, , BC,, BE, , BF,, BG, , BG, , CE, , FC, FE,, GE, , HK, , 2, , 0.86, -58, , 1.23, -49, , 1.00, -24, , 1.05, -50, , 1.18, -28, , 0.98-1.6, -120, , l.85, -22, , 3, 4, , -40, +125, +150, , -35, , -20, +100, +125, , -50, +70, +100, , -20, +125, +150, , -60, +200, +250, , -20, +200, +250, , 5, , +100, +125, , 30-90, , 35-95, , 40- 100, , 50-100, , 40-95, , 40-90, , 50-95, , 6, , 3, 21, , 17, 21, , 4, 21, , 35, , 24, 21, , 7, 10, , 17, 17, , 7, , G, , G, , P-F, , F, , F, , F, , F, , 8, , F, , P-F, F, G, F, G-E, , E, E, G, F, G, , F, G, F, F, E, , P, , G, F, G, , F, E, G, F, G, , G, F-G, , F, G, G, G, , 9, 10, 11, , E, , F, , F, , G, , G, , E, , G, , E, E, E, P, , G, G, G, F, F, G, G, G, G, P-F, P, P, G, , G, G, P, P, F-G, G, F-G, F-G, E, F-G, P, , F, G, E, P, F, , E, E, , E, , E, E, , F, , E, E, G, G, , p, , P, , P, , G, G, , P, E, , F, , P, F, E, F, F, , P, , G, , When an engineering plastic is used with, the structural foam process, the material produced exhibits behavior that is easily predictable over a large range of temperatures., Its stress-strain curve shows a significantly, linearly elastic region like other Hookean, materials, up to its proportional limit. However, since thermoplastics are viscoelastic in, nature, their properties are dependent on, time, temperature, and the strain rate. The, ratio of stress and strain is linear at low strain, levels of 1 to 2%, and standard elastic design, , E, F, G, E, G, , E, F, F, , P, P-F, G, , F, , p-p, , E, , E, E, F, G, F, F, F, , E, F, E, E, E, P-G, , F, F-G, F, , E, G, P-F, E, , P, P, , 12, 13, , 14, 15, 16, 17, 17, , E, , 18, , principles can thus be applied up to the elastic, transition point., Large, complicated products will usually, require more critical structural evaluation to, allow better prediction of their load-bearing, capabilities under both static and dynamic, conditions. Thus, predictions require careful analysis of the structural foam's crosssection., The composite cross-section of a SF product contains an ideal distribution of material, with a solid skin and a foamed core. The

Page 384 : 366, , 6 Plastic Material Formation and Variation, , Table 6·24 Example of elastomers per ASTM, D 2000 and SAE J 200, , Type ,j, ,j, Class, , Typical Rubber, , AA, , Natural rubber, styrene, butadiene, butyl, ethylene, propylene, polybutadiene,, Polyisoprene, Polysulfide, Ethylene propylene, styrene, butadiene (high temperature), Butyl, Chloroprene, chlorinated, polyethylene, Chloroprene, chlorinated, polyethylene, Nitrile, Nitrile, urethane, Polysulfide, nitrile, Ethylene propylene, Chlorosulfonated polyethylene,, chlorinated polyethylene, Nitrile, epichlorohydrin, Ethylene/acrylic, Ethylene propylene, Chlorinated polyethylene,, chlorosulfonated, polyethylene, Polyacrylate, (butyl-acrylate type), Polyacrylate, Silicone (high strength), Silicone, Fluorinated silicone, Silicone, Fluorinated rubbers, , AK, BA, BC, BE, BF, BG, BK, CA, CE, CH, DA, DE, DF, DH, FC, FE, FK, GE, HK, , manufacturing process can distribute a thick,, almost impervious solid skin that is in the, range of 25% of the overall wall thickness at, the extreme locations from the neutral axis, (Fig. 6-19). These are the regions where the, maximum compressive and tensile stresses, occur in bending., , The simply supported beam has a load applied centrally. The upper skin go into compression while the lower one goes into tension, and a uniform bending curve will develop. However, this happens only if the shear, rigidity or shear modulus of the cellular core, is sufficiently high. If this is not the case, both, skins will deflect as independent members,, thus eliminating the load-bearing capability, of the plastic composite structure., The fact that the cellular core provides resistance against shear and buckling stresses, implies an ideal density for a given foam wall, thickness. This optimum thickness is critically important in designing complex stressed, products. As a 6.4 mm (1/4 in.) wall, for example, plastics such as both modified polyphenylene oxide and polycarbonate exhibit the best, processing, properties, and cost in the range, of a 25% weight reduction. Laboratory tests, show that with thinner walls about 4 mm, (0.157 in.), this ideal weight reduction decreases to 15%. When the wall thickness, reaches approximately 9 mm (0.350 in.), the, weight can be reduced by 30%., However when the SF cross-section is analyzed, its composite nature still results in, a twofold increase in rigidity, compared to, an equivalent amount of solid plastic, since, rigidity is a cubic function of wall thickness., This increased rigidity allows large structural products to be designed with only minimal distortion and deflection when stressed, within the recommended values for a particular foamable plastic., Depending on the required analysis, the, moment of inertia can be evaluated three, ways. In the first approach, the cross-section, is considered to be solid material (Fig. 6-20)., The moment of inertia, Ix is:, Ix = bh3 /12, (6-1), where b = the width and h = the height., , '", , comp~elSion, , ~, .., p, , I~"; ., , ,", , ", , ,-, , I, , ~, , ~~@;, ~, .., , '.1.-,', , ",),f:, , Tension, , (a), , Fig.6·19, , (bl, , (e), , Composite cross-section of a structural foam product.

Page 385 : 6 Plastic Material Formation and Variation, , 367, , ~------b------~, , Fig. 6·20, , Cross-section of a solid material., , This commonly used approach provides acceptable accuracy when the load-bearing requirements are minimal, for example, in the, case of simple stresses and when time and, cost constraints prevent more exact analysis., The second approach ignores the strength, contribution of the core and assumes that the, two outer skins provide all the required rigidity (Fig. 6-21). The equivalent moment of inertia is then equal to:, , bearing capabilities without resorting to, overdesign and thus unnecessary costs. Such, an analysis produces maximum accuracy and, would thus be suitable for finite-element, analysis on complex products. However, the, one difficulty with this method is that the core, modulus and the as-molded variations in skin, thicknesses cannot be accurately measured., Plastics with a Memory, , (6-2), This formula results in conservative accuracy, since the core does contribute to the, stress-absorbing function. It also adds a builtin safety factor to a loaded beam or plate, element when safety is a concern., A third method is to convert the structural, foam cross-section to an equivalent I-beam, section of solid resin material (Fig. 6-22)., The moment of inertia is then formulated, as:, where bi = b( Ec) / Es, Ec = the modulus of, the core, Es = the modulus of the skin, ts =, the thickness of the skin, and hI = the height, of the equivalent web (core)., This approach may be necessary where, operating conditions require stringent load-, , Thermoplastics can be bent, pulled, or, squeezed into various useful shapes. But, eventually when heat is added, they return, to their original form. This behavior, known, as plastic memory, can be annoying. If property applied, however, plastic memory offers, interesting design possibilities for all types of, fabricated products., When most materials are bent, stretched,, or compressed, they alter their molecular, structure or grain orientation to accommodate the deformation permanently, but this is, not so with thermoplastics. They temporarily, assume the deformed shape, but they always, maintain the internal stresses that want to, force the material back to its original shape., Most TP products can be produced with, a built-in memory. That is, their tendency, to move into a new shape is included as an, , ~I, , '-~~, I-, , b, , Fig. 6-21, , I, , ~-----b------~, , Cross-section of a sandwich structure.

Page 386 : 368, , 6 Plastic Material Formation and Variation, , Fig.6-22 Cross-section of an I-beam., , integral part of the design. So after the products are assembled in place a small amount of, heat can coax them to change shape. Plastic, products can be deformed during assembly,, then allowed to return to their original shape., In this case the products can be stretched, around obstacles or made to conform to unavoidable irregularities without their suffering permanent damage., The time/temperature-dependent change, in mechanical properties results from stress, relaxation and other viscoelastic phenomena, that are typical of these plastics. When the, change is an unwanted limitation it is called, creep. When the change is skillfully adapted, to use in the overall design, it is referred to, as plastic memory., Even though potential memory exists in, all TPs, polyolefins, neoprenes, silicones, and, other cross-linkable TPs are example of plastics that can be given memory either by radiation or by chemically curing. Fluorocarbons, however, need no such curing. When, this phenomenon of memory is applied to, fluorocarbons such as TFE, FEP, ETFE,, ECTFE, CTFE, and PVF2, interesting hightemperature or wear-resistant applications, become possible., Orientation, , A thermoplastic's molecular orientation, can be accidental or deliberate. However, excessive frozen-in stress due to orientation can, be extremely damaging if products are subject to environmental stress cracking or crazing in the presence of chemicals, heat, and, so on. Initially the molecules are relaxed;, molecules in amorphous regions are in random coils, those in crystalline regions relatively straight and folded. During processing, , the molecules tend to be more oriented than, relaxed, particularly when sheared, as during, injection molding and extrusion., After temperature-time-pressure is applied and the melt goes through restrictions, (molds, dies, etc.), the molecules tend to be, stretched and aligned in a parallel form. The, result is developing directional properties, and dimensions. The amount of change, depends on the type of thermoplastic, the, amount of restriction, and, most important,, its rate of cooling. The faster the rate, the, more retention there is of the frozen orientation. After processing, products could be, subject to stress relaxation with changes in, performance and dimensions. With certain, plastics and processes there is an insignificant change. If changes are significant,, one must take action to change processing, conditions, particularly controlling the, cooling rate (Chapter 8, PROCESSING, AND PROPERTIES, ORIENTATION)., , Material Variable, , Even though equipment operations have, understandable but controllable variables, that influence processing, the usual most, uncontrollable variable in the process can be, the plastic material. The degree of properly, compounding or blending by the plastic, manufacturer, converter, or in-house by, the fabricator is important. Most additives,, fillers, and/or reinforcements when not properly compounded will significantly influence, process ability and fabricated product performances., With the passing of time and looking ahead, these material and equipment variabilities, continually are reduced due to improvement, in their manufacturing and process control

Page 387 : 6 Plastic Material Formation and Variation, capabilities. However they still exist. To ensure control of material, as previously reviewed, setting up controls via different tests, and setting limits are important. Even set, within limits, processing the materials could, result in inferior products. As an example, the material specification from a supplier will, provide an available minimum to maximum, value such as molecular weight distribution., It is determined that when material arrives all, on the maximum side it produces acceptable, products. However when all the material arrives on the minimum value process control, has to be changed in order to produce acceptable products., In order to judge performance capabilities, that exist within the controlled variabilities,, there must be a reference to measure performance against. As an example, the injection, mold cavity pressure profile is a parameter that is easily influenced by variations, in the materials. Related to this parameter, are four groups of variables that when put, together influences the profile: (1) melt viscosity and fill rate, (2) boost time, (3) pack and, hold pressures, and (4) recovery of plasticator. Thus material variations may be directly, related to the cavity pressure variation., Details on EQUIPMENTIPROCESSING, VARIABLE are in Chapter 8., A very important factor that should not, be overlooked by a designer, processor, analyst, statistician, etc. is that most conventional and commercial tabulated material, data and plots, such as tensile strength, are, mean values. They would imply a 50% survival rate when the material value below the, mean processes unacceptable products. Target is to obtain some level of reliability that, will account for material variations and other, variations that can occur during the product, design to processing the plastics (Chapter 5,, ANALYZING TESTING AND QUALITY, CONTROL)., Recycling, , Also called regrind and reclaiming. Most, processing plants have been reclaiming/, recycling reprocess able TP materials such, as molding flash, rejected products, blown, , 369, , film trim, scrap, and so on. TS plastics (not, remeltable) have been granulated and used, as filler materials. If possible the goal is to significantly reduce or eliminate any trim, scrap,, rejected products, etc. because it has already, cost money and time to go through a fabricating process; granulating just adds more, money and time., Also it usually requires resetting the process controls to handle it alone (or even when, blending with virgin plastics and/or additives), because it usually does not have uniform particle sizes, shapes, and melt flow characteristics. Keeping the scrap before/after granulating clean is a requirement. These behaviors as, well as overheating the plastic during the cutting action of a granulator can significantly influence their process ability and performance, of fabricated products., Figure 6-23 shows how regrind levels affect, the mechanical properties of certain formulations of plastics "once through" the fabricating process and blended with virgin material., The regrind, or scrap, amount is a percentage by weight. Figure 6-24 is an example of, the potential effects of the number of times, regrind influences the performance of an injection molded TP mixed with virgin plastics., Figure 6-25 is an injection molding flow diagram example. See in Chapter 7, THERMAL, PR 0 PERTY, Heat History, Residence Time,, and Recycling., Since scrap can be a mixture ranging from, fine dust to large irregular chunks of different shapes, thicknesses, etc., it is important, to use a granulator that provides the most, uniformity and the least heat and mechanical damage to the scrap. Material having this, range of size when granulating will at least influence product performances where critical, requirements exist. The material influences, the processing characteristics that in turn, effect the product's performances., Overheating during the cutting action of, the granulator can cause the most damage., For heat sensitive plastics to eliminate any, heat damage cryogenic granulating is used., Recognize that a granulator that handles soft, plastics will not work well when granulating hard plastic. One that handles thin plastic is not the proper type to handle thick, plastics. Two or more different performing

Page 388 : 370, , 6 Plastic Material Formation and Variation, Tensile strength (ASTM 0638-72), , Impact strength (ASTM 0256-73), , 12,000, , Percent elongation (ASTM 01238), , 60, SAN, , 40, , 10,000, , 'iii, , 0-, , £, C,, , 8000, , c, , ~, , U5, , ~, , 0, , C, 11, c, ~ 10, U5 9, , ~, , 'iii, c, , ""c::, , ~, , Polystyrene, , 6000, , ~, , 4000, , 0-, , ~, 0), c, , HDPE, , 0, , ill, , 8, , E, , 3, 2, , HDPE, , 2000, , SAN, , 4, 2, , Polystyrene, , 0, , 20, , 40, , 60, , 80, , 0, , 100, , Scrap content, %, , 20, , 40, , 60, , 80, , 100, , Scrap content, %, , 0, , 20, , 40, , 60, , 80, , 100, , Scrap content, %, , Fig. 6-23 Example of effect of regrind on plastics,, , granulators may be required to process thick, material to ensure that overheating is minimized. The first granulator is designed to handle the thick material. The next granulator, has the capability to process the first granulated plastics. The second granulated plastics, may require a finer operating granulator and, so on until the desired material is obtained., In summary recycling will reduce performance properties. The amount of reduction, Tensile Strength, , 1oo ......::---......---,-----,, 95, , =---t-----J 25, 40, , 90, , 60, , 85, 80~--~---L--~, , Impact Strength, 100 --..;:--......- - - , - - - - - ,, , can be very slight to undesirable amounts, during the first remelting process. Granulated, plastics that have been significantly degraded, may be reformulated by the addition of stabilizers, pigments, plasticizers, fillers, reinforcements, and/or other additives. These blends,, particularly the general purpose commodity, plastics, usually improves their process ability, and/or product performances., When RPs are granulated, the lengths of, the fibers are reduced. On reprocessing with, virgin materials or alone, their processability and product performances are definitely, change. So it is important to determine if the, change will affect final product performances., If it will, a limit for the amount of regrind mix, should be determined or no recycled RP is to, be used. Use it in some other product such as, simulated wood., Recycling Energy Consumption, , 95, , 25, , 90, , 40, , 85, 80~----~----~~--~60, 1st, 2nd, 3rd, 4th, Number of times molded, (Heat history effects performances), , Fig. 6-24 Example of effects of number of times, in recycled injection molded plastics., , Plastics have many advantages. Included, are the facts that they have the lowest energy consumption in the recycling processes, of about 2 MJ/kg (2 to 2.5 MJ/I) and when, incinerated the highest recovery energy content exists of about 42 MJ/kg. Some comparisons with other materials are provided., (1) Processing waste paper requires 6.7 MJ/kg, and as a general rule about twice as much, paper is needed compared to plastics for

Page 389 : 6 Plastic Material Formation and Variation, , 371, , Auger-fed, Granulator, , Fig. 6-25 Flow diagram: virgin plastics, molded products with runners, granulating runners, to regrind, blend with virgin plastics., , comparable applications. (2) In glass production, if one uses about 10% of recycled glass,, this only reduces the energy consumption of, the process by about 2 %; thus the use of, recycled glass requires about 8 MJ/kg, but, the comparative figure is higher when considered in relation to each product, as one needs, , about 10 to 20 times as much material compared with plastics. (3) The energy requirement for processing scrap steel and tin-plate, is about 6 MJ/kg. (4) Aluminum recycling requires about 50% of the energy needed to, make a product from virgin aluminum; about, 50 MJ/kg.

Page 390 : 372, , 6 Plastic Material Formation and Variation, , Design Source Reduction, This generally defines the design, manufacture, purchase, or use of materials or products, to reduce the amount of material used before, they enter the municipal solid waste stream., Because it is intended to reduce pollution and, conserve resources, source reduction should, not increase the net amount or toxicity of, waste generated throughout the life of the, product. The EPA has established a hierarchy, of guidelines for dealing with the solid waste, situation. Their suggestions include (logically) source reduction, recycling, waste-toenergy gains, incineration, and landfill. The, target is to reduce the quantity of trash., Recycling Method, This subject effects designers since many, products have the requirement by regulations or otherwise to use recycled plastics., Different methods are used to recycle materials to provide plastics with a continuing, life. Method used is influenced by factors such, as costs, quantity involved, weight involved,, size and shape, complexity of mixed types, of plastics, extended of contamination such, as metallic particles, continued availability of, material, etc. (Recognize that they can also, be used as energy sources through incineration that can be combined with production of, electricity and/or hot water for example)., In addition to granulating, the processes, used include depolymerization to thermalliquefaction and gasification (back to feedstocks, or intermediates), chemical pyrolysis, chemical depolymerization such as methanalysis, and glycolysis, alcoholysis, catalytic cracking,, gasification, hydrogenation, hydrolysis, reactive extrusion, and thermal steam of plastics., Each technique has advantages and drawbacks. Some require careful plastic sorting of, mixed materials, and cleaning (2)., The choice of recycling to materials or energy has to be decided by an economic audit., Recycling is preferable to landfill practice,, the costs of which are increasing and where, the favorable properties of plastics are not, used. Municipal authorities have to consider, the economics of recycling operations, tak-, , ing into account the cost of landfill. Factors, to consider are: revenue from recycled materials or produced energy, cost of recycling,, savings from non-disposal in landfill, and cost, of disposal in landfill of the remaining tonnage after recycling., While recycling can save energy and resources in the manufacturing process, getting, recyclables to market and then processing, into products also uses energy and generates, waste that must be managed. Use of fuels and, the environmental impact of preparing, collecting, sorting, and transporting recyclables, should be considered when developing an audit. The ideal target is that the recycling results in a profitable venture. An example is, when a town takes a positive approach to handling all kinds of waste, such as in Chatham,, MA, a profit is made over and above the, cost of separating, handling, delivery to customers, etc. the "waste.", Recycling limitation Criteria of logistic, technology and properties will determine, whether or not it is plausible to reclaim, and reuse plastic wastes. These criteria can, be assessed economically in a complex way, under the aspects of production and economy. Logistic criteria will cover the conditions of accrual according to location and, quantity. Technological criteria are the purity of type plastic, cleanliness, and geometry, (basic shape and uniformity). Property criteria result from the extent of damage of the, material during recycling., Reactive extrusion recycling This review, only concerns one of the recycling method, that is also called reactive compounding, or, REX (reactive extrusion). It refers to the performance of chemical reactions during plastic processing that includes recycling plastics, such as PET (202). The most common reactants are plastic or preplastic melts and, gaseous, liquid, or molten low molecular, weight compounds. A particular advantage, of the extruder as a chemical reactor is the, absence of a solvent as the reaction medium., No solvent-stripping or recovery process, is required, and product contamination by, solvent or solvent impurities is avoided. The, chemical reaction may take place in the melt

Page 391 : 6 Plastic Material Formation and Variation, phase or, less commonly, in the liquid phase,, as when bulk polymerization of monomers, performed in an extruder, or in the solid, phase when the plastic is conveyed through, the extruder in a slurry. The types of reactions developed include bulk polymerization,, graft reaction, interchain copolymer formation, coupling or branching reaction, controlled molecular weight degradation, and, functionalization or functional group modification (2)., , Web Site Connect Buyer and Seller of, Recycled Plastic, In keeping with its commitment to economically and environmentally responsible, recycling, the American Plastics Council, (APC) has a Web site feature that connects buyers and sellers of recycled plastics. The site, located at www.plasticsresource., comlrecycIinglmarketsdblindex.phtml allows, users to select the type of plastic they want, and a source location from which to obtain it., As an example users searching for vinyl, sources can browse through hundreds of, post-consumer residential, industrial, commercial and institutional sources. This site is, in addition to the searchable Directory of, North American Companies involved in, the Recycling of Vinyl (PVC) Plastics, located on the Vinyl Institute's Web page, at www.vinylinfo.orgldatabase/vinyidata2., These tools provide information to companies that are searching for specific, information about recycling to meet their, processing needs., Plastic Future and Biotechnology, We are now in the century of biotechnology. Biological breakthroughs influenced, , 373, , mankind that includes raising life expectancies by 10 years, commercial fuel cells using, corn stalks as the energy source to plastics., The advances made by scientists in DNA and, RNA have left no industry untouched including plastic (186)., The reliance of fossil fuels has been challenged by lower cost and renewable sources, that are more environmentally friendly. The, traditional chemical plant has met serious competition from green plants. Many, monomers are now made via fermentation,, using low-cost sugars as feedstock. Some, of the commodity monomers are under, siege by chemicals extracted from biomass., Monomer production has been expanded, to include many more monomers from, nature., Worldwide suppliers with bioengineering, capabilities are displacing established polymers with cost-effective and higher performing plastics. An explosion of novel polymers, has been made by enzymatic control. The use, of enzymes for polymerization has drastically, altered the landscape of polymer chemistry., Processors can request specific properties for, each application as opposed to the usual making do with what is available. The supplier can, deliver to the processor desired properties requested., There are methods to manipulate the backbones of polymers in several areas that include control of microstructures such as crystallinity, precise control of molecular weight,, copolymerization of additives (flame retardants), antioxidants, stabilizers, etc.), and direct attachment of pigments. A major development with all this type action has been, to provide significant reduction in the variability of plastic performances, more processes can run at room temperature and atmospheric pressure, and 80% energy cost reductions.

Page 392 : 7, Material Property, , Introduction, , Designing has never been easy in any material, particularly plastics, because there are, so many. Plastics practically provide more, types with the many variations that are available than any other material. Of the more, than 35,000 different plastics worldwide, only, a few hundred are used in large quantities., Unfortunately, some designers view plastics, as a single material because they are not, aware of all the types available (Appendix A,, PLASTICS DESIGN TOOLBOX)., Plastics are families of materials each with, their own special advantages. The major consideration for a designer is to analyze what is, required as regards to performances and develop a logical selection procedure from what, is available., The ranges of properties in plastics encompasses all types of environmental and, load conditions, each with its own individual, yet broad, range of properties (Fig. 1-9)., These properties can take into consideration, wear resistance, integral color, impact resistance, transparency, energy absorption, ductility, thermal and sound insulation, weight,, and so forth. There is unfortunately no one, plastic that can meet all maximum properties., Therefore, the designer has different options,, such as developing a compromise because, many product requirements provide options,, particularly if cost is of prime importance., , The combination approach permits using, plastics that have different properties. They, can just be stacked together, but with the, available processes they can also be put together so that each material retains its individuality yet has a bond with the adjoining, plastics. These processes of coinjection, coextrusion, and so on are reviewed in Chapter 8., Each of the individual plastics can provide, such characteristics as wear resistance, being a barrier to water, electrical conductor,, and adding strength. Low cost recycled (solid, waste) plastics can be "sandwiched" between, other expensive, high performance plastics, so they only act as a filler, increase strength,, etc., Plastics can also be combined with other, materials such as aluminum, steel, and wood, to provide specific properties. Examples include PVC/wood window frames and plastic/, aluminum-foil packaging material. All combinations require that certain aspects of compatibility such as processing temperature and, linear coefficient of thermal expansion or, contraction exist., The designer can use conventional plastics, that are available in sheet form, in I -beams or, other forms, as is common with many other, materials. Although this approach with plastics has its place, the real advantage with, plastic lies in the ability to process them, to fit the design shape, particularly when it, comes to complex shapes. Examples include

Page 393 : 7 Material Property, two or more products with mechanical and, electrical connections, living hinges, colors,, and snap fits that can be combined into one, product., Like other materials, hot enough fires can, destroy all plastics. Some burn readily, others, slowly, others only with difficulty; still others do not support combustion after the removal of the flame. There are certain plastics, used to withstand the reentry temperature of, 2,500°F (1,370°C) that occurs when a spacecraft returns into the earth's atmosphere; the, time exposure is parts of a millisecond. Different industry standards can be used to rate, plastics at various degrees of combustibility, (Chapter 2, HIGH TEMPERATURE)., Plastics' behavior in fire depends upon the, nature and scale of the fire as well as the surrounding conditions and how the products, are designed. For example, the virtually allplastic 35 mm slide projector uses a very hot, electric bulb. When designed with a metal, light and heat reflector with an air circulating fan, no fire develops. Therefore, designing in this type product environment requires, understanding all the variables so that the, proper plastics can be used., , Mechanical Property, Most plastics are used to produce products because they have desirable mechanical, properties at an economical cost. For this reason their mechanical properties may be considered the most important of all the physical,, chemical, electrical, and other considerations, for most applications. Thus, everyone designing with such materials needs at least some, elementary knowledge of their mechanical, behavior and how they can be modified by, the numerous structural factors that can be, in plastics (Chapters 2 to 6)., Plastics have the widest variety and range, of mechanical properties of all materials, (Figs. 1-8 and 7-1 and 7-2). They vary from, basically soft to hard, rigid solids. Great many, structural factors determine the nature of, their mechanical behavior, such as whether, a load occurs over the short term or the long, , 375, TOUGH, ASS, , t, , NYLON, , POLYCARSONATE, , ACETAL, , POLYPROPYLENE, POLYETHYLENE, , DAP, , VINYL, , POLYSTYRENE, , BRITTLE, , Fig. 7-1 Example of the range of mechanical, properties for plastics., , term (Chapter 2). As a rule, design is based, on certain minimum strength or minimum deformation criteria., Short-term testing is important in designs, and for quality control of plastics to ensure, the required properties of plastics used in, production. The short time data provides, the designer information that permit comparisons of one material with another. However,, a true comparison is possible only if both sets, of data were determined in exactly the same, way. For example, the speed of loading tensile test specimens influences performance, factors such as deformation. Also, comparing the impact resistance of a %in. specimen, with that of a 1/8 in. specimen will result in, a different analysis of the material's properties. Thus, it is necessary to describe the exact, testing conditions along with each set of data, sheets. The data from short-term testing give, the user an important overall picture of the, material (Chapter 5)., The long-term testing of certain plastics allows their strength properties to be identified rapidly. Three of the major control test, procedures for long-term testing and predicting product lifetime are creep, fatigue, and, impact as reviewed in Chapter 2. Figure 7-3, shows long-term tensile creep curves at 20°C, (49°F) for polypropylene and nylon; numbers in parenthesis refer to stress levels, in MPa. Figure 7-4 shows long-term tensile fatigue curves for dry nylon 6 that is, 4.5 mm (0.18 in.) thick, acrylic (PMMA) that, is 6.4 mm (0.25 in.) thick, and polytetrafluoroethylene (PTFE) that is 6.6 mm (0.26 in.), thick. The test frequency is at 1,800 cpm.

Page 394 : 7 Material Property, , 376, 20, A, , A. TP polyester with 30"10 fibers,, E"'1.1 x 10 psi (7.6 CPa), B. TP polyester with 15% fibers,, E"'670,000 psi (4.6 CPa), C. Acrylic, E=-440,000 psi (3.0 CPa), D. PC or PPD,E"'350,000 psi (2.4 CPa), E. TP polyesterl"'350,000 psi (2.4 CPa), F. Rigid PVC, E"'440,000 psi (3.0 CPa), C. HDPE foam (60 pet, 955 kg/m 3),, E"120,000 psi (827 MPa), H. LOPE foam (57 pcf, 915 kg/m 3 ), E:10,OOO psi (69 MPa), I. PUR foam (7 pct,112KC/m 3 ), , 15, , ..,:·iii,...., ><, , Ii 10, , 150, , 100, , 75, , a., '", , :.;;:, , E, , Ii, , £, , 50 en, , ~, E, , 5, , 25, , __--------.:C, H, , 0~~~----r---~--r-~_4~~~~-L0, , o, , 5, , 10, , 20, , 15, , 25, , 100, , Strain, percent, , Fig.7-2 An example of a range in tensile strength, modulus of elasticity, and elongation of some TPs, with and without chopped glass fibers by weight and type of reinforcement., , Toughness, Toughness is usually the most complex, factor to technically define and understand., Tough TPs are usually described as ones, , having a high elongation to failure or ones, in which a large amount of energy must, be expended to produce failure. For high, toughness a plastic needs both the ability to, withstand load and the ability to elongate, , .,, , .!:, , -..., , I II, , 105, , 10, , Time (s), , Fig.7-3, , Example of long-term tensile creep curves.

Page 395 : 7 Material Property, , is usually encountered, the result is a satisfactory combination of properties., , 35r---_,----~~~-----,.-----.5, , Nylon 6, , 28 I·············· ...··;····························;··· ", t'G, , 21, , ~, , 141····················,·························· , ...... ., , en, , iii, , ..............,' .............................. 4, , "'ZMMA!, ~, .................................. ,., , Cl.., ~, , ", , o~, , 10 3, , ____ ____ ____ ____, ~, , 10 4, , ~, , 105, , til, , 3, , ""'-, , 2, , iii, , 7 .........""', ......P_T_F_E_i.===~==1, ~, , ~o, , 106, , 10 7, , 377, , en, , ~, , Cycles to failure, , Fig. 7-4 Example of long-term tensile fatigue, curves., , substantially without failing except in the, case of RPs. The RPs can have high strengths, with low elongation., It may appear that factors contributing to, high stiffness are required. This is not true because there is an inverse relationship between, flaw sensitivity and toughness; the higher the, stiffness and the yield strength of a TP, the, more flaw sensitive it becomes. However,, because some load bearing capacity is required for toughness, high toughness can be, achieved by a high trade-off of certain factors. Crystallinity increases both stiffness and, yield strength, resulting usually in decreased, toughness. This is true below its glass transition temperature (Tg) in most noncrystalline, (amorphous) plastics, and below or above, the T g in a substantially crystalline plastic, (Chapter 6). However, above the Tg in a, plastic having only moderate crystallinity increased crystallinity improves its toughness., Furthermore, an increase in molecular weight, from low values increases toughness, but with, continued increases, the toughness begins to, drop., Cross-linking produces some dimensional, stability and improves toughness in a noncrystalline type of plastic above the T g, but, high levels of cross-linking lead to embrittlement and loss of toughness. This is one of the, problems with TSs for which an increase in, Tg is desired. Increased cross-linking or stiffening of the chain segments increases the T g,, but it also decreases toughness. A popular, way to increase toughness is to blend, compound, or copolymerize a brittle plastic with a, tough plastic. Although some loss in stiffness, , Deformation and Toughness, Deformation is an important attribute in, most plastics, so much so that it is the very, factor that has led them to be called plastic., For designs requiring such traits as toughness or elasticity this characteristic has its, advantages, but for other designs it is a, disadvantage. However, there are plastics, in, particular the RPs, that have relatively no deformation or elasticity and yet are extremely, tough (Fig. 7-5); (a) toughness related to heat, deflection or rigidity and (b) toughness or impact related to temperature for polystyrene, (PS) and high impact polystyrene (HIPS)., These types of behavior characterizes the, many different plastics available (Table 7-1)., Some tough at room temperature, are brittle, at low temperatures. Others are tough and, flexible at temperatures far below freezing, but become soft and limp at moderately high, temperatures. Still others are hard and rigid, at normal temperatures but may be made, flexible by copolymerization or adding plasticizers., By toughness is meant resistance to fracture. However, there are those materials that, are nominally tough but may become embrittied due to processing conditions, chemical, attack, prolonged exposure to constant stress,, and so on. A high modulus and high strength,, with ductility, is the desired combination of, attributes. However, the inherent nature of, plastics is such that their having a high modulus tends to associate them with low ductility,, and the steps taken to improve the one will, cause the other to deteriorate., As previously described (Chapter 2), the, area under short-term stress-strain curves, provides a guide to a material's toughness, and impact performance (Fig. 7-6). The ability of a TP to absorb energy is a function of, its strength and its ductility that tends to be, inversely related. The total absorbable energy is proportional to the area within the, lines drawn to the appropriate point on the, curve from the axis. The material in area A is

Page 396 : 7 Material Property, , 378, Notched 25, IZOD, Impact, Ft-Lb-In, , General, Purpose, Plastics, , Wet, , I, I, , : Engineering, : Plastics, I, , 'ZYTEL" ST, Range, , 20, Elastomers, 15, , lonomers, , Dry, , Thin Parts, , Polyethylene, Polycarbonate, Range, , 10, , 5, , TougLhness, , 100, , 200, , 300, , 400, , 500, , Heat Deflection Temperature, of at 66 PSI, , Rigidity_, , (a), , Temperature. of, -150, 30, , --130, , 30, , 120, , 210, , ,......, , 10, HIPS, , 7, , --,, ~, , 0,, c, , 2, , ;Q, 0.7, , E!, , E, , 0.1, , ~, , ~, , E!, , /, , 0.3, , .:::, 0,, c, , •, , 1;;, , a., , 7, , ./, , V, , 3, , t>en, , 300, 20, , 0.2, , 1;;, , t>en, , a., , E, 0.Q7, , PS, , :, , 0.03, , 0.01, -100, , -50, , 0, , I, , 50, , Temperature., , 100, , ...., , 0.02, , 0.007, 150, , °c, , (b), , Fig.7-5 Examples of toughness in plastics., , rubberlike and is just as tough (that is of equal, area) as material B, which is metallic. Most, plastics, like material B, fall between these, extremes, but some fall into both A and C., Toughness can be relate to moisture content, in the plastic (Fig. 7-7) based on the area under the tensile stress-strain curves., Soft, weak materials have a low modulus,, low tensile strength, and only moderate elon-, , gation to break. The elastic modulus or the, modulus or elasticity is the slope of the initial straight-line portion of the curve. Hard,, brittle materials have high moduli and quite, high tensile strengths, but they break at small, elongations and have no yield point. Hard,, strong plastics have high moduli, high tensile strengths, and elongations of about 5%, before breaking. Their curves often look as

Page 397 : 7 Material Property, , 379, , Table 7-1 Examples of toughness or fracture characteristics for TPs, Material, PMMA, PA, SAN, ABS, CA, HDPE, PA, PB, PC, POM, PP, PTP, PVC, LDPE, PB, TFE, , Unnotched, , Notched, , Brittle, , Brittle, , Ductile, , Brittle, , Ductile, , Ductile, , Polymethylmethacrylate, Polystyrene, Styrene-acrylonitrile copolymer, Acrylonitrile butadiene styrene, Cellulose acetate, High-density polyethylene, Polyamide (Nylon), Polybutene, Polycarbonate, Polyoxymethylene, Polypropylene, Polyethylene terephthalate, Polyvinyl chloride, Low-density polyethylene, Polybutene, Polytetrafluoroethylene, , though the material broke about where a, yield point might have been expected., Soft, tough plastics are characterized by, low moduli, yield values or plateaus, high, elongations of 20 to 1,000%, and moderately, high breaking strengths. The hard, tough plastics have high moduli, yield points, high tensile strengths, and large elongations. Most, plastics in this category show cold drawing, or necking during the stretching operation., From a practical viewpoint toughness is, readily understood, but technically there, tends to be no scientific method of measuring it. One definition of toughness is simply, the energy required to break the plastic. This, , energy is equal to the area under the stressstrain curve. The toughest plastics should be, those with very great elongations to break,, accompanied by high tensile strengths; these, materials nearly always have yield points., One major exception to this rule is reinforced, plastics that use reinforcing fibers like glass, and graphite., Stress-strain tests may be made in compression as well as tension. A modulus may, , Dryas molded, 0.2% moisture content, , Toughness, Relates to Area, Under Curve, , 50% relative humidity, average air exposure, 2.5% moisture content, , 100% relative humidity, saturated, 8.5 % moisture content, , Area C, , low, , Sirength, , High, , Fig. 7-6 Toughness tends to relate to the area, under the stress-strain curve., , 00, , 25, , 50, , 75 100 125 150 175 200 225 250275300, Strain, %, , Fig.7-7 Tensile stress-strain curves of three different moisture contents at 23°C (73°F) and different areas under the curves.

Page 398 : 380, , 7 Material Property, , be calculated from the initial slope of its, curve. And materials under compression are, much less brittle than when under tension., Thus, many plastics that are brittle when, tested in tension become ductile and show, yield points under compression, as for instance polystyrene. Typical values of ultimate, strength in compression for many plastics are, about twice that of the tensile strength. Flexural strength tests in which part of a specimen, is under tension and part under compression, generally give values of ultimate strengths, that are between the values for ultimate tension and compression (Chapter 2)., Stiffness, The same factors that influence thermal expansion dictate the stiffness of plastics. Thus,, in TS the degree of cross-linking and amount, of overall flexibility are important. In a TP, its crystallinity and secondary bond's strength, control its stiffness., Strength, The subject of strength is much more complex than stiffness, since so many different, types exist: short or long term, static or dynamic, etc. (Chapter 2). Some strength aspects are interrelated with those of toughness. The crystallinity of TPs is important for, their short term yield strength. Unless the, , u.., , o, , ",2, , 3, , 2:, , _ G L A S S V _ : TRANSITION ; . . RUBBERV':_FLOW_, , :- -:, , :, , ~'~--6~O~-8~O~~10~O~~1~20~-714~O--~1~670----TEMPERATURE (OC), , Fig.7.8 Example ofTPmodulusduringdifferent, temperature phases., , crystallinity is impeded, increased molecular weight generally also increases the yield, strength. However, the cross-linking of TSs, increases their yield strength substantially, but has an adverse effect upon toughness., Factors that influence thermal dimensional, stability also affect fatigue strength. This is a, result of the substantial heating that is often, encountered with fatigue, particularly in TPs., Temperature Effect, An examination of the effect of temperature on the modulus of elasticity (also viscosity) of a typical TP is shown in Fig. 7-8., As the temperature is increased the plastic, changes through different stages from a rigid, solid to a liquid through the stages of being glassy, in transition, rubbery, and flow., Figure 7-9 shows the effect ofTPs' degree of, crystallinity upon modulus vs. temperature., , High Crystallinity, , Moderate Crystallinity, , Low Crystallinity, , Temperature, , Fig.7·9 Effect of crystallinity upon modulus vs. temperature.

Page 399 : 7 Material Property, , 381, , THERMOSET RUBBER, FLEXIBLE PVC, 50A, 75A, 100A, THERMOPLASTIC ELASTOMERS, 75A, , 40D, , 55D, , 60D, , 72D, , POLYETHYLENE, LOW DENSITY, , HIGH DENSITY, POLYPROPYLENE, , Fig.7-10, , Durometer scale relationships and hardness ranges., , most notable electrical property of plastics is their ability as good insulators, but, there are considerably many other important electrical properties available to the, designer working with different plastics, (Chapter 4, ELECTRICAUELECTRONIC, PRODUCT)., Tables 7-5 to 7-7 show that there are different orders of magnitude between plastics, and metals. Depending on the application,, plastics may be formulated and processed to, exhibit a single property or a designed combination of electrical, mechanical, chemical,, thermal, optical, aging properties, and others. The chemical structure of polymers and, the various additives they incorporate provide compounds to meet many different performance requirements., There exists an extensive amount of all, kinds of electrical data worldwide to meet, all kinds of plastic products' electrical requirements. Examples of different properties with different plastics are given in, Tables 7-8 and 7-9 and Fig. 7-11. The major, , Other, Figure 7-10 shows durometer scale relationships and hardness ranges. The letter designations refer to the Shore hardness test, (Chapter 5, MECHANICAL PROPERTY,, Hardness)., The properties of TP and TS plastics in, Tables 7-2 and 7-3 show that there is a wide, range of properties exist. Of the over 35,000, plastics available, each have their inherent, properties and process abilities., Electrical Property, , Plastics and RPs offer the designer a, great degree of freedom in the design and, manufacture of products requiring specific, electrical properties (Table 7-4). Their combination of mechanical and electrical properties makes them an ideal choice foreverything from micro electroniccomponents to, large electrical equipment enclosures. The, , 1020, , Ge, , Polyethylene, Ethyl Cellu·, lose Nylon, , Cuo, Zno, , Ni, , Celluloid, , Phenol, Formaldehyde, , Urea Formaldehyde, , Conductors, , I, , Porcelain, , resin, , Teflon, Ceramics, , Cellulose, Acetate, , Cast Phenolics, , Epoxy Resins, Polyesters, Polyvinyl Butyral Plastics, , I, , Semi-Conductors, , Insulators, , Resistivity Spectrum, , Fig.7-11, , Spectrum of volume resistivity., , 1ci1

Page 400 : 7 Material Property, , 382, Table 7-2, , Example of properties for thermoplastics, , Resin Material, 1. Acetal, 2.ABS, 3. Acrylic, 4. Acrylic high impact, 5. Cellulose acetate, 6. Cellulose acetate, butyrate, 7. Cellulose propionate, 8. Chlorinated polyether, 9. Chlorotrifluoroethylene, 10. Ethyl cellulose, 11. Ethyl vinyl acetate, 12. FEP, 13. Nylon 6, 14. Nylon 6/6, 15. Nylon 6/10, 16. Polyallomer, 17. Polycarbonate, 18. Polyethylene low density, 19. Polyethylene medium, density, 20. Polyethylene high, density, 21. Polyethylene high, molecular weight, 22. Polypropylene, 23. Polystyrene, 24. Polystyrene high impact, 25. Polyurethane, 26. Poly(vinyl chloride), (flexible), 27. Poly(vinyl chloride), (rigid), 28. Poly(vinyl dichloride), (rigid), 29. Styrene acrylonitrile, (SAN), 30. TFE fluorocarbon, 31. Ionomer, 32. Phenoxy, 33. Polyphenylene oxide, 34. Polysulfone, , Impact, Strength, Notched Izod,, ft-lb/in.,, in. bar, , !, , Tensile, Strength,, psi x 103, , Tensile, Modulus,, psi x 103, , 1.2-2.3, 1.0-9.5, 0.4, 0.5-2.3, .5-5.6, 0.8-6.3, , 8.8-10, 3.5-10.5, 8.7-10.5, 5.5-8, 2.3-8.1, 2.6-6.9, , 400-410, 200-450, 380-430, , 0.9-10.2, 0.4, 3.5, 1.7-6, No break, No break, 0.9-4, 0.9-2, , 1.8-7.3, 6, 6, , Elongation,, (%), , Flexural, Strength,, psi x 103, , Compressive, Strength,, psi x103, , 12-75, 10-100, 3-6, 23-38, 10-70, 40-88, , 13-14, 5-15, 14-16, 8.5-12, 2.2-11.5, 1.8-9.3, , 18, 5-11, 14-17, 7-12, 2.2-10.9, 2.1-9.4, , 30-100, 60-160, 60-190, , 2.8-11, 5, 8-10, 3-6.7, , 3-9.6, , 160-280, 100-170, 345, 14-38, 50-80, , 500-1500, 350, 25-300, 60-300, 50-300, 400-650, 75, 20-800, 80-600, , 9-16.6, 14.6, 10.5, 4-5, 11-13.5, , 4-11, 5-13, 4-6, , 225-330, , 160, 150-190, , 10-40, , 2.3-6.5, , 20-40, , 3.0-15, 60-80, , 6-12, , 1.5-12, 2-3, No break, No break, , 2-3.2, 9.5-12.4, 11.2-13.1, 7-8.5, 2.9-4.2, 8-9, 1-2.4, 1.7-2.8, , 0.5-23, , 2.8-5, , 75-160, , 10-800, , 1-4, , 0.8-3.6, , >20, , 5.4, , 102, , 525, , 3.5, , 2.4, , 0.5-15, 0.25-0.65, 0.7-1.5, No break, Varied, , 2.3-5, 5-9, 3.5-8, 4.5-8, 1-4, , 150-250, 400-500, , 10-700, 1-2.5, , 4.5-6, 7-15, 5.5-12.5, 0.7-1, , 6-8, 11.5-16, 8-16, 20, , 0.4-22, , 6-9, , 200-600, , 5-40, , 8-15, , 10--11, , 0.8-6.3, , 7.5-8.8, , 348-450, , 65, , 14.2-17, , 0.3-55, , 10-12, , 500, , 1-3.2, , 17, , No break, 5.7-14, 1.5-12, , 2-5, 3.5-5.5, 8-9.5, , 50-100, 28-40, , 300-450, , 350-410, , 1.3, , 10.2, , 360, , testing organizations that set the conditions, and specifications pertaining to electrical, properties are the American Society for Testing and Materials (ASTM), Canadian Standards Association (CSA), Underwriters, Laboratories (UL), International Electrotechnical Commission (lEe), International, Organization for Standardization (ISO),, and American National Standards Institute, (ANSI)., , 200-450, 410-480, , 300-400, , 10-40, 100-600, , 12.5, , 100-450, , 75-400, 50-100, 50-80, 50-100, , 15-17.5, 4-1.2, , 12-14.5, 15.4, , 15.4, ( Continues), , Electromagnetic Compatibility, , The use of electronics has shown large, growth in a variety of kinds of computer, equipment, such as for data processing, transportation and industrial controls, automation, and medical devices. As plastic housings, become more widespread than traditional, metal housings, the issue of electromagnetic, compatibility (EMe) developed. EMC is the

Page 401 : 7 Material Property, Table 7-2, , 383, , (Continued), , Resin Material, 1. Acetal, 2.ABS, 3. Acrylic, 4. Acrylic high impact, 5. Cellulose acetate, 6. Cellulose acetate, butyrate, 7. Cellulose propionate, 8. Chlorinated polyether, 9. Chlorotrifluoroethylene, 10. Ethyl cellulose, 11. Ethyl vinyl acetate, 12. FEP, 13. Nylon 6, 14. Nylon 6/6, 15. Nylon 6/10, 16. Polyallomer, 17. Polycarbonate, 18. Polyethylene, low density, 19. Polyethylene, medium density, 20. Polyethylene, high density, 21. Polyethylene high, molecular weight, 22. Polypropylene, 23. Polystyrene, 24. Polystyrene, high impact, 25. Polyurethane, 26. Poly(vinyl chloride), (flexible), 27. Poly(vinyl chloride), (rigid), 28. Poly(vinyl dichloride), (rigid), 29. Styrene acrylonitrile, (SAN), 30. TFE fluorocarbon, 31. Ionomer, 32. Phenoxy, 33. Polyphenylene oxide, 34. Polysulfone, , Heat, Heat, Compressive, Distortion, Resistance,, Modulus,, Temperature, Continuous, of, OF, 264 psi, psi x 103, 410, 200-450, 350-430, 250--360, , 130, 180, , 70, 347, 400, , 345, , Coefficient, Thermal, Expansion,, in.lin.°C x 10- 5, , Thermal, Conductivity,, callcm2-sec°C-cm x 10-4, , Volume, Resistivity,, ohm-cm, , 255, 185-230, 167-198, 169-190, 111-195, 113-202, , 185, 160--235, 130--200, 140--195, 140--175, 140--175, , 8.1-8.5, 5.7-10, 5-8.5, 6.5-10.5, 8-16, 11-17, , 1.6-5.5, 5-8, 4.4, 4.0, 4-8, 4-8, , 1-1013, 1015 _10 17, >10 14, 10 16 _10 17, 1010_1012, 1010_1012, , 121-228, 185-210, 160-170, 150--200, , 140--175, 250--275, 390, 140--180, 120--170, 400, 250, 250, 220, 250, 250--270, 140--175, , 11-16, 8, 5-7, 10--20, 10--20, 8.3-10.5, 8.3, 10, 10, 8-11, 7, 10--20, , 4-8, 3.13, 4-6, 3.8-7, 8, 5.9, 5.9, 5.8, 5.5, 2-4, 4.6, 8, , 1012 _10 16, 1.5 x 1016, 1018, >10 18, 3.313-4.513, 1014 _10 15, 4.5 x 1012, >10 16, 2.1 x 1016, 1015 _10 18, , 150--180, , 10--20, , 8, , 1015 _10 18, , 124, 150--175, 200, 145, 115-140, 270, , 50--110, , 110--125, , 180--250, , 10--20, , 8, , 6 x 1015 _10 18, , 110, , 120, , 250, , 13, , 8, , >10 16, , 300--560, , 140--200, 167-203, 150-200, , 250, 150--180, 120--170, , 6-8.5, 6-8, 6.5-8.5, , 2.8-4, 1.9-3.3, 1-3, , 6.5 x 1016, 1017 _10 21, 10 13 _10 17, , 150--180, , 10--20, 7-25, , 5, 3-4, , 2-1011, 1011_1015, , 140--175, , 160--165, , 5-10, , 3-5, , 1012 _10 16, , 212-220, , 185-210, , 7-8, , 3-4, , 1015, , 7, , 3, , 1015, , 300-400, , 650, , 200--208, , 70--90, , 132, , 325, , 175-188, 375, 345, , 370, , 550, 140, , 5.5 (25--60°C), 12-13, 3.2-3.8, , 300, , 3.1-10-5, in.lin.oF, , >10 18, >10 16, 2.75-5 x 10-3, 1017, 1.8 BTU/h-sq, 5 x 1016, ft-ft lb, 6, 5.8, , (Continued), , ability of an electrical device to function normally without interference from or interfering with another electrical device. EMC regulations usually emphasize the containment of, electromagnetic interference (EMI) to specific levels across the designed frequency, ranges., , The nonconductive characteristics of plastics can become a major drawback in certain, applications. Because they are electrical insulators, they do not shield electronic impulses, generated by outside sources. Nor do they, prevent electromagnetic energy from being, emitted from equipment housed in a plastic

Page 402 : 384, , 7 Material Property, , Table 7-2, , ( Continued), , Resin Material, 1. Acetal, 2.ABS, 3. Acrylic, 4. Acrylic high impact, 5. Cellulose acetate, 6. Cellulose acetate, butyrate, 7. Cellulose propionate, 8. Chlorinated polyether, 9. Chlorotrifluoroethylene, 10. Ethyl cellulose, 11. Ethyl vinyl acetate, 12.FEP, 13. Nylon 6, 14. Nylon 6/6, 15. Nylon 6/10, 16. Polyallomer, 17. Polycarbonate, 18. Polyethylene low density, 19. Polyethylene medium, density, 20. Polyethylene high, density, 21. Polyethylene high, molecular weight, 22. Polypropylene, 23. Polystyrene, 24. Polystyrene high, impact, 25. Polyurethane, 26. Poly(vinyl chloride), (flexible), 27. Poly(vinyl chloride), (rigid), 28. Poly(vinyl dichloride), (rigid), 29. Styrene, acrylonitrile (SAN), 30. TFE fluorocarbon, 31. Ionomer, 32. Phenoxy, 33. Polyphenylene oxide, 34. Polysulfone, , Dielectric, Constant,, 60 Cycles, , Delectric, Strength, ST, ~ -in. Thickness,, volts/mil, , Power Factor,, 60 Cycles, , 3.7-3.8, 2.6-3.5, 3.7, 3.5-3.7, 3.5-7.5, 3.5-6.4, , 500, 300-450, 450-500, 450-480, 290-600, 250-400, , .004-.005, .003-.007, .04-.05, .04-.05, .01-.06, .01-.04, , 129, 45-90, No tracking, No tracking, 50-130, , 0.12-0.25, 0.2-0.4, 0.3, 0.2-0.3, 2.1-4.2, 0.9-2.2, , 3.4-4.2, 3, 2.65, , 300-450, 400, 450, , .01-.04, .01, .015, , 170-190, , 2.3, 2.1, 6.1, 3.6-4.0, 4.0-7.6, 3.2, 3.17, 2.28, 2.3, , 500, 300-400, 300-400, 300-400, 500-1000, 400, 450-1000, 450-1000, , .0002, , 0.4-0.6, .014, .04-.05, .0001-.0005, .0009, .0001-.0005, .0001-.0005, , >165, 140, 140, 140, 120, Melts, Melts, , 1.2-2.8, .01, Nil, 1.3-1.5, <.01, <.01, 1.5, 1.3, 0.4, <.01, 15, <.02, <.02, , 2.3, , 450-1000, , .0001-.0005, , Melts, , <.01, , R30-60, , 2.3, , 710, , .0003, , <.01, , RS5, , 2.1-2.27, 2.5-2.65, 2.5-3.5, , 450-1000, 500-700, 500, , .0001-.0005, .0001-.0005, .003-.005, , 6.7-7.5, 5-9, , 450-550, 300-1000, , .015-.017, .08--.15, , 0.60-0.80, 0.15-0.75, , M28,R60, , 3.4, , 425-1040, , .01-.02, , .07-.40, , R100-120, , Arc, Resistance,, sec, , >360, , 13-185, 60-100, 60-90, , Water, Absorption, Rockwell, 24hr, %, Hardness, , <.01, .03-.05, .05-.10, , 1200, , 0.11, , 2.8--3, , 400-500, , 0.23-0.28, , 2.1, 2.4-2.5, 4.1, , 400, 1000, 404-520, 400-500, 425, , 2.82, , enclosure. Government regulations have, been set up requiring shielding when the operating frequencies are greater than 10 kHz., Every electronic system has some level, of electromagnetic radiation associated with, it. If this level is strong enough to cause, other equipment to malfunction, the radiating device will be considered a noise source, and usually be subjected to shielding regula-, , <.0001, 0.1, .0012-.0009, , No tracking, 70, , .01, 0.1-1.4, 0.13, , .0008--.0056, , 122, , 0.22, , M94,R120, RSO-120, M84-97, M20-67, R35-118, R31-U6, R15-120, R100, R85-U2, R50-110, R3-7, R107-119, Rll8--123, RU1, R50-85, M80, RU8, RIO, R15, , R30-99, M60-80, M25--69, , RU8, M30-83, R58, D60-65, Rl13-U8, M69,R120, (Continues), , tions. This is especially true when EMI occurs, within the normal frequencies of communication. When the electronic noise is sufficient to, cause malfunctioning in equipment such as, medical devices, flight instrumentation, etc., the results could prove life threatening. Reducing the emission of and susceptibility to, EMI or radio frequency interference (RFI), to safe levels is thus the prime reason to shield

Page 403 : 385, , 7 Material Property, Table 7-2, , ( Continued), Flammability,, in.lmin, , Resin Material, 1. Acetal, 2.ABS, 3. Acrylic, 4. Acrylic high impact, 5. Cellulose acetate, 6. Cellulose acetate butyrate, 7. Cellulose propionate, 8. Chlorinated polyether, 9. Chlorotrifluoroethylene, 10. Ethyl cellulose, 11. Ethyl vinyl acetate, 12.FEP, 13. Nylon 6, 14. Nylon 6/6, 15. Nylon 6/10, 16. Polyallomer, 17. Polycarbonate, 18. Polyethylene low density, 19. Polyethylene medium density, 20. Polyethylene high density, 21. Polyethylene high, molecular weight, 22. Polypropylene, 23. Polystyrene, 24. Polystyrene high impact, 25. Polyurethane, 26. Poly(vinyl chloride) (flexible), 27. Poly(vinyl chloride) (rigid), 28. Poly(vinyl dichloride) (rigid), 29. Styrene acrylonitrile (SAN), 30. TFE fluorocarbon, 31. Ionomer, 32. Phenoxy, 33. Polyphenylene oxide, 34. Polysulfone, , Specific, Gravity, , Slow burning, Nonflam., Self-ext., Self-ext., Self-ext., Slow burning, Self-ext., Slow burning, Slow burning, Slow burning, Very slow, , 1.410--1.425, 1.01-1.07, 1.18-1.18, 1.11-1.18, 1.23-1.34, 1.15-1.22, 1.16-1.23, 1.4, 2.90--2.14, 1.11-1.13, 0.93-0.95, 2.14, 1.13-1.14, 1.13-1.15, 1.07-1.09, 0.90--.906, 1.2, .910--.925, .926-.940, 0.94-0.98, 0.94, , Slow burning, 0.5-2.5, 0.5-2.5, Slow burning, Self-ext., Self-ext., Self-ext., 0.47-0.7, Nonflam., 9-1.1, Slow burning, Self-ext., Self-ext., Self-ext., , 0.90--.0908, 1.05-1.06, 1.04-1.06, 1.20--1.26, 1.15-1.80, 1.33-1.58, 1.50--1.54, 1.07-1.08, 2.13-2.18, 0.94-0.96, 1.17-1.34, 1.06, 1.24-1.25, , 1.1, , 1.0--2, 0.6--0.7, 1.1-1.2, 0.5-2, 0.5-1.5, 0.5-1.5, Self-ext., Nil, , medical devices (and other devices) in whatever type of housing exist, including plastic., The usual plastics alone lack sufficient conductivity to shield EMI and RFI interference., Designers can reduce or eliminate sufficiently electromagnetic emissions from plastic, housings like those of medical devices and, computers just by shielding the inner emission sources with metal shrouds in the socalled tin can method. They may reach the, same effect by designing electronics to keep, emissions below standard limits or by incorporating shielding into the plastic housing, itself. Designers will often employ all three, strategies in a single design. What is most important is to attempt to locate all the shield-, , Mold, Shrinkage,, in.lin., .022, .003-.007, .002-.006, .004-.008, .001-.007, .003-.006, .001-.006, .004-.006, .010--.015, .01-.02, .03, .007-.011, .007-.015, .015, .01-.02, .005-.007, .01-.03, .01-.035, .01-.04, .03, .008-.025, .002-.006, .003-.005, .008-.012, .002-.004, , Clarity, Translucent to opaque, Opaque, Transparent, Translucent to opaque, Transparent, Transparent, Transparent, Semitranslucent to opaque, Transparent to opaque, Transparent to opaque, Transparent, Transparent to opaque, Transparent to opaque, Transparent to opaque, Transparent to opaque, Transparent, Transparent to opaque, Transparent to opaque, Translucent to opaque, Translucent to opaque, , .007-.008, .003-.004, .02-.06, .001-.005, .003-.004, , Translucent to opaque, Transparent, Translucent to opaque, Translucent to opaque, Transparent to opaque, Transparent to opaque, Translucent to opaque, Transparent, Transparent to opaque, Transparent, Transparent to opaque, , .0076, , Transparent to opaque, , ing in a relatively small volume within the, larger housing and then tin can it to provide, a simplified solution rather than spreading, it out., Among the shieldings incorporated into, housings, the most popular and useful, applied technologies are those for conductive coatings, zinc-arc spray, or electroless, plating. Other methods include the use of, conductive foils or molded conductive plastics, silver reduction, vacuum metalization,, and cathode sputtering. Although zinc-arc, spraying once accounted for about half the, market, conductive coatings surpassed it, and now maintains the largest single market, share. The properties of various coatings are

Page 404 : 386, , 7 Material Property, , Table 7-3, , Example of properties for thermoset plastics, , Resin Material, 1. Alkyd glass-filled, general purpose, 2. Alkyd-glass MAl 30, 3. Alkyd-glass MAl 60, 4. Alkyd mineral, 5. DAP glass MIL-M-19833, GDI-30, 6. DAP mineral (MDG), MIL-M-14F MIL-P-4389, 7. DAP orion MIL-F-14F, SD 1-5, 8. DAP glass MIL-M-14F, SDG, 9. DAP unfilled, 10. Epoxy glass, 11. Epoxy mineral, 12. Melamine cellulose, 13. Melamine cloth, 14. Melamine glass MMI 30, 15. Phenolic asbestos, MFA 30, 16. Phenolic cloth CFI-10, 17. Phenolic cloth CFI-20, 18. Phenolic flocklflour, 19. Phenolic glass, 20. Phenolic GP, 21. Phenolic GPI-lOO, 22. Phenolic MFE, 23. Phenolic mineral MFG, 24. Phenolic mineral MFH, 25. Phenolic mineral MFI-20, 26. Phenolic nylon, 27. Phenolic rubber/flour, 28. Urea cellulose, 29. Silicone, 30. Silicone mineral, , Impact, Strength,, izod, ft-lb/in., , Tensile, Strength,, psi x 103, , Flexural, Strength,, psi X 103, , Flexural, Modulus,, psi X 103, , Compressive, Strength,, psi X 103, , Heat, Distortion, °F@264psi, , 1.5-4, , 5-9, , 12-18, , 1700-2000, , 21-29, , >400, , 3-4, 8-10, .30-.35, 6-15, , 7-9, 5-9, 3-8, 7-9.5, , 14-19, 12-20, 6-15, 17-19, , 2000, 2000-2500, 2200-3000, 1250-1600, , 22-24, 24-36, 16-20, 24-45, , >400, >400, 350-400, 390-500, , .28-.40, , 5.5-6.5, , 9.6-10, , 1200, , 22-25, , 300-320, , .55-4.5, , 6.8, , 9-10.5, , 710, , 20-30, , 240-266, , 0.4-1.2, , 6.7-9.2, , 10-19, , 1300, , 25-30, , 350-500, , 0.3, 5.5, 0.35-0.5, .25-.35, .55-.90, 4-16, 3.7, , 4, 11.5, 6-11, 5-10, 7-10, 6-10, 8, , 7-9, 22, 19.5, 10-16, 12-15, 15-24, 16, , 600, 3000-3200, 900-1200, 1300-1600, 1600, 2400, 2500, , 22-24, 30-38, 37, 25-24, 30-35, 20-32, 24, , 310, 500, 260-360, 350-410, 310, 400, 400, , 1.05-2.2, 2.3, .34-.50, 9-17, .26-.38, 13, 0.5, 0.64-1.5, 0.26, 5, 0.5, 0.5, .24-.35, 8-20, .25-.39, , 6.5-7, 6.5-7.5, 6-9, 7-11, 6-9, 16.8, 9.2, 4-7, 5-8, 8.7, 8, 4, 5-10, 4-8, 2.5-4.4, , 0.5-10, 10-12.5, 7-12, 13.5-22, 7-12, 24.9, 17.5, 8.5-11.5, 6-9, 18.6, 12, 5.5-7, 10-18, 13-19, 6.8-8, , 1000-1200, 1000, 1000, 3000, 1000, 2865, 2600, 1400, 1500, 2500, 600, 400, 1300-1600, 2100-2500, 1250-2270, , 20-25, 22-25, 20-30, 14-35, 25-35, 39, 32, 17.5-20, 25-35, 34.5, 24, 16-18, 25-38, 10-13, 11-18, , 300-360, 300, 270-325, 600, 275-370, >550, 415, 320-500, 300-450, >500, 290, 250, 266-380, >900, 340-900, ( Continues), , described in Fig. 7-12 and Table 7-10. Other, conductive coatings are also used. Unlike, other shielding methods, conductive coatings, are usually applied to the interiors of housings and do not require additional design, efforts to achieve external aesthetic goals., All offer trade-offs in shielding performance,, the physical properties of the plastics, ease, in production, and cost., Often, differences in test measurements, and samples' configurations make comparisons difficult. The ASTM has a standard, that defines the methods for stabilizing materials measurement, thus allowing relative, , measurements to be repeated in any laboratory. These procedures permit relative performance ranking, so that comparisons of, materials can also be made. Nonetheless,, the designer will still have to confirm the, suitability of a material's shielding performance for each system through such conventional means as screen-room or open-field, testing. Each approach to shielding should, also be subjected to simulated environmental, conditions, to determine the shield's behavior during storage, shipment, and exposure, to humidity, which could accelerate the effects of aging of shielding materials. In this

Page 405 : 387, , 7 Material Property, Table 7-3, , (Continued), , Resin Material, 1. Alkyd glass-filled, general purpose, 2. Alkyd-glass, MAl 30, 3. Alkyd-glass, MAl 60, 4. Alkyd mineral, 5. DAP glass, MIL-M-19833 GDI-30, 6. DAP mineral, (MDG), MIL-M-14F, MIL-P-4389, 7. DAPorlon, MIL-F-14F, SD 1-5, 8. DAP glass, MIL-M-14F, SDG, 9. DAP unfilled, 10. Epoxy glass, 11. Epoxy mineral, 12. Melamine, cellulose, 13. Melamine cloth, 14. Melamine glass, MMI30, 15. Phenolic asbestos, MFA 30, 16. Phenolic cloth, CFI-lO, 17. Phenolic cloth, CFI-20, 18. Phenolic, flock/flour, 19. Phenolic glass, 20. Phenolic GP, 21. Phenolic, GPI-100, 22. Phenolic MFE, 23. Phenolic mineral, MFG, 24. Phenolic mineral, MFH, 25. Phenolic mineral, MFI-20, 26. Phenolic nylon, 27. Phenolic, rubberlfiour, 28. Urea cellulose, 29. Silicone, 30. Silicone mineral, , Thermal, Heat, Thermal, Conductivity,, Resistance,, Expansion cal/sec-cm2_oCcm x 10-4, Continuous OF in.l° C x 10-5, , Volume, Resistivity,, ohm/cm, , Dielectric, Constant,, 60 Cycles, , Dielectric, Strength,, STI/8Y.P.M., , 1 x 1015, , 6.7, , 275-375, , 6, , 350, , 300, , 2-5, , 10-15, , 350, , 2-4, , 10-15, , 300, , 2-5, , 8-12, , 1012 _10 14, , 5-5.6, , 375, , 275-400, 365-465, , 2-5, 2.7-3.5, , 15-25, 6-8, , 10 12 _10 14, 1012, , 5.7-6.3, 4.5, , 375, 350-400, , 350-440, , 3.5-4.2, , 13.7, , 1013+, , 5.2, , 350-450, , 300-350, , 4-5.4, , 6.3-6.9, , 1 x 1010, , 3.8, , 366-400, , 365-465, , 1.2-3.5, , 6.7, , 1013, , 4.25, , 420, , 350, 300-500, 550, 210, , 1.08-1.2, 3.7, 2-5.7, , 8.5, 18.1, 7-10.1, , 250, 300-400, , 2.5-3, 1.2-2, , 10.6, 11.5, , 450, , .5-1, , 14, , 275, , 2-3, , 9.3, , 5-8 x lOll, , 6.1-21.2, , 250-400, , 340, , 1.5-3, , 7, , 6 x 1010, , 5.2-21, , 300, , 300, , 2-3.9, , 7-8, , 2 x 1011, , 6-10, , 300-375, , 325-450, 300, , .8-1.6, 3-4.1, , 9.7, 5-8.1, 32, , 1 x 1012, 2 x lOll, , 5.6-7.2, 5-10, 5.4(lMC), , 350-400, 300-425, 382, , 325-425, , 1.1, 1.5-2.5, , 15, 15.87, , 4.5(lMC), 40-60, , 360, 150-250, , 400-450, , 1.5, , 10, , 9-15, , 250-350, , 475, , 1.5, , 14, , 1.6 x 1010, , 45, , 85, , 275, 275, , 7.5, 1.5-4, , 7.50-18, 5, , 1 x 1012, 3.4 x 109, , 4, 9, , 450, 300, , 170, 450-700, 400-700+, , 2.7, .8, 2.5-6, , 7-10.1, 7.5, 4-10, , .5-5 x 1011, 3 x 1014, 1 x 104, , 7-9.5, 4.35, 3.6-4.5, , 300-400, 250-280, 280-400, , 2 x 1016, 3.6, 450, 5.5(@ 100) 360 volts/mil, 3.8 x 1015, 1014 _10 16, 4.4, 400, 0.8-2.0 x 1012, 7.9-9.5, 300-400, 1-3 x 1011, 2 x 1011, , 8.1-12.6, 9.7-11.1, , 250-340, 170-240, 85, , 1 x 1012, 1, , X, , 1012, , ( Continued)

Page 406 : 3BB, , 7 Material Property, , Table 7-3, , ( Continued), , Resin Material, 1. Alkyd glass-filled, general purpose, 2. Alkyd-glass, MAl 30, 3. Alkyd-glass, MAl 60, 4. Alkyd mineral, 5. DAP glass MlL-M-19833, GDI-30, 6. DAP mineral, (MDG), MlL-M-14F, MlL-P-4389, 7.DAPorJon, MlL-F-14F, SD 1-5, 8.DAPglass, MlL-M-14F SDG, 9. DAP unfilled, 10. Epoxy glass, 11. Epoxy mineral, 12. Melamine, cellulose, 13. Melamine cloth, 14. Melamine glass, MMl30, 15. Phenolic asbestos, MFA 30, 16. Phenolic cloth, CFl-10, 17. Phenolic cloth, CFl-20, 18. Phenolic flock/flour, 19. Phenolic glass, 20. Phenolic GP, 21. Phenolic GPl-100, 22. Phenolic MFE, 23. Phenolic mineral, MFG, 24. Phenolic mineral, MFH, 25. Phenolic mineral, MFl-20, 26. Phenolic nylon, 27. Phenolic rubber/, flour, 28. Urea cellulose, 29. Silicone, 30. Silicone mineral, , Power, Factor,, 60 cycles, , Arc, Resistance,, sec, , Water, Absorption, %-24hr, , Specific, Gravity, , Mold, Shrinkage,, in.lin., , .01-.02, , 180+, , .07-.2, , 1.93-2.32, , .003-.006, , .005-.01, , 180+, , .05, , 2.3, , .001-.005, , .020--.030, , 180+, , .07-.10, , 2.02-2.13, , .001-.004, , .030--.045, .010--.017, , 180+, 130--180, , .05-.12, .05-.25, , m08, M108, , 2.17-2.24, 1.57-186, , .004-.007, .0009-.004, , .06-.40, , 140, , .2-.5, , MlOO, , 1.58-1.74, , .004--.008, , .025-.035, , 115, , .1-.2, , MI08, , 1.31-1.34, , .009-.010, , .010--.017, , 125-180, , .05, , E80, , 1.6-1.75, , .002-.004, , .008, .015, .011, .030--.080, , 120, 125-187, 180-190, 120--140, , .09, .03-.05, .06-.15, .1-.6, , Ml14-116, M105-115, M110, Ml18-124, , 1.27, 1.8, 1.85, 1.47-1.52, , .007, .0005, .002, .006-.015, , .1-.34, .14-.23, , 125-150, 180-186, , .3-.6, .09-.6, , 1.4-1.5, 1.9-2, , .003-.005, .001-.003, , 190, , .35, , M112, , 1.95, , .0005-.0015, , .8-1, , M95-107, , 1.36-1.40, , .002-.005, , E79, , 1.37-1.40, , .002-.005, , M95-116, M90--99, M95-117, , 1.34-1.38, 1.70-1.90, 1.34-1.46, 1.69, 1.85, 1.72-1.86, , .004-.008, .0009, .004--.008, .0001-.001, .002, .001-.002, , .16-.64, , Rockwell, Hardness, , .64, , 4, , .9-1, , .25-.3, .02-.05, .05-.5, .026(lMC), .013(lMC), .25-.50, , 80(15518), 10--60, 26-102, 125, 180+, 100-190, , .3-1, .5-1, .2-1, .03, .03, .12-.4, , .20, , 100-180, , .2, , M100, , 1.6-2, , .002-.005, , .28, , 165, , .04, , MI05, , 1.76, , .0001-.001, , .02, .14, , 80, 8-10, , .20, 1.4-2, , MI08, M50, , 1.22, 1.29-1.32, , .012-.016, .007-.010, , .035-.040, .003-.02, .002-.01, , 80-130, 175-240, 220--240+, , .5-.7, .10--.30, .05-.22, , Ml16-120, M87, M75-90, , 1.47-1.52, 1.88, 1.85-2.82, , .006-.14, .0005, .005-.009, , way degradation can be observed, along with, other problems that might occur in a product's service life., The Underwriters Laboratories utilizes a, combination of methods for environmental, conditioning and adhesion testing to evalu-, , M90-115, , ate various approaches to shielding and to, determine the plastic types that are suitable, for use in electronic devices. Their concern, is primarily safety should a metalized plastic, delaminate or chip off, creating an electrical, short that could cause a fire.

Page 407 : 389, , 7 Material Property, Table 7-6 Examples of conductivities using, different additives/fillers, , Table 7-4 Electrical property guide, ELECTRICAL PROPERTIES, , MOST PLASTIC MATERIALS, , POLYETHYLENE AND COPOLYMERS, CHLORINATED PVC (HIGH VOLTAGE), POLYSTYRENE AND COPOLYMERS, POLYPROPYLENE, OLEFINIC THERMOPLASTIC, RUBBERS, AROMATIC POLYESTERS, FLU ORO PLASTICS, , ACRYLICS, ALKYDS, FLUOROPLASTICS, CELLULOSICS, EPOXY, ALLYLS, SILICONE, ACETAL, POLYESTER(TS), POLYETHYLENE &, COPOLYMERS, POLYIMIDE, MELAMINES, POLYPHENLENE, SULFIDE, , NO TRACK, 75-420, 70-360, 50-310, 45-300, 115-250, 60-250, 158-240, 100-240, 135-235, 230, 95-200, 200, , To maximize results with any product,, the designer should reduce the circuit-noise, generation and susceptibility of the product to as much as possible. Consider the, choice of shielding early on in the design, process, before deciding on final packaging, to minimize the amount of external shielding, required. Doing so will also alleviate lastminute shielding fixes and, of course, a good, deal of exposure and delay in marketing the, product., , Design Concept, Many ideas for advancing electrical and, electronic systems have been adopted since, the early 1940s, which saw the start of high, electronic frequency radar systems. The earliest major use of plastics for electrical insulation early in last century come with, the advent of developments in electrical, , Fillers, , Conductivity a, S/cm, , Carbon black, Aluminum platelets, Steel fibers, Carbon fibers, Mica coated with nickel, , 0.01 to 0.1, 1 to 50, 1 to 50, 0.1 to 10, 1 to 10, , and telephonic installations requiring insulation. Phenolic plastic compounds initially, became the basic materials for insulating, wires and other related products. Since then, many new plastics, predominantly TPs, have, been developed and used for widely variant, applications., There are many thousands of outstanding, applications where plastics are used in electrical designs. The designers' imaginations, have excelled in developing new plastic products. An example is the folded membrane, and snap switches in controlling electronic, devices., Membrane technology is the technique of, producing fiat, thin, lightweight switch arrays, by joining two or more membranes. Each, membrane features etched or screened conductors placed face to face with a thin material to separate the active elements. A second,, surface-printed overlay is attached to the top, of the switch assembly to provide a graphic indication ofthe switch's location. Their advantages are low cost in high volumes, their moderate tooling charges, and their capability of, providing attractive, bright, durable frontal, graphics., , Table 7-5 Electrical conductivities of different materials, Material, Copper, Silver, Aluminium, Polyacetylene with iodine, iodine, Polypyrrole with phenylsulfonate, phenyl sulfonate, Polystyrene, , Conductivity a, S/cm, 5.9, 6.3, 3.6, 2.0, , 8.9, , a/a, S/(cm2 g), , 2.7, 0.8, , 6.6, 6.0, 1.3, 2.5, , x, x, x, x, , 104, 104, 105, 104, , 1.5 x 102, , 1.3, , 1.2, , X, , 102, , 10-16, , 1.05, , 9.5 x 10-17, , x, x, x, x, , 105, lOS, 105, 104, , Density a, g/cm3, lOA

Page 408 : 7 Material Property, , 390, , Table 7·7 Applications for conductive plastics where different additives and fillers are used, , Material, Thermoplastics, Acrylics, , Available Forms, , Characteristics, , Easily processed. Form, strong films. Temperature, range 200-250 F. Adaptable, for paint or spray., Fluorocarbons, Powder, emulsions Excellent high temperature, (PTFE,FEP,, properties. TFE to 500 F., PVF2 ), FEP is easier to mold, but, maximum use temperature is, 400 F. Nearly inert chemically., Nonflammable. Loading with, conductive filler improves, creep resistance. Low, coefficient of friction., Powder, solutions Excellent high temperature, Polyimides, properties, 400 to about 700 F., Difficult to process., Tough and chemical resistant., Polyolefins, Powder, pellets, (Polyethylene,, Weak in creep and thermal, resistance. Polyethylene, Polypropylene), maximum use temperature, 210 F, polypropylene 260 F., May be injection and extrusion, molded, vacuum formed., Low cost., General-purpose material. Many, Vinyls, Powder, pellets,, forms available including hard, (PVC,PVA,, organosols, PVAC,, and flexible types. Properties are, highly dependent on plasticizer, Copolymers), used. May be injection, extrusion,, compression molded, vacuum, formed. Low cost., Thermosets, Excellent humidity resistance., OiaUyl Phthalate Powder, (DAP, DAIP), Withstands temperatures over, 400 F. Easily processed., Dimensional stability excellent., May be compression, transfer, and injection molded. Low cost., , Epoxies, , Powder, solutions, , Powder, one, and two-part, liquids, and paste, , Many types of resins available,, providing wide spectrum of, properties. Easy to compound., Low shrinkage and excellent, dimensional stability. Good to, excellent adhesion. May be, cast or molded., , Applications, Coatings., , High-temperature, cable shielding,, gaskets, heatshrinkable tubing., , High-temperature, cable shielding,, conductive film., Antistatic sheet, and tiles, heatshrinkable tubing,, deicer boots., , Cable shielding,, antistatic sheet, and hose, RF, gaskets, heatshrinkable tubing., , Precision, potentiometers,, RF connectors,, waveguide, auxiliaries,, attenuators,, heating panels,, heated battery, cases., Coatings, sealants,, adhesives,, solderless, PC boards., , (Continues)

Page 409 : 7 Material Property, , 391, , Table 7-7 (Continued), Material, Phenolics, , Elastomers, Natural rubber, , Available Forms, , Characteristics, , Powder, solutions, , Excellent thermal stability to, over 300 F generally, and over, 400 F in special formulations., Broad choice of resins. May be, cast or compression, transfer,, or injection molded., , Precision, potentiometers,, RF connectors,, heating panels., , Solid, , Good physical properties and, resistance to cutting and, abrasion. Low heat and, ozone resistance., Good resistance to ozone, and abrasion., , Gaskets., , Applications, , Polyisobutylene, , Liquid, , Silicone, , Paste, liquid, for foaming, , Excellent chemical resistance., High temperature capability, to 500 F. New formulations, have higher tear strength, and lower compression set., , Urethane, , Liquid, , Exceptional abrasion, cut, and, tear resistance. Poor moisture, and heat resistance. Variety, of formulations leading to, different properties including, range of durometers without, plasticizers., , Thermal Property, In order to select materials that will maintain acceptable mechanical characteristics, and dimensional stability designers must be, Table 7-8, , Calking (nonsetting),, hose for transfer, of flammables, pipe, dope, electric fuse., Gaskets, antistatic, rollers, RF shielding,, heat shrinkable tubing,, setting and nonsetting, calking, deicer boots,, flexible heater tape., Antistatic rollers and, tires, hose for transfer, of flammables, strain, gages, pressure, transducers., , aware of both the normal and extreme thermal operating environments to which a product will be SUbjected. TS plastics have specific thermal conditions when compared to, TPs that have various factors to consider, , Resistivity and dielectric properties, Resistivity, , Material, ABS, Acrylic, Cellulose Ester, FEP, Nylon 6, Polycarbonate, Polyethylene, Alkyd, DAP (SD15), Phenolic MFE, Epoxy, , Volume Surface, 2 x 1016, , 1014, , 1018, , 1014, 1014, 1016, 1013, 1015, 1016, 1014, 1013, 109, 1014, , 3 x 1015, 1018, 1015, , 1016, 1019, 1013, 1016, , 1014, 1016, , Dielectric Constant/Dissipation Factor, 100Hz, , 1 kHz, , 1mHz, , 10 mHz, , .005/2.9, .062/3.6, .006/3.8, .0005/2.1, .031/4.2, .001/3.1, .0001/2.34, .02/6.0, .026/3.8, .013/5.4, .004/3.22, , .006/2.8, .058/3.2, .011/3.6, .0005/2.1, .024/3.8, .0013/3.1, .0001/2.34, .02/5.8, .020/3.7, .013/5.3, .004/3.25, , .008/2.8, .045/3.1, .024/3.3, .0005/2.1, .031/3.8, .007/3.1, .0001/2.34, .015/5.4, .016/3.6, .033/4.9, .004/3.25, , .007/2.8, .033/2.9, .022/3.2, .0005/2.1, .020/4.0, .011/3.1, .0001/2.34, , 100 mHz 1.000 mHz, .005/2.7, , .001/2.7, , .020/3.0, .014/2.1, .0008/2.09 .0007/2.05, .015/3.1, .0001/2.34 .0001/2.34

Page 410 : 7 Material Property, , 392, Table 7-9, , Examples of electrical, physical, and mechanical properties, ASTM, , PElt, , PESt, , ppst, , PSFt, , pct, , Physical, Specific gravity, g/c3, Water absorption, % by weight, , D570, , 1.27, 0.25, , 1.37, 0.43, , 1.30, 0.02, , 1.55, 0.3, , 1.20, 0.26, , Electrical, Dielectric strength, v/mil, Arc resistance, sec, Volume resistivity, ohm/cm, , D 149, D495, D257, , 710, 128, 1018, , 400, 120, 1016, , 380, 34, 1015, , 425, 39, 1017, , 425, 115, 1017, , D648, , 392, 338, , 397, 356, , 275, - ,, , 345, 302, , 265, 255, , 40, , 38, , 47, , 38, , 25, , 480,000, (3,310), 1.0, , 375,000, (2,586), 1.6, , 550,000, (3,792), 0.4, , 390,000, (2,689), 1.3, , 340,000, (2,344), 2.2, , 15,200, (104.8), , 12,200, (84.12), , 9,500, (65.5), , 10,200, (70.33), , 9,500, (65.5), , Thermal, HDT at 264 psi. OF, Long-term service, temp, UL index, of, Oxygen index, %, Mechanical, Flexural modulus, psi, (MPa), Impact strength, notched, Izod, ft.!lb'/in., Tensile strength, psi, (MPa), , D780, D256, D638, , 'Not UL listed., t Note: Glass filler can considerably extend the performance of the above polymers. PEl = polyetherimide; PES, poly ether sulfone; PPS = polyphenylene sulfide; PSF = polysulfone; PC = polycarbonate., , that influence the product's performances, and processing capabilities. TPs' properties, and processes are influenced by their thermal characteristics such as melt temperature (Tm), glass-transition temperature (Tg),, I, , -, , 80, r-.., , ...., , 70 1'-, , I, , !, , 60, , I, , 1, , dimensional stability, thermal conductivity,, thermal diffusivity, heat capacity, coefficient, of thermal expansion, and decomposition, (Td). Table 7-11 provides some ofthese data, on different plastics., t, , I, , I, , I, , I, , I, , - Electrodag coatings on 1/8-in. thick pOlyclarbo~ate sheet, I, 1.1 il\lef o\lef, ~, Q.'2.!f\\IS, ~i\e-.., I, ,.O!f\iI9fa , 9 -, , I, , I..-..=-, , ..........., , . sneet~:i_;;ilC~~t::±==*:::::1, ~ iI, ~S~II\lFefc:::_:=:::t-t--_+--4_--I, ./V~, , "~-""",,,, , , ~, , 1, , ~l:-.., , ......, , 1IS-in. sOlid a,\U!f\lnU!f\, , ID, 'C, , e-0, , 50, , ", , 40, , ~, c, , .., , ~, , iii, , c, , CI, , iii, , 30, , 20, , ~, , 0, , I, , ~~~~~==~1~.o~m~i~\g~ra~p~hi=te~==~~, , 10, , I, , 1.5 mil carbon, , I, , I, 10, , 100, , 1000, , 10,000, , Frequency, MHz, , Fig. 7-12, , =, , Comparing shielding effect of conductive coatings on a 1/8 in. thick PC sheets.

Page 411 : 7 Material Property, Table 7-10, , Conductive coating systems that provide EMIIRFI shielding on plastics, , Shielding System, , Advantages, , Conductive Coatings, Highly conductive (0.1 ohm per, Silver, square foot or less); applied by, conventional spray equipment;, easy application; electrically, stable (minimal change in, resistance with environmental, cycling); easily applied to selected, area; field repairable., Nickel, Low cost (15-30 cents per square, foot); good conductivity (less than, 1.0 ohm per square foot); applied, by conventional spray equipment;, easy application; relatively stable, (differs with manufacturer); easily, applied to selected area; field, repairable., Copper, Highly conductive (less than, 0.5 ohm per square foot); easy, application; low cost (15-30, cents per square foot)., Graphite, , ArclFlame, Spray, , Vacuum, Metalization!, Ion Plating, , Electrolysis, Deposition, , Conductive, Plastics, , 393, , Disadvantages, High cost, , Lesser quality formulations, available; some are stable,, some are not., , Oxidation can reduce conductivity, (resistance can change to effectively, make copper an insulator); some, may be alloys-if layered with silver,, cost will rise., Low cost (5-15 cents per square, Less conductivity (ranging, from 2 ohms to the thousands per, foot); easy application;, excellent ESD (electrostatic, square foot, depending upon, discharge) performance., the amount of graphite); modest, shielding capability (up to 30-40 dB)., Highly conductive (less than, Requires grit blasting to promote, 0.1 ohm per square foot;, mechanical bonding to plastic;, hard, dense coating., special applications equipment, required; requires special applicator, safety procedures for dust and fumes;, warps thermoplastics; not suitable, for thin-walled designs; not field, repairable., Highly conductive (less than 0.1 ohm Requires primer coat; entire part must, per square foot); controllable, be done, forcing exterior painting;, film thickness; not limited to, not field repairable; specialized, simple housing designs., application equipment; vacuum, chamber size a limiting factor;, requires specialized knowledge;, subject to corrosion in humid, atmosphere unless protected., Highly conductive (both nickel, Requires specialized equipment!, and copper less than 0.1 ohm, knowledge; entire part must be, per square foot)., coated, forcing exterior painting;, if copper is used it must be, protected by a nickel coating, or some other coating., Good thermal transfer;, Requires a secondary operation, elimination of secondary, for grounding., operation for shielding.

Page 412 : 0.9, 0.96, 2.2, 1.13, 1.35, 1.05, 1.05, 1.20, 1.20, 1.35, 2.68, 8.8, 7.9, 0.45, 6.7, , (56), (60), (137), (71), (84), (66), (66), (75), (75), (84), (167), (549), (493), (28.1), (418), , * = Crystalline resin. A = Amorphous resin., , Aluminum, Copperlbronze, Steel, Maplewood, Zinc alloy, , PP(C), HDPE(C), PTFE (C), PA(C), PET (C), ABS (A), PS(A), PMMA(A), PC (A), PVC (A), , Plastics, (morphology), , Density, glcm3, (lb'/ft.3), , 5 (41), -110 (-166), -115 (-175), 50 (122), 70 (158), 102 (215), 90 (194), 100 (212), 150 (300), 90 (194), , 168, 134, 330, 260, 250, 105, 100, 95, 266, 199, 1,000, 1,800, 2,750, 400, 800, (burns), , (334), (273), (626), (500), (490), (221), (212), (203), (510), (390), , Glass, Transition, Temperature, Tg °CeF), , Melt, Temperature, Tm,oC, (OF), , 2.8, 12, 6, 5.8, 3.6, 3, 3, 6, 4.7, 5, 3000, 4500, 800, 3, 2500, , (0.068), (0.290), (0.145), (0.140), (0.087), (0.073), (0.073), (0.145), (0.114), (0.121), (72.5), (109), (21.3), (0.073), (60.4), , Thermal, Conductivity, (10- 4 calls, ·cm 0C), (BTU/lb. OF), , 0.9 (0.004), 0.9 (0.004), 0.3 (0.001), 0.075 (0.003), 0.45 (0.002), 0.5 (0.002), 0.5 (0.002), 0.56 (0.002), 0.5 (0.002), 0.6 (0.002), 0.23, 0.09, 0.11, 0.25, 0.10, , Heat, Capacity, callg °c, (BTU/lb. OF), , Table 7-11 Examples of thermal properties of TPs (properties of common materials included for comparison), , (1.36), (5.4), (3.53), (2.64), (2.29), (1.47), (2.2), (3.45), (3.0), (2.4), (1900), (2200), (338), (10.5), (1430), , 3.5, 13.9, 9.1, 6.8, 5.9, 3.8, 5.7, 8.9, 7.8, 6.2, 4900, 5700, 1000, 27, 3700, , Thermal, Diffusivity, 10-4 cm2 /s, (10- 3 ft. 2 /hr.), , 19, 18, 11, 60, 27, , 81, 59, 70, 80, 65, 60, 50, 50, 68, 50, , (10.6), (10), (6.1), (33), (15), , (45), (33), (39), (44), (36), (33), (28), (28), (38), (128), , Thermal, Expansion, 10-6 cm/cm °C, (10- 6 in./in. OF), , ~, , ~, , ...., , .g, , ....'"ti, , ....~, 5·, , -, , ~, , '-l, , ~, , U.)

Page 413 : 7 Material Property, , try (DSC) curve (see Appendix B, TERMINOLOGY)., The T m is dependent on the processing, pressure and the time under heat, particularly during a slow temperature change for, relatively thick melts. Also, if the T m is too, low, the melt's viscosity will be high and more, power will be required for processing. If the, viscosity is too high, degradation will occur., There is the right processing window used for, the different plastics being melted., , 1-, , -, , u-, , -, , en, , 0', c::, , 0, , -, , ~, !!l U3, , "0, , "E, , "s;,, "0, , c.., , .-, , 600, , 395, , ~, ~, , ~, , ~, , Glass- Transition Temperature, , ~, , en, t:.-, , CD, , E, >., , "0, , !ll, , 0., , '", , "~, , "0, , c::, CD, ..c::, , c.., , o, , t- 0, =>, , u::, , v>, , c::, , 0, , ....--~, , u;, ~, 0, , c.., , tv>, , U, c.., , 200, Fig.7-13 Guide to classifying some of the plastics, by range of continuous heat., , All these thermal properties relate to, how to determine the best useful processing, conditions to meet product performance requirements. There is a maximum temperature or, to be more precise, a maximum, time-to-temperature relationship for all materials preceding loss of performance or decomposition. Figure 7-13 provides a temperature guide for continuous heating of plastics., , The glass-transition temperature (Tg) is, the point below that a TP behaves as glass, does; it is very strong and rigid, but brittle., Above this temperature it is neither as strong, nor rigid as glass, but neither is it brittle. At, T g the plastic's volume or length starts to in~, creases (Figs. 7-14 to 7-16). The amorphous, TPs have a more definite Tg., A plastic's thermal properties, particularly, its T g, influence its processability in many different ways. The selection of a plastic should, take this behavior into account. The operating temperature of a TP is usually limited to, below its Tg. A more expensive plastic could, cost less to process because of its lower T g, that results in a shorter processing time, requiring less energy for a particular weight,, etc., The glass transition generally occurs over, a relatively narrow temperature span and, , Residence Time and Recycling, , See Chapter 8, PROCESSING BEHAVIOR., Melt Temperature, , The T m occurs at a relatively sharp point, for crystalline materials. Amorphous materials basically do not have a Tm; they simply, start melting as soon as the heat cycle begins. In reality there is no single melt point,, but rather a range, which is often taken as, the peak of a differential scanning calorime-, , r,, Temperature, , Fig.7-14 Effect ofTg on the volume or length of, TPs.

Page 414 : 7 Material Property, , 396, , -.---..., , ttlOl1'h~_, , ., ., ., -t, ..., , Crystalline, , I, , Temperature, , Fig. 7-15 Solidification during processing of, glassy amorphous and crystalline TPs., , is similar to the solidification of a liquid to, a glassy state; it is not a phased transition., Not only do hardness and brittleness undergo rapid changes in this temperature region, but other properties such as the coefficient of thermal expansion and specific heat, change rapidly. This phenomenon has been, called second-order transition, rubber transition, or rubbery transition. The word transformation has also been used instead of, transition. When more than one amorphous, transition occurs in a plastic, the one associated with segmental motions of the plastic backbone chain, or accompanied by the, , 450-, , I, I, , >, , ...., U, ~, , '"<, ..., 0, -', , III, , '"::::>-', ::::>, 0, 0, , :;:, , I, I, I, I, , largest change in properties, is usually considered to be the glass transition., Designers should know that above T g' the, mechanical properties of TPs are reduced., Most noticeable is a reduction in stiffness by, a factor that may be as high as 1,000., The T g can be determined readily only by, observing the temperature at which a significant change takes place in a specific electric, mechanical, or physical property. Moreover, the observed temperature can vary, significantly, depending on the specific property chosen for observation and on details, of the experimental technique (for example,, the rate of heating, or frequency). Therefore,, the observed Tg should be considered to be, only an estimate. The most reliable estimates, are normally obtained from the loss peak, observed in dynamic mechanical tests or from, dilatometric data (ASTM D-20)., , Mechanical Property and Tg, Figures 7-17 and 7-18 provides examples, of modulus vs. Tg for amorphous and crystalline plastics. Temperature can help explain some of the differences observed in, plastics. For example at room temperature, polystyrene and acrylic are below their respective Tg values, we observe these materials in their glassy stage. In contrast, at room, temperature natural rubber is above its T g, [Tg = -75°C (-103°F);Tm = 30°C (86°F»),, with the result that it is very flexible. When it, , I, I, , AMORPHOUS, , ii, , ,.,0., , i, , 0, , I, , I, I, , I, , UNFILLED REINFORCED, , +, , CRYSTALLINE, , I, I, I, , I, , I, 0.450, , CROSS-LINKED, , DTUL, , X= Tg, -100, , C0, o, , 100, , 200, , O=MELT, , Oc, , Fig.7-16 Example of the dynamic and mechanical properties of TPs and TSs in relation to their, Tg and Tm., , TEMPERA TURE ---+0), , Fig.7-17 Modulus behavior of amorphous and, crystalline plastics showing Tg and melt temperatures.

Page 415 : 397, , 7 Material Property, High polymer amorphous, N, , Transition, , mm, , I, , UJ, , I, , <IJ, , ::>, , I, I, I, I, I, , :; 10 2, "0, 0, , E, , .;s<>, , I, , t, t, , 10 3, , 10, , .!1l, , Material partially crystalline, , I, , rubberelastic, region, glass, region, , t, , UJ, , 100, , region in, amorphous, portion, , 10-1, 9, , Temperature_, , 9, , Temperature _, , Fig.7-18 Modulus vs. temperature dependence going through different processing stages., , is cooled below its T g natural rubber becomes, hard and brittle., Dimensional Stability, , Dimensional stability is an important thermal property for the majority of plastics. It, is the temperature above which plastics lose, their dimensional stability. For most plastics, the main determinant of dimensional stability is their T g. Only with highly crystalline, plastics is T g not a limitation., Substantially crystalline plastics in the, range between T g and T m are referred to as, leathery, because they are made up of a combination of rubbery noncrystalline regions, and stiff crystalline regions. The result is that, such plastics as PE and PP are still useful at, the higher temperatures., , Thermal Conductivity and, Thermal Insulation, , Thermal conductivity is the rate at which, a material will conduct heat energy along its, length or through its thickness. ASTM tests, give an indication of how much heat must be, added to a unit mass of plastic in order to raise, its temperature 1°C. This is an important factor, since plastics are often used as effective, heat insulation in heat-generating applications and in structures where heat dissipation, is important. The high degree of the molecular order for crystalline TPs makes their val-, , ues tend to be twice those of the amorphous, types., The conductivity of plastics is dependent, on a number of variables and cannot be reported as a single factor. It depends mainly, on temperature and molecular orientation., Its dependence can be ascertained. However,, the molecular orientation may vary within a, product, resulting in a variation in thermal, conductivity. It is important for the designer, to recognize such a situation., For certain products, skill is required, to estimate a product's performance under, steady-state heat-flow conditions, especially, those made of RPs (Fig. 7-19). The method, and repeatability of the processing technique, can have a significant effect. In general, thermal conductivity is low for plastics and the, plastic's structure does not alter its value significantly. To increase it the usual approach, is to add metallic fillers, glass fibers, or electrically insulating fillers such as alumina., Foaming can be used to decrease thermal, conductivity., Heat Capacity, , The heat capacity or specific heat of a unit, mass of material is the amount of energy required to raise its temperature 1°C. It can, be measured either at constant pressure or, constant volume. At constant pressure it can, be larger than at constant volume, because, additional energy is required to bring about, a volume change against external pressure.

Page 416 : 398, , 7 Material Property, )C, , 0.63, , .---~--,------,-----:,--,---~--,, , 0.56, E 0.49, , ~, , 4.5, 4.0, , ········· .. ,·.. ·············,············? ......:~-=~=?3.5 ~u., , :;:., , 0.42, , :~, , 0.35 I···············;· .. "".r..·····;······· .. ··, , >., , 3.0, 2.5, , -g "';, , 2.0, , 0'<::', ~d, , E, , 0.14 t~:r:=:::~=t:=~-:=:TiPai1====t1.5, 1.0, , ~rrJ, , .<::., , 0.07, , U, , ...., , C, , 0, 0, , c;;, ~, , f-, , . :~--~~~~~r.===l, , .; ............ ;................!.............. !..., , ::>, '0, , PC, , 0.21, , :g~., :>-, , "'.-, , E;, G)-, , 0.5, ~-~-~-~-~-~--~-~-~O, , 5, , Fig.7-19, in RPs., , 10, , 15, , 20, 25, Glass. %, , 30, , 35, , 40, , Example of the effect on thermal conductivity by varying the glass fiber content (by weight), , The specific heat of amorphous plastics increases with temperature in an approximately linear fashion below and above T g ,, but a steplike change occurs near the T g . No, such stepping occurs with crystalline types., For plastics, heat capacity is usually reported during constant pressure heating., Plastics differ from traditional engineering, materials because their specific heat is temperature sensitive., , Thermal Diffusivity, Whereas heat capacity is a measure of energy, thermal diffusivity is a measure of the, rate at which energy is transmitted through a, given plastic. It relates directly to processability. In contrast, metals have values hundreds, of times larger than those of plastics. Thermal, diffusivity determines plastics' rate of change, with time. Although this function depends on, thermal conductivity, specific heat at constant, pressure, and density, all of which vary with, temperature, thermal diffusivity is relatively, constant., , Coefficient of Linear Thermal Expansion, Like metals, plastics generally expand, when heated and contract when cooled. Usually, for a given temperature change many, TPs have a greater change than metals., The coefficient of linear thermal expansion, (CLTE) is the ratio between the change of a, , linear dimension to the original dimension of, the material per unit change in temperature, (per ASTM standards). It is generally given, as cm/cm/oC or in.iin.i°F., The CLTE is an important consideration, if dissimilar materials like one plastic to another or a plastic to metal and so forth that are, to be assembled where material expansion or, contraction is restricted. The CLTE is influenced by the type of plastic (liquid crystal, for, example) and RP (particularly the glass fiber, content and its orientation). It is especially, important if the temperature range includes, a thermal transition such as T g . Normally,, all this activity with dimensional changes is, available from material suppliers., The design of products has to take into account the dimensional changes that can occur during fabrication and during its useful, service life. With a mismatched CLTE could, be destructive that includes factors such as, cracking or buckling., Expansion and contraction can be controlled in plastic by its orientation, crosslinking, adding fillers or reinforcements, and, so on. With certain additives the CLTE value, could be zero or near zero. For example, plastic with a graphite filler contracts rather than, expands during a temperature rise. RPs with, only glass fiber reinforcement can be used to, match those of metal and other materials. In, fact, TSs can be specifically compounded to, have little or no change., In a TS the ease or difficulty of thermal expansion is dictated for the most part by the, degree of cross-linking as well as the overall

Page 417 : 399, , 7 Material Property, stiffness of the units between the cross-links., The less flexible units are also more resistant, to thermal expansion. Such influences as secondary bonds have much less effect on the, thermal expansion of TSs. Any cross-linking, ofTPshasasubstantialeffect. With the amorphous type, expansion is reduced. In a crystalline TP, however, the decreased expansion, as a result of cross-linking may be partially, offset by a loss of crystallinity., , Thermal Stress, If a plastic product is free to expand and, contract, its thermal expansion property will, usually be of little significance. However, if, it is attached to another material, one having a lower CLTE, then the movement of the, part will be restricted. A temperature change, will then result in developing thermal stresses, in the part. The magnitude of these stresses, will depend on the temperature change, the, method of attachment and relative expansion, and the modulus characteristics of the, two materials at the point of the exposed heat., In its simplest form, thermal stresses can be, calculated by using the following equation:, , (7-1), where: (j = thermal stress, Ep = elastic modulus of elasticity, (Xl = CLTE of material #1,, (X2 = CLTE of material #2, and /:)" T = temperature change., The goal is to eliminate or significantly reduce all sources of thermal stress. This can be, achieved by keeping the following factors in, mind: (1) when adding material for local reinforcement, select a material with the same or, a similar CLTE, (2) where plastic is to be attached to a more-rigid material, use mechanical fasteners with slotted or oversized holes, to permit expansion and contraction to occur,, (3) do not fasten dissimilar materials tightly,, and (4) adhesives that remain ductile, such as, urethane and silicone, through the product's, expected end-use temperature range can be, used without causing stress cracking or other, problems., In addition to dimensional changes from, changes in temperature, other types of di-, , mensional instability are possible in plastics,, as in other materials. Water-absorbing plastics, such as certain nylons, may expand and, shrink as they gain or lose water, or even as, the relative humidity changes. The migration, or leaching of plasticizers, as in certain PVCs,, can result in slight dimensional change., , Decomposition Temperature, For applications having only moderate, thermal requirements, thermal decomposition may not be an important consideration., However, if the product requires dimensional, stability at high temperatures, it is possible, that its service temperature or processing, temperature may approach its temperature, of decomposition (Td) (Table 7-12). A plastic's decomposition temperature is largely determined by the elements and their bonding, within the molecular structures as well as the, characteristics of additives, fillers, and reinforcements that may be in them., , Aging at Elevated Temperature, Aging at elevated temperatures typically, involves exposing test specimens or products, at different temperatures for different extended time periods. Tests are performed at, room or the respective testing temperatures, for whatever mechanical, physical, or electrical property is of interest. These tests of aging, Table 7-12, , Examples of temperature, decomposition, Material, , DF, , (DC), , PP, PC, PVC, PS, PMMA, ABS, PA, PET, Fluoropolymer, , 610-750, 645-825, 390-570, 570-750, 355-535, 480-750, 570-750, 535-610, 930-1020, , (321-399), (341-441), (199-299), (299-399), (180-280), (249-399), (299-399), (280-322), (499-549), , Note: Adding certain fillers and reinforcements can raise, decomposition temperatures.

Page 418 : 400, , 7 Material Property, , can be used as a measure of thermal stability, in design as is done with other materials., , Temperature Index, The Underwriters Laboratories (UL) tests, are recognized by various industries to provide continuous temperature ratings, particularly in electrical applications. These ratings, include separate listings for electrical properties, mechanical properties including impact,, and mechanical properties without impact., The temperature index is important if the final product has to receive UL recognition or, approval., , cording to the manufacturer's recommendations, are described as equivalent to conventional products in coating properties and also, provide permanent fire resistance to the substrate on which they are applied., , Other, In addition to what has been presented,, the commercially available literature provides all kinds of the important behavioral, thermal/temperature properties that would, be important to designers' for certain specific requirements (181). Examples are given, in Figs. 5-9 and 7-20 to 7-23 and Tables 7-13, to 7-15., , Intumescent Coating, Other Behavior, These coatings bubble and foam to form a, thermal insulation when subjected to a fire., They have been used for many decades. Such, coatings cannot be differentiated from conventional coatings prior to the occurrence of, a fire situation. Thereupon, however, they, decompose to form a thick, nonflammable,, multicellular, insulative barrier over the surface on which they are applied. This insulative foam is a very effective insulation that, maintains the temperature of a flammable or, heat distortable substrate below its ignition, or distortion point. It also restricts the flow, of air (oxygen) to fuel the substrate., These coatings provide the most effective, fire-resistant system available but originally, were deficient in paint color properties. Since,, historically, the intumescence producing, chemicals were quite water-soluble, coatings, based thereon did not meet the shipping can, stability, ease of application, environmental, resistance, or aesthetic appeal required of a, good protective coating., More recently there have been developed water- resistant phosphorus-based intumescence catalyst. This commercially available product, as an example Phos-Chek P/30, tradename from Monsanto, can be incorporated (with other water insoluble reagents), into water-resistant intumescent coatings of, either the alkyd or latex-emulsion type., These intumescent coatings, formulated ac-, , Drying Plastic, Of the various plastics available, such TPs, as nylon, PC, PMMA, PUR, PET, and ABS, are among those categorized as hygroscopic., , o, I _~S~AE~10~2~0~S:I~:I____------------", -0.2"", -0.4, -0.6, , -0.8, -1.0t;;......_ - - - -, , -1.2, -1.4 ...._ - - -, , -1.6, -1.8, , .~, u, ~, , ~, , -2.41..-__- - 2.6L----'--_..L---'_---'--_-'----...L_--'--_L---I, , -273-253 -233 -213 -193 -173 -153 -133 -113 -93, Temperature. ·C., , Fig.7·20 Examples at low temperatures of thermal contraction in unfilled plastics and steel. With, RPs using TS plastics change can be significantly, reduced or even at zero (using graphite, etc.).

Page 419 : 7 Material Property, , Phenolic, , PPS, , 160'C, , PolYC8,bonaie, , PST, Polysullone, PET, , 120'C, ASS, Acelal, Nylon, PPO, , 6O' C, , 401, , adequate for nonhygroscopic plastics are simply not capable of removing water to the degree necessary for the proper processing of, hygroscopic types or their compounds, particularly during periods of high humidity., For the record let it be known that in the, past (half century ago) about 80% of fabricating problems was due to inadequate drying of all types of plastics when a processing, problem developed. Now it could be down, to 50%., , Fig,7-21 Simplified overview oftypical uses temperaturewise., , Moisture Influence, These absorb moisture, which then has to, be carefully removed before the plastics can, be fabricated into acceptable products (2, 3)., Low concentrations, as specified by the plastic supplier, can be achieved through efficient drying systems and properly handling, the dried plastic prior to and during molding,, extrusion, etc. (Figs. 7-24 and 7-25). When desired processor can have these hygroscopic, plastics properly dried and shipped in sealed, containers., Drying hygroscopic plastics should not be, taken casually. The simple tray dryers or mechanical convection hot-air dryers that are, -100, PTFE 95+, , -90, -80, -70, -60, , -50, , The effect of having excess moisture manifests itself in various ways, depending on the, process being employed. The common result is a loss in both mechanical and physical properties for hygroscopic and nonhygroscopic plastics (Fig. 7-26). During injection, molding splays, nozzle drool, sinks, and other, losses that may occur (3). The effects during extrusion can include gels, trails of gas, bubbles in the extrudate, arrowheads, wave, forms, surging, lack of size control, and poor, appearance (6)., Plastic Memory, Plastic memory is a phenomenon of TPs, that has been stretched while hot beyond its, heat distortion point to return to its original, processed or molded form. Different plastics have varying degrees of this characteristic, and degree of return is basically dependent, on temperature (Chapter 4, Thermoforming,, Memory)., , PVC 47±5, , -40, Epoxy 37±8, , Corrosion Resistance, , -30, PC 26±1, Nylon 2S±3, Polyester 21±2"\,., , ~~1~W4~r20, ~~ ~~:::W-< 10, pp 17, , Paraffin· 15, , -, , 0, , Fig.7-22 Limiting oxygen index values for a few, plastics., , Corrosion is fundamentally a problem associated with metals. Since plastics are electrically insulating they are not subject to this, type of damage. Plastics are basically noncorrosive. However, there are those that can, be affected when exposed to corrosive environments. It is material deterioration or destruction of materials and properties brought, about through electrochemical, chemical,

Page 420 : 402, , 7 Material Property, , Limiting oxygen index, (decreases with Increasing, temperature), I, , I, , I, , No fire, , Fig. 7-23, , Summarizing the requirements for a fire., , and mechanical actions. Direct attack by an, electrochemical, or galvanic action, is the, most common. It is the tendency of different, metals going into solutions when exposed to, natural or man-made electrolytes. The difference in electrical potential can cause damage., Basically corrosion resistance is the ability, of a material to withstand contact with ambient natural factors or those of a particular artificially created atmosphere without degraTable 7-13, , dation or change in properties. Since plastics, (not containing metallic additives) are not, subjected to electrolytic corrosion, they are, widely used where this property is required, alone as a product or as coatings and linings for material subjected to corrosion such, as in a chemical and water filtration plants,, mold/die, etc. Plastics are used as protective, coatings on many different products such as, steel rod, concrete steel reinforcement, etc., , Examples of environmental factors that could effect certain plastics, , Parameter, , Manifestation and Effects, , Radiation, Temperature, Physico chemical factors, Organic solvents, Stress factors, , Solar, nuclear, thermal, Elevated, depressed, cyclic around the 'norm', Chemical attack, physical changes such as plasticiser bleed, Vapour absorption, dissolution, stress corrosion cracking, Sustained stress, cyclic stress, compression set (in rubbers), under continuous loading, Microorganisms, fungi, bacteria, animals, insects can destroy, materials or change their properties, Air-borne particulate erosion from dust or water precipitation, Oxygen, ozone, carbon dioxide, nitrogen oxides, Gases: sulphur oxides, halogen compounds, Mists: aerosols, salt, alkalies, Particulates: sand, dust, grease, Surface damage, , Biological factors, Wind, Normal air constituents, Air contaminants, Combined action of, wind and water, Water, Freeze-thaw, Use factors, , Solid (snow, ice), liquid (rain, condensation, standing water),, vapour (relative humidity). Rain, hail, sleet or snow may, have physical effects, Thermal expansion, Normal wear and tear, abuse during installation, abuse by, user application outside the designed use conditions

Page 421 : Ductile, Ductile, Ductile, , 175, 700--1000, 350--900, 200--1000, 50--100, 300--900, 300--500, 40--75, 3, 500--1000, 500--700, , 3000--5000, 1500--3000, 3500-4500, 6000--7000, 9000--12,000, , 1200--2500, 2500--3000, 8000--9000, 11,000, 4000, 5000, , Opaque, Cloudy, Opaque, Clear, Clear and cloud, Clear, Opaque, Opaque, High clarity, Cloudy, Cloudy, , Yes, Yes, Damaged, Yes, Yes, Marginal, Stabilized, , Yes, , Yes, Yes, , Yes, , Yes, Yes, Marginal, , Distorts, , Marginal, to poor, Yes, , 1.1-1.4, 1.15, , 1.04--1.14, , 1.12, 1.1-1.4, 1.40, , 1.08, , 0.86-0.96, , SAN (styrene, acrylonitrile), , Polyethylene, (all types), Polypropylene, , PVC, Flexible, Rigid, Polyester PET(polyethylene, terephthalate), Styrene, ABS (acrylonitrile, butadiene-styrene), Polycarbonate, Polysulfone, Acrylic, (polymethylmethacrylate), Polymethyl-pentene, , Yes, Yes, , Marginal, , 0.9-1.2, , 350, 0.5-150, 50--300, , 2-5, 2-30, 110, 20--100, 2-15, , 25-100, , 2500, 6500, 7800, , 6000, 7000, 9000, 10,000, 10,000, , 3400, , Clear, Clear, Clear, , High clarity, Opaque and clear, Clear, Clear, High clarity, , Clear, , Yes, Yellows, Yes, , Yes, Yes, Yes, Yes, Yellows, , Marginal, , Yes, Distorts, Distorts, , Distorts, Distorts, , Yes, Yes, Distorts, , Yes, , 1.21, 1.45, 1.35, , 1.05, 1.06, , 1.20, 1.25, 1.19, , 0.83, , 0.9, , Marginal, , Yes, , 2.10--2.15, Yes, , Yes, , Distorts, , 1.19-1.23, , Cellulosics, ( cellulose-acetatepropionate), Fluoroplastics, (TFE, FEP), Thermoplastic, elastomers (TPE), Natural rubber, Polyurethane, (polyether, aliphatic), Polyamide, (nylon 6--6), Silicone rubber, Butyl rubber, Polyacetal, , Stiff, , Ductile, Ductile, Stiff, , Ductile, Stiff, Stiff, Also, films, Very stiff, Stiff, , Ductile, , Ductile, , Very stiff, , Ductile, Ductile, Stiff, , Ductile, , Ductile, , Ductile, , 10-50, , 1000-7000, , Stiff, or, Ductile, , Clear, , Visual, Clarity, , Elongation, to Break, (%), , Steam, (@121°C), , Specific, Gravity, , Radiation, (2.5 Mrd), , Tensile, Strength, PSI Yield, , Sterilization, , Example of mechanical and physical properties of plastics after sterilization, , Polymer, Material, , Table 7-14, , Easy, , With care, With care, Easy, , Easy, Easy, , With care, Can burn, With care, , Easy, , Easy, , Easy, , Special, Special, Easy, , With care, , Special, Easy, , Easy, , With care, , Easy, , Relative, Ease, Process, , Labware/parts, , Molded parts, Molded parts, Molded parts, , Lab ware, Molded parts, , Containers, Syringes, Film bags, and tubing, Molded parts, Containers, Molded parts, , Containers Caps, , Molded parts, Film bags, Stoppers/parts, Film, tubing,, and components, Packaging film, and catheters, Tubing/parts, Stoppers/seals, NonHuid path, molded parts, Molded parts, , Flexible tubing, , Burettes/tubes, , Leading, Medical, Uses, , ~, , -I::.., , ~, , ~, , ....(':>, , .g, , ....~, :::;., ......, ~, , '"

Page 422 : 404, , 7 Material Property, Table 7-15(a) Guide to relative radiation stabilization of medical plastic devices, where dose (kilogray) in ambient air and room temperature at which elongation, changes by 25 %, 0, , 25, , 50, , 100, , 200, , 300, , 400, , 500, , Thermosels, POlystyrenes, Polyethylenes, Polyesters, Engineering, , highpertormance, , Polycarbonatei, Polysulfone, Polyurethanes, PVC, Fluoropolymers, high performance, , ABS, Elastomers, Acrylic (PMMA), Nylon, Cellulosics, Polypropylene, lradiationgradesl, , FEP, Polypropylene, (naluraQ, , References:, , ........t--t-----+-----t- . NASA/Jet Propulsion Laboratories. "Effects of, Radiation on Polymers & Elastomers" (1988)., , -+--1------+----1- . Skeins & Williams, "Ionizing Radiation Enact on, Selected Biomedical Polymers:, , Acetals, , -1__+--+---+----+, , PTFE, , -11---1--+-----+-----+ . Ley, "The Effects of Irradiation on Packaging, , Complex corrosive environments results, in at least 30% of total yearly plastics production being required in buildings, chemical, plants, transportation, packaging, and communications. Plastics find many ways to save, some of the billion dollars lost each year, by industry due to the many forms of, corrosion., One example is the use of rigid selfexpanding closed cell polyurethane foams as, a method to inhibit corrosion of the interior, surfaces of metal (steel, etc.) structural cavities exposed to seawater and moisture is one, of many example of plastic providing corrosion protection. Unfilled metal cavities are a, general feature of various structures or products used in the marine, building, electronics,, , . Kiang, "Effect of Gamma Irradiation on Elastomeric, Closures," POA, (1992)., Materials" (1976)., , automotive, heavy equipment, and aerospace, products., Premature deterioration of the internal, surfaces of these cavities is associated, with the fact that they are usually poorly, protected from corrosion and provide a, region for the accumulation and stagnation, of salt laden debris and/or moisture during, exposure to marine environments. Preferred, application of protective paints during products manufacture is often prohibited because, welding or other joining operations could, damage or destroy preexisting coatings., Rigid polymer foamed in-place are used in, regions that are difficult or impossible to, access for conventional surface applications, of protective plastic paints, etc. (238).

Page 423 : 7 Material Property, Table 7-1S(b), , 405, , Guide to radiation stability of plastics, Material, , Radiation Stability, , Polystyrene, Polyethylene, various densities, , Excellent, Good/Excellent, , Polyamides (nylon), , Good, , Polyimides, Polysulfone, Polyphenylene sulfide, Polyvinyl chloride (PVC), , Excellent, Excellent, Excellent, Good, , Polyvinyl chloride/Polyvinyl acetate, Polyvinylidene dichloride (Saran), Styrene/acylonitrile (SAN), Polycarbonate, , Good, Good, Good/Excellent, Good/Excellent, , Polypropylene, natural, Polypropylene, stabilized, , Poor/Fair, , Fluoropolymers:, Polytetrafluoroethylene (PTFE), Perfluoro alkoxy (PFA), Polychlorotrifluoroethylene, (PCTFE), Polyinyl fluoride (PVF), Polyvinylidene fluoride (PVDF), Ethylene-tetrafluoroethylene, (ETFE), Fluorinated ethylene propylene, (FEP), Cellulosics:, Esters, Cellulose acetate propionate, Cellulose acetate butyrate, Cellulose, paper, cardboard, Polyacetals, , Poor, Poor, Good/Excellent, , Comments, High-density grades not as stable, as medium- or low-density grades., Nylons 10, 11, 12, 6-6 are more stable, than 6. Film and fiber are less resistant., Natural material is yellow., Yellows. Antioxidants and stabilizers, prevent yellowing. High-molecularweight organotin stabilizers improve, radiation stability; color-corrected, radiation formulations are available., Less resistant than PVc., Less resistant than PVc., Yellows. Mechanical properties not greatly, affected; color-corrected radiation, formulations are available., Physical properties greatly reduced when, irradiated. Radiation-stabilized grades,, utilizing high molecular weights and, copolymerized and alloyed with, polyethylene, should be used in most, radiation applications. High-dose-rate, E-beam processing may reduce, oxidative degradation., When irradiated, PTFE and PFA are, significantly damaged. The others show, better stability. Some are excellent., , Good/Excellent, Good/Excellent, Good, Fair, Esters degrade less than cellulose does., Fair, Fair, Fair/Good, Fair/Good, Poor, , ABS, , Good, , Acrylics (PMMA), Polyurethane, , Fair/Good, Good/Excellent, , Irradiation causes embrittlement., Color changes have been noted, (yellow to green)., High-impact grades are not as radiation, resistant as standard-impact grades., Aromatic discolors; polyesters more, stable than esters. Retains physical, properties., ( Continued)

Page 424 : 406, , 7 Material Property, , Table 7-1S(b), , (Continued), , Material, , Radiation Stability, , Liquid crystal polymer (LCP), , Excellent, , Polyesters, , Good/Excellent, , Thermosets:, Phenolics, , Excellent, , Epoxies, Polyesters, , Excellent, Excellent, , Allyl diglycol carbonate, (polyester), Polyurethanes:, Aliphatic, Aromatic, Elastomers:, Urethane, EPDM, Natural rubber, Nitrile, Polychloroprene (neoprene), , Excellent, Good/Excellent, , Excellent, Excellent, Good/Excellent, Good/Excellent, Good, , Good, , Styrene-butadiene, Polyacrylic, Chlorosulfonated polyethylene, Butyl, , Good, Poor, Poor, Poor, , Chemical Resistance, Part of the wide acceptance of plastics is, from their relative compatibility to chemicals, as compared to that of other materials. Because plastics are largely immune to the electrochemical corrosion to which metals are, susceptible, they can frequently be used profitably to contain water and corrosive chemicals that would attack metals. Plastics are, often used in corrosive environments for, , Commercial LCPs excellent;, natural LCPs not stable., PBT not as radiation stable as, PET., Includes the addition of mineral, fillers., All curing systems., Includes the addition of mineral or, glass fibers., Maintains excellent optical properties, after irradiation., , Excellent, , Silicone, , Comments, , Darkening can occur. Possible, breakdown products could be, derived., , Discolors., Discolors. The addition of, aromatic plasticizers renders the, material more stable to, irradiation., Phenyl-methyl silicones are, more stable than are methyl silicones., Platinum cure is superior to peroxide, cure; full cure during manufacturing, can eliminate most postirradiation, effects., , Friable, sheds particulates., , chemical tanks, water treatment plants, and, piping to handle drainage, sewage, and water, supply. Figures 7-27 and 7-28 use glass fiber, TS polyester RPs. Structural shapes for use, under corrosive conditions often take advantage of the properties of RPs., However, certain plastics are subject to attack by aggressive fluids and chemicals, although not all plastics are attacked by the, same media. It is thus most practical to select a plastic to meet a particular design

Page 425 : 407, , 7 Material Property, Ambient Conditions - 75° F, 50% Relative Humidity, (55° F Dew Point), , \, , J, , 6, , -, , ---, , IJ, Internal, Vapor, Pressure, , High, External, Pressure, , /"", , MIGRATION, INWARD, , External, Vapor, Pressure, , <1, , (dry) = +0, , (55°d.p.) = -.214 psi, '" P = -.214 psi, , Fig. 7-24 Mechanics of moisture absorption in plastics., , performance condition. For example, some, plastics like HDPE are immune to almost, all commonly found solvents. Polytetrafluoro ethylene (PTFE) in particular is noted, principally for its resistance to practically, all-chemical substances. It includes what has, been generally identified as the most inert, material known worldwide., It is important to recognize that all materials will have problems in certain environments, whether they are plastics, metals,, aluminum, or something else. For example,, the chemical effect and/or corrosion of metal, surfaces has a damaging effect on both the, static and dynamic strength properties of, metals because it ultimately creates a reduced, cross-section that can lead to eventual failure., The combined effect of corrosion and stress, on strength characteristics is called stress corrosion. When the load is variable, the com-, , bination of corrosion and the varying stress, is called corrosion fatigue., This problem can be controlled in several, ways. One is to select the best material, such, as stainless steel, copper alloy, or titanium., Another is to use a nonmetallic protective, coating of plastic. Certain systems like plating can reduce fatigue strength. Shot peening, rather then plating seems to produce much, greater improvement, but shot peening, plating, and then baking can bring the fatigue, limit to a point lower even than that of the, base metal. The point in this review is that, all materials have their limitations and must, be critically analyzed if no prior experience, exists upon which to draw., For example, RP underground gasoline, storage tanks have this experience. A, Chicago service station's May 1963 installation was stillieaktight and structurally sound, , Hopper Conditions - 350° F, (-40 Dew Point), , \, , r, , ---, , Low, External, Pressure, , (), , 0, , MIGRATION, OUTWARD, Internal, Vapor, Pressure, , 350°F=+27.4, , External, Vapor, Pressure, , (_40° d.p.) = -.002 psi, il P = + 27.4 psi, , Fig.7-25 Mechanics of moisture migrating out of plastics.

Page 426 : 408, , 7 Material Property, , 90r-----~~--;_--~~--~~----_4, , ~, E 80r-----+---~~----~---3~----_4, , 5, , 0701r-----+_----~--~~----_+--~~, ~, 60~----+_----;_----~~~_+----~, , 50~----~----~----~----~~--~, .01, , Fig. 7-26 Example of the effects of moisture on, the mechanical properties of an 1M hygroscopic, PET plastic., , when unearthed in May 1988. The tank was, one of sixty developed by Amoco Chemical Co. It was fabricated in two semicylindrical sections of fiber glass-woven roving and, chopped strand mat impregnated by an unsaturated isophthalic TS polyester plastic selected for its superior resistance to acids, alkalis, aromatics, solvents, and hydrocarbons., The two sections were bonded to each other, and to end caps with RP lap joints. Today the cylinder would be a single, unified, , Fig.7-28, , Fig. 7-27 Water filtration tank (20 ft D, 32 ft H), could be the largest low-pressure RP molded tank, ever built and shipped in one piece., , Gasoline marina 4,000 gallon tanks being installed.

Page 427 : 409, , 7 Material Property, construction as seen in Fig. 7-28. The demand, for this type of petroleum storage tank has, grown rapidly worldwide as environmental, regulations have become more stringent., Today's underground tanks must last thirty, or more years without undue maintenance., To meet these criteria they must be able to, maintain their structural integrity and resist, the corrosive effects of soil and gasoline, including gasoline that has been contaminated, with moisture and soil., The RP tank just reviewed that was removed in 1988 met these requirements, but, two steel tanks unearthed from the same site, at that time failed to meet them. There was no, record of how long the steel tanks had been in, service, but one was dusted with white metal, oxide and the other showed signs of corrosion at the weld line. Rust had weakened this, joint so much that it could be scraped away, with a pocketknife., Tests and evaluations were conducted on, the tank that had been twenty-five years in, the ground and also on similarly constructed, tanks unearthed at five and a half and seven, and a half years that showed the RP tanks, could more than meet the service requirements. Table 7-16 provides factual, useful, data from these tests., The chemical and corrosion resistance of, plastics is well known. Most materials supTable 7·16, , pliers have developed long-term data for the, commonly used and other chemicals as well., Great care must be taken in selecting them,, particularly regarding environmental conditions. For instance, two materials that do not, attack a plastic when used separately may, be troublesome when used in combination, or diluted with water. And additives such, as fillers, plasticizers, stabilizers, colorants,, and catalysts can decrease or increase the, chemical resistance of unfilled or neat plastics. Temperature is also important in all, cases; careful tests must be made under the, actual conditions of use in making a final, selection., Of especial importance to chemical resistance, particularly in the RPs, is the processing method used. If, for example, a chemical, and a mechanical component act simultaneously, cracking or fiber debonding can occur in the plastic, considerably accelerating, the diffusion of the aggressive media to the, glass fibers. Whereas the diffusion of aggressive media such as acids and alkalis proceeds slowly in plastics, these media advance, rapidly along glass fibers. The serviceability of these types of plastics in a corrosive, media can be guaranteed only if proper attention is given to processing variables like, voids, including the fiber orientation and, construction., , Data on RP underground gasoline storage tanks unearthed after different time periods, Test Results, Age at Testing, , Property, , 5.5 Years, , 7.5 Years, , 25.0 Years, , Buried-excavated, Flexural strength: Psi, MPa, Flexural modulus: Psi, MPa, Tensile strength: Psi, MPa, Tensile modulus: Psi, MPa, Tensile elongation: %, Notched Izod, impact strength: ft.-lb'/in., J/m, , 117/65-8/21170, 19,500, 134, 725 x 103, 4,992, 10,700, 74, 1,160 x 103, 7,260, 1.11, , 4/4/64-10/24171, 24,200, 167, 795 X 103, 5,482, 13,600, 94, 1,053 X 103, 8,000, 1.25, , 5/15/63-5/11188, 22,400, 154, 635 X 103, 4,378, 10,500, 72, 1,107 X 103, 7,630, 1.13, , 9.7, 518, , 11.0, 587, , 14.1, 753

Page 428 : 410, , 7 Material Property, , Friction, Wear, and Hardness Property, , Friction is the resistance against change in, the relative positions of two bodies touching one another. If the area of contact is a, plane, the relative motion will be a sliding, one and the resistance will be called sliding, or kinetic friction. If the material in the area, of contact is loaded beyond its strength, abrasion or wear will take place. Both phenomena, are affected by numerous factors such as the, load, relative velocity, temperature, and type, material., Although plastics may not be as hard as, metal products, there are those that have excellent resistance to wear and abrasion. Plastic hardware products such as cams, gears,, slides, rollers, and pinions frequently provide, outstanding wear resistance and quiet operation. Smooth plastic surfaces result in reduced friction, as they do in pipes and valves., The frictional properties of TPs, specifically the reinforced and filled types, vary in, a way that is unique from metals. In contrast to metals, even the highly reinforced, plastics have low modulus values and thus, do not behave according to the classic laws, of friction. Metal-to-thermoplastic friction is, characterized by adhesion and deformation, resulting in frictional forces that are not proportional to load, because friction decreases, as load increases, but are proportional to, speed. The wear rate is generally defined as, the volumetric loss of material over a given, unit of time. Several mechanisms operate simultaneously to remove material from the, wear interface. However, the primary mechanism is adhesive wear, which is characterized, by having fine particles of plastic removed, from the surface., The presence of this powder is a good indication that the rubbing surfaces are wearing, properly. Conversely, the presence of melted, plastic or large gouges or grooves at the interface normally indicates that the materials, are abrading, not wearing, or the pressure velocity (PV) limits of the materials may be exceeded (Chapter 4, BEARING, PV Factor)., The ease and economy of manufacturing gears, cams, bearings, slides, ratchets,, and so on with injection-moldable TPs have, , led to a widespread displacement of metals, in these types of applications. In addition, to their inherent processing advantages, the, products made from these materials are able, to dampen shock and vibration, reduce product weight, run with less power, provide corrosion protection, run quietly, and operate, with little or no maintenance, while still giving the design engineer tremendous freedom., These characteristics can be further enhanced and their applications widened by, fillers, additives, and reinforcements. Compounding properly will yield an almost limitless combination of an increased loadcarrying capacity, a reduced coefficient of, friction, improved wear resistance, higher, mechanical strengths, improved thermal properties, greater fatigue endurance and creep, resistance, excellent dimensional stability, and reproducibility, and the like., Different test results are available to the, designer wanting friction and wear data as, well as the usual mechanical short and long, term data, corrosion resistance, readings, and, so on. The data presented include the load, and velocity capabilities of a bearing material as expressed by the product of the unit, load P based on the projected bearing area, and linear shaft velocity V. The symbol PV denotes the important property of the pressurevelocity relationship., Wear tests are conducted such as using a, thrust-washer test apparatus. A sample thrust, washer is mounted in an antifriction bearing, equipped with a torque arm. The test specimen holder is drilled to accept a thermocouple temperature probe. The raised portion of, the thrust washer bears against a dry, coldrolled, carbon-steel wear ring with a 12- to, 16-microinch finish at an 18 to 22 Rockwell, C scale hardness at room temperature. Each, evaluation is conducted with a new wear ring, that has been cleaned and weighed on an analytical balance. The bearing temperature and, friction torque is continuously monitored., The test duration is dependent upon the period required to achieve a 360-degree contact between the raised portion of the thrust, washer and the wear ring. The average wear, factor and duration of this break-in period, are then reported. The wear factors reported

Page 429 : 7 Material Property, , for each compound is based on its equilibrium wear rate independent of break-in wear., The coefficient of friction data can be obtained with the same thrust-washer test apparatus. The test specimen is run in against, the standard wear ring until a 360-degree, contact between the raised portion of the, thrust washer and the wear ring is achieved., The temperature of the test specimen is then, allowed to stabilize at the test conditions, (generally 40 psi, 50 fUmin., room temperature, and dry). After thermal equilibrium, occurs, the dynamic frictional torque generated is measured with the torque arm that is, mounted on the antifriction bearing. An average of a minimum of five readings is taken., Although hardness is a somewhat nebulous term, it can be defined in terms of the, tensile modulus of elasticity. From a more, practical side, it is usually characterized by, a combination of three measurable parameters: (1) scratch resistance; (2) abrasion or, mar resistance; and (3) indentation under, load. To measure scratch resistance or hardness, an approach is where a specimen is, moved laterally under a loaded diamond, point. The hardness value is expressed as the, load divided by the width of the scratch. In, other tests, especially in the paint industry,, the surface is scratched with lead pencils of, different hardnesses. The hardness of the surface is defined by the pencil hardness that first, causes a visible scratch. Other tests include a, sand-blast spray evaluation., The material's loss in weight or the change, in optical transmission usually measures abrasion resistance and reflectance after a sample has been exposed to an abrasive surface., This is usually done under load, for a predetermined number of cycles or a time period, specified by ASTM methods., Tests for indention under load are performed basically like the ASTM measure the, hardness of other materials, such as metals, and ceramics. There are at least four popular, hardness scales in use. Shore A and Shore D, is for soft to relatively hard plastics and elastomers. Barcol is used from the mid-range of, Shore D to above it as well as RPs. Rockwell, M is used for very hard plastics (Chapter 5,, MECHANICAL PROPERTY, Hardness),, , 411, , Plastic-to-Metal Wear, , Most studies on the wear and friction characteristics of plastics have concentrated on, plastic versus plastic or plastic versus steel, wear rings in the same finish and hardness., However, the increased use of aluminum in, structural and bearing components has resulted in available, reliable wear-property, data involving plastics run against aluminum, surfaces. In addition, cost-reduction programs in the business-machine and appliance, industries, which have led to the elimination, of some parts-finishing operations, have resulted in characterizing the action between, rough metal surfaces and plastics., Plastic-to-Plastic Wear, , The wear characteristics of one plastic as, opposed to another vary widely, even among, materials that have good natural lubricity., When an application calls for plastic-toplastic bearings, shafts, gears, or other wear, members, the combination of materials must, be chosen carefully. Because plastics are not, rigid, they do not behave according to the, classic laws of friction. It is these deviations, that cause some of the unexpected results, when plastics are run against metals., Frictional forces are not proportional to, load-friction increases with increasing speed,, and the static coefficient of friction is lower, than its dynamic one. When two viscoelastic, low-modulus materials are run against each, other, additional inconsistencies result., Despite these differences, one trend remains clear. It is the wear factor generated, when TP is run against itself is extremely high,, unless it is operating temperature and pressure are quite low. In applications requiring, all-plastic components, the wear rate can be, reduced, if crystalline plastics are being used,, by running dissimilar plastics against each, other. If amorphous plastics are involved,, or if environmental or manufacturing procedures require that only a single compound be, used, that compound should contain an internallubricant, like PTFE at loadings of 15 to, 20wt%.

Page 430 : 412, , 7 Material Property, , Wear is often greater on a moving surface, when dissimilar NEAT plastics are paired., Similar behavior occurs with pairs consisting, of lubricated, unreinforced plastics running, against themselves or against dissimilar lubricated plastics. The addition of a reinforcing, fiber generally produces increased wear in a, mating, unreinforced plastic. The addition of, reinforcing fibers to both surfaces may result, in decreased wear, compared to that in unreinforced plastics., The wear factors of glass-fiber RPs are, lower than those with carbon-fiber materials, when run against a carbon-reinforced material, because glass fibers are much harder than, carbon ones. Lubricating RPs with PTFE dramatically reduces the wear factors in both, similar or dissimilar mating plastics. During, the initial break-in period a film of PTFE is, transferred to the mating surface, thus creating a PTFE-to-PTFE bearing condition that, lowers the wear factors for both the moving and stationary surfaces. The addition of, a PTFE lubricant to the mating material reduces the detrimental effects of glass fibers,, with respect to wear, on an opposing surface., Selecting Plastic, , Much of the market success or failure of, a plastic product can be attributed to the initial choice of material. Even though the range, of plastics has become large and the levels, of their properties so varied that in any proposed application only a few of the many plastics will be suitable., A compromise among properties, cost, and, manufacturing process generally determines, the material of construction. Selecting a plastic is very similar to selecting a metal. Even, within one class, plastics differ because of, varying formulations, just as steel compositions vary (tool steel, stainless steel, etc.)., There are, of course, products for which no, plastics is satisfactory, and the interests of the, producer and consumer alike are best served, by using some other material., For many applications, however, plastics, have superseded metal, wood, glass, natural, fibers, etc. Many developments in the elec-, , tronics and transportation industries and in, packaging and domestic goods, have been, made possible by the availability of suitable, plastics. Thus comes the question of whether, to use a plastics and if so, which one., As an initial step, the product designer, must anticipate the conditions of use and the, performance requirements of the product,, considering such factors as life expectancy,, size, condition of use, shape, color, strength,, and stiffness. These end use requirements can, be ascertained through market analysis, surveys, examinations of similar products, testing, and general experience. A clear definition of product requirements will often lead, directly to choice of the material of construction. At times incomplete or improper product requirement analysis is the cause for a, product to fail., Whether the product is a new model of an, established commodity or a completely new, development, a list can be made of the properties the material or group of materials to, be employed must possess, and of those that, are also most desirable. By reference to the, relevant material properties and prices, an, analysis can be made to determine the plastic, most likely to be suitable from all requirements., As reviewed within each one of the major, classes of plastics (PE, PVC, PC, etc.) there, are usually a very wide variety of specific formulations, each of which has slightly different, properties and/or processing capabilities at, various costs. Prices, too, will tend to vary depending upon the supplier, the current state, of the market, and the volume of plastic that, the processor is prepared to purchase., Computerized Database, The use of computers in design and related, fields is widespread and will continue to expand. It is increasingly important for designers to keep up to date continually with the, nature and prospects of new computer hardware and software technologies. For example,, plastic databases, accessible through computers, provide product designers with property data and information on materials and

Page 431 : 7 Material Property, processes. To keep material selection accessible via the computer terminal, there are design database that maintain such information, as graphic data on thermal expansion, specific, heat, tensile stress and strain, creep, fatigue,, programs for doing fast approximations of, the stiffening effects of rib geometry, educational information and design assistance, and, more., With the over 35,000 plastics reviewing, what is available as well as keeping up with, the constantly proliferating new and replacement types for a specific set of design requirements can seem daunting. Nevertheless,, with a logical approach to design this can, be done in a practical manner. However, it, would probably be impossible to keep up to, date manually even for the veteran. Manual searching capable of doing the job at an, affordable cost has become difficult to arrange. On-line computerized databases can, cut through this information overload by organizing a material's properties into a manageable format (Appendix A: PLASTICS, DESIGN TOOLBOX). An example of a simplified readout is shown in Table 7-17. Such, programs not only significantly reduce time, but also present a host of new options., Besides doing a relatively fast, efficient, materials search on what is available today,, , 413, , some databases also offer integration with, CAD/CAE/CAM systems to support designing, finite element analysis, processing,, testing, and other programs. To make the, databases more practical and useful, major, international agreements are being arrived at, to set uniform methods for sample preparation and test methods. Basically, numerous, test standards exist that in many cases are, either not in accord with the different data, available or are only regionally., In order to meet the rising demand for information thousands of databases are available worldwide. Nearly all supply technical, literature, economic information, patent references, and manufacturers' addresses. Materials databases with numerical values are a, relatively small part of these programs. Because the majority of these databases are, from individual manufacturers of plastics,, there is only limited comprehensive, neutral, information on most materials in these software programs., The German federalist ministries of the, Economy and of Research and Technology, recognized this situation and during the 1980s, launched programs to assist in the development of comprehensive factual databases., Within this framework, the Deutsches, Kunststoffinstitut (DKI being the German, , Table 7-17 Example of a simplified readout for TPs' toughness or fracture behavior, Izod impact test results, , Material, PMMA, PA, SAN, ABS, CA, HDPE, PA, PB, PC, POM, PP, PTP, PVC, LDPE, PB, TFE, , Polymethylmethacrylate, Polystyrene, Styrene-acrylonitrile copolymer, Acrylonitrile butadienne styrene, Cellulose acetate, High-density polyethylene, Polyamide (Nylon), Polybutene, Polycarbonate, Polyoxymethylene, Polypropylene, Polyethylene terephthalate, Polyvinyl chloride, Low-density polyethylene, Polybutene, Polytetrafluoroethylene, , Unnotched, , Notched, , Brittle, , Brittle, , Ductile, , Brittle, , Ductile, , Ductile

Page 432 : 414, , 7 Material Property, , Plastics Institute) established the materials, database called Polymat. This program brings, greater availability into a plastics market in, which a general perspective is becoming increasingly difficult to obtain. This database, contains information on plastics and elastomers, supplying about thirty to fifty properties for each material. Initially some six, thousand plastics, from about seventy manufacturers, were stored., The concept of the Polymat database was, based on the following criteria: (1) the, data-base is neutral, independent of rawmaterial manufacturers; (2) anyone can use, the database; (3) all the products on the, European market should, if possible, be included; (4) since testing is carried out in accordance with a variety of different international, standards, the relevant standard, as well as, the testing conditions, is registered; (5) during, the search, all properties should be capable, of being linked with one another as desired;, and (6) the sources used for the database, are the technical data sheets and additional information supplied by raw-material, manufacturers, and various lectures, publications, and measured data from different, institutes., In order for such an extensive project to remain manageable, certain requirements were, necessary. Initially the data were confined to, TPs, TSs, TPEs, and casting plastics. To be, included in this group were the TSEs, reinforced plastics, foams, semifinished products, and others. Polymat completed its initial, work in 1989. New plastics products on the, market and updated additional information, on existing products are continually added., Data no longer available are still accessible, to the user in a memory file., Each plastic in this database is first characterized by descriptive data such as its trade, name, manufacturer, product group, form of, supply, or additives. Then follows complex, technical information on each material, with, details of fields of application, recommended, processing techniques, and special features., The central element of this material database, is the numerical values it gives on a wide, range of mechanical, thermal, electrical, optical, and other properties. All these items can, , be searched for individually or in the combination of properties that was the subject of, the enquiry., A number of material suppliers offer information on their products on electronic devices (floppy discs, CDs, etc.) for use on personal computers. An important one, called, Campus, is a database concept started by four, German material manufacturers who use a, uniform software. This database, initially developed jointly by BASF, Bayer, Hoechst,, and Hulls, provided for other manufacturers to join. The present consortium has more, than 50 materials suppliers worldwide. It is, given in the form of diskettes in German,, English, French, Italian, or Spanish. Each, diskette contains the uniform test and evaluation program and the range of the respective material producers. It runs on IBMcompatible personal computers under the, MS-DOS operating system., In order to understand the possibilities of, these two databases, a comparison can be, made of a central database like Polymat and, Campus. The Polymat central database provides the following: (1) all the products of, the various firms represented are included;, (2) the search is independent of the manufacturers and can be performed for all the products of all the manufacturers; (3) available, are not only the values contained in the list, of basic values but other data specified in such, standards as DIN, ASTM, and BS (although a, search can nevertheless be confined to products whose data conform to the list of basic, values); (4) the information is presented only, once and is then maintained centrally; and, (5) a selection can be made between a greater, number of materials and manufacturers., The manufacturers' database, Campus,, provides use that is free of charge and no, charges for data transmission. The actual, value of the table of basic values described, in Campus lies in its effect on the standardization and streamlining oftesting. In the long, term, the nonparticipants in the material market will not be able to remain outside this, development., This comparison shows how these two, electronic information systems are not comparable, because they pursue completely

Page 433 : 7 Material Property, different objectives. The material manufacturers' databases provide information on, products whose manufacturer and product, classes are already known. Polymat also gives, information if the manufacturer and product, classes are not known, but only ifthe requirements with regard to the material can be described. Polymat can also be used if a replacement material is being sought for a product, that can no longer be supplied. Furthermore,, Polymat is also capable, for example, of answering the question of possible manufacturers of nylon 6, or of how many different nylon, 6 grades an individual manufacturer can supply. If only the trade name is known, its manufacturer or distributor can be traced. This, is especially important in the case of foreign, products sold by a trading company under the, same trade name., When Polymat was being established, it, was necessary to decide on whether to charge, the material manufacturer but not the user,, or make no charge to the manufacturer but, charge the user. DKI chose not to charge the, user., Neither database generally offers the possibility of integrating into it the greater number of values and test data that may already, be established by users or processors. These, organizations have data for their own internal use, and their goal has been to integrate, all these types of data sources. Such in-house, databases are at present available under operating system BS 2000 and in conjunction, with the database software known as Adabas., With regard to the common European, market, the European Economic Community (EEe) has undertaken numerous activities concerned with materials and material, information systems. In one demonstration, program for material databases eleven such, databases from various countries in the EEC, are being cooperatively developed with joint, standards for terminology, data presentation,, database access, and the user interface of, search commands, aids, and menus. For the, materials class of plastics, Polymat was selected to participate in this cooperative work., Interesting developments occur from which, the users of central material databases in the, entire EEC area can benefit., , 415, , Electronic marketplacelE-commerce In, addition to the many databases available, and person-to-person contacts, E-commerce, in plastics has been conducted through, suppliers' web sites or the dot-commerce, independent web sites that link material, buyers with sellers in transactions or auction, formats. During the year 2000 five plastic, producers/suppliers and various elastomer, producers/suppliers created a new and, important business model of a joint-venture, web site. It provides multiple companies, to join forces to do business. This is a, strategy some observers call competition, and others regard as just another form of, selling in an electronic format. Regardless, of how it is perceived, the model will help, propel e-commerce into the mainstream, of processor procurement due to the size, and wealth of the companies involved. The, plastic model example is the largest online, business-to-business site todate., The five major TP producers agreed during April 2000 to form a joint-venture web, site offering their materials and related goods, to injection molders. BASF, Bayer, Dow,, DuPont, and Ticana/Celanese signed a letter of intent to form a neutral business-tobusiness market-place focused on delivering, products and related services (including plastics from other suppliers) to injection molders around the globe. The injection molding, market worldwide is a $50 billion/yr. business., This site can also serve other processes like, extrusion., A few days after the above announcement, GE Plastics, a pioneer in the use of the Web,, said that it would enhance the e-commerce, offerings available through its Polymerland, distribution unit. It is targeted to expand the, site beyond transactional e-commerce., Also in existence is the joint-venture web, site for leading elastomers suppliers that include Bayer, CK Witco Corp., DSM Elastomers, DuPont-Dow Elastomers L.L.c.,, Flexsys, M.A. Hanna Rubber Compounding, and Zeon Chemicals L.P. They targeted, to create www.ElastomerSolutious.com. a, global marketplace and customer-focused,, web-based community devoted solely to the, sale of elastomers and associated products.

Page 434 : 416, , 7 Material Property, , During the year 1999 TradeXchange was, formed as a joint-venture web site through, which General Motors, Ford, and DaimlerChrysler source their purchases. Their total, purchases are at $240 billion annually., All this marketplace action of the new, electronic is targeted to enable customers, all over the world to purchase high-quality, TPs, other plastic-related materials, molding, equipment, tooling, maintenance supplies,, packaging materials, and related services., , RAPRA free internet search engine The, number of plastic-related web sites is increasing exponentially, yet searching for relevant information is often laborious and costly., During 1999 RAPRA Technology Ltd., the, UK-based plastics and rubber consultancy,, launched what is believed to be the first free, Internet search engine focused exclusively, in the plastics industry. It is called Polymer, Search on the Internet (PSI). It is accessible at www.polymersearch.com. Companies, involved in any plastic-related activity are, invited to submit their web-site address for, free inclusion on PSI. RAPRA Technology's, Table 7-18(a), , ~, G/R, , Criteria, , R~sin, , Groups, , Styrcnics, ABS, SAN, Polyslyrene, , Olefins, Polyethylene, Polypropylene, , Other Crystalline, Resins, Nylon., , 6, 616, 6110.6112, Polyester, Poly.cet.1, Aryl.tes, PPO, Polycarbonatc:, Polysulfonc, PolyethcrsulCone, M~ified, , High Temp. Resins, PPS, , Polyamide-imide, , Fluorocarbons, FEP, , ETFE, , Selection Worksheet, Selecting an optimal material for a given, product must obviously be based on analysis, of the requirements to be met. A simplified, approach involves comparing the specific service requirements to the potential properties, of a plastic. What follows is a simplified but, practical material-selection approach. This, "longhand" system is a basis of the fastest, computerized databases., It follows these steps: (1) select the design, criteria from a worksheet [Table 7 -18( a)] and, check off only the major criteria across the, worksheet, keeping it simple but realistic; (2), refer to the selection chart [Table 7-18(b)], and transfer the bold-faced numerical rating, in each selected criteria column to the worksheet, for example, if toughness is one criterion, list 6, 4, 1,2,4, and 2 on the worksheet, from top to bottom in the toughness column;, (3) add up the numbers across the worksheet, , Selection worksheet, Strength, , Material, Char41ctcri.slic§, , USA office is in Charlotte, NC (tel. 704-5714005)., , In~, , Short-Tenn Long·Tenn, licit, Heat, , Sliffness Tuulthness ResistanC1:, , Resistance, , Environmenial, Resistance, , Wear and, Dimensional, Accuracy in Dimensional Frictional, Molding, Stability, Properties, , Point, Subtotal, , Point, Cost, , Tot.1

Page 435 : 7 Material Property, Table 7-18(b), Design, Criteria, , Glass-reinforced TP compound selection sheet, Strength, and, Stiffness, , Styrenics, ABS, SAN, Polystyrene, , Olefins, Polyethylene, Polypropylene, , G/R, Resin, Groups, , Other Crystalline, Resins, Nylons, 6, 616, 6110. 6112, Polyester, Polyacetal, , Long-Tenn, Heat, , Toughness, , Short-Tenn, Heat, Resistance, , 3, , 6, , 6, , 6, , 5, , 4, , 4, , 5, , 2, I, 3, , 4, , 5, , 1, , Arylates, , Modified PPO, Polycarbonate, Polysulfone, Polyelhersutfone, High Temp. Resins, PPS, Polyamide-imide, , Fluorocarbons, FEP, , ETFE, , 417, , 4, , 2, , 3, 2, 6, , 2, 3, 1, 4, , 5, 3, 1, 2, 3, , 1, 2, , 1, , 2, 4, 2, , 1, 3, 2, 5, 4, 3, 2, 1, 2, 1, 2, 1, , 2, 3, 1, 2, , Resistance, , 2, I, 3, 1, 2, 4, 3, 2, 1, 2, , 4, 3, 1, 1, , Environ~, , Dimensional, , mental, Resistance, , Accuracy, , in Molding, , 3, 4, , 2, , 1, 2, , 4, , 5, 1, 2, 2, 2, 3, , 4, , 4, , 5, 2, 1, , Frictional, Propenics, , 5, 5, , 1, , 6, 3, 5, 4, 3, 2, 1, , Wear and, , Dimensional, Stability, , 4, 3, 2, 1, 2, 4, 3, 2, 1, , 2, 3, , 1, , 1, 2, , 4, , 2, , 2, 1, , 6, , 2, 1, , 4, 2, 1, 6, , Cost, , 6 ~2, 3 11, 3, 2, 3, 4, 1, 4, 3, , 2, 1, , 1, 2, , :3, 2, , 2, , 1, , 4 !4, 4 ;5, 1 :6, , Rllinls: I-mosl desirable; 6-IClJI desirable. Large numbcn indicate aro\lp classification. srmll numbers the specific resins within that IrouP., , in Table 7-18(a) to the "point subtotal" column to find the plastic group with the lowestpoint subtotal, that will be the best for a given, application on a performance basis; (4) add, in the cost factor and total it, to find again, the plastic group with the lowest number,, again the best for the application on a costperformance basis., Finally, repeat the first four steps, but this, time use the small numbers on the selector, chart and only for the plastic group that was, found to be the best. The plastic with the lowest final total will be the best for the application on a cost-performance basis., Such a selector worksheet can include specifically what the designer requires, with appropriate numerical ratings. Tables 7-18(c), and 7-18(d) provide examples of how to use, these simplified worksheets in evaluating different products., , Other Guide, The material information and data presented in this chapter and other sections, , have provided a variety of useful selection, guides; they are assembled in the INDEX under Selection gnide. Additional guides are in, Tables 7-19 to 7-27_1t should be remembered, that the values given here and elsewhere in, this book are representative rather than precise_ These values vary depending on the, specific type of material, the manufacturing process, and the condition and method, of testing. Thus, for example, the tensile, strength of a PC given in one table could be, quite different from that in another table. The, procedure to follow is to properly identify a, plastic, usually by its manufacturer's name,, its trade name, the manufacturer's grade or, identification listing, and by what its data, sheet says about its properties., , Preliminary Consideration, The remainder of this chapter provides a, summary overview on plastic materials. This, section reviews different types of plastics. The, descriptions are brief listing a few of their, main characteristics. Details cannot be included since so many different formulations

Page 436 : 418, , 7 Material Property, Gasoline powered chain-saw housing resulting in Nylon 6 ot 6/6, , Table 7-18(c), Malerial, Characteristics, , Strength, and, Sliffness, , Toughne.s, , Short-Term, Heal, Resisfance, , Long-Term, Hea', Resislancc, , Environ.., , Dimensional, , men,al, Resistance, , Accuracy, in Molding, , Dimensional, Slabilily, , We.. and, Frictional, Properties, , Point, , Poinl, , Subto.al, , Cos,, , Total, , ~, , x x, , x, , x, , 3, , 6, , 6, , 6, , 21, , Olefins, Polyelhylene, Polypropylene, , 5, , 4, , 4, , 3, , 16 1 17, , ::a, Resin, , Groups, , Styrcnics, ABS, SAN, Poly.lyrene, , 2 23, , Olher Crystalline, , Resins, Nylons, , 1, , 6, 616, 6110, 6112, Polyester, Poly..e ••1, , 4, , 5, , 2, 3, I, 4, 5, , 1, , 2, I, 3, , 2, , 4, , 4, , I~, , 2, 5, , 2, , 3 ::11, , 8, , 10, 12, 16, , 3, , 4, I, , 14, IJ, 17, , Arylale., , Modified PPO, Polycarhonale, Polysulfone, Polyelhenulfone, High Temp. Resin., PPS, Polyamide-imide, , 3, , 2, , 3, , 5, , 13 4 17, , 2, , 4, , 1, , 2, , 9 5 14, , 6, , 2, , 2, , 1, , Fluorocarbons, , FEP, , ETFE, , Charac1eristics, , Slrenglh, and, Sliffnes., , ~ x, SAN, , Short-Tenn, Heal, , Long-Tenn, He.1, , Resistance, , Resistance, , Environ-, , Dimensional, , menIal, Resistance, , Accuracy, in Molding, , Dimensional, Stabilily, , We", and, , Frictional, , Painr, , Properties, , Subtolal, , Co.., , Poinl, TOlal, , 2, , 23, , x, , x, , 3, , 6, , 6, , 6, , 21, , 5, , 4, , 5, , 3, , 17 1 18, , 1, , 2, , 4, , 4, , 11, , 3, , 3, , 3, , 5, , 14 4 18, , 2, , 1, , 2, , :6, , 6, , 2, , 1, , 10 6 16, , Cnlen., , ReslD, Groups, , Slyrenic., ABS, , Toughness, , x, , 'ign, , (lI~, , 6 17, , Impeller for chemical handling pump resulting in PPS, , Table 7-18(d), Malerial, , 11, , PolySlyfene, Olefin., Polyelhylene, PolypropylCJl!', Other Crystalline, Resins, Nylons, 6, , 616, 6110,6112, Polyesler, Polyacctal, , 3 14, , Arylale., , Modified PPO, Polyearbonare, Polysulfone, Polyelhenulrone, High Temp. Resins, , PPS, , Polyamide-Imide, , 2, , 2, I, , 1, , I, 2, , Fluorocarbons, , FEP, ETFE, , 1, , ~5 ~11

Page 437 : 419, , 7 Material Property, Table 7-19, , Example of the range of mechanical properties for plastics, , THERMOPLASTIC ELASTOMERS, POL YMETHYlPENTENE, POL YBUTYLENE, FURAN, SILICONE, POLYETHYLENE. COPOLYMERS, CELLULOSICS, THERMOSET POl VESTER, AL)(YD, VINYL ESTER, NYLON IINCLUDING AROMATICSI, THERMOPLASTIC POLYESTERS, IINCLUDINQ AROMATICS), POLYCARBONATESI ALLOYS, POt. YSULFONES, POl YSTY RENE I COPOLYMeRS, (EXcePT ASS), EPOXy, POLYPHENYLENE SULFIDE, , THERMOSET POL VESTER, ALKYD, VINYL ESTER, NYLON (INCLUDING AROMATICSI, POLYIMIOES, POLYAMIDE-IMIDES, THERMOPLASTlC POLYESTERS, (INCLUDING AROMATICS), POL YSULfOHES, POLYSTYRENE I COPOLYMERS, (EXCEPT ADS), , PoLVACETAL, PHENOLIC, , PHENOlIC, , Aas, , "'0 BASED, POt,..YIMIDES, , EPOXY, , POLYURETHANE, PVC. CCPOL YMERS, , FLUOROI"LASTIC I CCPOL YMERS, POL YPAQPYLENE, PHENOLIC, , ASS, , EPOXY, , POLYSTYRENE, THERMCPLASTIC POLYESTERS, POLYAMIDE-IMIDES, POLYIMIOES, ALKYD, VINYL ESTER, , POL. YPHENVLENE SULFIDE, , ppaBASED, UREAS, PVC • COPOLYMERS, , POL VaU'TYLENES, THERMQlLASTtC ELASTOMERS, FLUOAOP'LASTlCS, , NYLONS, , CELLULOSICS, POI.. VTHYLEHE • COPOLYMERS, POLYURETHANE, , PVC. CCPDI.."MERS, , EPOXY, THERMOSETTING POL YE$TERS, ALKYDS, , VINYL ESTERS, , POL VPROPYLENE, POL YCA"BONATE, MELAMINES, PHENOliC, POLYIMIDE, ALLYLS, ACRYLIC, , ASS, P'POBASED, PQLYARYL ETHOR, GL.ASS-REINFORCED SILICONE, POL YSTYREHE, YMERS, , ca-ex., , MELAMINE, , are available that in turn provide many different characteristics. They are available via, hard copy or software and kept up to date by, material suppliers and other organizations., Should a need arise for data at conditions different from those available for the design, it, would not be too difficult or costly to obtain, the needed information., As a general rule, it is considered desirable to examine the properties of three or, more materials before making a final choice., Material suppliers should be asked to participate in type and grade selection so that, their experience is part of the input. The technology of manufacturing plastic materials, as, with other materials (steel, wood, etc.) results, in that the same plastic compounds supplied, from various sources will generally not deliver the same results in a product. As a matter of record, even each individual supplier, furnishes their product under a batch number, so that any variation can be tied down to, the exact condition of the raw-material production. Taking into account manufacturing, tolerances of the plastics, plus variables of, equipment and procedure, it becomes apparent that checking several types of materials, from the same and/or from different sources, is an important part of material selection., , Experience has proven that the so-called, interchangeable grades of materials have to, be evaluated carefully by the designer as to, their affect on the quality of a product. An, important consideration as far as equivalent, grade of material is concerned is its processing characteristics. There can be large differences in properties of a product and test data, if the process ability features vary from grade, to grade. It must always be remembered that, test data have been obtained from simple, and easy to process shapes and do not necessarily reflect results in complex product, configurations., The problem of acquiring complete knowledge of candidate material grades should be, resolved in cooperation with the raw material suppliers. It should be recognized that, selection of the favorable materials is one of, the basic elements in a successful productconfiguration design, material selection, and, conversion into a finished product (Appendix, A: PLASTICS DESIGN TOOLBOX)., Individual families of plastics such as polyolefins, polystyrenes, nylons, and polyvinyl, chlorides are compounded to produce many, different individual plastics. The polyolefin, is actually made up of its families of polyethylenes, polypropylenes, etc. In turn the

Page 440 : 422, Table 7·22, , 7 Material Property, Examples of plastics' extreme temperature applications, Comments, , Polymer, Polyphenyls, Polyphenylene oxide, Polyphenylene sulfide, Polybenzyls; polyphenethyls, Parylenes (poly-p-xylylene), Polyterephthalamides, Polysulfanyldibenzamides, Polyhydrazides, Polyoxamides, Phenolphthalein polymers, Hydroquinone polyesters, Polyhydroxybenzoic acids, Polyimides, Polyarylsiloxanes, eaxboranes, Polybenzimidazoles, Polybenzothiazoles, Polyquinoxalines, Polyphenylenetriazoles, Polydithiazoles, Polyoxadiazoles, Polyamidines, Pyrolyzed polyacrylonitrile, Polyvinyl isocyanate ladder, polymer, Polyamide-imide, Polysulfone, Polybenzaylene benzimidazoles, (pyrrones), , Decompose at 530°C (986°F); infusible, insoluble polymers., Decomposes close to 500°C (932°F); heat cures above 150°C, (302°F) to elastomer; usable heat range -135 to 18SOe, (-211 to 36SOF), Melts at 270 to 315°C (578 to 599°F); cross-linked polymer stable, to 450°C (842°F) in air; adhesive and laminating applications., Fusible, soluble, and stable at 400°C (752°F); low molecular weight., Melt above 520°C (968°F); insoluble; capable of forming films;, poor thermal stability in air; stable to 400 to 525°C, (752 to 977°F) in inert atmosphere., Melting points up to 455°C (851°F); fibers have good tenacity,, elongation, modulus., Melting points up to 330°C (626°F); soluble; good fiber properties., Dehydrate at 200 e (392°F) to over 400°C (752°F) to form, polyoxadiazoles; good fiber properties., Some melting points above 400°C (752°F); give clear, flexible films., Melting points of 300°C (572°F) to over 400°C (752°F); formable, into fiber and film., Soluble polymers with melting points of 33SOe (635°F) to over, 400°C (752°F)., Films melt at 380 to 450°C (716 to 842°F); stable to oxidation but, not to hydrolysis; tough, flexible films; good thermal stability., eommerical film, coating, and resin stable up to 600°C (1,112°F);, continuous use up to 300°C (572°F)., Good thermal stability 400 to 500°C (752 to 932°F); coatings,, adhesives., Stable in air and nitrogen at 400 to 450°C (752 to 842°F);, elastomeric properties for silane derivatives up to 538°C, (I,OOO°F); adhesives., Developmental laminating resin, fiber, film; stable 24 hours at, 300°C (572°F) in air., Stable in air at 600°C (1,112°F); cured polymer soluble in, concentrated sulfuric acid., Stable in air at 500°C (932°F); tough, somewhat flexible resins;, make film, adhesive., Thermally stable to 400 to 500°C (752 to 932°F); make film,, fiber, coatings., Decompose at 525°C (977°F); soluble in concentrated sulfuric acid., Decompose at 450 to 500°C (842 to 932°F); can be made into, fiber or film., Stable to oxidation up to 500 a e (932°F); can make flexible, elastomer., Stable above 900°C (1,625°F); fiber resists abrasion with, low tenacity., Soluble polymer that decomposes at 385°C (725°F); prepolymer, melts above 405°C (761°F)., Service temperatures up to 288°C (550°F); amenable to, fabrication., Thermoplastic; use temperature -102°C ( -152°F) to greater than, 150°C (302°F); acid and base resistant., Thermally stable to 600°C (1,112°F); insoluble in common, solvents; good mechanical properties., (Continues), G

Page 441 : 423, , 7 Material Property, Table 7-22, , (Continued), Polymer, , Comments, , Polybenzoxazoles, , Stable in air to 500°C (932°P); insoluble in common solvents except, sulfuric acid; nonflammable; chemical resistant; film., High melt and tensile strength; tough; resilient; oil and solvent, resistant; adhesives, coatings., Thermoplastic up to 350°C (662°P); thermosetting at 357°C (707°P);, cured material has good thermal stability to 500°C (932°P);, amenable to fabrication., Soluble B-staged material; amenable to fabrication; good thermal, stability., Retention of properties in air up to 399°C (750 P)., Polymers stable to better than 400°C (752°P)., Soluble; high molecular weight; infusible; improved tensile strength;, high thermal stability to 525°C (977°P) in air; film forming., , Ionomer, Diazadiphosphetidine, Phosphorous amide epoxy, Phosphonitrilic, Metal polyphosphinates, Phenylsilesesquioxanes, (phenyl-T ladder polymers), , Table 7-23, , 0, , Examples of tensile stress relaxation of TP RPs at elevated temperatures, Decrease in Applied Stress (%) with Time* at Temperature, , Base, Resin, , Glass, (wt%), , 73°P, (23°C), , 200 P, (93.3°C), , 300 P, (149), , 350 P, (176), , 400 P, (204), , 450 P, (232), , PES, PEl, PPS, PEEK, PEEK, HTA, PEK, , 30, 30, 40, 30, 40t, 30, 30, , 7/8/9, 7/9/11, 3/5/9, 13/14/16, 19/21125, 7/7/8, 12/13115, , 20/21125, 13/16/25, 20/21122, 17/21123, 21123/27, 14/16/22, 15/18/20, , 33/35/39, 32/34/38, 26/27/28, 25/28/30, 29/32/37, 23/27/35, 18/21124, , 35/40/57, 34/39/55, 26/28/32, 28/32/35, 33/35/40, 30/35/50, 23/25/29, , 61174/90, 58/69/86, 26/33/34, 30/33/40, 35/37/42, 39/47/59, 26/27/30, , XlXIX, XlX/X, XIX/X., 32/38/40, 36/38/43, 45/63/55, 27/28/31, , 0, , 0, , 0, , 0, , 500 P, (260), 0, , 0, , XlXIX, XlXIX, X/XIX, 32/38/41, 38/39/44, XlX/X, 28/29/32, , *Three values indicate percent stress relaxation for 1 h, 5 h, and 15 h. Example: 7/8/9 indicates 7% at 1 h, 8% at 5 h,, and 9% at 15 h., tLong-carbon (Verton) composite (ICI-LNP). X indicates sample would not sustain the test load. Initial stress for, all tests was 2,500 psi., , How They Rank in Stress Relaxation, , Temperature (OF), Base, Resin, , Glass, (wt%), , 73, (23°C), , 200, (93.3), , 300, (149), , 350, (176), , 400, (204), , 450, (232), , 500, (260), , PES, PEl, PPS, PEEK, PEEK, HTA, PEK, , 30, 30, 40, 30, 40*, 30, 30, , 3, 4, 1, , 6, 5, , 6, 5, 2, , 7, 6, 2, , 7, 2, 1, , 7, , 3, 4, , 1, , 5, 1, , X, X, 2, 3, 4, 5, 1, , X, X, X, 2, 3, 4, 1, , X, X, X, 2, 3, X, 1, , 6, 7, 2, 5, , 3, 4, , 3, , 4, , The lower the number, the higher the retained stress at the indicated temperature., *Long-carbon (Verton) composite (ICI-LNP).

Page 442 : 7 Material Property, , 424, Table 7-24, , Overview of plastics' chemical resistance, , FLUOROPLASTICS, POLYIMIDES, POLYOLEFINS, ACETALS, POLYPHENYLENE SULFIDE, ALLYLS, EPOXIES, IONOMERS, POLYAMIDE·IMIDE, , Table 7-25, , POLYESTERS (TP "TS), SILICONES, PHENOLICS, POLYSULFONES, NYLONS, VINYLS, POLYURETHANES, ACRYLICS, ALKYDS, STYRENE·ACRYLONITILE, AMINOPLASTICS, POLYARYL ETHER, POLYARYL SULFONE, , STYRENICS, CELLULOSICS, POLYCARBONATE, , Examples of qualitative plastics environmental ratings, , Material Family, , Abrasion, Resistance, , Weather, Ability, (Natural), , Paint, Ability', , ABS, Acetal, Acrylic, Allyl, ASA, Cellulosic, Epoxy, Fluoroplastic, Melamine-formaldehyde, Nylon, Phenol-formaldehyde, Poly (amide-imide), Polyarylether, Polybutadiene, Polycarbonate, Polyester (TP), Polyester-fiberglass (TS), Polyethylene, Polyimide, Polyphenylene oxide, Polyphenylene sulfide, Polypropylene, Polystyrene, Polysulfone, Polyurethane (TS) (TP), SAN, Silicone, Styrene butadiene, Urea formaldehyde, Vinyl, , F, G, P, G, F, F-P, G, G, G, G, G, VG, G, G, F, G, G, G, VG, G, G, G, P, G, VG, F, F, G, G, G, , F-P, F, G, F, P, F-G, F, E, F-G, F-P, G, F, F, F-G, F, F, G, P, F-P, F-G, G, F-P, F-P, F-P, E-G, F, VG, G, F, G, , No, No, No, No, No, No, Yes, No, Yes, Yes, Yes, No, No, No, No, No, Yes, No, No, Yes, No, No, No, No, No, No, No, No, Yes, No, , Transparent, , Translucent, , Yes, Yes, Yes, , Yes, , Yes, Yes, Yes, Yes, Yes, Yes, Yes, Yes, Yes, Yes, Yes, Yes, , Yes, Yes, Yes, , Yes, Yes, Yes, Yes, Yes, Yes, Yes, , 'Those with "No" require special paint, primer, or prepainting surface preparation., Code: E = Excellent; VG = Very Good; G = Good; F = Fair; P = Poor., , Yes, Yes, Yes

Page 443 : 425, , 7 Material Property, Table 7-26, , Examples showing permeability of plastics, , Type of Polymer, ABS (acrylonitrile butadiene, styrene), Acetal-homopolymer and, copolymer, Acrylic and modified acrylic, Cellulosics acetate, Butyrate, Propionate, Ethylene vinyl alcohol copolymer, Ionomers, Nitrile polymers, Nylon, Polybutylene, Polycarbonate, Polyester (PET), Polyethylene, Low density, Linear low density, Medium density, High density, Polypropylene, Polystyrene, General purpose, Impact, SAN (styrene acrylonitrile), Polyvinyl chloride, Plasticized, Unplasticized, Polyvinylidene chloride, Styrene copolymer, (SMA) Crystal, Impact, , Specific Gravity, (ASTMD 792), , Water Vapor, Barrier, , Gas Barrier, , Resistance to, Grease and Oils, , 101-1.10, , Fair, , Good, , Fair to good, , 1.41, , Fair, , Good, , Good, , Fair, Fair, Fair, Fair, Fair, Good, Good, Varies, Good, Fair, Good, , Fair, Fair, Fair, Very good, Fair, Very good, Varies, Fair, Fair, Good, , Good, Good, Good, Good, Very good, Good, Good, Good, Good, Good, Good, , Good, Good, Good, Good, Very good, , Fair, Fair, Fair, Fair, Fair, , Good, Good, Good, Good, Good, , 1.04-1.08, 1.03-1.10, 1.07-1.08, , Fair, Fair, Fair, , Fair, Fair, Good, , Fair to good, Fair to good, Fair to good, , 1.16-1.35, 1.35-1.45, 1.60-1.70, , Varies, Varies, Very good, , Good, Good, Very good, , Good, Good, Good, , 1.08-1.10, 1.05-1.08, , Fair, Fair, , Good, Good, , Fair, Fair, , 1.1-1.2, 1.26-1.31, 1.15-1.22, 1.16-1.23, 1.14-1.21, 0.93--0.96, 1.12-1.17, 1.13-1.16, 0.91--0.93, 1.2, 1.38-1.41, 0.910--0.925, 0.900--0.940, 0.926-0.940, 0.941--0.965, 0.900--0.915, , materials in a family could have extremely, different properties; some having relatively, opposite properties. This action results in, having one family, such as polyethylene with, its relatively many thousands of formulations,, having all kinds of properties. This is an excellent situation since it can be said; "there is, a plastic for your design.", In the following list of materials brief explanations of performances and limited applications are given for a few of the different, plastics. What is presented will provide some, degree of familiarity with the variations of, properties existing in the different plastics., Throughout this book many different properties are reviewed. The order in which the following descriptions of plastics are arranged, , are alphabetically with TPs in the first list followed by the TS plastics., , Thermoplastic, TPs come in greater variety than TSs. They, also tend to be more readily to specialty compounding as copolymers, multipolymers, alloys and blends, often customized for costeffective adaptation to specific application, requirements. Unlike TSs, they are in most, cases reprocess able without serious losses of, properties., When compared to TSs, they can have limitations of heat-distortion temperatures, cold, flow and creep, and are more likely to be

Page 444 : 7 Material Property, , 426, Table 7-27, , Guide to elastomers vs. performances, , TSEs, High Cost, , Fluouroelastomer, Acrylate, Epichlorohydrln, Nltfl7e, Chlorosulfonsted Polyethylene, Polychloroprene, EPOM, Butyl Rubber, Natural Rubber, SBR, , Low Cost, , Low Performance, Commodity, , Special Purpose, , High Performance, Specialties, , TPEs, High Cost, , Polyamides, Copo/yesters, Urethanes, Elsstomeric Alloys, Olefinic Blends, , Low Cost, , Styrenics, Low Performance, Commodity, , Special Purpose, , damaged by chemical solvent attack from, paints, adhesives, and cleaners. When injection molded, dimensional integrity and ultimate strength are more dependent on the, proper process control molding parameters, than is generally the case with TSs (where, cross-linking offset such problems)., Acetal This crystalline plastic is strong,, stiff, and has exceptional resistance to abrasion, heat, chemicals, creep and fatigue. With, a low coefficient of surface friction, it is especially useful for mechanical products such as, gears, pawls, latches, cams, cranks, plumbing, parts, etc. It is chrome platable., Acrylic These polymethyl methacrylate, (PMMA) plastics have high optical clarity,, , High Performance, Specialties, , excellent weatherability, very broad color, range, and hardest surface of any untreated, thermoplastic. Chemical, thermal and impact properties are good to fair. Normally, an exterior material used as optical lenses,, automotive taillights, decorative nameplates,, aircraft glazing, illuminated signs, medical devices, etc. Used as an opaque colored sheeting thermoformed to produce an outer coating behind which glass-fiber-reinforced TS, polyester plastics are sprayed to produce, camper tops, swimming-pool steps, plumbing, fixtures with weatherability and repairability, reported superior to polyester gel coats. Like, plywood, there are outdoor weather resistant grades and indoor nonweather resistant, grades. (Plastic used in plywood determines, their outdoor grade.)

Page 445 : 7 Material Property, Acrylonitrile-butadiene-styrene ABS is a, terpolymer that provides a tough, hard, rigid, plastic with adequate chemical, electrical and, weathering characteristics, low water absorption, and resistance to hot-and-cold water cycles. Used for electronic instrument housings,, telephones, sports gear, automotive grilles,, and furniture. It is electroplatable, good as, a structural foam, and available as a tinted, transparent., Cellulosic They are tough, transparent,, hard or flexible natural polymers made from, plant cellulose feedstock. With exposure to, light, heat, weather and aging, they tend to, dry out, deform, embrittle and lose gloss., Molding applications include tool handles,, control knobs, eyeglass frames. Extrusion, uses include blister packaging, toys, holiday decorations, etc. Cellulosic types, each, with their specialty properties, include cellulose acetates (CAs), cellulose acetate butyrates (CABs), cellulose nitrates (CNs),, cellulose propionate (CAPs), and ethyl, celluloses (Ee)., Chlorinated polyether They are corrosion, and chemical resistant whose prime use has, been to fabricate products and equipment, for the chemical and its processing industries., Uses also include pumps, water meters, bearing surfaces, etc., , 427, , Expandable polystyrene EPS is a modified PS prepared as small beads containing, pentane gas which, when steamed, expand to, form lightweight, cohesive masses for forms, used to mold cups and trays, package fragile products for shipment, etc. Similar dimensionally stable forms molded from EPS are, used as cores for such products as automobile sun visors with surface overlays, etc., Fluoroplastic FPs have superior heat and, chemical resistance, excellent electrical properties, but only moderate strength. Variations include PTFE, FEP, PFA, CTFE,, ECTFE, ETFE, and PVDF. Used for bearings, valves, pumps handling concentrated, corrosive chemicals, skillet linings, and as a, film over textile webs for inflatables such, as pneumatic sheds. Excellent human-tissue, compatibility allows its use for medical, implants., Ionomer They are in the polyolefin family. Their inter chain ionic bonding distinguished them from the other plastics. Performances include being extremely tough, very, high tensile strength, and excellent abrasion, resistance. Clarity, strength, and good adhesion of ionorner films to metal surfaces are the, important properties that have led them into, its widespread use in food packaging. Often, as a heat-seal layer in TP structures (coextruded films, etc.)., , Chlorinated polyethylene CPEs provide, a very wide range of properties from softl, elastomeric to hard. They have inherent oxygen and ozone resistance, have improved, resistance (compared to PEs) to chemical, extraction, resist plasticizers, volatility, and, weathering. Products do not fog at high temperatures as do PVCs and can be made flame, retardant., , Nylon (Polyamide) PA is a crystalline, plastic and the first and largest consumption, of the engineering thermoplastic. This family, of TPs are tough, slippery, with good electrical properties, but hygroscopic and with, dimensional stability lower than most other, engineering types. Also offered in reinforced, and filled grades as a moderately priced metal, replacement., , Ethylene-vinyl acetate EVAs (in the polyolefin family) have exceptional barrier properties, good clarity and gloss, stress-crack resistance, low temperature toughnesslretains, flexibility, adhesion, resistance to UV radiation, etc. They have low resistance to heat and, solvents., , Parylene The melting point of these film, and coating plastics ranges from 290 to 400°C, (554 to 752°F), and Tg from 60 to lOO°C (14, to 212°F). Their cryogenic performances are, excellent. Physical properties are unaffected, by thermal cycles from 2°K to room temperature. Good thermal endurance in air, absence

Page 446 : 428, , 7 Material Property, , of air, and inert atmosphere. They are generally insoluble up to 150°C (302°F). Weather, resistance is poor., Phenylene oxide Based (PPO) plastic that, is a choice for electrical applications, housings for computers and appliances, both neat, and in structural foam form. It has superior dimensional stability, moisture resistance, due to styrene components, which, however,, cause some sacrifice of weather and chemical resistance. Use includes automobile wheel, covers, pool plumbing, consumer electronic, external and internal components., Polyarylate It is a form of aromatic, polyester (amorphous) exhibiting an excellent balance of properties such as stiffness,, UV resistance, combustion resistance, high, heat-distortion temperature, low notch sensitivity, and good electrical insulating values., It is used for solar glazing, safety equipment,, electrical hardware, transportation components and in the construction industry., Polybutylene It is a polyolefin used for, cold and hot water piping. As a blown film, it is used for food packaging., Polycarbonate It is a tough, transparent, plastic that offers resistance to bullets and, thrown projectiles in glazing for vehicles,, buildings, and security installations. It with, stands boiling water, but is less resistant to, weather and scratching than acrylics. It is, notch-sensitive and has poor solvent resistance in stressed molded products. Use includes coffee makers, food blenders, automobile lenses, safety helmets, lenses, and many, nonburning electrical applications., Polyester, thermoplastic TP polyesters, have different grades. Polybutylene terephthalate (PBT) a crystalline polymer and, an excellent engineering material. It has, marginal chemical resistance but resists moisture, creep, fire, fats, and oils. Molded items, are hard, bright colored, and retain their impact strength at temperatures as low as -40°F, (-40°C). Uses include auto louvers, underthe-hood electricals, and mechanical parts., , Polyethylene terephthalate (PET) an amorphous polymer is available in an engineering, grade. It is extensively used in beverage bottles and films., Polyetheretherketone PEEK is a hightemperature, crystalline engineering TP used, for high performance applications such as, wire and cable for aerospace applications,, military hardware, oil wells and nuclear, plants. It holds up well under continuous, 450°F (323°C) temperatures with up to 600°F, (316°C) limited use. Fire resistance rating is, UL 94 V-O; it resists abrasion and long-term, mechanical loads., Polyetherimide This is an engineering, amorphous thermoplastic. It has superior, strength, heat resistance, flame resistance,, UV resistance and is transparent, although, of amber brown color. Solvent resistance is, especially good against aircraft grade fuels, and lubricants, but methylene chloride and, trichloroethane attack it. Resistance to creep, at lower stress loadings and good retention of, strength at sustained high levels of heat are, claimed to exceed those of other high performance engineering thermoplastics. Applications include printed circuit boards, heater, housings, electrical components, steam sterilizable disposable and reusable parts., Polyethylene PEs are the leading plastics family in total volume sold worldwide., These polyolefin materials are relatively inexpensive, easy to process and so versatile, that they dominate the packaging and disposable fields. Crystalline in structure, they are, varied by chain length, or molecular weight, into low density (LDPE), linear low density (LLDPE), medium density (MDPE),, high density (HDPE) ultra high density, (UHMWPE), etc. There are also cross-linked, polyethylene (XLPE) that by chemical or irradiation treatment becomes a TS with outstanding heat resistance and strength. As a, family PEs are strong and flexible, very highly, chemical resistant, and require special treatments to cement or paint. All kinds of markets use them with packaging being its major, outlet. They are blow molded into containers

Page 447 : 7 Material Property, and bottles and molded into boxes, buckets,, etc. They are extruded for films, trash bags,, and laminated coatings., Polyimide It is a high-cost heat and fire resistant plastic, capable of withstanding 500°F, (260°C) for long periods and up to 900°F, (482°C) for limited periods without oxidation. It is highly creep resistant with good low, friction properties. It has a low coefficient of, expansion and is difficult to process by conventional means. It is used for critical engineering parts in aerospace, automotive and, electronics components subject to high heat,, and in corrosive environments., Polyphenylene sulfide PPS is able to resist, 450°F (232°C), and has good low temperature, strength as well. It has low warpage, good dimensional stability, low mold shrinkage. Use, includes hair dryers, cooking appliances, and, critical under-the-hood automotive and military parts., Polypropylene One of the high volume, plastics has superior resistance to flexural fatigue stress cracking, with excellent electrical, and chemical, properties. This versatile polyolefin overcomes poor low temperature performance and other shortcomings through, copolymer, filler, and fiber additions. It is, widely used in packaging (film and rigid), and, in automobile interiors, under-the-hood and, underbody applications, dishwashers, pumps,, agitators, tubs, filters for laundry appliances, and sterilizable medical components, etc., Polystyrene One of the high volume plastics, is relatively low in cost, easy to process,, has sparkling clarity, and low water absorption. But basic form (crystal PS) is brittle,, with low heat and chemical resistance, poor, weather resistance. High impact polystyrene, is made with butadiene modifiers: provides, significant improvements in impact strength, and elongation over crystal polystyrene, accompanied by a loss of transparency and little other property improvement. PS is used, in many different formulations., , 429, , Polysulfone It is a high performance, amorphous plastic that is tough, highly heat, resistant, strong and stiff. Products are transparent and slightly clouded amber in color., Material exhibits notch sensitivity and is, attacked by ketones, esters, and aromatic, hydrocarbons. Other similar types in this, group include polyethersulfone, polyphenylsulfone, and polyarylsulfone. Use includes, medical equipment, solar-heating applications and other performance applications, where flame retardance, autoclavability and, transparency are needed., Polyurethane, thermoplastic TPU has excellent properties except for heat resistance, (usually only up to 250°F 121°C). It is used, in alloys with ABS or PVC for property enhancement. Typical uses are in automobile, fascias and exterior body parts, tubing, cord,, shoe soles, ski boots and other oil and wear, resistant products., Polyvinyl chloride PVCs are high-volume, plastics extensively used that are low in, cost with moderate heat resistance and good, chemical, weather and flame resistance. They, qualify for packaging, pipe and outdoor construction products (siding, window profiles,, etc.), and a host of low-cost disposable products (including FDA-grade medical uses in, blood transfusion, storage, etc.). PVCs come, in a variety of grades, flexible to rigid. They, are tough, can be transparent (as in blow, molded bottles and jugs), and are also a, good alloying plastic to improve properties, and reduce costs (ABS/PVC, etc.). There, are polyvinyl acetates (PVAs), polyvinyl, alcohols (PVAs), polyvinyl butrals (PVBs),, chlorinated PVCs, etc., Styrene-acrylonitrile Related to ABS,, SAN is hard, rigid, and transparent. It has, no butadiene. Excellent chemical and heat, resistance, good dimensional stability, and, ease of processing characterize it. Special, grades are available that have improved, UV stability, vapor-barrier characteristics,, and weatherability. SAN is used for tinted, drinking glasses, low-cost blender jars and, water pitchers, and other consumer goods

Page 448 : 430, , 7 Material Property, , with longer life expectancies than ordinary PS., Styrene maleic anhydride SMA is a, copolymer made with or without rubber, modifiers. They are sometimes alloyed with, ABS and offer good heat resistance, high impact strength and gloss but with little appreciable improvement in weatherability or, chemical resistance over other styrene based, plastics., Thermoset Plastic, Alkyd They are easy to mold, have high, heat resistance, and excellent electrical performance, and may be light-colored., Allyl They have high heat and moisture, resistance, good electrical performance in automotive and aerospace uses, good chemical, resistance, dimensional stability, low creep, (see DiaUyl phthlate)., Amino (melamine and urea) Melamine, formaldehyde (MF) have excellent electrical properties, heat and moisture resistance,, abrasion resistance (good for dinnerware and, buttons); in high-pressure laminates it is resistant to alkalies and detergents. They are, used as the plastic for counter tops. Urea, (urea formaldehyde) has properties similar, to melamine and is used for wall switch plates,, light-colored appliance hardware, buttons,, toilet seats, and cosmetics containers. Unlike MFs they are translucent, giving them a, brightness and depth of color somewhat similar to opal glass., Diallyl phthlate DAPs' major use IS III, electrical connectors since they perform well, in electrical circuits. Used also in RP laminates and molding compounds competing, with TS polyester types. They offer longer, shelf life in the B-stage, less shrinkage during curing, higher heat resistance, etc., Epoxy They have overall the highest performance of all the thermosets. Properties in-, , clude very high strength in tension, compression, flexural loadings, very low shrinkages,, hard, superior adhesion to other materials,, etc. Used with glass cloth to make RP circuit boards, tooling surfaces for metals, and, RP castings. Can be cured chemically with or, without heat., Phenolic phenol formaldehydes (PFs) are, the low-cost workhorse of the electrical industry (particularly in the past); low creep,, excellent dimensional stability, good chemical resistance, good weatherability. Molded, black or brown opaque handles for cookware are familiar applications. Also used as, a caramel colored impregnating plastics for, wood or cloth laminates, and (with reinforcement) for brake linings and many under-thehood automotive electricals. There are different grades of phenolics that range from, very low cost (with low performances) to, high cost (with superior performances). The, first of the thermosets to be injection-molded, (1909)., Polyester, thermoset TS polyesters have, an excellent balance of properties, a roomtemperature cure and is a major plastic used, to make glass-fiber reinforced parts for automobiles, boats, and aircraft parts; used also, with other type reinforcing agents. Commodity types have moderate weatherability, high, molding shrinkages with wavy surfaces and, warpage. Low-profile (polystyrene, etc.) additives reduce shrinkage and surface waviness to almost nil. This has led to major, growth in such applications as automobile exterior body panels, instrument housings and, microwave dinnerware in the form of bulk, molding compounds (BMC) and sheet molding compounds (SMC)., Polyurethane, thermoset TSUs have durometers range from soft cushion to glass, hard with superior wear resistance. Use includes skateboard wheels, solid tires, floor, coatings, marine finishes, etc. A major use, for soft-foam is automotive bumpers; another, is upholstery. Property improvements are, made with different added fibers and fillers in

Page 449 : 7 Material Property, reaction molded products to improve cut, strength resistance, stiffer moduli, reduce, waviness caused by heat and weathering, etc., Silicone They have excellent heat resistance up to 260°C (500°F), chemical resistance, good electricals, compatible with human body tissues, etc. and a high cost. There, are the room temperature vulcanizing (RTV), types that cure and cross-link at ambient temperatures, catalyzed by moisture in the air. It, is a good sealant and excellent for making, flexible molds for casting. It is widely used, for human implants., Property Category, A guide to selecting materials is provided, (not in any order of priority) by using examples of categories with a few properties. Many, more categories as well as many more properties exist since many different plastics exist, with their many modifications (via additives,, alloying, etc.). They can be used as a guide to, meet specific requirements for the product, being designed., Elasticity If the product requires flexibility, examples of the choices includes, polyethylene, vinyl, polypropylene, EVA,, ionomer, urethane-polyester, fluorocarbon,, silicone, polyurethane, plastisols, acetal, nylon, or some of the rigid plastics that have, limited flexibility in thin sections., Odor and taste Polystyrene, styreneacrylonitrile, polyethylene, acrylic, ABS,, polysulfone, EVA, polyphenylene oxide, and, many other TPs are examples of satisfactorily, odor-free. FDA approvals are available for, many of these plastics. Food packaging and, refrigerating conditions will also eliminate, certain plastics. There are TPs and melamine, as well as urea compounds that are suitable, for this service., Temperature Thermal considerations will, quickly eliminate many materials. For products operating above 450°F (232°C), ex-, , 431, , amples of plastics used include the silicones, polyirnides, hydrocarbon plastics,, methylpentenes, or glass-bonded mica plastics may be required. A few of the organic, plastic-bonded inorganic fibers such as bonded ceramic wool perform well in this field.Epoxy, diallyl phthalate, and phenolic-bonded glass fibers may be satisfactory in the 450, to 550°F (232 to 288°C) range. A limited, group of ablation materials are made for atmospheric reentry of space vehicles (Chapter 2, HIGH TEMPERATURE)., Between 250 and 450°F (121 and 232°C),, plastics used include glass or mineral-filled, phenolics, melamines, alkyds, silicones, nylons, polyphenylene oxides, polysulfones,, polycarbonates, methylpentenes, fluorocarbons, polypropylenes, and diallyl phthalates., The addition of glass fillers to the thermoplastics can raise the useful temperature range as, much as lOO°F and at the same time shortens, the molding cycle., In the 0 to 212°F (-18 to lOO°C) range,, a broad selection of materials is available., Low temperature considerations may eliminate many of the TPs. Polyphenylene oxide can be used at temperatures as low as, -275°F (-165°C). TS materials exhibit minimum embrittlement at low temperatures., Flame resistance The underwriters ruling on the use of self-extinguishing plastics for contact-carrying members and many, other components introduces critical material selection problems. All TSs are basically self-extinguishing. Nylon, polyphenylene oxide, polysulfone, polycarbonate, vinyl,, chlorinated polyether, chlorotrifluoroethylene, vinylidene fluoride, and fluorocarbon, are examples of TPs that may be suitable, for applications requiring self-extinguishing, properties. Cellulose acetate and ABS are, also available with these properties. Glass, reinforcement improves these materials, considerably., Impact As reviewed although impact, strength of plastics is widely reported, the, properties have no particular design values, and can be used only to compare relative

Page 450 : 432, , 7 Material Property, , response of materials. Even this comparison, is not completely valid because it does not, solely reflect the capacity of the material to, withstand shock loading, but can pick up, discriminatory response to notch sensitivity, (Chapter 5, MECHANICAL PROPERTY,, Izod Impact)., A better value is impact tensile, but unfortunately this property is not generally reported. The impact value, with this limitation,, can broadly separate those that can withstand, shock loading versus those that are poor in, this response. Therefore, only broad generalizations can be obtained on these values., Comparative tests on sections of similar size, which are molded in accordance with the proposed product must be tested to determine, the impact performance of a plastics material. Polycarbonate and ultrahigh molecular, weight PE are outstanding in impact strength., The laminated plastics such as glass-filled, epoxy, melamine, and phenolic are outstanding in impact strength., , Electric arc resistance Electrical devices, often require arc resistance, as a high-current,, high-temperature are will ruin many plastics. Some special arc resisting plastics are, available. The most serious cases may require materials such as glass-bonded mica or, mineral-filled fluorocarbon products. Lesser, arcing problems may be solved by the use of, polysulfone, TS polyester-glass, DAP-glass,, alkyd, melamine, urea, or phenolic. With lowcurrent arcs, general-purpose phenolic, glassfilled nylon or polycarbonate, acetal, and urea, are examples of what may be used very satisfactorily. A coating of fluorocarbon film will, improve are resistance in some cases. All circuit breaker problems must be scrutinized, with respect to product performance under short-circuit conditions and mechanical, shock (Chapter 5, ELECTRICAL PROPERTY)., Radiation In general, plastics are superior to elastomers in radiation resistance but, are inferior to metals and ceramics. The materials that will respond satisfactorily in the, range of 1010 and 1011 erg per gram include, , polyurethane, polystyrene, mineral-filled TS, polyester, silicone, glass or asbestos-filled, phenolic, certain epoxies, and furane. The, next group of plastics in order of radiation, resistance includes polyethylene, melamine,, urea formaldehyde, unfilled phenolic, and, silicone plastics. Those materials that have, poor radiation resistances include methyl, methacrylate, unfilled TS polyester, cellulose,, polyamide, and fluorocarbon., , Transparency Examples of maximum, transparency is available in acrylic, polycarbonate, polyethylene, ionomer, and styrene, compounds. Many other TPs may have, adequate transparency., Applied stress There are TPs that will, craze or crack under certain environmental, condition. Products that are highly stressed, mechanically must be checked very carefully. Polypropylene, ionomer, chlorinated, polyether, phenoxy, EVA, and linear polyethylene are examples that offer greater freedom from stress crazing than some other, TPs. Solvents may crack products held under, stress. TSs is generally preferable for products under continuous loads., Color Urea, melamine, polycarbonate,, polyphenylene oxide, polysulfone, polypropylene, diallyl phthalate, and phenolic are examples of what is needed in the temperature, range above 200°F (94°C) for good color stability. Most TPs will be suitable below this, range., Moisture Deteriorating effects of moisture are well known as reviewed early in, this chapter (OTHER BEHAVIOR, Drying, Plastic). Examples for high moisture applications include polyphenylene oxide, polysulfone, acrylic, butyrate, diallyl phthalate,, glass-bonded mica, mineral-filled phenolic,, chlorotrifluoroethylene, vinylidene, chlorinated polyether chloride, vinylidene fluoride,, and fluorocarbon. Diallyl phthalate, polysulfone, and polyphenylene oxide have performed well with moisture/steam on one, side and air on the other (a troublesome

Page 451 : 7 Material Property, combination), and they also will withstand, repeated steam autoclaving. Long-term studies of the effect of water have disclosed, that chlorinated polyether gives outstanding performance. Impact styrene plus 25%, graphite and high density polyethylene with, 15% graphite give long-term performance in, water., , Chemical The chemical resistance of, plastics is well known as reviewed early in, this chapter (OTHER BEHAVIOR, Chemical Resistance). The data serves as an excellent initial guide. Most material makers have, developed long-term data for commonly used, chemicals. Great care must be exercised in, this selection because environmental conditions are very impertinent to include in the, selection. Note when two materials do not, attack a plastic when used separately may be, troublesome when used in combination or diluted with water., Chlorinated poly ether is formulated particularly for products requiring, good chemical resistance. Other materials exhibiting, good chemical resistance include all of the, fluorocarbon plastics, ethylpentenes, polyolefins, certain phenolics, and diallyl phthalate compounds. Additives such as fillers,, plasticizers, stabilizers, colorants, and type, catalysts can decrease the chemical resistance, of unfilled plastics. Certain chemicals in cosmetics will affect plastics, and tests are necessary in most cases with new formulations., Temperature condition is also very important to include in the evaluation. Careful tests, must be made under actual use conditions in, final selection studies., Surface wear Hardness is not necessarily the proper index for scratch resistance., In general, the TSs have the best abrasion, resistance. Acrylic, ABS, and SAN are examples of plastics that have good fingernail scratch resistance. Tests simulating actual, conditions are necessary to obtain the best results. When abrasive wear is the problem, ultrahigh molecular weight polyethylene, urethane, high density polyethylene, Nylon 11,, and polyester film are examples of good per-, , 433, , formers (Chapter 7, OTHER BEHAVIOR,, Friction, Wear, and Hardness)., , Permeability Different plastics provide, different permeability properties. As an example polyethylene will pass wintergreen,, hydrocarbons, and many other chemicals. It, is used in certain cases for the separation, of gases since it will pass one and block, another. Chlorotrifluoroethylene and vinylidene fluoride, vinylidene chloride, polypropylene, EVA, and phenoxy merit evaluation, (Chapter 4, PACKAGING, Permeability)., Electrical Electrical considerations will, limit the use of certain plastics, and published, data are reasonably comparable on similar, sections. Final tests must be made on the, actual section under field environmental conditions to make sure that the design is adequate. High frequency, high temperature applications are the most difficult to solve. High, altitude, high voltage applications with the, included ozone problems are often solved, by use of glass-bonded mica, which matches, the thermal expansion rate of steel and prevents corona gap formation. Vacuum impregnation with epoxy plastic may be suitable, for some products. All organic plastics except polyimide can give off vapors that may, cause contact failure when used in a vacuum, (Chapter 4, ELECTRICALIELECTRONIC, PRODUCT)., Dimensional stability There is plastics, with very good dimensional stability, and they, are suitable where some age and environmental dimensional changes are permissible., These materials include polyphenylene oxide, polysulfone, phenoxy, mineral-filled phenolic, diallyl phthalate, epoxy, rigid vinyl,, styrene, and various RPs. Such products will, gain from an after-bake for dimensional stabilization. Glass fillers will improve the dimensional stability of all plastics., Materials using plasticizers could be a, problem. Materials that exhibit substantial, moisture absorption are not stable dimensionally. Many organic plastics show a high, thermal expansion differential in comparison

Page 452 : 434, , 7 Material Property, , with mating metal products, and this can, cause serious trouble if tight dimensional relations and tightly bonded inserts must be, maintained., Phenolic glass and a diallyl phthalate glass, material are available with very low shrinkage. Glass and other mineral fillers minimize, the thermal expansion differential problem., Phenoxy and polyphenylene oxides are examples of being low in shrinkage and thermal, expansion., The TPs change dimensions rapidly as they, approach the cold flow point. Great care must, be taken in the selection of critical dimensional control products for applications such, as machines and instruments. Critical dimen-, , sions may be held best by included or assembled inserts in materials that have questionable stability (Chapter 4, JOINING AND, ASSEMBLY)., Weathering Many plastics has short lives, when exposed to outdoor conditions. The, better materials include acrylic, chlorotrifluorethylene, vinylidene fluoride, chlorinated polyether, polyester, alkyd, and black, linear poly-ethylene. Black materials are, best for outdoor service. Some of the, styrene copolymers are suitable for certain, outdoor uses (Chapter 2, WEATHERINGI, ENVIRONMENT).

Page 453 : ________ 8 ________, Plastic Processing, , Overview, , The successful design and fabrication of, good plastic products requires a combination, of sound judgment and experience. Designing acceptable products requires behavioral, knowledge of plastics that includes their advantages and disadvantages (limitations) and, some familiarity with processing methods., Until the designer becomes familiar with processing, a qualified fabricator must be taken, into the designer's confidence early in development and consulted frequently during, those early days. The fabricator and mold, or die designer should advise the product, designer on materials behavior and how to, simplify processing. Understanding only one, process and in particular just a certain narrow, aspect of it should not restrict the designer., Worldwide extrusion consumes approximately 36wt% of all plastics. 1M follows by, consuming 32wt%. However there are just, in USA about 80,000 injection molding machines (IMMs) and about 18,000 extruders, operating to process the many different types, of plastics. Consumption by other processes is, estimated at 10wt% blow molding, 8% calendering, 5 % coating, 3 % compression molding, 3%, and others 3%. Thermoforming, which, is the fourth major process used, consumes, principally at least 30% of the extruded sheet, and film that principally goes into packaging., , Growth of the processing equipment can, be related to the prediction made in mid-1999, by the Freedonia Group Inc. (Cleveland,, OH, tel. 440-646-0484). Their Plastics Processing Machinery Report reviews that USA, m~chinery sales demand will rise at 5.8% per, year to $1.5 billion by year 2003. IMM is, the largest category that accounts for 51 % of, all the machinery sales. By 2003 blow molding machines will grow the fastest reaching, $505 million, extrusion will reach $440 million, and thermoforming will reach $455 million. They also reported that there are now, over 350 USA machinery builders with five, having over 50% of sales., Influence on Performance, , It is important to understand what happens, to plastics during the manufacture of products and how it fits into the overall manufacturing operation (Table 8-1). With proper, fabricating controls, products are reproduced, meeting performance requirements at the, minimum cost., A design evaluation of the product will, often hinge on what is the best process of, fabrication for the product in question. Sometimes the necessity for certain elements in the, design such as thin sections, long delicate inserts, requirements of exact concentricity, or

Page 454 : 436, , 8 Plastic Processing, Table 8·1, , Manufacturing analysis diagram, , MANUFACTURING ANALYSIS, RELEASE, TOOLING, (MOLDIDIE), FOR, MANUFACTURE, , SETUP, PROCESSING, SPECIFICATION, , extremely high accuracy of dimensions, make, it desirable to use one technique of processing rather than another. There is also the possibility that the process desired for a selected, material could not be used because the plastics melt flow and/or other characteristics are, not suitable. Result could be determining if, the selected material can be modified for the, process desired with no loss in meeting performance requirements, finding another plastic, or developing a compromise., The different fabricating methods and processing behaviors are reviewed explaining effects on the properties of the different plastic, that relate to design. Examples include processing parameters such as melt temperature, with flow rate or fill rate, die or mold temperature, and packing pressure in injection molding, draw-down ratio in extrusion, and draw, ratio in thermoforming (Fig. 8-1). Details on, how fabricating equipment is to be setup and, operated are reviewed in many sources (1-3,, 6-10,20,37)., Excessively high processing temperatures, can increase the rate of thermal decompo-, , sition of plastics or develop deleterious effects. Too Iowa processing temperature can, cause melt viscosity of these materials to be, too high, thereby requiring excessive pressure (energy) to fill the mold or extrude the, sheet or profile. High melt viscosity and high, processing pressure can lead to high shearing stresses in the material and may impart, increased molecular orientation to the final, product. Molecular orientation makes the, product anisotropic; its properties are not, the same when measured in different directions. Thermoforming at sheet temperatures, that are too low can lead to excessive tensile, stresses. Likewise, low fill rate, high packing, pressure, and low mold temperature in injection molding, high draw-down ratio in extrusion, or high draw ratio in thermoforming, may cause increased bulk orientation in the, resulting products., Basically, with the higher pressures it is, possible to develop tighter dimensional tolerances with higher mechanical performance,, but there is also a tendency to develop undesirable stresses (orientations) if the processes

Page 455 : 8 Plastic Processing, , 437, , PRODUCT, I, I, I, I, I, I, Process, measures, , Information, , ~!----... on quality, , -----, , Product, dimensions, , Fig.8·1 Simplified diagram applicable to fabricating., , are not properly understood or controlled., A major exception is reinforced plastics processing at low or contact pressures. Regardless of the process used, its proper control will, maximize performance and minimize undesirable process characteristics., Practically all processing machines can, provide useful products with relative ease,, and certain machines have the capability of, manufacturing products to very tight dimensions and performances. The proper coordination of plastic and machine facilitates, these type of performances. This interfacing of product and process requires continual updating because of continuing new developments in manufacturing operations that, provide advantages such as meeting tighter, tolerances, reduce cost, etc.. The information, presented throughout this book will make, past, present, and future developments understandable in a wide range of applications., Most products are designed to fit processes, of proven reliability and consistent production. Various options may exist for processing different shapes, sizes, and weights (Table, 8-2). Parameters that will help one to select, the right options are (1) setting up specific, performance requirements; (2) evaluating, materials' requirements and their processing capabilities; (3) designing products on the, basis of material and processing characteristics, considering product complexity and size, (Fig. 8-2) as well as a product and process, , cost comparison (Tables 8-3 and 8-4); (4) designing and manufacturing tools (molds, dies,, etc.) to permit ease of processing; (5) setting up the complete line, including auxiliary equipment, testing, and providing quality control, from delivery of the plastics to the, equipment through production to the product; and (7) interfacing all these parameters, by using logic and experience or obtaining a, required update on technology., Plastics usually are obtained in the form, of granules, powder, pellets, and liquids. Processing mostly involves their physical change, (thermoplastics), though in some cases chemical reactions occur (thermosets) (Chapter 6)., The following reviews primarily pertain to, processing TPs since over 90wt% of all plastics processed are TPs. Processing TSs will, also be included in appropriate processes., The common features of these processes are, , Blow Molding, Injecll on Molding, , f---Com pression, , ~1Thennofonnlng, , 1 I-~Extrusion, /, , Small, , Large, Part Size, , Fig. 8·2 Overview guides for processing characteristics in regard to size and complexity.

Page 456 : 1. Prime process., 2. Secondary process., A. Combine two or more parts with ultrasonics, adhesives, etc., B. Short sections can be molded., C. Also calendering process., , 2, , 2, , I,C, , 2, , 2,B, , 1, 1, , 1, , 2, , 2, , 2, , Matched Mold, Spray-up, , 2,B, , 1, , Compression and, Transfer Molding, , 2, , 2, 2, , 1, , 2, , Rotational, Molding, , 1, , 2, 2, , 2,A, , 1, , Reaction Injection, Molding, , 1, , 1, , 2,A, , 1, 1, , Thermoforming, , Blow, Molding, , 1, , Extrusion, , 1, 1, , 1, , 2,A, , Injection, Molding, , Examples of competitive processes vs. different products, , Bottles, necked, containers, etc., Cups, trays, open, containers, etc., Tanks, drums, large, hollow shapes, etc., Caps, covers, closures, etc., Hoods, housings,, auto parts, etc., Complex shapes,, thickness changes, etc., Linear shapes, pipe,, profiles, etc., Sheets, panels,, laminates, etc., , Table 8-2, , OQ, , '"'", S·, , ~, ~, , "tI, ~, , ~, , ::l"., , '", , "tI, , S-, , 00, , &, 00

Page 457 : 8 Plastic Processing, , 439, , Table 8-3 Detailed guide to product size, , J, , PRODUCT SIZE, , I, , I, , I, OVER 250 D F, , THERMOSEn, , I, , I I, I, , LOW-PRESSUR E, LAMINATION, FILAMENT WINDING, , aJMPRESSION, , HIGH-PRESSURE, LAMINATION, POST FORM, , ADHESIVE BOND, , MACHINE, PULTRUSION, , I~LLPART I, I, , I, , LARGE PART, OVER 1lqft, OVER S'", , LESS THAN 1 .. It, LESS THAN Sib, , I, UNDER 250°F, THERMOPLASTICS, , I, , I, LARGE AREA, , I, THEAMOfORM, , FOAM, , I, , l, , I, , I, , I, LDNG LENGTHS, , J, , HEAT SEAL, , WELD, , ROTOFORM, , BLOW MOLD, , DYER_F, , THERMOSETS, , ~, , I, HIGH·VOLUME, , I, , LEXTRUDE I, , I, , STRUCTURAL, , I, , l, , I, , ~, LESS THAN 25DoF, , THERMOPLASTICS, , I, , I, , LOW-VOLUME, , HIGH·VOLUME, , I, , COMPA ESSION, TRANSFER, INJECTION, LAMINATION, PULTRUSION, , ADHESIVE BOND, , I, , I, , CASTING, , MACHINING, , LOW PRESSURE, , LAY-UP, POST FORM, SPRAY-UP, RESIN TRANSFER, , I, INJECTION, BLOW MOLD, THERMOFORM, EXTRUSION, , ROTOFORM, , RIM, , I, , J, I, , LOW·YOLUME, , ~, MAOfINE, , THERMOFORM, COMPR ESSION, CASTING, ROTOFORM, FOAM, ADHESIYE_D, , FOAM, RIM, , Table 8-4 Cost comparison of products vs., processes (cost factor x material cost =, purchased cost of product), Cost Factor, Process, , Overall, , Average, , Blow molding, Calendering, Casting, Centrifugal casting, Coating, Cold pressure, molding, Compression, molding, Encapsulation, Extrusion forming, Filament winding, Injection molding, Laminating, Match-die molding, Pultrusion, Rotational molding, Slush molding, Thermoforming, Transfer molding, Wet lay-up, , 11/16 to 4, l 11z to 5, 1% t03, l 11z to 4, l 11z to 5, l 11z to 5, , 11/S to 2, 2 11z to 3%, 2 to 3, 2 to 4, 2 to 4, 2 to 4, , 1% to 10, , l 11z to 4, , 2 to 8, 11/16 to 5, 5 to 10, 1% t03, 2 to 5, 2 to 5, 2 to 4, 11/4 to 5, l 11z to 4, 2 to 10, l 11z to 5, l 11z to 6, , 3 to 4, 11/S to 2, 6 to 8, 13/16 to 2, 3 to 4, 3 to 4, 2 to 311z, l 11z to 3, 2 to 3, 3 to 5, 1 %t03, 2 to 4, , (1) mixing, melting, and plasticizing; (2) melt, transporting and shaping; and (3) finishing., Mixing, melting, and plasticizing produce a, plasticized melt, usually made in a screw, ( extruder or inj ection). Melt transporting and, shaping involves applying pressure to the hot, melt in order to move it through a die or into, a mold. The final feature of processing, finishing, is the usual solidification of the melt. As, summarized in Table 8-5, certain processes, are unique to certain plastics., Many product designs are inherently limited by the economics of the process that, must be used to make them. For example, to, date TSs are not blow molded, and they have, limited extrusion possibilities. Many hollow, products, particularly very large ones, may, be produced more economically by the rotational process than by blow molding. The, need for a low quantity of products may eliminate certain molding processes and indicate, the use of casting or others., The extrusion process has fewer process, control problems with TPs than does injection molding but has greater problems, in dimensional control and shape. During

Page 458 : 440, Table 8·5, , 8 Plastic Processing, Example of properties and processes for the major TS plastics in RPs, , Thermosets, Polyesters, , Epoxies, , Phenolic resins, Silicones, Melamines, Diallyl, a-phthalate, , Processes, , Properties, Simplest, most versatile, economical,, and most widely used family of, resins; good electrical properties,, good chemical resistance,, especially to acids, Excellent mechanical properties,, dimensional stability, chemical, resistance (especially to alkalis),, low water absorption, selfextinguishing (when, halogenated), low shrinkage,, good abrasion resistance,, excellent adhesion properties, Good acid resistance, good electrical, properties (except arc resistance),, high heat resistance, Highest heat resistance, low water, absorption, excellent dielectric, properties, high arc resistance, Good heat resistance, high impact, strength, Good electrical insulation, low water, absorption, , extrusion when the plastic leaves the die, it, can be relatively stress-free. It is drawn in size, and passed through downstream equipment, from the extruder to form its shape as it is, cooled, usually by air and/or water. The dimensional control and the die shape required, to achieve the desired product shape are usually solved by trial-and-error settings. With, the more experience one has in the specific, plastic and equipment to be used, less or no, trial time is needed., Other analyses can be made. Compression and injection molds, which are expensive and relatively limited in size, are employed when the production volume required, is great enough to justify the molds' costs and, the sizes are sufficient to fit available equipment's limitations. Extrusion produces relatively uniform profiles of unlimited lengths., Casting is not limited by pressure requirements and large products can be produced., Calendered sheets are limited in their width, by the width of the material's rolls, but are, unlimited in length. Vacuum forming is not, greatly limited by pressure, although even a, small vacuum distributed over a large area, , Compression molding, filament winding,, hand lay-up, mat molding, pressure bag, molding, continuous pultrusion, injection, molding, spray-up, centrifugal casting,, cold molding, encapsulation, Compression molding, filament, winding, hand lay-up, continuous, pultrusion, encapsulation, centrifugal, casting, , Compression molding, continuous, lamination, Compression molding, injection molding,, encapsulation, Compression molding, Compression molding, , can build up an appreciable load. Blow molding is limited by equipment that is feasible for, the mold sizes. Rotational molding can produce relatively large parts., The tendency of injection molding and, extrusion to align long chain molecules in, the direction of flow results in their having, markedly greater strength in that direction, than at right angles. With an extruded pressure pipe, for example, its major strength, could be in the axial/machine direction. With, changes in processing controls, different directional properties can be obtained such as, providing higher strength in the circumferential direction. If in an injection mold the plastic flows in from several gates, the melts must, unite or weld where they meet causing points, of potential weakness and undesirable markings on the product's surface. Careful gating, with proper processing control can eliminate, or reduce weld lines., The nature of the process may have profound influence on such properties as impact strength. Figure 8-3 compares the impact, strengths of three PP formulations that were, processed either by injection or compression

Page 459 : 441, , 8 Plastic Processing, , ,, , 0, , 0.5, , 1.0, , Pan thickness. in., , THICKNESS, mm, 1.5, 2.0, , 3.0, , 2.5, , 3.5, 12, II, , ., , B., , ...r, , :r, , 7, , 5, , 6, , 4, , 5, , ~, , w, :I: 3, , all moterials, , ~, , ::;, , ...I, , «, , u., , injection, , 2, , M.' .• ,.,, 0, , 1.5, , 8.75, , 10, , 110 I-......:l"r---t---+---t---i--I---t, , '-', Z, 8 w, , '-', Z 6, , U, , 6.25, , 10.!, , w, , V>, , 5.0, , , 1r..., , 7, , ...a:, , ..., «, !..., , 3.15, , ~:=-, , 0, , m"~J, , :::t:iS:=----.::-.:..~, , 0.02, , ...a:, ...Uon, «, !..., , G, u:;, , 4 :I:, , ~, , 3 ::;, , ;;t, , ~ ~-~-~-~-~-~-~-~, , 0.05, , 010, , 0.15, , 0.20, , 0.25, , 030, , 0.35, , 0.40, , Pan thickness. mm, , Fig. 8·4 Example of cycle time during 1M of TPs, as a function of product thickness., , u., , 0, 0.14, , THICKNESS, in., , Fig.8.3 Example of the effect of processing conditions on impact for PP with different melt index, flow behaviors., , molding. In this example the 1M process, resulted in a drastic reduction of impact, strength over that offered by the CM. Varying the processing conditions can reverse this, situation., Sometimes certain products are most economically produced by fabricating them with, conventional machining out of compression, molded blocks, laminates or extruded sheets,, rods or tubes. Also at times it may be advantageous to design a product for the postmolding assembly of inserts to reduce fabricating, time and gain cost benefits. However specialized equipment is available for very efficient, automatic insert molding during 1M that provides gains over secondary operations., If the processing is to be subcontracted, the, choice of fabricator should place no limits on, a design. There is a way to make a product if, the projected values justify the price; any job, can be done "at a price." The real limiting, factors are factors such as tool design considerations, material shrinkages, subsequent assembly or finishing operations, dimensional, tolerances, undercuts, insert inclusions, parting lines, fragile sections, production rate or, cycle time (Fig. 8-4), and cost to fabricate., Applying the following principles, applicable to virtually all manufacturing processes,, , will aid the designer in specifying products that can be produced at minimum cost:, (1) maintain design simplicity; (2) use standard materials and components; (3) specify, liberal tolerances; (4) employ the most processable plastics; (5) collaborate with manufacturing people; (6) avoid secondary operations; (7) designing what is appropriate to, the expected level of production; (8) utilize, special process characteristics; and (9) avoide, processing restrictions., In light of the many types of behavior plastics that can manifest and the considerable, effect this behavior can have on the performance of the finished product, it behooves, designers to become familiar with specific, behavior characteristics of each plastic considered for an application. Recognize potential problems. A major cause for problems, is not of poor product design but instead that, the processes operated outside of their required operating window. This subject will, be reviewed latter in this Chapter under, PROCESS CONTROL., As an example to plastic behavior, in-mold, decorating with coatings and/or decorative, material is routine and very successfully accomplished. However there are several coating treatments that can embrittle the surface, of a plastic product, including contamination with certain chemical agents, oxidative, degradation or cross-linking of the plastic, molecules by heat aging or exposure to ultraviolet light. Under certain circumstances, cracks starting in this brittle surface layer can, propagate into the underlying ductile plastic

Page 460 : 442, , 8 Plastic Processing, , at sufficiently high velocity to induce a brittle, failure of the entire product. Surface embrittlement can have a significant effect on the, observed stress/strain, fatigue, and impact behavior of the plastic., Plastic products are made by a variety of, basic manufacturing processes. As an example a major method such as extrusion has, subdivisions that include profile, pipe, tube,, film, sheet, coating, post forming, etc. equipment In injection molding there are subdivisions such as coinjection, gas assist, foam, inmold decorating, etc. equipment. There are, literally hundreds of processes used with only, about the dozen, as reviewed in this chapter,, that are principally used (2)., Processing and Material Behavior, The flow patterns resulting from the conditions of a particular fabricating process are, very important in influencing product performances. The melting of plastics follows different phases that effect performances. An, example is its modulus of elasticity as shown, in Fig.7-8. As the temperature increases, the, plastic goes through the phases of glassy, transition, rubbery, to melt flow., Reinforcing fibers, specifically the glass, fibers, are brittle. Thus, when they are used, in conjunction with a brittle matrix, as are, certain TSs, it might be expected that the, composite would have low fracture energy. In, fact, this is not true, and the impact strength, of most glass-TS RPs is many times greater, than the impact strengths of either the fibers, or the matrix. Impact strength is higher if the, bond between the glass fibers and the matrix, is relatively weak, because if it is so strong, that it cannot be broken, cracks will propagate across the matrix and fibers, and very, little energy will be absorbed. Thus, there is, a conflict between the requirements for maximum tensile or flexural modulus or strength, (long glass fibers and strong interface bonds), and maximum impact strength., , production run, many variables have to be, considered. These include the plastic materials with their variabilities, geometry of the, product that includes thicknesses, toolmaking quality applied in producing the die or, mold, and very important the fabricating, conditions and processes fluctuations inherent during processing. Computer programs, developed have made it possible to provide model guides that tend to understand, the complex (controllable) interactions of, these many factors. This allows molders to, more accurately predict product dimensions, and to model the relationship between the, control of the molding process and the product tolerances., This interplay of the many variables is extremely complex and involves a matrix of the, many variables. As an example in the molding, simulation TMconcept system programmed, Molding & Cost Optimization (MCO) of, Plastics & Computer Inc., Dallas, TX, there, are well over 300 variables. It is not reasonable to expect a person using manual methods to calculate these complex interactions, even if molding only a modest shaped product without omissions or errors. Computerized process simulation is a practical tool to, monitor the influence of design alternatives, on the process ability of the product and to, select molding conditions that ensure the required product quality (3)., Process used provides different control capabilities. As an example closed molding, (injection, compression, etc.) provides fine, detail on all surfaces. Open molding (blow, molding, thermoforming, spray-up, etc.) provides detail only on the one side in contact, with the mold, leaving the second side freeformed. Continuous production (extrusion, and pultrusion) yields products of continuous, length. Hollow (rotational or blow) produces, hollow products. These processes can be used, creatively to make different types of products. For example, two molded or thermoformed components can be bonded together, to form a hollow product, or they can be blow, molded., , Tolerance and Dimensional Control, To predict product dimensions and the fluctuation of dimensions (tolerances) during a, , Shrinkage After preliminary study, the, designer has to define the geometry. This process usually passes through several stages,

Page 461 : 8 Plastic Processing, beginning with preliminary drawings and, sketches that indicate the basic design and, functions. More detailed sketches will show, the appropriate wall thickness, ribs, radii, and, other structures, including the tolerances that, are required to be met. Tables 8-6 to 8-8, provide guides to shrinkages and tolerances, (Chapter 2, INSTABILITY BEHAVIOR,, Shrinkage/Tolerance )., Using the calculated shrinkage theory can, dictate how much oversize to cut the tool, (mold or die) if a product has a relatively, simple shape. For other shapes some critical, key dimensions of the product will, more often than not, not be as predicted from the, shrink allowance, particularly if the item is, long, complex, or require tight tolerance. The, important factors that influence the shrinkage of a specific plastic in using a specific machine, such as injection molding, by causing, it to vary and not follow the values like those, in Table 8-6 to 8-8, are flow direction, wall, thickness, flow distance, and the presence of, reinforcing fibers., Determining shrinkage involves more than, just applying the appropriate correction factor from a material's data sheet. Shrinkage, is caused by a packing pressure and volumetric change in a plastic as it cools from a, molten to a solid form. Shrinkage is not a single event but occurs over a period of time., Most of it happens in the mold or die, but it, can continue for up to twenty-four to fortyeight hours after being molded. This so-called, postmold shrinkage may require a constraining cooling fixture. Additional shrinkage can, occur when frozen-in stresses are relieved, by annealing or exposure to high service, temperatures., The main considerations in mold or die, design affecting shrinkage are to provide, adequate cooling (required temperature control), and structural rigidity. Cooling conditions is the most critical especially for crystalline plastics. The cooling system must be, adequate for the heat load. Slow cooling increases shrinkage by giving plastic molecules, more time to reach a relaxed state. In crystalline types, having longer cooling time leads, to a higher level of crystallinity, which in turn, accentuates shrinkage. Proper cooling, along, with having an overall melt-flow analysis of, , 443, , how the material will react in the mold, by the, mold designer, will eliminate or at least be capable of controlling the potential problems of, shrinkage and warpage. This analysis can also, include the best gate locations in molds., A number of the computer-aided flowsimulation programs now offer modules designed (targeted) to forecast shrinkage and,, to a limited degree, warpage from the interplay of plastic and mold temperatures, cavity, pressures, stress, and other variables in moldfill analysis. The predicted shrinkage values in, various areas of the product should be used, as the basis for sizing the mold cavity, either, by manual input or feed-through to the mold, dimensioning program., Computer-aided flow-simulation programs are also available for dies. All the, programs can successfully predict a certain, amount of shrinkage under specific conditions that can be applied to experience. The, actual shrinkage is finally determined after, molding or extruding the products. When, not in spec process control changes can meet, the requirements unless some drastic error, had been included in the analysis., Inspection and tolerance Inspection variations are often the most critical and most, overlooked aspect of the tolerance of a fabricated product. Designers and processors, base their development decisions on inspection readings, but they rarely determine the, tolerances associated with these readings., The inspection variations may themselves be, greater than the tolerances for the characteristics being measured, but without having, a study of the inspection method capability, this can go unnoticed., Inspection tolerance can be divided into, two major components: the accuracy variability of the instruction and the repeatability of, the measuring method. The calibration and, accuracy of the instrument are documented, and certified by its manufacturer, and it is periodically checked. Understanding the overall inspection process is extremely useful in, selecting the proper method for measuring, a specific dimension. When all the inspection methods available provide an acceptable level of accuracy, the most economical, method should be used.

Page 462 : 444, , 8 Plastic Processing, Table 8-6 Guidelines for nominal TP mold shrinkage rates per ASTM, 1/2 in. thick test specimens, , 1/4, , &, , Avg. Rate' per ASTM D 955, Material, ABS, Unreinforced, 30% glass fiber, Acetal, copolymer, Unreinforced, 30% glass fiber, HDPE,homo, Unreinforced, 30% glass fiber, Nylon 6, Unreinforced, 30% glass fiber, Nylon 6/6, Unreinforced, 15% glass fiber + 25% mineral, 15% glass fiber + 25% beads, 30% glass fiber, PBT polyester, Unreinforced, 30% glass fiber, Polycarbonate, Unreinforced, 10% glass fiber, 30% glass fiber, Polyether sulfone, Unreinforced, 30% glass fiber, Polyether-etherketone, Unreinforced, 30% glass fiber, Polyetherimide, U nreinforced, 30% glass fiber, Polyphenylene oxide/PS alloy, Unreinforced, 30% glass fiber, Polyphenylene sulfide, Unreinforced, 40% glass fiber, Polypropylene, homo, Unreinforced, 30% glass fiber, Polystyrene, Unreinforced, 30% glass fiber, 'Rates in in.lin. (Courtesy ICI-LNP), , 0.125 in., (3.18 mm), , 0.250 in., (6.35 mm), , 0.004, 0.001, , 0.007, 0.0015, , 0.D17, 0.003, , 0.021, NA, , 0.D15, 0.003, , 0.030, 0.004, , 0.013, 0.0035, , 0.016, 0.0045, , 0.016, 0.006, 0.006, 0.005, , 0.022, 0.008, 0.008, 0.0055, , 0.012, 0.003, , 0.018, 0.0045, , 0.005, 0.003, 0.001, , 0.007, 0.004, 0.002, , 0.006, 0.002, , 0.007, 0.003, , 0.011, 0.002, , 0.013, 0.003, , 0.005, 0.002, , 0.007, 0.004, , 0.005, 0.001, , 0.008, 0.002, , 0.011, 0.002, , 0.004, NA, , 0.015, 0.0035, , 0.025, 0.004, , 0.004, 0.0005, , 0.006, 0.001

Page 463 : 445, , 8 Plastic Processing, Table 8·7 Example of wall thickness ranges and tolerances for RPs, Thickness Range', Molding Method, , Min.,, mm (in.), , Max.,, mm (in.), , Maximum, Practicable Buildup, Within Individual, Part, No limit; use cores, No limit; use many, cores, No limit; over three, cores possible, 3-13 mm e/s-1/2 in.), 3-115 mm e/s-4 1/2 in.), 10-13 mm; 19-25 mm, (%-1/2 in; %-1 in.), Min. to max. possible, Min. to max. possible, , Normal Thickness, Tolerance, mm (in.), , Hand lay-up, Spray-up, , 1.5 (0.060), 1.5 (0.060), , 30 (1.2), 13 (0.5), , ±0.5 (0.020), ±0.5 (0.020), , Vacuum-bag molding, , 1.5 (0.060), , 6.3 (0.25), , Cold-press molding, Casting, electrical, Casting, marble, , 1.5 (0.060), 3 (.125), 10 (.375), , 6.3 (0.25), 115 (4.5), 25 (1), , EMCmolding, Matched-die, molding: SMC, Pressure-bag molding, Centrifugal casting, , 1.5 (0.060), 1.5 (0.060), , 25 (1), 25 (1), , 3 (.125), 2.5 (0.100), , 6.3 (.25), 4.5% of, diameter, , 2:1 variation possible, 5 % of diameter, , Filament winding, , 1.5 (0.060), , 25 (1), , Pipe, none; tanks,, 3:1 around ports, , Pultrusion, , 1.5 (0.060), , 40 (1.6), , None, , Continuous, laminating, Injection molding, Rotational, molding, Cold stamping, , 0.5 (0.020), , 6.3 (1/4), , None, , ±0.25 (0.010), ±O.4mm for, l50-mm diameter, (0.015 in. for, 6-in. diameter);, ±0.8 mm for, 750-mm diameter, (0.030 in. for 30-in., diameter), Pipe, ±5%; tanks,, ±1.5mm, (0.060 in.), 1.5 mm, ±0.025 mm, eh6 in. ±0.001 in.);, 40 mm, ±0.5 mm, (1 11z in., ±0.020 in.), ±1O% by weight, , 0.9 (0.035), 1.3 (0.050), , 13 (0.5), 13 (0.5), , Min. to max. possible, 2:1 variation possible, , ±0.13 (0.005), ±5%, , 1.5 (0.060), , 6.3-13, (0.25-0.50), , 3:1 possible as required, , ±6.5% by weight;, 6.0% for flat parts, , ±0.25 (0.010), ±0.5 (0.020), ±0.4 (0.015), ±0.8 (.031), ±0.13 (0.005), ±0.13 (0.005), , 'Thickness may be varied within parts, but prolonged cure times, slower production rates, and the possibility of, warpage may result. If possible, the thickness should be held uniform throughout a part., , As the overall fabricating tolerance is analyzed into the sources of its variation components, the potential advantage of analytical, programs comes into play with their ability, to efficiently process all these factors. All the, empirical tolerance ranges for each tooling, method and inspection method are stored in, data files for easy retrieval. For each critical dimension the program sums all the com-, , ponent tolerances and computes a ± overall tolerance for each critical dimension. The, program then provides a tabulated estimate, of the achievable processing tolerances and, pinpoints the areas that contribute most of, the overall required tolerance. This information is useful in identifying the needed tolerances that in practice can be expected to, exceed the initial design tolerance.

Page 464 : 446, , 8 Plastic Processing, , Table 8-8, , Recommended dimensional tolerances for RPs, , Dimension,, mm (in.), , Class A', (Fine Tolerance),, mm (in.), , Class Bt, (Normal Tolerance),, mm (in.), , Class C", (Coarse Tolerance),, mm (in.), , 0-25 (0-1), 25-100 (1-4), 100-200 (4-8), 200-400 (8-16), 400-800 (16-32), 800-1,600 (32-64), 1,600-3,200 (64-128), , ±0.12 (±0.005), ±0.2 (±0.008), ±0.25 (±0.010), ±OA (±0.016), ±0.8 (±0.030), ±1.3 (±0.050), ±2.5 (±0.100), , ±0.25 (±0.010), ±OA (±0.016), ±0.5 (±0.020), ±0.8 (±0.030), ±1.3 (±0.050), ±2.5 (±0.100), ±5.0 (±0.200), , ±OA (±0.016), ±0.5 (±0.020), ±0.8 (±0.030), ±1.3 (±0.050), ±2.0 (±0.080), ±3.8 (±0.150), ±7.0 (±0.280), , 'Class A tolerances apply to parts compression molded with precision matched-metal molds. BMC, SMC, and, preform are included., t Class B tolerances apply to parts press molded with somewhat less precise metal molds. Cold-press molding, casting,, centrifugal casting, rotational molding, and cold stamping can apply to this classification when molding is done with, a high degree of care. BMC, SMC, and preform compression molding can apply to this classification if extra care is, not used., "Class C applies to hand lay-up, vacuum bag, and other methods using molds made of RP/C material. It applies to, parts that would be covered by Class B when they are not molded with a high degree of care., , Establishing initial design tolerances is often done on an arbitrary, uninformed basis., If the initial estimated tolerance proves too, great, a lower shrink plastic could be used to, reduce the shrinkage range. However, if the, key dimension was across a main parting line,, the tooling could be redesigned to eliminate, the condition and consequently reduce variation from tool construction. Even with all, these data processed by a computer, estimating tolerances is difficult if they are not properly interrelated with the highly dependent, factors of the material behavior and tooling, designs., , Viscoelasticity, The flow of plastics is compared to that of, water in Fig. 8-5 to show their different behaviors. The volume of a so-called Newtonian, fluid, such as water, when pushed through an, opening is directly proportional to the pressure applied (the straight dotted line), the, flow rate of a non-Newtonian fluid such as, plastics when pushed through an opening increases more rapidly than the applied pressure (the solid curved line). Different plastics, generally have their own flow and rheological rates so that their non-Newtonian curves, are different., , With plastics there are two types of deformation or flow; viscous, in which the energy causing the deformation is dissipated,, and elastic, in which that energy is stored., The combination produces viscoelastic plastics. See Chapter 2, MATERIAL BEHAVIOR, Rheology and Viscoelasticity, regarding their effects on fabricated products., Not only are there two classes of deformation, there are also two modes in which, deformation can be produced: simple shear, and simple tension. The actual action during, melting, as in the usual screw plasticator is, extremely complex, with all types of sheartension combinations. Together with engineering design, deformation determines the, pumping efficiency of a screw plasticator and, , -'=, , "", , I, , £1, , ;;:, , 0, ....J, , Low - - - _ . High, Pressure, Fig.8-5 Rheology and flow properties of plastics, (solid curve) and water (dotted curve).

Page 465 : 8 Plastic Processing, controls the relationship between output rate, and pressure drop through a die system or, into a mold., Shear rate When a melt moves in a direction parallel to a fixed surface, such as with a, screw barrel, mold runner and cavity, or die, wall, it is subject to a shearing force. As the, screw speed increases, so does the shear rate,, with potential advantages and disadvantages., The advantages of an increased shear rate, are a less viscous melt and easier flow. This, shear-thinning action is required to "move", the melt., A disadvantage observed with higher shear, rates is that too high a heat increase may occur, potentially causing problems in cooling,, as well as degradation and discoloration. A, high shear rate can lead to a rough product, surface from melt fracture and other causes., For each plastic and every processing condition there is a maximum shear rate beyond, which such problems can develop., When water (a Newtonian liquid) is in, an open-ended pipe, pressure can be applied to move it. Doubling the water pressure, doubles the flow rate of the water. Water does, not have a shear-thinning action. However,, in a similar situation but using a plastic melt, (a non-Newtonian liquid), if the pressure is, doubled the melt flow may increase from, 2 to 15 times, depending on the plastic used., As an example, linear low-density polyethylene (LLDPE), with a low shear-thinning action, experiences a low rate increase, which, explains why it can cause more processing, problems than other PEs. The higher-flow, melts include polyvinyl chloride (PVC) and, polystyrene (PS)., ModeIlPrototype Building, , Model building or prototyping is a key step, in product design. This stage, which is usually, expensive and time consuming, often account, for more than half the time taken for design., Almost every type of new product design involves creating one or more prototypes prior, to production. Different modeling systems, that have recently become available now per-, , 447, , mit making them in a matter of a few hours, or overnight where previously modeling was, only available that took from days to months, (Chapter 3, PROTOTYPE and Chapter 4,, BOOK SHELVE)., For designers using CAD, even seeing a, product on a high-resolution graphics screen, is sometimes not enough. The physical design can bring to life a high-tech design, along, with formerly unnoticed flaws. By quickly, forming 3-D conceptual models from design, ideas, designers can evaluate a design concept, demonstrate its feasibility, and then sell, the new idea., Prototyping basically provides a 3-D model, suitable for use in the preliminary evaluation of form, design, performance, and material processing of products, molds, dies, etc., When properly used this automatic/fast system can accelerate product development, improve product quality, and time to the market, for a product., Processing Behavior, , Understanding and measuring melt flow, during processing is important for two reasons. First, it provides a means for determining whether a plastic can be formed into a, useful product such as a usable extruded extrudate, completely fill a mold cavity, provide, mixing action in a screw, meet product thickness requirements, etc. Second, the flow is an, indication of whether its final properties will, be consistent with those required by the product. The target is to provide the necessary, homogeneous-uniformly heated melt during, processing to have the melt operate completely stable and working in equilibrium., In practice, even though with the developments that has occurred in the past and continues this perfect stable situation is never, achieved and there are variables that affects, the output. If the process is analyzed one can, decide that two types of variables affect the, quality and output rate. They can be identified as (1) the variables of the machine's design and manufacture and (2) the operating, or dynamic variables that control how the machine is run.

Page 466 : 448, , 8 Plastic Processing, c ...., (l)-§,, ....., >.o .(l), , ,, , Wide or Broad, , ~ MWD Material, , .... ~ ....~, , (l), , ,a .... '", , E"'z:J .-:::, "'.cO, u E, , a, , (l), , Low, , \, , \, , \, , ,,, , Molecular Weight Distribution, , High, , (a), , t, , Dlstnbullon, C, , C, , 'iii, , 'iii, , o, , Wide, , o, I/), , :;:, , ~, , o, , o, , I/), , :;:, , Temperalure, Shear ----to-, , Shear, (b), , (e), , Fig. 8·6 Melt flow rates as a function of molecular weight distribution., , Rheology and Melt Flow, , Rheology is the science of the deformation and flow of matter under force. It is concerned with the response of plastics to mechanical force. An understanding of rheology, and the ability to measure rheological properties such as molecular weight and melt flow, is necessary before flow behavior can be controlled during processing. Such control is essential for the fabrication of plastic materials, to meet product performance requirements, (Chapter 2, MATERIAL BEHAVIOR,, Rheology and Viscoelasticity)., Molecular Weight Distribution, and Melt Flow, , One method of defining plastics is to use, their molecular weight (MW), a reference to, the plastic molecules' weight and size. Here, MW refers to the average weight of plastics, that is always composed of different weight, molecules. These differences are important to, the processor, who uses the molecular weight, distribution (MWD) to evaluate materials. A, narrow MWD enhances the performance of, plastic products. Wide MWD permits easier, processing. Melt flow rates is dependent on, , the MWD. Figure 8-6 relates melt flow to, MWD starting with (a) MWD curves and followed with (b) viscosities vs. shear rates as, related to MWD and (c) factors influencing, viscosities. With MWD differences of incoming material the fabricated performances can, be altered; the more the difference, the more, dramatic change occurs in the products., MW is the sum of the atomic weights of all, the atoms in a molecule. It represents a measure of the chain length for the molecules that, make up the polymer and in turn the plastic that influences processing performances to, meet product performance (2). The MWD is, basically the amount of component polymers, that go to make up a polymer. Component, polymers, in contrast, are a convenient term, that recognizes the fact that all plastic materials comprise a mixture of different polymers, of differing molecular weights., The average molecular weight is the sum, of the atomic masses of the elements forming, the molecule, indicating the relative typical, chain length size of the polymer molecule., Many techniques are available for the determination of these molecular weight characteristics that can be related to processing performance. For example, two plastics, may have exactly the same or similar average MWs but very different MWDs with the

Page 467 : 8 Plastic Processing, , result that processing performances and performance properties of the products vary. Result could be OK but also not OK., Melt Flow and Viscosity, , When reviewing the subject of plastic melt, flow, the subject of viscosity is involved. Basically viscosity is the property of the resistance, of flow exhibited within a body of material., Ordinary viscosity is the internal friction or, resistance of a plastic to flow. It is the constant ratio of shearing stress to the rate of, shear. Shearing is the motion of a fluid, layer, by layer, like a deck of cards. When plastics, flow through straight tubes or channels they, are sheared and the viscosity expresses their, resistance., The melt index (MI) or melt flow index, (MFI) is an inverse measure of viscosity. High, MI implies low viscosity and low MI means, high viscosity. Plastics are shear thinning,, which means that their resistance to flow decreases as the shear rate increases. This is due, to molecular alignments in the direction of, flow and disentanglements., Viscosity is usually understood to mean, Newtonian viscosity in which case the ratio of, shearing stress to the shearing strain is constant. In non-Newtonian behavior, which is, the usual case for plastics, the ratio varies, with the shearing stress (Fig. 8-5). Such ratios, are often called the apparent viscosities at the, corresponding shearing stresses. Viscosity is, measured in terms of flow in Pa's, with water as the base standard (value of 1.0). The, higher the number, the less flow., Newtonian flow It is a flow characteristic, where a material (liquid, etc.) flows immediately on application of force and for which, the rate of flow is directly proportional to the, force applied. It is a flow characteristic evidenced by viscosity that is independent of, shear rate. Water and thin mineral oils are examples of fluids that posses Newtonian flow., Non-Newtonian flow Plastic melts are, non-Newtonian. They have basically abnormal flow response when force is applied. That, , 449, , is, their viscosity is dependent on the rate of, shear. They do not have a straight proportional behavior with application of force and, rate of flow. When proportional, the behavior has a Newtonian flow. Deviations from, this ideal behavior may be of several different types. One type called apparent viscosity, may not be independent of the rate of shear;, it may increase with shear rate (shear thickening or shear dilatancy or decrease with rate, of shear (shear thinning or pseudoplasticity)., The latter behavior is usually found with plastic melts and solutions. In general such a dependency of shear stress on shear rate can, be expressed as a power law. Another type, is where the viscosity may be time dependent, as for material exhibiting thixotropy or, rheopexy (2, 3, 6)., Melt Flow Rate, , MFR tests are used to detect degradation, in fabricated products where comparisons, as, an example, are made of the MFR of pellets, to the MFR of product. MFR has a reciprocal, relationship to melt viscosity. This relationship of MW to MFR is an inverse one; as the, MFR increases, the MW drops. MW and melt, viscosity is also related; as one increases the, other increases., Melt index test The melt indexer (extrusion plastometer) is the most widely used, rheological device for examining and studying plastics in many different fabricating processes. It is not a true viscometer in the sense, that a reliable value of viscosity cannot be calculated from the flow index that is normally, measured. However, it does measure isothermal resistance to flow, using an apparatus, and test method that are standard throughout, the world. The standards used include ASTM, D 1238 (U.S.A.), BS 2782-105C (U.K.), DIN, 53735 (Germany), JIS K72 10 (Japan), ISO, RI 133/R292 (international), and others., In this MI instrument the plastic is contained in a barrel equipped with a thermometer and surrounded by an electrical heater, and an insulating jacket. A weight drives a, plunger that forces the melt through the die

Page 468 : 450, , 8 Plastic Processing, , t~=~nSile, ~, , ill, 2, , a.., c, , J, , Impact Strength., Abrasion Resistance, Chemical Resistance, Melt Viscosity., Long Term Load Bearing Properties., Environmental Stress CraciOng Resistance, Melt Strength, , Brittleness Temperature, , Me" Index. gms/10 minutes, , o, , 20, , Fig.8-7 Effect of MI on the properties of polyethylene., , opening, using a standard opening of 2.095, mm (0.0824 in.) and a length of 8 mm (0.315, in.). The standard procedure involves the, determination of the amount of plastic extruded in 10 min. The flow rate (expressed in, gl10 min.) is reported. As the flow rate increases, viscosity decreases. Depending on, the flow behavior. changes are made to standard conditions (die opening size, temperature, etc.) to obtain certain repeatable and, meaningful data applicable to a specific processing operation., The MI test equipment is easy to operate,, provides repeatable results, and low cost to, operate. It is widely used for quality control, and for distinguishing between members of a, single family of plastics. Specifically, this MI, makes a single-point test that provides information on resistance to flow at only a single, shear rate. Because variations in branching, or MWD can alter the shape of the viscosity curve, the MI may give a false ranking of, plastics in terms of their shear rate resistance, to flow. To overcome this problem, extrusion, rates are sometimes measured for two loads,, or other modifications are made., In summary, the MI is an indicator of the, average molecular weight (MW) of a plastic, and is also a rough indicator of processability. Low MW materials have high MIs and, are easy to process. High MW materials have, low MIs and are more difficult to process, as, they have more resistance to flow, but they, are processable. End-use physical properties, , improve as the MI decreases (Figs. 8-7 and, 8-8). Because processability simultaneously, decreases, MI selection for a given application, is a compromise between properties and processability. Table 8-9 lists typical MI ranges, for the more common plastic processes and, materials. Materials with other MIs are still, processable, but they usually require more, sophisticated start-up procedures and operating process controls. Table 8-10 shows how, MI and density interrelate., Melt Flow and Elasticity, , As a melt is subjected to a fixed stress or, strain, the deformation versus time curve will, show an initial rapid deformation followed, by a continuous flow. Elasticity and strain are, compared in Fig. 8-9 that provides (a) basic, deformation vs. time curve, (b) stress-strain, deformation vs. time with the creep effect,, (c) stress-strain deformation vs. time with, the stress-relaxation effect, (d) material exhibiting elasticity, and (e) material exhibiting, Table 8-9 Typical melt index ranges for, common process, Process, , MIRange, , Injection molding, Rotational molding, Film extrusion, Blow molding, Profile extrusion, , 5-100, 5-20, 0.5-6, 0.1-1, 0.1-1

Page 469 : 451, , 8 Plastic Processing, Table 8-10 Performance influenced by MI and, density of plastics, , Rigidity, Heat resistance, Stress crack, resistance, Permeation, resistance, Abrasion, resistance, Clarity, Flex life, Impact strength, Gloss, Vertical crush, resistance, Cycle, Flow, Shrinkage, Parison, roughness, Parison sag, Pinch quality, Parting line, difference, , LU, CI, , C!:l, Z, , Cii, ~, , Decreases, Decreases, Increases, Increases, , Increases, Increases, , Decreases, , Flow Performance, , Decreases, Decreases, , Increases, Increases, Decreases, , Increases, , ~, z, , c::, , Decreases, Increases, Decreases, Decreases, , With, Increasing, Density, , Increases, , Cii, , u, , Decreases, Decreases, Decreases, Increases, Increases, , With, Increasing, Melt Index, , Increases, , A, , «, LU, , Decreases, Decreases, Increases, , plasticity. The relative importance of elasticity (deformation) and viscosity (flow) depends on the time scale of the deformation., For a short time elasticity dominates, but over, a long time the flow becomes purely viscous., This behavior influences processes., Deformation contributes significantly to, process-flow defects. Melts with only small, deformation have proportional stress-strain, behavior. As the stress on a melt is increased,, the recoverable strain tends to reach a limiting value. It is in the high stress range, near, the elastic limit, that processes operate., Molecular weight, temperature, and pressure have little effect on elasticity; the main, controlling factor is MWD. Practical elasticity phenomena often exhibit little concern for, the actual values of the modulus and viscosity., Although MW and temperature influence the, modulus only slightly, these parameters have, a great effect on viscosity and thus can alter, the balance of a process., , B, , In any practical deformation there are local stress concentrations. Should the viscosity, , /, ", , ";. ;/, , A. BARRIER PROPERTIES, HARDNESS, TENSILE STRENGTH, CHEMICAL RESISTANCE, B. FLEXIBILITY, ELONGATION, C. RIGIDITY, CREEP RESISTANCE, HEAT RESISTANCE, D.CLARITY, REDUCED SHRINKAGE, E. SURFACE GLOSS, , F. TOUGHNESS, STRESS CRACK RESISTANCE, , •, INCREASING MELT INDEX _ _ _ _ _ _ _ _ _, , Fig.8-8 Effect of density and MI changes on the properties of polyethylene, with properties increasing, in the direction of the arrows.

Page 471 : 8 Plastic Processing, distorted, causing defects called melt fracture, or elastic turbulence. To reduce or eliminate, this problem, the entrance to the die or mold, is tapered or streamlined., , Sharkskin During flow the melt next to, the metal tends not to move, whereas that in, the center flows rapidly. When the melt flow, pressure is relieved, its flow profile is abruptly, changed to a uniform velocity. This change requires rapid acceleration of the surface layer,, resulting in high local stress. If this stress exceeds some critical value the surface breaks,, giving the rough appearance called sharkskin. With the rapid acceleration, the deformation is primarily elastic. Thus the highest, surface stress, and worst sharkskin, will occur, in plastics with a high modulus and high viscosity, or in high molecular weight plastics of, narrow MWD at low temperatures and high, processing rates. The addition of controlled, heating, locally reducing the viscosity, is, effective in reducing sharkskin., Nonplastication This condition produces, uneven stress distribution, with consequent, lumpiness. The product could appear ugly or, have a fine matt finish. With a wide MWD, their could be a lack of gloss., Volatile There are plastics that contain, small quantities of material that boil at processing temperatures, or they may be contaminated by water absorbed from the atmosphere. These volatiles may cause bubbles, a, scarred surface, and other defects. Processing, methods of removing volatiles are used such, as drying materials to be processed, vented, plasticator barrels, etc. (Chapter 7, OTHER, BEHAVIOR, Drying Plastic)., Shrinkage The transition from room temperature to a high processing temperature, may decrease a plastic's density by up to 25 %., Cooling causes possible shrinkage (up to 3 % ), and may cause surface distortions or voiding, with internal frozen strains. As discussed in, other chapters, this situation can be reduced, or eliminated by special techniques, such as, controlled cooling under pressure., , 453, , Melt structure High shear at a temperature not far above the melting point may, cause a melt to take on too much molecular, order. In turn, distortion could result., Thermodynamic, With the heat exchange that occurs during, processing, thermodynamics becomes important. It is the high heat content of melts, (about 100 cal/g) combined with the low rate, of thermal diffusion (10- 3 cm2 /s) that limits, the cycle time of many processes. Also important are density changes, which for crystalline, plastics may exceed 25% as melts cool. Melts, are highly compressible; a 10% volume, change for a force of 700 kg/cm2 (10,000 psi), is typical. A surface tension of about 20 g/cm, may be typical for film and fiber processing, when there is a large surface-to-volume, ratio (Appendix B, TERMINOLOGY,, Thermodynamic) ., , Residence Time, It is the amount of time a plastic is subjected to heat during the fabrication of plastics such as in a plasticator during extrusion,, injection molding, or blow molding. Too long, a residence time (and/or to high a heat) can, result in over heating the melt. Depending, on the plastic being melted a relatively minor, to a definite major problem could result lowering the fabricated product's performance., With recycled plastics the residence time includes the previous melting action time plus, the reprocessing melt action time. If there is, a third recycling of the same plastic, add that, time period .... and so on., , Chemical Change, The chemical changes that can occur, during processing and effect product performances include (1) continued polymerization and cross-linking, which increases viscosity; (2) depolymerization or damaging of, molecules, which reduces viscosity; and (3)

Page 472 : 454, , 8 Plastic Processing, , complete changes in the chemical structure,, which may cause color changes. Already, degraded plastics may catalyze further, degradation., Trend, Because melts have different properties, and there are many ways to control processes,, detailed factual predictions of final output, are difficult to arrive. Research and hands-on, operation have been directed mainly at explaining the behavior of melts or plastics like, with other materials (steel, glass, and so on)., Modem equipment and controls are overcoming some of this unpredictability. Ideally,, processes and equipment should be designed, to take advantage of the novel properties of, plastics rather than to overcome them., Processing And Property, Problem/Solution, In order to understand potential problems, and their solutions, it is helpful to consider, the relationships of machine capabilities,, plastics processing variables, and part performance. Chapter 3, FEATURE INFLUENCING PERFORMANCE provides a preliminary analysis to this subject., A distinction should be made between machine conditions and processing variables., Machine conditions are basically temperature, pressure, and processing time (such as, screw rotation/rpm, and so on) in the case of a, screw plasticator, die and mold temperature, and pressure, machine output rate (lb'/hr),, and the like. Processing variables are more, specific such as the melt temperature in the, die or mold, melt flow rate, and pressure used., The distinction between machine conditions and fabricating variables is a necessary, one to avoid mistakes in using problem-andsolution or cause-and-effect relationships to, advantage. If the processing variables are, properly defined and measured, not necessarily the machine settings, they can be directly, , correlated with the products' properties. For, example, if one increases cylinder temperature, melt temperatures do not necessarily, also increase. Melt temperature is also influenced by screw design, screw rotation rate,, back pressure, and dwell times. It is much, more accurate to measure melt temperature, and correlate it with properties than to correlate cylinder settings with properties., The problem-solving approach that ties, the processing variables to products' properties includes considering melt orientation,, polymer degradation, free volume/molecular, packing and relaxation, cooling stresses, and, other such factors. The most influential of, these four conditions is melt orientation,, which can be related to molded-in stress or, strain., Plastic degradation can occur from excessive melt temperatures or abnormally long, times at temperature, called the residence, time or heat history from plasticator to cooling of the product. Excessive shear can result from poor screw design, too much screw, flight-to-barrel clearance, cracked or wornout flights, and such. Orientation in plastics, refers simply to the alignment of the meltprocessing variables that definitely affect the, intensity and performance of orientation., Plastic with a Memory, Thermoplastics can be bent, pulled, or, squeezed into various useful shapes. But, eventually, especially if heat is added, they, return to their original form. This behavior,, known as plastic memory, can be annoying., If properly applied, however, plastic memory, offers interesting design possibilities for all, types of fabricated parts (Chapter 6, PLASTICS WITH A MEMORY)., Orientation, A plastic's molecular orientation can be, developed during processing. Initially the, melted molecules are relaxed. During processing the molecules tend to be more

Page 473 : 455, , 8 Plastic Processing, Table 8-11 Effects of orientation of polypropylene films, Stretch (%), Properties, , None, , 200, , 400, , 600, , 900, , Tensile strength, psi, (MPa), Elongation at break, %, , 5,600, (38.6), 500, , 8,400, (58.0), 250, , 14,000, (96.6), 115, , 22,000, (152.0), 40, , 23,000, (159.0), 40, , Properties, Tensile strength, psi (MPa), MD*, TDt, Modulus of elasticity. psi, MD, TD, Elongation at break, %, MD, TD, , As Cast, , Uniaxial, Orientation, , Balanced, Orientation, , 5,700 (39.3), 3,200 (22.1), , 8,000 (55.2), 40,000 (276), , 26,000 (180), 22,000 (152), , 150,000 (1,030), 4000,000 (2,760), , 340,000 (2,350), 330,000 (2,280), , 96,000 (660), 98,000 (680), 425, 300, , 300, 40, , 80, 65, , *MD = Machine direction., tID = Transverse direction and direction of universal orientation., , oriented than relaxed, particularly when, sheared, as during flow in an injection mold or, through an extrusion die. After temperaturetime-pressure is applied and the melt goes, through restrictions (molds, dies, etc.), the, molecules tend to be stretched and aligned, in a parallel form. The result is a change in, directional properties and dimensions., The amount of change depends on the type, of thermoplastic, the amount of restriction,, and, most important, its rate of cooling. The, faster the rate, the more retention there is, of the frozen orientation. After processing,, products could be subject to stress relaxation,, with changes in performance and dimensions., With certain plastics and processes there is, an insignificant change. If changes are significant and undesirable, one must take action, to change the processing conditions, particularly increasing the cooling rate., By deliberate stretching, the molecular, chains of a plastic are drawn in the direction, of the stretching, and inherent strengths of, the chains are more nearly realized than they, are in their naturally relaxed configurations., Stretching can take place with heat during or, after processing by blow molding, extruding, , (review in this Chapter EXTRUSION, Orientation), thermoforming, etc. Products can, be drawn in one direction (uniaxially) or in, two opposite directions [biaxially, also called, bioriented (BO)], in which case many properties significantly increase uniaxially or biaxially (Table 8-11 and Fig. 8-10)., Molecular orientation results in increased, stiffness, strength, and toughness (Table, 8-12); as well as resistance to liquid and, gas permeation, crazing, microcracks, and, others in the direction or plane of the orientation. The orientation of fibers in reinforced plastics causes similar positive influences. Orientation in effect provides a means, of tailoring and improving the properties of, plastics., Considering a fiber or thread of nylon-66,, which is an unoriented glassy polymer, its, modulus of elasticity is about 2,000 MPa, (300,000 psi). Above the Tg its elastic modulus drops even lower, because small stresses, will readily straighten the kinked molecular, chains. However, once it is extended and has, its molecules oriented in the direction of the, stress, larger stresses are required to produce, added strain. The elastic modulus increases.

Page 474 : 456, , 8 Plastic Processing, , Table 8·12 Effect of molecular orientation on the impact properties of polypropylene films, ASTM Tensile Impact, ft.-lb./in. 2, Temperature, Room, , -20°F (-29°C), , 40, avove test limit, , 500, , Material, Unoriented PP, Oriented PP, , o, , High-Energy Fatigue Impact (55 lb. weight @ 50-in. height) (24.9 kg weight at 127-cm height), Number of drops to failure, , Material, Steel, Unoriented PP, 41 x 103 psi tensile, Oriented PP, 28 x 103 psi, 32%, elongation, , 12, 1, 130, , Graph (a), , f, , >t-, , o::, UJ, a., o, 0::, , a., , :i., u, , ~, , -, , isUJ - - - - -_ __, :l;, , -, , elongation to, fracture, , energy to break, , INCREASING ORIENTATION, , _, , Graph (c), Graph (b), , Glass, transition, temperature, , Flexibility, , Increasing temperature - - - -••, Increasing temperature, , Fig.8·10 Effect of orientation on the properties of plastics., , ~

Page 475 : 8 Plastic Processing, The next stop is to cool the nylon below, its Tg without removing the stress, retaining its molecular orientation. The nylon becomes rigid with a much higher elastic modulus in the tension direction [15,000 to 20,000, MPa (2 to 3 x 106 psi)]. This is nearly ten, times the elastic modulus of the unoriented, nylon-66 plastic. The stress for any elastic, extension must work against the rigid backbone of the nylon molecule and· not simply, unkink mol~cules. This procedure has been, commonly used in the commercial production of man-made fibers since the 1930s via, DuPont., Another example of the many oriented, products is the heat-shrinkable material, found in flat or tubular films or sheets. The, orientation in this case is terminated downstream of an in-line extrusion-stretching operation when a cool enough temperature is, achieved. Orientation can also be performed, as a secondary operation. Reversing the operation, shrinkage occurs. The reheating and, subsequent shrinking of these oriented plastics can result in a useful property. It is used,, for example, in heat-shrinkable PE wrapping, of packages, flame-retardant PP tubes, flat, communication cable wraps, furniture webbings, pipe fittings, medical devices, and many, other products (Chapter 4, TRANSPARENT AND OPTICAL PRODUCT, Polarized Lighting)., , 457, , makes one aware that many steps are involved in processing and all must be properly understood and coordinated (Fig. 1-3)., Basically the FALLO approach diagram consists of: (1) designing a product to meet performance and manufacturing requirements, at the lowest cost; (2) specifying the proper, plastic material that meet product performance requirements after being processed;, (3) specifying the complete equipment line by, (a) designing the tool (mold, die) "around", the product, (b) putting the "proper performing" fabricating process "around" the tool,, (c) setting up auxiliary equipment (up-stream, to down-stream) to "match" the operation, of the complete line, and (d) setting up the, required "complete controls" (such as testing, quality control, troubleshooting, maintenance, data recording, etc.) to produce "zero, defects"; and (4) purchasing and properly, warehousing plastic materials. Using this type, of approach leads to maximizing product's, profitability., Tooling, Tools include dies, molds, mandrel, jigs, fixtures, punch dies, etc. for shaping and fabricating parts (Tables 8-13 and 8-14)., Mold, , Directional Property, Another important orienting fabricating procedure concerns applying directional, properties to reinforced plastics. This subject is reviewed in Chapter 3, DESIGN, CONCEPT, Reinforced Plastic Directional, Property., , FALLO Approach, All processes fit into a scheme that requires, the interaction and proper control of different operations. An example is the FALLO, (Follow ALL Opportunities) approach that, , Molds are used in many plastic processes, with many of the molds having common assembly parts (Fig. 8-11). Many molds, particularly for injection molding, have been, preengineered as standardized products that, can be used to include cavities, different runner systems, cooling lines, unscrewing mechanisms, etc. (Table 3-17)., There are different types of injection molds, that permit processing plastics by different, techniques (Fig. 8-12). To meet different, product shape requirements mold design operations range from simple to very complex, (Figs. 8-13 to 8-15) designs. Target is to design, pr~ducts that will require the easiest mold, to design. A mold can be a highly sophisticated/ expensive piece of equipment. It can

Page 476 : AL, , I, , FILLED, EPOXY, , I, , MEHANITE, , I, , CASTAL, , I, , srEEL, , FILLEDIRIM, EPOXY, , I, , I, , I, , srEEL, , STEEL, ) CAST AL, ( MACHINE, H08BED, ELECTRO MACH. AL, FORM .., BACK·UP, KIRKSITE, ELECTROFORM, .. BACK UP, , SoC., , I, , I, , HI VOL, , I, , HI VOL, , HI VOL, , LOW VOL, , Table 8-13 Guide to tooling selection, , FILLED, EPOXY, , I, , FIBERGLAS, , I, AL, I, PLASTER, I, EPOXY·, , LOVOl, STEEL, IMACH, HOBBEDI, , I, , HI VOL, , I, AL, I, , I, , ,, , AL, , PLASTIC, , I, , SPRAYED, METAL, , I, , PLASTIC, , I, , SILICONE, , I, , i, , ELASTOMER, , I, , SPRAYED, METAL, , I, , ELASfOMER, , I, , PLASTIC, ITP OR TSI, , DIP METAL, , DIPPED METAL, , ELECTRO FORM, , I, , STEEL, , WOOD, , I, , I, , I, , SPRAY METAL, , ELECTRDFORMED, , ~.----:!'ELASTOMER, I, , SHEET, METAL, , LD VOL, , I, , ELECTRDFORM, , I, , CAST AL, , I, , HI VOL, , R;;TOF~~, , PLASTIC, , PLASTER, , I, WOOD, I, , LO, , I, , AL, , I, , PL.ASTER, , I, AL, , HI, , ELECTJOFORM, , LOVOL, , I, , ~, , ~., , ~, , §, , ...., '"t:;., , is", , '"tI, , 00, , 00

Page 477 : 8 Plastic Processing, Table 8·14, , 459, , Average properties and relative cost of certain tool alloys, , Alloy, Designation, , Tensile, Strength, 0.2% Yield, , Working, Hardness, , Coeff. of, Thermal, Expansion, , Thermal, Conductivity, , AISI4140, AISI P20, AISI H 13, UNS S42000, PH 15.5, MAR 18(300), , KSI, 100, 120, 180, 200, 175, 290, , Rockwell C, 27-30, 28-35, 40-45, 28-30, 38-40, 48-56, , 106 lOP, 12.7, 7.1, 7.1, 6.5, 6.2, 5.6, , BTU/FT2/HRloP, 19, 17, 17, 15, 12, 17, , comprise of many parts requiring high quality metals and precision machining. To capitalize on its advantages, the mold may incorporate many cavities, adding further to its, complexity., Production molds are usually made from, steel for pressure molding that requires heating or cooling channels, strength to resist, the forming forces, and/or wear resistance to, withstand the wear due to plastic melts, particularly that which has glass and other abrasive fillers. However most blow molds are, cast or machined from aluminum, beryllium, copper, zinc, or Kirksite due to their fast, heat transfer characteristics. But where, they require extra performances steel is, used., , Cost Index, (AISI4140=1), 1.0, 1.3, , 3.5, 2.5, 4.5, 7.5, , The design and construction of a mold, plays a significant role in the dimensional, integrity of its product. The cavity that forms, the final product can be shaped using a, variety of steel removal methods from jig, grinding to wire-feed electrical discharge, machining. Each removal method has a corresponding range of variation. Although the, tolerances of these processes are geometry, dependent, some processes are more accurate than others. Studies can be performed to, determine an average range of variation for, each method. Among other important tool, design and construction considerations for, determining tool performance for a given dimension are the mold's construction details,, such as its main parting lines. All these factors, , Ring, - - - - - - - -- - -Sprue Bushing, , ~----------Locat i ng, , -Front Cay. Retainer PI., H..;t---Water Channels, , Guide Pin Bushing, Rear Cay. Retainer PI., 10.."'-I+<H*---Push-back PIO, Support Plate, , I __-i+--l!;!~~~===Ejector, , Pin, Sprue Lock Pin, Support P,llar, Ejector Reta iner PI., , ,., , \, , "''' Ejector Plate, LClamp Slot, Ejector Housing, , Fig.8.11 Two-part standard mold.

Page 478 : 460, , 8 Plastic Processing, INJECTION MOlD, TOP CLAMPI NG PLATE, COOLING LINES, , *"". . . . '"'t-"._-WATER, , CAVITY PLATE, , (j), , -CAVITY AND MOLDED PART, MOLD SEPARATES, -RUNNER, PUNCH OR FORCE PLATE, :'~if-H:"'-;-"":::1-- PUNCH OR FORCE, , ®, , SUPPORT PLATE, EJECTOR HOUSING, -EJECTOR PLATES, , UNNER PLATE, , >-~~dI.".~~~r~mM!.'7m~~~-, , MOLD SEPARATES, CAVITY PLATE, , ,.,.,.'Ht'--<--, , (j), , ®, , MOLD SEPARATES, PUNCH OR FORCE PLATE, , @, , KNOCKOUT PINS, , I~~~~~~==;~~~~~~~,--I, ~, , -, , EJ ECTOR HOUSI NG, EJECTOR PLATES, , .......~...=Ol'--I-- HOT, , \"i!!!I.~I(II, , RUNNE R, , ~~~~~:;~~~., ~~t;~---ELECTRIC, frl, MAN I FOLD HEATED, -INSULATED NOZZLE, ~i---<·--MOLD, , SEPARATES, , Fig.8·12 Types of molds., , add to the overall variations in related, dimensions of the mold's products (3, 7, 9,, 10,20)., , Die, The function of a die is to accept the available melt from an extruder and deliver it, , to takeoff equipment as a shaped extrudate, (profile, film, sheet, pipe, filament, etc.) with, minimum deviation in cross-sectional dimensions and a uniform output by weight, at the, fastest possible rate (Figs. 3-34 to 3-36). A, well-designed die should permit color and, compatible plastic changes quickly with little off-grade material. It will distribute the

Page 479 : 461, , 8 Plastic Processing, , I'K-o---'-I-ELECTRIC HEATER, -INSULATED RUN ER, , CAVITY AND MOLDED PART, ~"---<, , -, , MOLD SEPARATES, I NSULATING SHEll, , -........--- MOLTEN POLYMER, , HOT MANIFOLD, , ~~-<.-, , MOLD SEPARATES, , INJECTION MOLD, , I'E9ffl"740f7'i"'iT~~-HEATI N GUN IT, , Fig. 8·12, , melt in the die flow channels so that it exists, with a uniform density and velocity. Figure, 8-16 is an example of one type of die; different, designs are use to extrude different products., The flow rate is influenced by all the variables that can exist in preparing the melt during extrusion such as die heat and pressure, with time in the die. Unfortunately, in spite of, , ( Continued), , all the sophisticated plastic flow analysis and, the rather mechanical computer-aided design, capabilities, it is very difficult to design a die., Experience (most important) with an empirical approach must be used, as it is quite difficult to determine the optimum flow channel geometry from engineering calculations., It is important to employ rheological flow

Page 480 : 462, , 8 Plastic Processing, , A, , L_, , ~, , A, , A, , ~, , A-A, , A-A, this, , not this, , parting line, , A-A, , A-A, , this, , this, , this, , Fig.8·13 Methods of molding holes or openings in sidewalls without undercutting mold movement., , properties and other melt behavior via the, applicable CAD programs for the type of die, required. The most important ingredient is, experience, which, for the novice, is hopefully, properly recorded in a computer program., Nevertheless, die design has remained more, , Fig.8·14 Slide within a slide mold., , of an art than any other aspect of process design. Dies can work only if the operator of, the processing line has developed the important ability to debug through proper process, controls., A well-built die with adjustments (temperature changes, restrictor/choker bars, valves, and other devices) may be used with a particular group of materials. Usually a die is designed for a specific plastic meeting its particular rheological behaviors. To simplify the, processing operation, the die design should, consider certain factors. If possible the goals, are to have the extrudate (product) of a, uniform wall thickness (otherwise the heat

Page 481 : 8 Plastic Processing, , 463, , that when a melt is extruded from the die,, there is some swelling (as reviewed latter in, the Extrusion section). After exiting the die,, it is usually stretched or drawn down to a size, equal to or smaller than the die opening. The, dimensions are then reduced proportionally, so that in an ideal plastic the drawn-down, section is the same as the original section., Because of the melt -elasticity effects of the, material, it does not draw down in a simple, proportional manner; thus, the draw-down, process is a source of errors in the profile., Errors are significantly reduced in a balanced, situation such as circular extrudate. These errors must be corrected by modifying the die, and takeoff equipment., There are substantial influences on a material created by the flow orientation of the, molecules, so there are different properties, in the flow direction and perpendicular to, the flow. These differences have a significant effect on the performance of the part, (Chapter 2)., The pumping pressure required on the, melts entering the different designed die, heads differs to meet their melt flow patterns, within the die cavities. The pressure usually, varies as follows: (1) blown and lay-flat films, at 13.8-41.3 MPa (2000-6000 psi); (2) cast, film, sheet, and pipe at 3.5-27.6 MPa (5004000 psi); (3) wire coating at 10.3-55.1 MPa, (1500-8000 psi), and (4) monofilament at, 6.9-20.7 MPa (1000-3000 psi)., Fig.8-15, , Method of molding threaded caps., , transfer problem is magnified); to minimize, the use of hollow sections; to minimize narrow or small channels; and to use generous, radii on all comers, such as a minimum of, 0.5 mm (0.02 in.). An "impossible" or difficult, process can still be designed, but it requires, extensive experience (both practical and theoretical), with trial-and-error runs, to make it, practical., , Basics of Flow, The non-Newtonian behavior of a plastic, melt makes its flow through a die somewhat, complicated. One characteristic of plastic is, , Injection Molding, , Continued development in the 1M process is due to its worldwide, large sales of, 1M equipment that are required to meet new, processing demands. Equipment involved is, approximately $4.5 billion/yr. (USA $1.35, billion/yr) with estimates at 30% in machines,, 60% in molds, 6% in robots, and 4% in hot, runners. Marketwise 55% are technical products (electronic, mechanical, medical, etc.),, 20% automotive, 10% packaging, and 15%, others. Worldwide approximately $180 billion/yr. sales exist for 1M products (2, 3)., The 1M process is greatly preferred by designers because the manufacture of products

Page 482 : 8 Plastic Processing, , 464, , MANIFOLD CHAMBER, THAT CAN, INCLUDE TEAR·DROP SHAPE ., DIE BLADE, ADJUSTMENT, , ADJUSTABLE, DIE BLADE, , DIE, , DELIVERY, FROM eXTRUDER, , BODY--VAi'lm.~, , Fig.8-16 Simplified schematic of an extruder sheet die., , in complex 3-D shapes can be more accurately controlled dimensionwise and tolerancewise with 1M than with other processes., As its method of operation is much more, complex than others, 1M requires a thorough, understanding of the process. There are basically two IMM systems that are the reciprocating and two-stage systems (3)., Figure 8-17 shows a reciprocating schematic of the load profile that highlights the way, in which the melt is plasticized (softened) and, forced into the mold, the clamping system, for opening and closing the mold under pressure; the type of mold used, and the machine, controls. There are many different types or, designs of IMMs (1M machines) that permit, molding many different type products based, on factors such as quantities, sizes (from micro to large sizes), shapes, product performances, type plastic and/or economics (3)., Nozzle, , Plastic moves from the hopper onto the, feeding portion of the reciprocating extruder, screw. The flights of the rotating screw cause, the material to move through a heated extruder barrel where it softens (is made fluid), so that it can be fed into the shot chamber, (front of screw). This motion generates pressure [usually 50-300 psi (0.35-2.07 MPa)],, which causes the screw to retract. When the, preset limit switch (or a position transducer), is reached the shot size is met and the screw, stops rotating. Basically at a preset time the, screw acts as a ram to push the melt into the, mold. Injection takes place at high pressure, [usually 2,000-5000 and also up to 30,000 psi, (14-35 up to 210 MPa)]. There is also limited use of lower pressure operations [usually down to 50-300 psi (0.34-2.07 MPa)]., The low pressure systems have been used in, molding foams that are small to very large, , Screw, 2.25 in. dia., (4 sq. in.), , Hopper, , 1, Sprue, , Mold, Runner, Gato 12,000 psi, , r;::::::::;::;=::::;-,, , Hydraull C, , ~~==rF.l, , Cylinder,, 7.16mdia., (40sq. in.), , r~==~~~~~@~~@~~~~, , Molded part, 4,000 psi, , 20,000 psi on melt, (80,000 Ibs/4 sq. in ... 20,000 psi), 15,000 psi, , t, Oil from, pump, , ~ 2,000, , psl, , Fig.8-17 Example of pressure loading on the plastic melt during 1M.

Page 483 : 8 Plastic Processing, products, decorative products such as overor in-molding, etc. Adequate clamping pressure must be used to eliminate mold opening, that would cause flashing. The melt pressure, within the mold cavity can range from 1 to, 15 tons/sq. in. The pressure used is dependent on the plastic's rheologylfiow behavior, (Chapter 2)., Time, pressure, and temperature controls, indicate whether the performance requirements of a molded product are being met., The time factors include the rate of injection,, duration of ram pressure, time of cooling,, time of plastication, and screw RPM. Pressure requirement factors relate to injection, high and low pressure cycles, back pressure, on the extruder screw, and pressure loss before the plastic enters the cavity which can, be caused by a variety of restrictions in the, mold. The temperature control factors are in, the mold (cavity and core), barrel, and nozzle, as well as the melt temperature from back, pressure, screw speed, frictional heat, and so, on in the plasticator., Even though most of the literature on, processing specifically identifies or refers to, thermoplastics (TPs) as in this book, some, thermosets (TSs) are used (TS polyesters,, phenolics, epoxy, etc.). The TPs reach maximum heat prior to entering "cool" mold cavities, whereas the TSs reach their maximum, temperature in "hot" molds (Fig. 6-3)., 1M is a repetitive process in which melted, (plasticized) plastic is injected or forced into a, mold cavity(s) where it is held under pressure, , until removed in a solid state, basically duplicating the cavity of the mold. The mold may, consist of a single cavity or a number of similar or dissimilar cavities, each connected to, flow channels or runners that direct the flow, of the melt to the individual cavities. Three, basic steps occur: (1) raising the plastic temperature in the injection or plasticizing unit, so that it will flow under pressure, (2) allowing the plastic melt to solidify in the mold via, the mold's cooling action, and (3) opening the, mold to eject the molded product(s)., There can be a single gate or multiple gates, in a mold cavity that depends on melt flow, pattern desired in the cavity. Other considerations exist such as determining whether, a high flow rate or low melt flow rate is required in the cavity. Target is to eliminate or, reduce any potential weld lines that can effect strength and/or appearance (Fig 8-18),, and whether a smooth process sequence is, used or an abrupt change is introduced during the cycle. These are only a few of the considerations that have to be made in order to, produce a suitable product (3, 223)., Depending on how the melt flow enters, and is distributed in the cavity, its strength, (and other properties) can be orientated to, meet performance requirements. Note that in, Fig. 8-19 melt spreads in a branching pattern., Fig. 8-20 is an example where the highest, stress is parallel in the orientation direction., An example of locating a gate to obtain required performance of a product that is being subjected to flexing in service is shown in, SURFACE HIGHLY ORIENTED, , v, , E, o, , C, , I, , T, , Y, , P, R, , ~, , t, , , /, , CORE ORIENTATION, FRON BULK-SHEAR - -, , \, , 465, , \', , I, L, E, , SUB-SURFACE ORIENTATION, FROM HIGH SHEAR NEAR WALL, , Fig.8-18 Flow paths are determined by product shape and gate locations.

Page 484 : 466, , 8 Plastic Processing, , Cavity, Parting li ne, , (A), , Fig.8-19, , (B), , Flow pattern in a center gated circular product., , Fig, 8-21: (a) edge gated, (b) center gated,, and (c) edge gated on left side failed whereas, edge gated (between fingers) did not fail., Melt flow paths are determined by product shape and gate location. As shown in, Fig. 8-22 flow fronts that meet head on will, weld together, forming a weld line. Parallel, fronts tend to blend, however they can produce a less distinct meld line that usually results in a stronger bond. If the flow fronts do, not have the ideal melt conditions (low temperature, insufficient melt packing, etc.) bond, could be very weak; in fact there could be no, bond. Adjusting melt conditions will result, in maximizing the bond strength (Figs. 8-23, and 8-24)., The primary inherent features of molded, products remain unchanged despite some, very major hardware developments and, widely varying techniques for controlling the, , STRESS PARALLEL TO ORIENTATION, , STRESS PERPENDICULAR TO ORIENTATION, , Fig. 8-20 Effect of orientation during melt flowing through a cavity., , process technology that keeps simplifying, the IM process. The final specific properties, and property distributions will dependent on, the selected process parameters and conditions. The evolution from traditional techniques to very sophisticated, adaptive methods have been accelerated since about the, 1970s. Distinct product performance and cost, advantages are gained when special sequencing is implemented with advanced process, control., The pace of development has increased, with the commercialization of more engineering plastics and high performance plastics that were developed for load-bearing, applications, functional products, and products with tailored property distributions., Polycarbonate compact discs, for example,, are molded into a very simple shape, but, upon characterization reveal a distribution, of highly complex optical properties requiring extremely tight dimension and tolerance, controls (3, 223)., Many of the new plastics, blends, and, material systems require special, enhanced, processing features or techniques to be successfully injection molded. The associated, materials evolution has resulted in new plastics or grades, many of which are more viscoelastic. That is, they exhibit greater melt, elasticity. The advanced molding technology, has started to address the coupling of viscoelastic material responses with the process, parameters. This requires an understanding, of plastics as viscoelastic fluids, rather than as, purely viscous liquids, as is commonly held

Page 485 : 8 Plastic Processing, , 467, , Direction of, Orientation, (a), , Fig. 8·22, , (b), , Examples of weld and meld lines., , thin wall products such as cell phones, mobile modems, and personal organizers. These, high-flow plastics typically have lower average molecular weights, resulting in reduced, viscoelastic behavior., The basic steps of the 1M process produce unique structures in all molded products, whether they are miniature (micro) electronic components, compact discs, or large, automotive bumpers. These structures have, frequently been compared to plywood with, several distinct layers, each with a different, set of properties. In all 1M products, a macroscopic skin-core structure results from the, flow of melt into an empty cavity. Identifiable, zones or regions within the skin are directly, , (c), , Fig.8·21 Effect of edge (a) or center gating (b) a, mold showing (c) edge performed but center failed, (view on right side)., , in the past. The importance of this new insight is apparent when a root-cause analysis is performed on some of today's molded, defects, such as surface blemishes and variations in gloss. Exceptions in the materials, development arena are high flow plastics for, , Fig. 8·23 Example of weld lines where the gate, was located at the top center of the telephone, handset.

Page 486 : 468, , 8 Plastic Processing, , ~5, , o, , ~4.5..--, , _ __, , 15 4, is, 3.5, z, , ;3, ~, , 2.5, , '"~2, :>, , ~ 1.5, , ....__ ,-, , SINGLE GATED NOTCHED, SPECIMENS, , ---...,..------DOUBLE GATED WELD LINE, SPECIMENS, , g, ... 1, , 380, , 4DO, , 420, 440, 460, 480, STOCK TEMPERATURE - • F, , 500, , 520, , Fig. 8·24 Izod impact strength of ABS plastic vs., stock (melt) temperature., , related to the flow conditions and the temperature difference between the cold cavity, walls and the hot plasticized melt., The basics observed in molded products, are always the same; only the extent of the, features varies depending on the process, variables, material properties, and cavity contour. That is the inherent hydrodynamic skincore structure characteristic of all 1M products. However, the ratio of skin thickness to, core thickness will vary basically with process conditions and material characteristics,, flow rate, and melt-mold temperature difference. These inherent features have given rise, to an increase in novel commercial products, and applications via coinjection, gas-assisted,, low pressure, fusible-core, in-mold decorating, etc., The 1M process is a manufacturing technology that has been modified, extended, and refined for over a century. Many different methods and techniques have been introduced to, improve the process and make it more economical in the manufacturing environment., Although these advances have been significant, a technical analysis reveals that relatively few conceptual difference exist between the early process patents and today's, methodology (223, 224)., , Thickness of Section and Rib, Plastic products should be designed with, the minimum wall thickness that will provide, the specified structural requirements. This results in saving material and higher molding, , output due to the rapid transfer of heat from, the molten plastic to the cooler mold surfaces. Wall thicknesses should be made as, uniform as possible to eliminate distortion,, internal stresses, and cracking. Ribs can be, used to increase product strength without increasing wall thickness. This approach not, only provides strength, but improves material flow and helps prevent distortion during, cooling (Appendix A: PLASTICS DESIGN, TOOLBOX)., Holes are often required in molded products. They should be designed and located, so as to introduce a minimum of weakness, and to avoid complication in production. This, means, for example, that several holes should, not be located close together unless a thicker, wall section is provided. Where many design, problems posed problems due to holes, it is, often less expensive to drill after molding,, particularly when holes must be deep in proportion to their diameter. However incorporating holes in a mold can be routine., , Designing bucket By way of another example consider a common household bucket., The analysis that a typical molder might, make follows. The mechanical properties required are moderate namely tensile strength, of 6,000-8,000 psi and impact strength of, about 1 ft-Ib/in. (Izod). It must be sufficiently, rigid to hold 2 gal of water but some flexibility is desirable in order to absorb bumps and, knocks during its use. Electrical properties, are clearly unimportant, but water resistance, and dimensional stability at moderately elevated temperatures must be good. Heat resistance must be adequate to deal with very, hot water (80 a C) but not necessarily with any, heat over 100a e., It must he produced in large quantities,, over 100,000 per year and, being a domestic utility item, it should be priced low such, as $3.00 at retail. Market studies indicate that, it should be available in a wide range of colors. The size, quantity needed, and price suggest an 1M in a TP material. A study of the, cost and properties of the various plastics will, show that in general the TPs will have the, required properties at a lower cost than will, the TSs. In addition they are more adaptable

Page 487 : 8 Plastic Processing, to high speed mass production techniques,, such as 1M. Problems will arise when a specific manufacturing process must be used due, to its availability at the manufacturing company. This situation will dictate a new analysis based on the limitations of the available, process., As an example the cellulosics are ruled out, due to poor dimensional stability at elevated, temperatures. They will begin to distort at, around 50°C (122°F). The polystyrenes, even, the rubber-modified types, are also subject, to heat distortion above 80°C (176°F). Looking farther down the list of mechanical properties we note that high density polyethylene (HDPE) is available in grades which, do not distort until they reach temperatures, above 110°C (230°F). Moreover, the past experience of other processors has shown that, HDPE is often a logical and effective choice, for this type of product. Further analysis, shows that the tensile and impact strength is, sufficiently great for our purpose and that the, material is available in a wide range of colors. Finally, the current published prices of, the material place it well within the range of, the economics of the decision., Much of this design is usually based on the, molder's experience. It does not use very scientific selection principles but uses a practical approach (Fig. 1-4). The most important source of product design ideas is usually,, when available, from the competitor's product lines. The list of materials quoted cannot, be considered exhausted. Very often special, grades of various plastics are made to meet, a demand for some particular modification, of one or other property. New advances in, copolymers have greatly increased the range, of properties available to the plastic designer., In general, the more rigid the specification, covering end use, the easier the selection, becomes., , 469, , mold capabilities, plastics processing variables (Fig. 8-25), and product performances., As reviewed a distinction has to be made, between machine conditions and processing, variables., The nomograph shown in Fig. 8-26 is a simplified approach in determining shrinkage, of a molded plastic. Each plastic has its own, mold shrinkage behavior that is related to, specific molding conditions. As an example, by over pressure packing the cavity one could, literally have zero shrinkage immediately after molding. However it could have excess dimensional changes there after. In the nomograph a straight line connects a thickness, as, an example, of 3 mm (1.2 in.) on line (1) to, a gate area of 4.5 mm2 (0.0072 in 2 ) on line, (3). [A gate could be 1.5 mm (0.06 in.) thick, times 3 mm (0.12 in.) wide.] Line from (1) to, (3) intersects line (2) at 0.020 mm/mm (0.020, in.lin.) that is the estimated plastic shrinkage, at a mold temperature of 93°C (200°F)., This simplified approach is only a guide, to show what is happening when only considering thicknesses and gate sizes. Since, many other variables exist (change in thicknesses, melt flow behavior, melt temperature/pressure/speed, heat transfer through, the mold, etc.) experience provides the guide, lines that involve the product design and processing behavior. Software programs have, been developed to analyze these type variables that provides some type of relation to, shrinkage., Productivity is directly related to cycle, time. There usually is considerable common, knowledge about a geometry and process, conditions that will provide a minimum cycle time. Practices such as using thinner wall, sections, cold or hot runners for TPs or hot or, cold ones for TSs narrow sprues and runners,, the optimal size and location of coolant (or, heat) channels, and lower melt or mold heat,, will decrease the solidification time reducing, the cycle time., , Productivity, In order to fabricate a cost-performance, effective molded product and understand potential problems vs. solutions, it is helpful, to consider the relationships of machine-to-, , Modified 1M Technique, A few of these techniques will be reviewed, that provide designers different capabilities

Page 488 : 470, , 8 Plastic Processing, , t, , SHRINKAGE, , WITH FLOW, , ~---~­, , -ACROSS FLOW, , t, , SHRINKAGE, IN LINE, OF FLOW, , MOLD TEMPERATURE-, , t, , SHRINKAGE, , WITH FLOW, , GATE AREA -, , t, , =-A~, MELT TEMPERATURE -, , CAVITY THICKNESS -, , t, , SHRINKAGE, , t, , POST, MOLDING, SHRINKAGE, OF, CRYSTALLINE, POLYMER, , ------, , \ . . RESTRICTED GATE, , ~E, , t, , SHRINKAGE, , ANNEALED, , AGEING TIME _, , ~, CAVITY THICKNESS -, , PACKING TIME -, , &'", , RE~, , t, , DEGREE, OF, ORIENTATION, IN MOLDING, , PACKING, TIME, , -, , MELT, TEMPERATURE, , Fig. 8-25 Examples of how 1M behaves, including shrinkage., , to fabricate products. An example is the profile molding. During traditional molding, the, cavity walls are stationary. In some cases, it is, advantageous to move the walls during the, filling step or the cavity packing step. Different methods are used in the mold that includes movement of the cavity walls perpendicular to the parting line, and rotation or, sliding of the cavity walls. Rotating a core during the filling step adds a biaxial orientation, to the plastic especially on the surface. Flexural properties, as well as other mechanical, properties, are greatly improved. Polystyrene, drinking cups and polypropylene syringes, are two examples that readily show large, improvements., , Co injection molding Coinjection molding produces products that can help one, , visualize the unique structures created in 1M, products (3). As an example plastic "A" is injected first from one plasticator and fills only, a portion ofthe cavity. Next, Plastic "B" is injected sequentially behind "N' from another, plasticator and maintains the basic pressuredriven flow field. When "A" and "B" are metered in the correct proportions for the relative size of the skin region and core region,, the result is a molded product that exhibits a, core "B" completely encased by a skin ("A"),, when the cross section is viewed. For cosmetic, applications, a second small portion of skin, material "A" is injected after "B" to complete, the skin formation at the gate. Coinjected, products with two different colored plastics, yield an easy identification of the skin and, core regions. They have been producing different type shaped structures since the 1950s

Page 489 : 8 Plastic Processing, Nomograph in English units, Part, , Thickness, in., , 1.00, 0.80, 0.60, , Mold, , Shrinkage, in.!in., , 0.20, 0.15, 0.10, 0.08, 0.06, 0.04, , .001, .002, , .035, .030, , .004, , .025, , _ _ _ _ .008, , --, , 0.40, 0.30, , Gate Area, in,2, , .020, , .015, , .015, , .030, , .010, , .060, .100, , .003, .006, .010, .020, , 0.03, , .040, , (2), , .080, , (3), , 0.02 (l), , Nomograph in SI units, , Part, , Thickness, , Gate Area, , mm, Mold, , 20, 15, , Shrinkage, , mmlmm, , mm', 0.6, 0.8, 1.0, 1.5, 2, 3, 4, , 10, 8, , .035, .030, , 6, , .025, , :, , _ _ .020, , ~, 10, , 2, 1.5, , .015, , 20, , 1.0, 0.8, 0.6, , .010, , 8, 15, 30, , 40, 80, (2), , 60, 100, , (3), , 0.4, (1), , Fig. 8-26 Example in determining shrinkage., , such as sandwich, corrugated, tubular, T, U,, etc. 1M machines and their special molds are, available that can produce two or more coinjection plastics., It is important to understand that a similar skin and core exist in all injection molded, products, although it is generally difficult to, distinguish the skin-core interface without an, enhancing characterization technique. The, two different materials must have a certain, degree of compatibility (Table 8-15). They, can be highly filled, fiber reinforced, impact, modified, UV stabilized, foamed, or using, 100% recycle core with a skin that protects the core and provides desirable performances. If the two plastics are not compatible,, a third can be used as an interlayer providing, the proper bonding., , 471, , Gas-assist injection molding The GAIM, process provides the designer unique molding capabilities such as exceptional structural, strength at low weight. It uses a gas, usually, nitrogen with pressures up to 3,000 psi (21, MPa), with the melt in the mold so that channels are formed within the melt. Different, systems are used but basically they are all similar (3). Gas can be injected through the center of the IMM nozzle as the melt travels to, the cavity or it can be injected separately into, the mold cavity. In a properly designed tool, run under the proper process conditions, the, gas with its much lower viscosity than the melt, remains isolated in the gas channels of the, product without bleeding out into any thinwalled areas in the mold producing a balloonlike pressure on the melt., The gas channels are those areas that have, been thickened to achieve functional utility, in the product or to promote better melt flow, during cavity filling. This action provides a, high degree of packing the melt against the, cavity walls. Gas pressure is held until the, melt solidifies. This coring action results in, reducing cycle time and quantity of plastic, used while developing a more structurally, sound product (increases section stiffness),, ability to improve surface flatness, reduce, warps and sinks over thick sections, etc. Thick, parts can easily be made without voids, sink, marks, etc., In this process the plastic is injected and, only partially fills the cavity. Gas is then injected. In all cases the gas pressure in the core, advances the melt front in the cavity until filling is completed, and prevents the plastic skin, from collapsing away from the cavity walls, during solidification. An integral skin is in, contact with the cavity walls and the gas remains in the core region of the molded product. Because the gas is at a pressure greater, than atmospheric pressure, the gas pressure, must be reduced before the product is ejected, to avoid distorting the product as the restraining cavity walls are removed. Control of the, size and location of the gas core is more difficult with highly compressible gas, but techniques and sequences are being refined to, yield products that exhibit an acceptable level, of reproducibility.

Page 490 : 8 Plastic Processing, , 472, Table 8·15, , Guide to compatibility of plastics for coinjection, , Materials, Acrylic ester acrylonitrile, , +, +, , Cellulose acetate, , +, , ASS, , +, +, , +, , -, , +, , Nylon 6, Nylon 6/6, , +, +, , +, +, , -, , -, , +, , Polycarbonate, , +, +, , HDPE, lOPE, Polymethylmethacrylate, , -, , -, , +, , +, , +, , +, +, , +, +, , +, , +, , General·purpose PS, , o, +, +, , SoftPVC, , 0, , Styrene acrylonitrile, , +, , 0, , -, , +, , -, , o, , -, , +, , o, , -, , 0, , -, , 0, , +, , +, , +, , +, , -, , 0, , +, , -, , -, , + +, + +, + +, , -, , +, , +, , -, , +, +, +, +, , +, , +, , o, , +, , =, , +, , +, , +, , -, , a + :;r. good adhesion. poor adhesion. 0 = no adhesion, blank Indicates no recommendation (combination not vet tesled)., to (I deterioration 0/ adhesion between raw material$ /or skin and core., , Injection-compression, molding Also, called ICM, coining, and injection stamping., ICM is a variant of injection molding. The, essential difference lies in the manner in, which the thermal contraction in the mold, cavity that occurs during cooling (shrinkage), is compensated. With conventional injection, molding, the reduction in material volume, in the cavity due to thermal contraction is, compensated basically by forcing in more, melt during the pressure-holding phase., By contrast with ICM, a compression mold, design is used where male plug fits into a female cavity rather than the usual flat surface, parting line mold halves for 1M (Fig. 8-27)., The melt is injected into the cavity as a short, shot thereby not filling the cavity. The melt, in the cavity is literally stress-free; it is literally poured into the cavity. Prior to receiving melt, the mold is slightly opened so that a, closed cavity exists; the male and female parts, , +, , + -, , PPO, , Polytetramethylene terephthalate, , -, , +, , PP, , + 0, , -, , Polyoxymethylene, , Rigid PVC, , +, , +, , +, , +, , Hlgh·impact PS, , o, , +, + -, , +, , Ethyl vinyl acetate, , +, , -, , -, , +, , +, , + +, , +, , +, , +, , The addition of /fners or reinforcements leads, , are engaged so the cavity is closed. After the, melt is injected, the mold automatically closes, producing a relatively even melt flow. Upon, controlled closing, a very uniform pressure, is applied to the melt. Sufficient pressure is, applied to provide a molded product without, stresses., , Soluble core molding The soluble core, technology (SCT) is called by different names, such as soluble fusible metal core technology, (FMCT), fusible core, lost-core, and lost-wax, techniques (3). In this process, a core [usually molded of a low melting alloy (eutectic, mixture) but can also use water soluble TPs,, wax formulations, etc.] is inserted into a mold, such as an injection molding mold. This core, can be of thin wall or solid construction., If the product design permits, it can be supported by the mold halves or spider type pin, supports that are used to have it "floating"

Page 491 : 473, , 8 Plastic Processing, Injection/CompreSSion- Coining, Mold F Illing, , Inject ion Math ine, , Precompression, , Mold Compressed, , Fig. 8-27, , Schematic of coining that combines injection molding and compression molding., , within the cavity; during plastic molding, the, pins will melt. After the plastic solidifies, the, core is removed by applying a temperature, below the melting point of the plastic. Core, material is poured through an existing opening or will require drilling a hole in the plastic., This technique is a take off and similar to the, lost wax molding process started during the, ancient Egyptian times fabricating jewelry., Also the 1944 all plastic airplane used the lost, wax process to bag mold its RP sandwich construction (review latter in this chapter REINFORCED PLASTIC, Process, Lost-wax)., Over-molding Over-molding is also, called in-mold assembly, two-color rotary, or, two-color shuttle. Two materials are molded, so that the first molded shot is over-molded, by the second molded shot; first molded part, is positioned so the second material can be, molded around, over, sections, or through, it. The two materials can be the same or, different and they can be molded to bond, together or not bond together. If materials, , are not compatible, the materials will not, bond so that a product such as a universal or, ball-and-socket joint can be molded in one, operation. If they are compatible, controlling, the processing temperature can eliminate, bonding. A temperature drop at the contact, surfaces can occur in relation to the second, hot melt shot to prevent the bond., In addition to universal or ball-and-socket, joints, other examples of this products using, this technique include inner-door panels for, automobiles where woven or nonwoven textiles are placed in a mold and the melt is injected. In-mold labeling is another application that goes beyond just a printed message., Individual labels or continuous film can be, indexed in the mold at the beginning of each, cycle. Besides printing on the film, the film, can serve many other functions (increasing, impact, toughen plastic, etc.), or the film can, contain additives and stabilizers to protect, the surface of the molded product., Certain applications of over-molding are, not restricted to a low pressure. Two-shot

Page 492 : 8 Plastic Processing, , 474, Resin, , Screw, , Thermocouples, , Barrel, , Feed, Section, , Fig. 8·28, , Compression, Section, , Cross-section of a single-screw extruder., , molding is an example where a plastic is, molded into a shape, then placed in another, cavity before a second plastic is injected. The, first plastic injected serves as a solid mold, wall for the second cavity. Keys for a computer keyboard, knobs, and other items are, often molded this way to provide information that does not fade or wear away with, use. Many variations exist, including molding, an elastomer over a rigid plastic, and molding a frame around a lens or optical window., Each step in over-molding is essentially the, standard molding process even though the, integral structure might resemble a product, molded by coinjection molding., Extrusion, , The extruder, that offers the advantages of, a completely versatile processing technique,, is unsurpassed in economic importance by, any other process. This continuously operating process, with its relatively low cost of, operation, is predominant in the manufacture of shapes such as profiles, films, sheets,, tapes, filaments, pipes, rods, in-line postforming, and others. The basic processing concept, is similar to that of injection molding (1M), in that material passes from a hopper into a, plasticating cylinder in which it is melted and, dragged forward by the movement of a screw., The screw compresses, melts, and homogenizes the material. When the melt reaches the, end of the cylinder, it may be forced through, a screen pack prior to entering a die that gives, the desired shape with no break in continuity, , (Fig. 8-28). The screen pack is a filter that restricts unmelted plastic and/or contaminants, from entering the die (6)., Practically only thermoplastics go through, extruders; no major markets have been developed to date for extruded thermosets., A major difference between extrusion and, 1M is that the extruder processes plastics, at a lower pressure and operates continuously. Its pressure usually ranges from 1.4 to, 10.4 MPa (200 to 1,500 psi) and could go, to 34.5 or 69 MPa (5,000 or possibly 10,000, psi). In 1M, pressures go from 14 to 210 MPa, (2,000 to 30,000 psi). However, the most important difference is that the 1M melt is not, continuous; it experiences repeatable abrupt, changes when the melt is forced into a mold, cavity. With these significant differences, it is, actually easier to theorize about the extrusion melt behavior as many more controls are, required in 1M., Good-quality plastic extrusions require, homogeneity in terms of the melt-heat profile and mix, accurate and sustained flow, rates, a good die design, and accurately controlled downstream equipment for cooling, and handling the product. Four principal factors determine a good die design: internal, flow length, streamlining, construction materials, and uniformity of heat control. Heat, profiles are preset via tight controls that, incorporate cooling systems in addition to, electric heater bands. Barrels external surfaces can include the use of forced air ad/or, water jackets to aid in controlling the melt, temperature. In some machines a water bubbler channel is located within the screw.

Page 493 : 475, , 8 Plastic Processing, , ~~(", , ![:7~E~, , /f, ~, , (( H?,-*WS, POOR, , BETTER, , POOR, , BETTER, , POOR, , BETTER, , POOR, , BETTER, , POOR, , BETTER, , BEST, , POOR, , BETTER, , BEST, , Fig. 8-29, , Influence of product design on meeting desired shapes., , The design of the product should consider, ease of processing (Figs. 8-29 to 33 and Table, 8-16)., Excellent guides for determining the initial, orifice die openings for different profiles are, shown in Fig. 8-34 (6)., , Drawdown, from pull rolls, , Drawdown, from pull rolls, Die, , Fig. 8-30, , Effect of die land length on melt swell., , On leaving the extruder, the melt (extrudate) is drawn by a pulling device, at which, stage it is subject to cooling, usually by water, and/or blown air. This is an important aspect, of downstream control if tight dimensional, requirements are to exist or conservation of, plastics is desired. The processor's target is, to determine the tolerance required for the, pull rate and to see that the device meets the, requirements. Even if tight dimensional requirements are not required, the probability, is that better control of the pull speed will, permit tighter tolerances so that a reduction, in the material's output will occur., As the molecules of the melt flow are, aligned in the direction of the output, from the die, the strength of the plastic is

Page 494 : 476, , 8 Plastic Processing, , 00, 00, Die Shape, , Ole Shape, , l, , l, , Pari Shape, , Part Shape, , ;', , ,,~, ;.,, , ~, , ", , ta::, . ., 0, , '", , Die, , Square Section Requires, , Distorted Die, , Product, , Square Die Yields, , Distorted Section, , Fig.8·31 Effect of die orifice shape on the extrudate., , SLOW, COOL, , a, , DIE EXIT, , SLOW, , HEAT, FAST, , COOL, , Q, , ,\,, . " " ' FAST, ~HOT, , UO, ~t>, , COLD, , STRETCH, HOT, STRETCH, , Fig. 8·32 Examples of how temperature, pressure, and takeoff speed (time) variations can potentially influence the shape of the extrudate., , characteristically greater in that direction, than at right angles. Depending on the product's use, this mayor may not be favorable., Using appropriate devices and controls the, degree of orientations can be varied. If desired a balanced strength in both directions, can be produced (6)., The success of any continuous extrusion, process depends not only upon uniform quality and conditioning of the raw materials but, also upon the speed and continuity of the feed, of additives or regrind along with virgin plastic upstream of the extruders hopper. Variations in the bulk density of materials can exist, in the hopper, requiring controllers such as, weight feeders, etc., In extrusion an extensive theoretical analysis has been applied to facilitate understanding and maximize the manufacturing, operation. However, the real world must be, understood and appreciated as well. The opera tor has to work within the limitations ofthe, materials and equipment (the basic extruder, and all auxiliary upstream and downstream, equipment). The interplay and interchange of, process controls can help to eliminate problems and aid the operation in controlling the, variables that exist. The greatest degree of, instability is due to improper screw design,, or using the wrong screw for the plastic being processed. Screws are designed to meet, the melt requirements for a specific type of, plastic., For uniform and stable extrusion it is, important to check periodically the drive, system, the take-up device, and other equipment, and compare it to its original performance. If variations are excessive, all kinds of, problems will develop in the extruded product. An elaborate process-control system can, help, but it is best to improve stability in, all facets of the extrusion line. Some examples of instabilities and problem areas include, (1) non-uniform plastics flow in the hopper;, (2) troublesome bridging, with excessive barrel heat that melts the solidified plastic in the, hopper and feed section and reduces or stops, the plastic flow; (3) variations in barrel heat,, screw heat, screw speed, screw power drive,, die heat, die head pressure, and the take-up, device; (4) insufficient melting or mixing

Page 495 : 477, , 8 Plastic Processing, Dimensions of die orifice, , 1<.-.. --..------....-.-.......-............-_....... 1.378 in. - ... - ...-- ...........- ..-, , +. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -. -. 1.370 in. - ..... ., , ', , ...., , [, ~, , Dimensions of final product, , i<' ................................................................................ ·1.252 in .................................................., , 0.147 in. Rad, , 0.147, 0.060 in ., , ....·.. ·.... ·_·.._ -............ ·..·--1.245 in. - -......- - - -.........- .. - . -.............---~, , Fig. 8-33, , Example of changes in a PVC profile shape from the die orifice to the product where no, dimensions remained the same., , capacity; (5) insufficient pressure-generating, capacity; (6) wear or damage of the screw or, barrel; and (7) melt fracture/sharkskin, and, so on. Finally, one must check the proper, alignment of the extruder and the downstream equipment. Proper alignment is a, must for high-quality, high-speed output., Regardless of their particular designs, all, extruders have the function of conveying, plastic and converting it into a melt. For, this purpose, both single- and multiple-screw, extruders are suitable, but they all have, individual characteristic features. Practical, and theoretical data show that each type, has its place (6). The single-screw machine, dominates. However, other types are available, such as twin-screw extruders, which, are often used to achieve improved dispersing and mixing, as in the compounding of, additives., , Modified Extrusion Technique, A few of these techniques will be reviewed., Co extrusion Co extrusion provides multiple molten layers usually using two or more, extruders with two or more melts going, through one die where they are bonded together. This technique permits using melt, heat to bond the various plastics (Tables 8-17, to 19), or using the center layer as an adhesive. Coextrusion is an economical competitor to conventional laminating processes by, virtue of its reduced materials handling costs,, raw materials costs, and machine-time cost., Pinholing is also reduced with coextrusion,, even when it uses one extruder and divides, the melt into at least a two-layer structure., Other gains include elimination or reduction, of delamination and air entrapment.

Page 496 : Wall thickness, Angles, Profile dimensions,, ±mm (in.), 0-3 (O-lls), 3-13 e/8- lh), 13-25 (%-1), 25-38 (1-1 l/z), 38-50 (l llz-2), 50-75 (2-3), 75-100 (3-4), lOO-125 (4-5), 125-180 (5-7), 180-250 (7-10), , Dimension, ±8%, ±3°, , 0.25 mm (0.010 in.), 0.38 mm (0.015 in.), 0.50 mm (0.020 in.), 0.68 mm (0.027 in.), 0.90 mm (0.035 in.), 0.94 mm (0.037 in.), 1.3 mm (0.050 in.), 1.7 mm (0.065 in.), 2.4 mm (0.093 in.), 3.0 mm (0.125 in.), , 0.25 mm (0.010 in.), 0.50 mm (0.020 in.), 0.63 mm (0.025 in.), 0.68 mm (0.027 in.), 0.90 mm (0.035 in.), 0.94 mm (0.037 in.), 1.3 mm (0.050 in.), 1.7 mm (0.065 in.), 2.4 mm (0.093 in.), 3.0 mm (0.125 in.), , 0.18 mm (0.007 in.), 0.30 mm (0.012 in.), 0.43 mm (0.017 in.), 0.63 mm (0.025 in.), 0.75 mm (0.030 in.), 0.90 mm (0.035 in.), 1.3 mm (0.050 in.), 1.7 mm (0.065 in.), 2.4 mm (0.093 in.), 3.0 mm (0.125 in.), , 0.18 mm (0.007 in.), 0.25 mm (0.010 in.), 0.38 mm (0.015 in.), 0.50 mm (0.D20 in.), 0.63 mm (0.025 in.), 0.75 mm (0.030 in.), 1.1 mm (0.045 in.), 1.5 mm (0.060 in.), 1.9 mm (0.075 in.), 2.4 mm (0.093 in.), , Polypropylene, , ±8%, ±3°, , ABS, , ±8%, ±2°, , Polystyrene, , ±8%, ±2°, , Rigid Vinyl (PVC), , Table 8-16 Guide for dimensional tolerances for profiles, , 0.25 mm (O.OlO in.), 0.38 mm (0.015 in.), 0.50 mm (0.020 in.), 0.75 mm (0.030 in.), 0.90 mm (0.035 in.), 1.0 mm (0.040 in.), 1.7 mm (0.065 in.), 2.4 mm (0.093 in.), 3.0 mm (0.125 in.), 3.8 mm (0.150 in.), , ±lO%, ±5°, , Flexible Vinyl, (PVC), , 0.30 mm (0.012 in.), 0.63 mm (0.025 in.), 0.75 mm (0.030 in.), 0.90 mm (0.035 in.), 1.0 mm (0.040 in.), 1.1 mm (0.045 in.), 1.7 mm (0.065 in.), 2.4 mm (0.093 in.), 3.0 mm (0.125 in.), 3.8 mm (0.150 in.), , ±lO%, ±5°, , Polyethylene, , ~, , ()Q, , '", S·, , ~, , '"tl, ~, ('), , ('), , '":::l'., , B", , '"tl, , 00, , Ocl

Page 497 : 8 Plastic Processing, , 479, , 1.0, , OR LIP = 12jlQL X 2. (H ~ BI, ~, F, , .9, , ;DJ, , .8, u., fo-, , Z, , UJ, , u, , u., , LIP = pressure drop, jl = vIscosity, a : volumetric flow rate, L = length of channel, F = flow coefficient, B '" maximum dimension, H = minimum dimension, , r-H-j, , .7, , iB----J, , u.., , w, 0, , ·~i, , u, 'l:, 0, , RECTANGLE, , ...J, , U., , l=r, , (f), (f), , W, , ...J, , Z, 0, , Vi, , z, , w, , ~, , 0, , .4, , ····SQUARE, (F=.4217), , .3, , -CIRCLE, , ( F"'~), 12B, .2L-__~__~__- L__~__~__~____L-__~__~~, .1, .2, .3, .4, .5, .6, .7, .8, .9, 1.0, , o, , ASPECT RATIO. H/B, , Fig. 8-34, , Guide to developing orifice die openings., , In the past, a processor desiring to enter the, field had little choice of equipment, but the increased interest in coextrusion has produced, a proliferation of equipment. With rapidly, changing market conditions and the endless, Table 8-17, , LDPE, HDPE, PP, Ionomer, Nylon, EVA, , introduction of useful materials, the design of, machines has become much more involved. It, is important that the processor have flexibility in making selections, but not at the expense of performance, dependability, or ease, , Examples of compatibility between plastics for coextrusion, LDPE, , HDPE, , PP, , Ionomer, , Nylon, , EVA, , 3, 3, 2, 3, 1, 3, , 3, 3, 2, 3, 1, 3, , 2, 2, 3, 2, 1, 3, , 3, 3, 2, 3, 3, 3, , 1, 1, 1, 3, 3, 1, , 3, 3, 3, 3, 1, 3, , Code: 1. Layers easy to separate., 2. Layers can be separated with moderate effort., 3. Layers difficult to separate.

Page 498 : 8 Plastic Processing, , 480, Table 8·18, , Comparison of feedblock and multimanifold coextrusion dies, , Characteristic, Basic difference, , Cost, Operation, Number of layers, Complexity, Control flow, , Layer uniformity, Thin skins, Viscosity range, Degrudable core material, Heat sensitivity, Bonding, , Feedblock, , Multimanifold, , Melt streams brought together, outside die body (between, extruder and die) and flow, through the die as a, composite, Lower, Simplest, Not restricted: seven- and, eight-layer systems are, commercial, Simpler construction: no, adjustments basically, Contains adjustable matching, inserts, no restrictor bar, , Each melt stream has a separate, manifold: each polymer spreads, independently of others: they, meet at die pre-land to die exit, , Individual layer thickness, correction of ±1O percent, Better on dies >40 in., Usually limited to 2/1 or 3/1, viscosity range of materials, Usually better, More, Potentially better: layers are, in contact longer in die, , of operation. One should provide for the material or layer thickness necessary in product, changeover without allowing high scrap rates., The goal should be to incorporate scrap regrind within the layered construction., Table 8·19, , Higher, Generally restricted to three, or four layers, More complex, Has restrictor bar or flow dividers, in each polymer channel; but, with blown film dies control is by, individual extruder speed or, gearboxes, Restrictors and manifold can, meet ±5 percent, Better on dies <40 in., Range usually much greater, than 3/1, Less, , It is important to be able to control the individuallayer distribution across the width of, the die. As the viscosity ratio or thickness ratio of the plastics being combined increases,, the individual layer distributions of the, , General comparison of metalized coextruded polyethylene and aluminum foil, , Tensile strength MD, CD, Mullen strength, Gurley stiffness MD, CD, WVTR (gm/csU24 hrs.), Oxygen transmission (cc/csl/24 hrs.), Light transmission, Seal type, Seal range (40 psi, 15 sec.), Deadfold (subjective) (1-10 Scale), Flex crack resistance (subjective) (1-10 Scale), , Metalized Coextruded, Polyolefin, , Foil Laminate', , 18-19, 12-13, 19-20, 70-75, 42-47, Approx ..05, Approx.lO, Slightly less than 1 %, Fin onlyt, 350-500°F, 4, 8, , 18-19, 11, 17, 117-112, 72-77, .0006, Less than .004, Approx.O%, Fin or Lap, 160-350°F, 7, 5, , *.0003" gauge foil, wax laminated to 121/2# paper, wax laminated to 81/2# tissue., tWhile a lap seal is technically possible, the bond is too weak to be considered commercial.

Page 499 : 8 Plastic Processing, plastic composite film can become displaced., To offset this situation proper die design with, control of the line is required., A number of techniques are available for, coextrusion, some of them patented and, available only under license. Basically, three, types exist: feedblock, multiple manifolds,, and a combination of these two (Table, 9-18). Productions of coextruded products, are able to meet product requirements that, range from flat to complex profiles. Figure, 8-35 (a) shows a typical 3-layer co extrusion, die and (b) examples of rather complex profiles that are routinely extruded., , Special shape Some special dies, shown, in Figs. 8-36 and 8-37, produce interesting, flow patterns and products, such as tubular, to flat netting shapes. Figure 8-37 has a mesh, produced by extrusion from a counter rotating die design, originally patented in 1956. A, postextrusion stretching process follows the, exiting mesh. For circular output a counter, rotating mandrel and orifice have semicircular shaped slits through which the melt, flow emerges. If one part is held stationary,, a rhomboid or elongated pattern is formed;, if both parts rotate, a true rhombic mesh is, formed. When the slits overlap, a crossing, point is formed where the emerging threads, are "welded." For flat netting, the slide action, is in opposite directions., In-line postforming In-line postforming,, or post extrusion processing, refers to the processing that may be done to the extrudate,, usually just after it emerges from the die, but before the material has a chance to cool., When the material is worked in such a state it, is known as in-line processing, as opposed to, cutting, forming, or other processing, which, is done on the cold extrusion in a secondary, operation., In-line processing is done automatically,, with little or no extra labor on the part of, the machine operator. Heat required can be, retained from the extrusion operation. The, extra processing, which may involve shaping,, cutting, re-forming, or surface modification, of the extrudate, can considerably increase, the value of the extrusion without materially, , 481, , increasing its processing cost. It may also be, done to enable the use of a lower-cost die,, as for example flattening a tubular extrusion, into an oval so that a much lower cost circular, die can be used., This is a popular forming technique that, has provided both performance and cost, advantages, principally for long production, runs. It is applied as the plastic sheet, film,, or profile exits an extruder. Upon leaving the, die, and retaining heat, the plastic is continuously postformed. With this type of in-line, system the hot plastic is reduced only to the, desired heat of forming. All it may require is, a fixed distance from the die opening. Cooling can be accelerated with blown air, a water spray, and/or a water bath. This equipment, like others, requires precision tooling, with perfect registration., Examples of some postforrning techniques, are shown in Fig. 8-38 (a) in-line postforming embossing, (b) in-line vacuum postforming embossing with water cooled temperature control, (c) in-line vacuum-pressure, postforming using water-cooled dies/molds,, (d) in-line coil postforming, and (e) in-line, fixed-rotating ring postforming., , Coating, Extrusion coating is used extensively in a, varity of different applications that include, wire coating, steel coating (protect steel),, wood coating (decorative), etc. Figure 8-39, shows sections of a profile (could be any, shape in any length) in line with an extruder, where a crosshead diehead is used to apply, the plastic coating (6)., , Orientation, The following information is a continuation of what has been reviewed earlier in, this chapter (PROCESSING AND PROPERTY, Orientation). Orientation consists of, a controlled system of stretching heated plastic material (molecules) to improve their, strength, stiffness, optical, electrical, and, other properties. This process, which has been

Page 501 : 483, , 8 Plastic Processing, , 01, , ,, , A=====, , ~~I :------~-, , CMa/AIU~E UPS ~.~, , :,, , ' ,--",', , c., , ====:::::j, , Flat t\8nf1g •.••• WI1h Ifill.rant po .. ions 01 d>a !;ps, , Rotatng mandrel d;e, make. pot1Q<ated tUMg, , BEAAINCl, , A, , eoa .....l cable witJ'i 8 spira) spacer web that, , eeps coated wtr8 ., the center, , INIEBMIUENT, STOI'OFFS, , seCTiONAA, , Val'yW'lO lube wa ll thdtness using an o$Ci'", , lamg mandrel in cross head tube die, , Fig. 8-36, , A, , SECTlONM, , O;t1er""t porloratOd tubing po.em;, uslog osdllating mandrel doe, , Examples of special action dies that produce round and flat products., , used for almost a century, became prominent, during the 1930s for stretching fibers up to, ten times. Later it was adapted to stretching, extruded film and sheet and, more recently, , Fig.8-37 Example of netting as it exits a die that, is available in almost every conceivable form., , other processes such as blow-molded products. Many other products take advantage, of its benefits for producing tape, pipe, profile, and thermoformed products, etc. (Table, 8-20). Practically all plastics can undergo orientation, although certain types find it particularly advantageous (PET, PP, PVC, PE,, PS, PVDC, PVA, and PC). Of the 15 million, tons of plastic film sales annually worldwide,, about 16% are sales of oriented material., In extrusion the most important orienting processes are used with flat film and, sheet, blown film, and blow molding. During, these processes the stretch or blow-up ratios, determines the degree of flat or circumferential orientation and the pull rate of the, hot plastic determines degree of orientation, (6). The optimum stretching heat for amorphous plastics (PVC, etc.) is just above the, glass transition temperature; for the crystalline types (PET, PE, and so on) it is just, below the melting point. During the stretching process the molecular structure changes,, thus usually necessitating an increase in heat

Page 502 : 484, , 8 Plastic Processing, EXlAUDATE, , VACUUM, DRUM, DRUM SECTION, , PRESSURE -FORMING DIES, ","~ '", , UPPER CONVEYOR, , - --, , ROTATING, MANDREL, , ROTATING RING, TWISTED, , cZ?Zz(@-------'lf, Fig. 8-38 Different products that are postformed in line during extrusion.

Page 503 : 485, , 8 Plastic Processing, PULL ROLLS, , •, , COOL.ING AIR, , . 6b., , -,,'-:), , RADIANT HEATERS, , CUTOFF UNIT, , FEED ROLLS, , FINISHED-PARTS, COLLECTOR, , Fig. 8-39, , Continuous in line extrusion system coating short length parts,, , if further deformation is planned. Afterward., the orientation is "frozen in" by lowering the, heat or, with crystalline types, set by increasing the crystalline portion., With orientation, the thickness is reduced, and the surface enlarged. If film is longitudinally stretched in the elastic state, its thickness and width are reduced in the same ratio., A conventional unorienting extrusion film or, sheet line is shown in Fig. 8-40. In orienting film or sheet the processor uses a tentering frame (typically used in textile weaving),, which is enclosed in a heat-controlled oven,, with a very accurate and gentle air flow used, to hold the oven air temperature at the required orienting heat (Fig. 8-41). The frame, has continuous speed control and diverging, tracks with holding clamps. As the clamps, move apart at prescribed diverging angles the, hot plastic is stretched in the transverse direction, resulting in single orientation (0). To, obtain bidirectional orientation (BO) an inline series of heat-controlled rolls are located, between the extruder and tenter frame. The, rotation of each succeeding roll is increased,, , based on the longitudinal stretched properties desired., In this Fig. 8-41 view (a) the feeder-roll, speed to puller-roll speed ratio can be set,, such as 1:4, and simultaneously the ratio of, width can be set as 1:4. The machined direction ratio is usually accomplished prior to, the plastic's entering the temperature controlled oven that contains the tenter frame,, by having it move around heat-controlled, rolls where the rotational speed of the rolls, increases from one roll to the next. View, (b) is a schematic of the drawdown phenomenon with swell to produce orientation, in the machined (longitudinal) direction., Blow Molding, , BM can be divided into three major processing categories: (1) extruded BM (EBM), with continuous or intermittent melt (called, a parison) from an extruder and which principally uses an unsupported parison (Fig. 8-42),, (2) injection BM (IBM) with noncontinuous, , Hopper Dryer, Rubber Pull Rolls, , Fig. 8-40, , Conventional extruded film or sheet line.

Page 504 : 486, Table 8·20, , 8 Plastic Processing, Examples of different oriented TP products, , Ranges of Application, , Rate of, Stretching, , Demands Made, , Thermoplastic, , Carpet basic weave, , Low shrinkage, High strength, Temperature stability, Specific splicing tendency, Matt surface, , 1:7, 1:5, , PP, PETP, , Tarpaulins, , High strength, , 1:7, , Sacks, , High strength, High friction value, Specific elongation, Weather resistant, High tensile strength, Specific elongation, Good tendency to splicing, High tensile strength, High knotting strength, High strength, Low shrinkage, Abrasion resistant, Low shrinkage, Specific elongation, Temperature resistance, UV-resistance, Low static charge, Uniform coloration, Textile-type handle, Low shrinkage, Wear resistance, Weather resistance, Elastic recovery, Uniform coloration, Defined splicing, Effective surface, Low specific gravity, High knotting strength, Low splicing tendency, Supplencess, UV-resistance, High strength, Low splicing tendency, Fiber properties, , 1:7, , PP, PE, PE, PE, , Ropes, , Twine, Separating weave, Filter weave, Reinforcing weave, , Tapestry and home, textiles, , Outdoor carpets, , Decorative tapes, Knitted tapes, sacks, and, other packagings,, seed and harvest, protective nets, Packaging tapes, Fleeces, , melt (called a preform) and which principally, uses a preform supported by a metal core pin, (Fig. 8-43), and (3) stretched/oriented EBM, and IBM to obtain bioriented products pro-, , 1:9 to 1:11 (15), , PP, , 1:9 to 1:11, 1:7, , PP, PP/PE, PP, , 1:7, 1:5, , PP, PETP, , 1:7, 1:5, , PP, PETP, , 1:7, , PE, , 1:7, , PP, , 1:5, , PETP, , 1:6, , PPwith, blowing agent, PP, PE, , 1:6.5, , 1:9, 1:7, 1:7, , PP, PETP, PP and blends, , viding significantly improved performanceto-cost advantages (Fig. 8-44). These BM, processes offer different advantages in producing different types of products based on

Page 505 : 8 Plastic Processing, , 487, , 8, , OVEN, , (al, Tensile strength, Nono. iented, Oriented (machine direction), Oriented (transverse direction), , 5.000 pSi, 4.000 psi, 25.000 psi, EXTRUDER, , DRAWDOWN, PULLER, , DIE SWELL, , 400%, , '-----i, DIE, , (b), , Fig.8-41, , Use of tender frame to biorient film or sheet., , the plastics to be used, performance requirements, production quantity, and costs (20)., Basically the BM lines have an extruder, with a die or an injection machine with a mold, to form the parison or preform, respectively., In turn the hot parison or preform is located, in a mold. Air pressure through a tubular pintype device located usually at the parting line, of the mold will expand the parison or preform to fit snugly inside their respective mold, , cavities. Blow molded products are cooled via, the water cooling systems within mold channels. After cooling, the blown products are, removed from their respective molds., The nature of these processes requires the, supply of clean compressed air to "blow" the, hot melt located within the blow mold. Other, gases can be used, such as carbon dioxide,, to speed up cooling of the blown melt in, the mold. The gas usually requires at least a, , PRESS, PLATEN, , U, , Compressed air inflates, par/son, , Blown canta/nerO, being ejected, .., , Fig. 8-42 Basic extrusion blow molding process.

Page 506 : 488, , 8 Plastic Processing, , 9), 8m), ~, , ~c=[Ill, , D, , ), , ~, , Blow molding and ejection, , . . Injecting preform, , Fig.8-43, , ==={illr---------, , Basic injection blow molding process., , ", , I!',' ':,.~.::..., , U=, , Inject preform, , Reheat preform, , m, , I·, , /, , I, I, , .~,, , !, r, , J (, , i, , Iii, , ! ~--r--L, I, , !, ~/ ( !, L.j "'''~-' / L.J, Stretch blow molding and, ejection, r ,, , L... ~, , I, , (, , l.~j, , I ~ \...., , Fig. 8-44 Basic stretched blow molding process.

Page 507 : 8 Plastic Processing, Table 8-21, , 489, , Hollow and structural BM shapes, , Industry, , Application, , Required Properties, , Automotive, , Spoilers, Seat backs, Bumpers, Underhood tubing, Work stations, Hospital furniture, Office furniture, Outdoor furniture, Air-handling equipment, Air-conditioning housings, Housings, Ductwork, Exterior panels, Flotation devices, Marine buoys, Sailboards, Toys, Canoes/kayaks, Tool boxes, ice chests, Trash containers, drums, Hot-water tanks, , Low temperature, impact, cost, Heat distortion, strength/weight, Low temperature, impact dimensional stability, Chemical resistance, heat, Flame retardance, appearance, Flame retardance, cleanability, Flame retardance, cost, Weatherability, cost, Flame retardance, hollow, Heat distortion, cost, Flame retardance, cost, Cost, Weatherability, cost, Low temperature, impact strength cost, weatherability, Low temperature, impact strength cost, weatherability, Low temperature, impact strength cost, weatherability, Low temperature, impact strength cost, weatherability, Low temperature, impact strength cost, weatherability, , Furniture, , Appliance, Business, machine, Construction, Leisure, , Industrial, , Low temperature, impact strength, cost, Low temperature, impact strength, cost, Low temperature, impact strength, cost, , pressure of 30 to 90 psi (0.21 to 0.62 MPa), for EBM and 80 to 145 psi (0.55 to 1 MPa), for IBM. Some of the melts may go as, high as 300 psi (2.1 MPa). However, stretch, EBM or IBM often requires a pressure up to, 580 psi (4 MPa). The lower pressures generally create lower internal stresses in the, solidified plastics and a more proportional, stress distribution; the higher pressures provide faster molding cycles and ensuring conforming to complex shapes. With any lower, pressures or lower melt stresses is improved, resistance to all types of strain (tensile, impact, bending, environment, etc.)., Production can increase usually by at least, 20 to 40% by using aggressive, turbulent, chilled air at about -35 C (-30 F) that is, allowed to escape following the blowing action. This action can provide several changes, of air through the blow pin during a single blowing cycle. Blow molded bottles are, predominantly fabricated using the extrusion, and injection molding process with or without stretching/orientation., Plastic shrinkage is dependent on many, factors, such as plastic density, stock temperD, , D, , ature, mold temperature, product thickness,, and blowing air pressure. Once the operating conditions are established, tolerances of, ±5% may be expected. Typical polyethylene, blow molding shrinkage is as follows:, Low-Density Polyethylene:, Thickness up to 0.075 in.: 0.010-0.015 in.lin., Thickness over 0.075 in.: 0.015-0.030 in.lin,, High-Density Polyethylene:, Thickness up to 0.075 in.: 0.020-0.035 in.lin., Thickness over 0.075 in.: 0.035-0.055 in.lin., Different products are blow molded, (Table 8-21). Table 8-22 provides cost data, comparing different BM processes with different plastics., , Complex Irregular Shape, Extruded blow molded 3-D products are, produced. This approach provides the designer with a relatively very important approach in the art of hollow formed products., It is an ideal approach that has many cost-toperformance advantages. Complex, irregular

Page 508 : 490, Table 8·22, , 8 Plastic Processing, Fabricating cost comparison of 16 oz. BM bottles, , 1.O-Machine cost incl., head, molds, ancillaries, (lie. fee, stretch PVC and PET), 2.O-Hourly machine costs, Depre'n, 5 yr., 30 K hr, $/hr., Financing cost,, 5 yr. 12.5%, Labor, 1 man, Energy at $.06 per kWh, Floor space, Maintenance and consumable mtl., Total hourly me costs, 3.O-Bottle specs., hourly/annual prod., 3.1-16 oz. finish wt. (454 g), -regular 37 g (1.3 oz), -stretch PVC 20 g (0.7 oz), -stretch PET 20 g (0.7 oz), Cycle time/bottles per hour, bottles per yr., millions, 4.O-Annual costs, 4.1-16 oz. (454.g), Resin:-37 g, $.70/lb. ($70/0.45 kg, or $1.54 kg), -20g, $.66/1b ($1.46 kg), -20g, $.60/lb ($1.32 kg), Machine costs, total p.a., Royalty (PET), Du Pont-per year, Cost per thousand, , Standard Extrusion, Blow-molding, 2-Parison Head, 4-Fold, , Stretch Blow, Molding PVC (2), Single-paris on, Heads 4-Fold, , Stretch Blow, Molding PET, , $270,000, , $450,000, , $850,000, , $9.00, , $14.85, , $28.33, , 2.80, , 4.65, , 10.20, , 13.00, 2.50, 1.50, 2.25, $31.05/hr., , 13.00, 5.35, 2.00, 3.75, $43.60/hr., , 8.4 sec./l,714, 10,286, , 7.5 sec./l,920, 11,520, , 13.00, 11.00, 4.00, 4.50, $71.03/hr., , 4,000, 24,000, , $585,200, $334,950, $634,360, 186,300, $771,500, , 261,600, $596,550, , 426,180, $1,060,540, 30,000, , $75.00, , $51.78, , $45.44, , Notes: 1. Figures are not to be considered as absolute costs, but rather reflect comparisons between various machine, options., 2. All calculations are based upon 100 percent efficiency., 3. All bottle weights are finish weights (flash being co~Sidered 100 percent reusable)., , shapes can be blown to meet different practical structures, from small to large products., For example, double-walled components are, easily produced. Unfortunately very few designers are familiar with this technique., Examples of different blow molded shapes, are shown in Figs. 8-45 to 8-48., , This technique is also called nonaxisymmetric blow molding. In conventional EBM, the parison enters the mold rather in a, straight tube. In 3-D BM the parison is laid, or oriented in the mold prior to closing. It, is manipulated in the tool cavity providing, complex geometric products that can have

Page 509 : 491, , 8 Plastic Processing, Corrugated for, structure, , \ Structural, ribs (2), , Structural ribs (2), , PL, , Fig. 8-45, , /, , Box detail formed, by compression, welding slol Is, pinched oul, , Compressed flange with, slots pinched out, , Double-walled structural BM panels., , uniform or nonuniform wall thicknesses, corrugated or noncorrugated sections, and so on., There are different techniques used for placing the parison into position such as; (1) articulate the extruder nozzle, (2) articulate the, mold platen, and (3) robotically orient the, parison before the mold closes. Thus, different shaped BM products are fabricated. Sequential BM can be used to integrate hard, and soft regions of different plastics on a single tubular structure (parison)., , Coextrusion or Coinjection, The use of BM multi-layer plastics is a, technology that provides the advantages of, taking advantage of using differing materials, including plastic foams that are systematically combined to meet cost to performance requirements (Fig. 8-49). Techniques, are basically similar to what has been reviewed for INJECTION MOLDING and, EXTRUSION.

Page 510 : 492, , 8 Plastic Processing, , Obsem proper blow, ratio for side d u e l / T r i m aller mOld~, , ~~, (J, ~ r, --".,~, Slots are a, , Trim, , Compressed flange for mtg., , ~--=~_Single, , piece, , Fig.8-46, , Example of BM auto spoiler air duct., , Collapsibility Container, An interesting and practical design involves a bellows-collapsible bottle produced, in conventional EBM equipment. These, "foldable" in contrast to "passive" bottles, provide advantages and conveniences such, as (1) reducing storage, transportation, and, disposal space; (2) prolonging product freshness by reducing oxidation and loss of carbon, dioxide because as the contents is removed, its contents is also reduced; and (3) providing continuous surface access to foods such, as mayonnaise and jams. Best of all, they provide the consumer with a different, futuristic,, fascinating package (Figs. 3-16 and 3-17)., , EBM and IBM Comparison, With EBM, compared to IBM, the advantages include lower tooling costs and incor-, , poration of blown handle-ware, etc. Disadvantages could be controlling parison swell,, producing scrap, limited wall thickness control and plastic distribution, etc. If desired,, solid handles can be molded during the blow, molding process. Trimming can be accomplished in the mold for certain designed, molds, or secondary trimming operations are, included in the production lines., With IBM, the main advantages are that, no flash or scrap occurs during processing, it, gives the best of all thicknesses and plastic, distribution control, critical bottle neck finishes are easily molded to a high accuracy, it, provides the best surface finish, etc. Disadvantages could include its high tooling costs,, only solid handle-ware, and it "was" reported, in the past that they were restricted or usually limited to very small products (however, large and complex shaped products were fabricated once the market developed). Similar comparisons exist with biaxial orienting, EBM or IBM. With respect to coextrusion,, the two methods also have similar advantages, and disadvantages, but mainly more advantages for both., , Blow Molding-Compression-Stretched, Processes basically go through the following stages: (1) starts with an extruded sheet,, (2) circular blanks are cut from the sheet,, (3) compression molded into the desired, preliminary shape; during the compression action, the blank can be simultaneously stretched, (4) blow stretching can take, place after compression molding, and (5) any, , o, Fig.8-47 Simple complex EBM shape that includes a threaded core using a 3-part mold.

Page 511 : 8 Plastic Processing, , Fig.8·48, , 493, , Corrugated/bellow shape., , trimming that may be required is the final, step. There are the CSBM (compression, stretch-blow molding) patents that include:, (1) those held by Valyi Institute for Plastic, Forming (VIPF) located at the University, of Massachusetts-Lowell; (2) Dynaplast S.A., has the Co-Blow system; (3) American Can's, OMNI container; (4) Petainer's cold forming, process; (5) Dow Chemical's solid phase, forming; (6) Dow Chemical's coforming, (COFO); and (7) others., Thermoforming, , Thermoformed (3-D shape) plastics provide a great variety and quantities of marketable products, in a wide size range from, millions of drinking cups or containers (each, , in ounces) to millions of pick -up truck storage, wells (each about 100 lb.) and so on to complex shapes. The process of thermoforming, is considered one of the four major fabricating processes following extrusion, injection, molding, and blow molding. Since the plastic, sheets and films used in thermoforming are, products from extruders, the name extrusionthermoforming is sometimes used. The use of, the terms thermoforming or forming in the, plastics industry do not include such operations as molding, casting, extrusion, etc. in, which shapes or products are "formed" (1)., At least 30wt% percent of all extruded, products are thermoformed. They have many, advantages over other manufacturing methods. For the mass production of products, (packaging, picnic dishes, cups, etc.) sheets, and films can be produced in-line with

Page 512 : 494, , 8 Plastic Processing, , Body layer, Bonding agent, Barrier layer, Bonding agent, Body layer Incl. regrind, , Fig. 8-49, , Coextruded blow molded bottle., , thermoforming equipment. The other major, procedure is a secondary operation where, rolls or flat sheets or films of materials are, feed into the thermoforming equipment. Extruding sheet or film in-line requires dedicaTable 8-23, , tion and control to ensuring that the extruder, is operating efficiently as well as the thermoformer. For those with this type production,, advantages exist including cost savings., The process basically forms the sheet after it has been heated to the point at which, it is soft and flowable, and then applying differential pressure (atmospheric pressure, air, pressure, vacuum, or their combinations) to, make the sheet or film conform to the shape, of the male or female mold producing many, different products (Table 8-23). The more, precise and controlled pressure applied, the, more efficient in reproducing products at the, lowest cost occurs (Fig. 8-50)., The following different thermoforming, techniques are used to form/shape plastics: air-assist, air-slip, billow, blister package, blowing, bubble, clamshell, cold forming,, comoform cold forming, drape, drape with, bubble stretching, draw, form and spray,, form, fill, and seal, form, fill, and seal with zipper on-line, forging, plug, plug and ring, prebillow, pre printing, pressure, sag, scrapless,, shrink wrapping, slip, snap-back, solid-phase, pressure, stretch, vacuum, etc. (1, 6, 9). The, different techniques influence the capability, to provide different depth-to-width forming, ratios (Chapter 3, Thermoforming). Unless, a scrapless forming process is used, thermoformed products require trimming. Different, , Examples of thermoformed products, , Polystyrene, Polystyrene foam, Acrylic, Rigid vinyls, Acrylonitrile butadiene, styrene CABS), Cellulose acetate, Cellulose propionate, Cellulose acetate butyrate, High-density polyethylene, Nylon, Polycarbonate, Polypropylene, , Various packaging applications, including transparent meat trays,, trays for cookie and candy boxes, blister packages, Meat trays, egg cartons, take-out food containers, Signs and other outdoor applications like motorcycle windshields,, snowmobile hoods, and recreational-vehicle bubble tops, Lighting panels, signs, relief maps, bus-interior panels, dishes and, trays for chemicals, blister packages, automobile dashboards, Recreational-vehicle components, luggage, refrigerator liners,, business-machine housings, Blister packages, rigid containers, machine guards, Machine covers, safety goggles, signs, shipping trays, displays, Skylights, outdoor signs, pleasure-boat tops, toys, Camper tops, canoes, sleds, Reusable trays, outdoor signs, surgical equipment, meat trays, Outdoor lighting, face shields, machine guards, aircraft panels, and ducts, signs, Truck-fender liners, drinking cups, juice and dairy-product, containers and lids, test-tube racks

Page 513 : 495, , 8 Plastic Processing, , Fig. 8-50 ABS 76 x 230 in. sheets are conveyed to an IR heating oven in back of the console and in, turn formed into 15 ft outboard-powered runabouts in less than 10 minutes., , type cutters are used depending on shape of, product and plastic used., Also popular is the use of thermoforming, coextruded sheets or films (Figs. 8-51 and 52)., , Temperature Control, Forming requires thorough, fast, and uniform radiant heat from the surface to the, core to the surface of the sheet or film. As, a general guide, to achieve these conditions,, sheet plastics over 0.040 in. (1.02 mm) should, use sandwich-type (under and over the sheet), heater banks. To ensure that sufficient heat, INSERT, , is used, heaters should have capacities of at, least 4 to 6 kW/sq. ft. Various type heating, elements are used., The cycle time is controlled by the heating, and cooling rates, which in turn depend on, the following factors: the temperature of the, heaters and the cooling medium, the initial, temperature of the sheet, the effective heat, transfer coefficient, the sheet thickness, and, thermal properties of the sheet., Different plastics absorb radiant heat more, efficiently at various wavelengths, which in, turn are effected by the temperature of, the emitting heater. Thus it requires that, the proper wavelength be used for what the, CLAMP STRIP, (RECLAIMABLE), , I, , CLAMP STRIP, (RECLAIMABLE), COLOR OR CLEAR, \, , ,\, \, , I"\, , COLOR OR CLEAR, , Fig. 8-51 Bonding two co extruded thermoformed parts to produce a gasoline fuel tank., , Fig. 8-52 The addition of an extruded single, plastic clamping strip at each side of a co extruded, sheet permits scrap reclaim of the trim waste.

Page 514 : 496, , 8 Plastic Processing, , material requires to perform most efficiently, performance wise and energy costwise. With, an in-line operation from an extruder delivering heated sheet to the thermoformer, energy savings from 30 to 40% can occur with, reduced floor space., , Thermoforming Thermoset Plastic, Practically all thermoforming material, used are TPs, however TS plastics can be, thermoformed. As an example commercial, roll-fed thermoforming machines are forming TS polyimide film (for electrical parts), at temperatures as high as 540°C (lOOO°F)., Prior to being roll-fed, they are sheet-fed., Other TS plastics formed include CPET and, B-staged reinforced TS polyester plastics., The TPs are formed above their glass transition temperatures. Specialty products such, as TS polyester-glass fiber reinforced plastics, have been made into boat hulls, etc., , Thermoforming vs. Injection Molding, Thermoforming (TF), wherever applicable, can offer certain advantages over injection molding (1M). TF has lower capital, equipment investments, particularly molds, and mold delivery times and maintenance., Very large products can be formed. Products with different thickness can usually be, formed on the same mold only requiring minor heating and cooling cycle changes. Fewer, stresses can occur with no weld lines., Many products that are 1M cannot be, TF; the most popular competition is producing products such as drinking cups where, both sides have advantages and disadvantages. The major advantage with 1M is providing products that meet tighter tolerances, and quality control as well as a multitude, of rigid shapes. However, TF cups can meet, the customer's performance requirements, at a lower cost particularly when they are, stretched-oriented during their forming operation. Other applications for TF products, exist such as automobile parts (Chapter 4,, World's First AII·Plastic Car Body). To date, over ten times more plastic is 1M than TF., , Foaming, , All markets practical use foamed plastic, materials. Guide to consumption by weight, is insulation 24%, packaging 18%, cushioning 15%, transportation 12%, consumer 4%,, furniture 6%, flooring 6%, bedding 4%, appliance 2%, and other 9%. Many different, foamed plastic products are produced, and, practically all the processes can be used to, make them, particularly extrusion, injection, molding, calendering, casting, and RIM. Almost all plastics can be used to make these, cellular-core structures, which range from, flexible to very rigid objects (Table 8-24). Basically, the plastic is mixed with a blowing, agent classified as either physical or chemical., Foamed plastics, whether TPs or TSs, are, a special category in the plastics family. They, are available with open-celled construction,, closed or interconnecting construction, or in, combination. Their densities range from 1.6, to over 960 kg/m3 (0. 1 to over 60 Ib/ft3). They, can be rigid, semirigid, or flexible, and colored or plain. The range of properties they offer in terms of their insulating value, rigidity,, compressive strength, cushioning and loading, structural characteristics, and others can, be very extensive (Tables 8-25 and 8-26)., Their performance depends to a great extent, on the type of base plastic used, the type of, blowing system, and the method of processing. Each plastic can include fillers or reinforcements to provide certain improved desirable properties., There are many ways in which foams, can be processed and used: as slabs, blocks,, boards, sheets, molded shapes, sprayed coatings, extruded profiles, "foamed in place", in existing cavities, in which the liquid material is poured and allowed to foam, and, as structural foams (Chapter 6, STRUC·, TURAL FOAM). Conventional equipment, such as extruders, injection, or compression machines is used. However specially designed machines are available to just produce, foamed products., The foaming methods vary widely. One approach is to whip air into suspension or a solution of the plastic, which is then hardened, by heat curing. A second is to dissolve a gas

Page 515 : Foamedin, Place, , Syntactic, Castable, , 2-5, 50-60, Density, lb.lft. 3, (kg/m3), (800-960), (32-80), 1000, Tensile strength,, D 1623, 20-54, (6.89), psi (MPa), 8,00022-85, Compression strength D 1621, 13,000, at 10% deflection,, (0.15-0.59) (55.1-89.6), psi (MPa), 19-21, Impact strength,, ft.-lb'/in., Continuous, Maximum service, temperature, at 300, dry, OF (0C), 225, 275, (149), (135), 1.0, Thermal conductivity D2326 0.20-0.22, BTu/in'/hr.-ft.2OF (W/mK), (0.14), (0.29-0.032), 100, D 696, 5, Coefficient of linear, expansion, 10-6, in.lin.-oF, , ASTM, Test, , Phenolics, , Properties of a few rigid plastics foams, , Property, , Table 8-24, , (0.29), 40-60, , 2.0, , 2--4, (32-64), 1,000, (6.89), , (0.033), 30--40, 25, , (0.046--0.049), 38, , 165-175, (74-79), 0.23, , 180-200, (82-93), 0.32-0.34, , 270, (132), , 200, (93.3), , (0.17-0.28), 0.21, , (0.014-0.12), , (51.7), 45, , (37.9), 18, , 2.0, (32), 42-68, (0.29-0.47), 25--40, , Molded, , 200-250, (93-121), 0.15-0.21, , (0.48-1.90), , 4-8, (64-130), 90-290, (0.62-2.00), 70-275, , Polyurethane, Rigid Closed, Cell, , (0.024-0.030) (0.022-0.030), 40, 30--40, , 165-175, (74-79), 0.17-0.21, , 2-5, (32-80), 180-200, (1.24-1.38), 100-180, at5%, (0.69-1.24), , Extruded, , Polystyrene, , 50, (800), 5,500, (37.9), 7,500, , 5.5-7.0, (88-112), 110-210, (0.76--1.45), 2-18, , Polystyrene, MediumDensity, Foam, , 50, (800), 3,300, (22.7), 5,500, , Polyvinyl, Chloride Phenylene, Oxide, Rigid, Closed Foamable, Resin, Polycarbonate, Cell, , -l:l.., '-l, , \Q, , CI(), , '"'"S·, , ~, , ("), , 0, , '"i:l, ...,, , ("), , ::l-., , '", , S-, , '"i:l, , 00

Page 516 : 498, , 8 Plastic Processing, , Table 8-25, , Examples of properties for flexible foams, , Material, Polyphenylene oxide, Polycarbonate, Epoxy resin, Isocyanurate, Polyether, Polystyrene, Polystyrene, Polyurethane, ABS, Acetal, Nylon 6/6, Polybutylene terephthalate, Polyimide, Polysulfone, Polyvinylchloride, , Specific, Gravity, , Elongation, at Break, (%), , Heat Deflection, Temperature °C, (OF), , Thermal Conductivity, W/mK (BTU-in.lhr., ft. 2 . OF), , 15.0, 4.0, , 96 (205), 128 (262), , 0.124 (0.860), 0.151 (1.05), 0.7 (4.8), 0.1 (0.69), , 3.5, , 101 (214), , 0.8, 0.8, 0.78, 0.032, 0.08, 0.17, 1.04, 0.11, 0.86--1.1, 1.130, 0.97, 1.1, 0.87, 0.6, , 0.65 (4.5), 0.3 (2.1), 4.1, 1.3, , 3.5, 370.0, , in a mix, then expand it when the pressure, is reduced. Another is to let a liquid component of a mix be volatilized by heat. Similarly,, water produced in an exothermic chemical, reaction can be volatilized within the mass by, the heat of reaction. A different technique, lets carbon-dioxide gas be produced within, Table 8-26, , 72 (162), 153 (307), 255 (491), 207 (405), 277 (531), 177 (351), , the mass by chemical reaction. A related way, is for a gas such as nitrogen to be liberated, within the mass by the thermal decomposition of a chemical blowing agent. Also tiny, beads of plastics (EPS, etc.) or even glass microballoons can be put into a plastic mix or, syntactic foam or the like., , Examples of thermal properties of foams compared to wood, Wood, (red oak), , Property, , Polystyrene, , Urethane, , Polyethylene, , Density, lb.lcu. ft., (kg/m3), Insulation Value (K factor,, BTU-in.lhr. OF ft. 2 ), (W/m. K), Linear coefficient of thermal, expansion, in.lin. OF, Maximum temperature for, continuous use, OF caC), Heat of Combustion, BTU/lb. (MJ/kg), BTU/cu. ft., BTU/board ft., Ignition temperature, (ASTM D 1929-62T), Flash ignition temp., OF (0C), Self-ignition temp., OF caC), Surface flame spread, (ASTM E 84-61, "Tunnel Test"), , 1.0-3.0, (16-48), , 1.5-2.5, (24-40), , 2.0, (32), , 0.24--0.30, (0.030-0.043), 4 x 10-5, , 0.14-0.16, (0.020-0.023), 5 X 10- 5, , 0.35, (0.050), 8 X 10-5, , 170-180, (77-82), , 250, (121), , 160, (71), , 16,000 (37.18), 32,000, 2,660, , 11,000 (25.56), 22,000, 1,840, , 16,000 (37.18), 32,000, 2,660, , 650-700 (343-371), 735-915 (391-490), , 600 (316), 975 (524), , 650 (343), 660 (349), , 500 (260), 500 (260), , 40-80, , NonFR, , 100, , 10-25, , 0.7, , 8,000 (18.59), 320,000, 26,600

Page 517 : 8 Plastic Processing, Blowing Agent, Also called foaming agents. Depending on, the basic plastic and process, different blowing agents are used to produce gas and thus, to generate cells or gas pockets in the plastics., They are divided into the two broad groups, of physical blowing agents (PBAs) and chemical blowing agents (CBAs)., With PBAs the compressed gases often, used are nitrogen or carbon dioxide. These, gases are injected into a plastic melt in the, screw barrel under pressure (higher than the, melt pressure) and form a cellular structure when the melt is released to atmospheric pressure or low pressure. The volatile, liquids are usually aliphatic hydrocarbons,, which may be halogenated, and include materials such as carbon dioxide, pentane, hexane, methyl chloride, etc. Polychlorofluorocarbons were formerly used but they have, now been phased out due to environment, problems., CBAs, generally solid materials, are of, two types: inorganic and organic. Inorganics include sodium bicarbonate, by far the, most popular, and carbonates such as zinc or, sodium. These materials have low gas yields, and the cell structure they create is not uniform. Organics are mainly solid materials, designed to evolve gas within a defined temperature range, usually called the decomposition temperature range. This is their most, important characteristic and allows control, over gas developments through both pressure and temperature. This increased control, of the CBAs produces a finer and more uniform cell structure as well as better surface, quality on the foamed plastic. There are over, dozens of different types available that decompose at temperatures from at least 220, to 700 P (105 to 370°C) and possible higher., Many of these CBAs can be made to decompose below their decomposition temperature, through the use of activators., Recognize that only certain CBAs can be, used with certain plastics. They have to be, compatible chemically and start gassing at the, required temperature. If they are not compatible different problems develop such as, discoloration, property losses, etc. A CBA, 0, , 499, , with a temperature over the melting temperature of the plastic will not gas to form gas, etc., Formation and Curing of Rigid, Polyurethane Foam, PUR are a broad class of highly crosslinked plastics prepared by multiple additions of poly-functional hydroxyl or amino, compounds. Typical reactants are polyisocyanates [toluene diisocyanate (TDI)] and, polyhydroxyl molecules such as polyols, glycols, polyesters, and polyethers. The cyanate, group can also combine with water; this reaction is the basis for hardening of the one-part, foam formulations., They are foamed by the expansion and capture of gaseous blowing agents that are added, to the reactants or formed during the polymerization reaction. Inert low temperature, boiling hydrocarbons or fluorocabons are often incorporated into foam precursors that, are kept in pressurized containers. When the, pressure is released the gas expands within, the plastic producing the frothing action. Reaction of the cyanate group with water produces carbon dioxide gas as a blowing agent., Also produced in this reaction are ammines, that further combine with isocyanate to form, substituted ureas., Most rigid polyurethane foams have a, closed cell structure. Closed cells form when, the plastic cell walls remain intact during the, expansion process and are not ruptured by, the increasing cell pressure. Depending on, the blowing process a small fraction (5-10%), of the cells remain open. Closed cell structures provide rigidity and obstruct gaseous, or fluid diffusional processes., One component formulation consists of, prepolymers that are intermediate between, monomers and the final polymer product., When released from a pressurized container, the foaming gas expands and the prepolymer (containing unreacted cyanate groups), reacts with the moisture (water) in air to complete the polymerization reaction and cure., Because curing depends on the presence of, moisture, when foam forming reactants are, applied to occluded areas, such as cavities,

Page 518 : 500, , 8 Plastic Processing, , the rate of solidification will be dependent on, the venting conditions available. Poor venting, will inhibit expansion of the blowing agent, and the chemical reactions necessary for a, cure. Cure times depend on the ability of, moisture to reach the expanded prepolymer, material., Processing of rigid foams from two part, formulations involves combining measured, quantities of the polyisocyanate with a polyhydroxyl such that there are no or limited reactive isocyanate functional groups. Moisture, is not required to complete the cure. Once the, reactants are combined the mixture is poured, into a form where expansion and polymerization take place simultaneously. Cure times, are usually very fast, on the order of minutes., , does the cooling. To facilitate removal, particularly for complex shapes, mold-release, agents are used., An outstanding property of EPS is its, extremely low density (when compared to, other processes), that by alteration of the, preforming treatment can be varied according to the end use. Other types of plastics, are employed to produce expandable plastic, foam (EPF), including PE, PP, PMMA, and, ethylene-styrene copolymers. They can use, the same equipment, with only slight modifications. These plastics have different properties from those of EPS and open up different markets. They provide improved sound, insulation, resistances to additional heat deformation, better recovery of shapes in moldings, and so on., , Expandable Polystyrene, Syntactic Foam, EPS molding illustrates the use of blowing agents. Plastic beads containing a blowing agent are supplied to the molder in solid, form. Each about O. 1 to O. 3 mm in diameter, these beads or spheres contains a small, amount of a hydrocarbon liquid, usually pentane that is used as the blowing agent., The process involves two major steps. The, first consists of a preexpansion of the virgin, beads by heat (steam, hot air, radiant heat, or, hot water). Steam is the most used medium as, it is the most practical and most economical., The next step conveys these beads, usually through a plastic transport tube by air,, to the mold cavity. The final expansion occurs in the mold usually with steam heat, either by having live steam go through perforations in the mold itself or by means of steam, probes in the cavity that are withdrawn as the, beads are expanding. During expansion the, beads melt together, adhering to each other, and form a relatively smooth skin, filling the, cavity or cavities. With some products multiple cavities can be used. After the heat cycles the cooling cycle starts. Because the EPS, is an excellent thermal insulator, it takes a, relatively long time to remove its heat prior, to demolding compared to a solid plastic., With insufficient time the product will distort., Directing a water spray on the mold usually, , In syntactic foams, instead of employing a, blowing agent to form bubbles in the mass,, preformed bubbles of glass, ceramics, and/or, plastic are embedded in a matrix of an unblown plastic. The preformed bubbles are, combined with a foamed plastic to provide, cells. Reducing weight is one obvious objective, but this change may be accompanied by, other properties. A mixture of micro spheres, and the plastic can be formulated into a moldable mass that can then be shaped or pressed, into cavities and molds much as molding sand, and clay. The properties of the finished hardened or cured mass can then be tailored by a, suitable plastic formulation. Synthetic wood,, for example, can be created by a mixture of, TS polyester plastic and small hollow glass, spheres (Table 8-27)., Syntactic foam contains an orderly arrangement of hollow sphere fillers. They, are usually glass microspheres approximately, 100 microns (4 mils) in diameter, provide, strong, impervious supports for otherwise, weak, irregular voids. As a result, syntactic foam has attracted considerable attention both as a convenient and relatively lightweight buoyancy material and as a porous, solid with excellent shock attenuating characteristics. The latter characteristic is achieved

Page 519 : 8 Plastic Processing, Table 8-27, , 501, , Example of syntatic foams used in deepwater floatation material, , Foam, Density, lb.lft. 3, , Glass, Microballoons, , Epoxy, Macroballoons, , 24, 27, 30, 32, 34, 35, 38, 42, , Yes, Yes, Yes, Yes, Binary, Yes, Yes, Yes, , Yes, Yes, Yes, No, No, No, No, No, , Uniaxial, Compressive, Yield, Strength,, psi', 1,700, 2,800, 2,500, 7,300, 10,500, 10,000, 10,000, , Hydrostatic, Compressive, Strength,, psi', , Method of, Preparation, , Resin, System, , 1,800, 2,300, 3,000, 7,000, 16,000, 14,000, 14,000, 15,000, , Pack-in-place, Pack-in-place, Infiltration, Pack-in-place, Infiltration, Vacuum cast, Cast, Cast, , Polyester, Epoxy, Polyester, Polyester, Epoxy, Epoxy, Polyester, Polyester, , 'To convert psi to pascals (Pa), multiply by 6.895 x 103 ., , through crushing of the spheres and filling in, the voids with plastic., , Static and dynamic property The uses of, these foams or porous solids are used in a variety of applications such as energy absorbers, in addition to buoyant products. Properties of, these materials such as a compressive constitutive law or equation of state is needed in, the calculation of the dynamic response of, the material to suddenly applied loads. Static, testing to provide such data is appealing because of its simplicity, however, the importance of rate effects cannot be determined by, this one method alone. Therefore, additional, but numerically limited elevated strain-rate, tests must be run for this purpose., Interest in the use of syntactic foam as a, shock attenuator led to studies of its static, and dynamic mechanical properties. Particularly important is the influence ofloading rate, on stiffness and crushing strength, since oversensitivity of either of these parameters can, complicate the prediction of the effectiveness, of a foam system as an energy absorber., Results of uniaxial strain static and gas, gun compression tests on syntactic foam, have been conducted. The foam was buoyant, and composed of hollow glass microspheres, (average diameter 100 microns) embedded, in an epoxy plastic. Static testing consists of, compressing a 0.25 cm x 2.5 cm dia. wafer, between carefully aligned 2.5 cm dia. steel, pistons. Lateral expansion of the wafer is, , suppressed by mounting it in a thick-walled, (10 cm OD, 2.5 cm ID) cylinder, The degree, of expansion is monitored by a circumferential strain gage mounted on the outside of the, cylinder. Dynamic testing is conducted using, a wave generated gas gun., Accordingly an experimental and analytical program was undertaken to establish the, magnitude of the rate effect over the range, of interest. From a materials testing standpoint, it is clear that the rate range is bounded, from below zero, which is well approximated, by the so-called static testing machines, and, from above by rates achieved under instantaneous impact, which are approached in gas, gun tests. Assuming monotonicity of the material behavior over this extended rate range,, one may argue that data from the bounding, experiments will exhibit the maximum discrepancy and hence provide a gross measure, of the material sensitivity to rate effects. The, experiments conducted in this program were, designed to follow this philosophy., Test results provides the hypothesis that, syntactic foam is rate insensitive and that, the static uniaxial strain stress-strain curve, actually represents the general constitutive, relation. Disagreement between the experimental data and the predicted behavior is, greatest at low stresses (1 kbar) where experimental stresses are about double those, predicted analytically. The discrepancy decreases at the higher stress levels and virtually, disappears at and beyond 7 kbar. This range

Page 520 : 8 Plastic Processing, , 502, 80, , .'S", , 60, , c:, , .2, , e!, , J, , 40, 6 pcf, , .><, , If'", , 20, , 1.0, , 2.0, , 30, , Stalic Loading ~i, , Fig. 8-53 Example of how a closed-cell PE foam, density affects both its cushioning and its loading., , of disagreement would extend somewhat further (to about 9 kbar) were the transient current readings rather than the plateau values, used in the intermediate stress range., , Cushioning Design, When plastic foams are used to cushion, products, as they are in packaging, there are, specific design approaches to use. It is widely, held that the lower density closed-cell foams, that are usually priced lower provide superior, cushioning performance, but this assumption, is usually incorrect. Figure 8-53 illustrates, how closed-cell PE foams with differing densities but the same type and thickness behave, under the same dynamic cushioning conditions. These curves represent the amount of, mechanical shock experienced during an impact. The lower the curve goes, the greater, the cushioning efficiency. For densities above, 2 pcf (lb/ft3) the maximum cushioning efficiency of each material is not significantly different, but the loading at which this maximum, efficiency will occur will vary dramatically., , Density effect If a 40 g package were to, be designed according to Fig. 8-53 using a 6.0, pcf foam, the foam would measure 3 in. thick, at a loading of about 1.35 psi. If an identical, package were then produced using a 2.2 pcf, foam, its shock performance would not go as, , low as 40 g's but would instead produce about, 60 g's, or 50% more shock. In order to return to 40 g's, the 2.2 pcf package would need, to be redesigned. One approach would be, to greatly increase the thickness of the pads, constructed from the lower density foam, to, provide adequate protection. This approach, would, however, increase the package size,, impair handling and shipping efficiency, and, possibly result in higher costs. The 6.0 pcf, foam could, however, be reliably used at 1.2, psi in the thickness shown in Fig. 8-53., Another approach is to keep the 2.2 pcf, foam thickness the same, but decrease the, loading from 1.35 to 0.87 psi, to get back to the, 40 g level. Although this approach keeps the, package size the same, nearly twice as much, foam must be used to meet the lower loading. The lower density foam must therefore, cost less than half as much as the high density type on a cost-per-unit volume basis if, using the lower density one is to result in a, cost savings. Below a density of about 2.2 pcf, the cushioning efficiency can begin to change, with the density. This situation is shown in, Fig. 8-54 where the test results for PE foams, in several densities below 3 pcf are compared., , Creep resistance Thus, lowering the density produces a considerably higher deceleration and reduces cushioning performance., Also significant is the narrower range of usable static loadings at the bottom of the, 180 ,---.--.--,--,--,---.--.--,--,, 1~ r---r--+--+-~--~--r--+--~~, , ~, .~ 120, '§, , .!!, , ~90t------t--+-:~fC.--+---I-"""""""","--I---=-o---i, .><, , ~, a., , 60 r-~E:;;;""''''''''''':l;;oo''''''''''''-~--t-', , 00, , 0.3, , 0.6, , 0.9, , 1.2, , 1.5, , 1.8, , 2.1, , 2.4, , 27, , Static Loading (psi), , Fig.8-54 A closed-cell PE foam at different densities compared to its cushioning efficiency.

Page 521 : 8 Plastic Processing, curves that resulted when the density was, reduced. Important consideration in comparing foams of different densities is their, compressive creep resistance, and their ability to resist undergoing a permanent thickness loss during their time under load. As, the density decreases, so does the creep, resistance., Although it may seem logical for a lowerdensity foam to cost less to produce because, it contains less plastic, this is not necessarily true. The manufacturing rates, the amount, and cost of the blowing agent, and the amount, and cost of the base plastic all influence the, final cost. As a result, very low density foams, can actually be more costly to make than others. Thus, it should not be assumed that the, cost of a foam will be proportional to its density. Incidentally, this cost situation can also, occur with solid plastics in certain shapes,, thicknesses, and types, but in solids the problem is rare. Cushioning performance is therefore not improved merely by increasing a, foam's density. In order to be certain that a, material selected is appropriate and efficient,, the designer should carefully compare documented performance data., Foam Reservoir Molding, This low pressure process, also known as, elastic reservoir molding, consists of making, basically a sandwich of plastic-impregnated, open-celled flexible polyurethane foam between the face layers of fibrous reinforcements. When this plastic composite is placed, in a mold and squeezed, the foam is compressed, forcing the plastic outward and, into the reinforcement. The elastic foam exerts sufficient pressure to force the plasticimpregnated reinforcement into contact with, the heated mold surface. Other plastics are, used., Reinforced Plastic, , The term reinforced plastic (RP) refers to, combinations of plastic (matrix) and reinforcing materials that predominantly come, , 503, , in fiber forms such as chopped, continuous,, woven and nonwoven fabrics, etc. and also, in other forms such as powder, flake, etc., They provide significant property and/or cost, improvements than the individual components; primary benefits include high modulus,, high strength, oriented strength, lightweight,, high strength-to-weight ratio, high dielectric, strength and corrosion resistance, and long, term durability (7, 10,62)., Also called composite. The term composite denotes the thousands of different combinations of two or more materials that include, in comparison, a few RPs. If referring, to composites that incorporate plastics, consider calling them plastic composites. However the more descriptive and popularly used, worldwide term is reinforced plastic. In USA, annual consumption of all forms of RPs is, over 31h billion lb (1.6 billion kg). Both thermoset (TS) and thermoplastic are used. At, least 90wt% use glass fiber and about 45wt%, of them use TS polyester plastic. This RP, market started during the early 1940s using, contact or low pressure TS polyester plasticsglass fiber fabricating systems that were practically all hand lay up with bag molding. In, the mean time many different plastics with, different reinforcements have been used with, rather many different RP processes. All these, combinations meet different requirements., In the mean time their products have gone, worldwide into the deep ocean waters, on, land, and into the air including landing on, the moon and in spacecraft., The RP industry is a mature industry. Improved understanding and control of processes continue to increase performance and, reduce variability. Fiber strengths have risen, to the degree that 2-D and 3-D RPs can be, used producing very high strength and stiff, RP products having long service lives of over, a half century. Thermoplastic RPs (RTPs),, even with their relatively lower properties, when compared to thermoset RPs (RTSs) are, used in about 55wt% of all RP parts. The, RTPs are practically all inj ection molded with, very fast cycles using short glass fiber producing highly automated and high performance, parts (Fig. 6-15). Included in these RTPs are, stamp able reinforced thermoplastics.

Page 522 : 504, , 8 Plastic Processing, , fairly linear to failure and they are less timedependent. For high performance applicaRPs can be characterized many different tions, they have their first damage occurring, ways such as type and construction of rein- at stresses just below ultimate strength. They, forcement used to those with high impact and are also much less temperature-dependent,, fatigue strength properties. Testing for tensile particularly RTSs (reinforced TSs). The postress-strain (S-S) properties over a range of tential complications that arise relate princihigh-test rates with areas under the S-S curves pally to the directional effects resulting from, is a potential method for estimating relative the fiber construction (Chapter 6, REINtoughness. Comparing fatigue strength for FORCED PLASTIC)., notched and unnotched conditions at various, When constructed from any number and, ratios of minimum to maximum stress is use- arrangement of RP plies, the stiffness and, ful in structural design (Chapter 2)., strength property variations may become, Depending on construction and orienta- much more complex for the novice. Like, tion of stress relative to reinforcement, it may other materials, there are similarities in that, not be necessary to provide extensive data the first damage that occurs at stresses just, on time-dependent stiffness properties since below ultimate strength. Any review that, their effects may be small and can frequently these type complications cause unsolvable, be considered by rule of thumb using es- problems is incorrect. Reason being that an, tablished practical design approaches. When RP can be properly designed, fabricated and, time dependent strength properties are re- evaluated to take into account any possible, quired, creep and other data are used most variations; just as with other materials. The, effectively. There are many RP products that variations may be insignificant or significant., have had super life spans of many decades. In- In either case, the designer will use the recluded are products that have been subjected quired values and apply them to a safety, to different dynamic loads in many different factor; similar approach is used with other, environments from very low temperatures to materials (Appendix A: PLASTIC DESIGN, very high corrosive conditions, etc. An exam- TOOLBOX)., The fabricator has a variety of alternaple is aircraft primary structures (10, 14, 62)., tives to choose from regarding the kind, form,, amount of reinforcement to use, and the proRP Directional Property, cess vs. requirements (Table 8-28). With the, many different types and forms (organics, inWith RPs an opportunity exists to op-· organics, fibers, flakes, and more) available,, timize design by focusing on a material's practically any performance requirement can, composition, product geometry, and orienta- be met and molded into any shape. Possible, tion. However what is involved basically is shapes range from very small to extremely, in "tailor-making" the RP material. The ar- large, and from simple to extremely complex., rangement and the interaction of the usual, stiff, strong fibers dominate the behavior of, Orientation of reinforcement The behavRPs with the less stiff, weaker plastic matrix ior of RPs is dominated by the arrangement, (TS or TP). A major advantage is that direc- and the interaction of the stiff, strong fibers, tional properties can be maximized. Basic de- with the less stiff, weaker plastic matrix. The, sign theories of combining actions of plastic features of the structure and the construcand reinforcement have been developed and tion determine the behavior of RPs that is, used successful since the 1940s (7, 10, 37)., important to the designer. A major advanWhen compared to unreinforced plastics, tage is the fact that directional properties can, the analysis and design of RPs is simpler in be maximized in the plane of the sheet. As, some respects and perhaps more complicated shown in Fig. 8-55 they can be isotropic, orin others. Simplifications are possible since thotropic, etc. Basic design theories of comthe stress-strain behavior ofRPs is frequently bining actions of plastics and reinforcements, RP Characterization

Page 523 : 3~50g1ass-, , Reinforcement, wt%, , lO~Z80, , 7~ZlO, , 1.~Z.5, , 1.~3.0, , 6.9-17, , 6.9--Z1, , 5.5-17 0.8-2.5, , lZ-30, , 1~, , 7-35, , 8~ZlO, , 7~Z80, , 5~Z40, , 17~210, , 6~1,050, , 4.~.0, , 28--41, , 6~150, , 41~1,050, , I~Z80, , 14~340, , 15-40, , 1~30, , 21~340, , Z5-30, , Z7~1,600, , ZI~I,350, , 15-40, , 53~1,350, , Z~50, , 3~50, , 3~70, , 210-480, , 1~150, , 2,4~3,ZOO, , Z,15~3,2OO, , 45-70, , 31~0, , I~Z70, , 6~1,850, , 4.~9.0, , 2~Z, , 8~250, , 55~1,7oo, , 53~1,050, , 15-30, , 1~21O, , 10-40, , 6.2-14 0.9-2.0, , 25-30, , 17~21O, , 210--640, , 15-25, 43~1,150, , 7~280, , 12~210, , 11m, , ksi, , 0.ZZ-D.33 1.5-Z.3, , 0.ZZ-D.Z7 1.5-1.85, , 0.Z7-D.33 1.9-2.3, , 0.27-D.33 1.9--Z.3, , 0.19-D.26 1.3-1.8, , 48-300 0.ZZ-D.33 1.5-2.3, , ~360, , 12~3oo, , 54~720, , 48~720, , 12~240, , 96-264 0.19-D.25 1.3-1.7, , 35~, , 4O~500, , ZO~3OO, , 4O~5oo, , 175-Z05, , 35~, , 175-Z30 350-450, , 95-150, , Z05-Z60, , 175-Z05 350-400, , 175-205, , 205-260, , 35~0, , OF, , 175-205, , °C, , ft 2 • of, , 48-144 0.17-D.23 1.2-1.6, , Heat, Distortion, at 1.8MPa, , Btu·, in.lb·, , Thermal, Conductivity, , ft ·lbf/ft W/m· K, , Impact, Strength, , 15-30, , 1~170, , 16-28, 1~21O, , MPa, , ksi, , Compressive, Strength, , 18-30, , 11~190, , 11-17 1.6-2.5, , 5.5-12 0.8-1.8, , 9-18, , MPa, , Flexural, Strength, , 8-20, , GPa, , ksi, , 1<f psi, , Tensile, Modulus, , 55-140, , 6~120, , MPa, , Tensile, Strength, , Overview of RP properties and processes, , polyester, Compression(a) 15-30 glassSMC, Compression(a) 25-50 glass, matpolyester, Filament, 3~Oglassepoxy, winding(a), Pultrusion(b), 4~Oglass, matpolyester, 3~50glass, Pultrusion(b), matpolyester, Pultrusion( c), 3~55 glass, mat and, rovingvinyl, ester, resin, 3~55 glass, Pultrusion(c), mat and, rovingpolyester, resin, , Spray(a), , Process, , Table 8-28, , ~120, , 8~130, , 8~IZ0, , 8~160, , lZ~160, , 12~240, , 12~180, , 8~160, , kV/cm, , Z~300, , ZO~3Z5, , ZO~3OO, , ZOO-4OO, , 300-400, , 30~, , 300-450, , 20~, , kV/in., , Dielectric, Strength, , v., ~, , O"Q, , ....;:s'"~, , ~, , 0, , ....'"tl, , ~, , '":::to, , 5"', , '"tl, , 00

Page 524 : 8 Plastic Processing, , 506, , Orthotropic or Unidirectional, , Variations." Propen-es WIth, , Angles of SUBSS, , At 0 ', , Bidirectional, VariaUQns In PropertteS, Wlth Angle 01 Slress, , At 45, , At 90', , II, , AIO and 90 ' AI 45, , m, , Orthotropic or Unidirectional, , 1m Bidirectional, S, , Isotropic Or Planar, , Propenles Independent, 01 Angle 01 Siress, , Isotropic or Planar, , o Unraintorced Plastics, , At any angle, , (b), , (a), , o, , Onholropic, , o -90', , Btdll8Clional, aU directions IsotropIC, 45 Bldll8Cloonal, 45' OrthOlropo<:, , ~--, , Unrelnlorced PlaShes, , O ~-------------, , o, , Sua in, , High, , (0), , Fig.8-55 Overview of RPs directional properties: (a) polar directional, (b) different fiber orientations, and tensile fracture characteristics, and (c) stress vs. strain diagrams of RPs., , have been developed and used successfully., As an example, woven fabrics that are generally directional in the 0° and 90° angles contribute to the mechanical strength at those, angles. The rotation of alternate layers of fabric to a layup of 0° , +45 90° , and -45° alignment reduces maximum properties in the primary directions, but increases in the +45° and, -45° directions. Different fabric and/or individual fiber patterns are used to develop, different property performances (Figs. 8-56, and 57)., A microscopic view of an RP reveals, groups of fibers surrounded by the matrix., For example, glass fibers at about 0.01 mm, (4 x 10-4 in.) in diameter may comprise from, 10 to 90wt% of the area of a given cross0, , ,, , section. Theories are available to predict, overall behavior based on the properties of, fiber and plastic constituents' (10). In a practical design approach, the behavior can use, the original approach analogous to that used, in wood, where individual fiber properties, are neglected; only the gross properties, measured at various directions relative to the, grain, are considered. This was one of the initial evaluation approaches used during the, 1940s (10)., Terminology regarding directional properties used with RPs include the following:, 1. Anisotropic construction It is one in, which the properties are different in different directions along the laminate flat plane; a

Page 525 : 8 Plastic Processing, 0", , Fig.8-56 Properties of style 181 glass fabric (bidirectional type); parallel lay-up with 60wt% glass, content., , material that exhibits different properties in, response to stresses applied along the axes in, different directions., 2. Balanced construction In woven RPs,, equal parts of warp and fill fibers exist. Its, construction is one in which reactions to tension and compression loads result in extension or compression deformations only, and, , Fig.8-57 Properties of style 143 glass fabric (unidirectional type); parallel lay-up with 60wt% glass, content., , 507, , which in flexural loads produce pure bending of equal magnitude in axial and lateral, directions. It is an RP in which all laminae at, angles other than 0° and 90° occur in ± pairs, (not necessarily adjacent) and are symmetrical around the central line., 3. Biaxial load It is a loading condition in, which a specimen/product is stressed in two, different directions in its plane, i.e., as an example it is a loading condition of a pressure, vessel under internal pressure and with unrestrained ends., , 4. Bidirectional construction It is an RP, with the fibers oriented in various directions, in the plane of the laminate usually identifies, a cross laminate with the direction 90° apart., 5. Isotropic construction Identifies RPs, having uniform properties in all directions., The measured properties of an isotropic material are independent on the axis of testing., The material will react consistently even if, stress is applied in different directions; stressstrain ratio is uniform throughout the flat, plane of the material., 6. Isotropic transverse construction Refers, to a material that exhibits a special case of orthotropy in which properties are identical in, two orthotropic dimensions but not the third., Having identical properties in both transverse but not in the longitudinal direction., 7. Nonisotropic construction A material or, product that is not isotropic; it does not have, uniform properties in all directions., 8. Orthotropic construction Having three, mutually perpendicular planes of elastic, symmetry., 9. Quasi-isotropic construction It approximates isotropy by orientation of plies in several or more directions., 10. Unidirectional construction Refers to, fibers that are oriented in the same direction,, such as unidirectional fabric, tape, or laminate, often called UD. Such parallel alignment is included in pultrusion and filament, winding applications., 11. Z-axis construction In RP, it is the reference axis normal (perpendicular) to the X-Y, plane (so-called flat plane) of the RP.

Page 526 : 508, , 8 Plastic Processing, , H etergeneouslhomogeneouslanisotropic, RP materials are heterogeneous; which, means varied. The material's composition, varies from point to point in a heterogeneous, mass. However, for design purposes, many, heterogeneous materials are treated as homogeneous. This is because a "reasonably", small sample of material cut from anywhere, in the body has the same properties as, the body. The term homogeneous means, uniform. As one moves from point to point, in a homogeneous material, the materials', composition remains the same. An unfilled, (unreinforced) TP is an example of this type, of material., In an anisotropic material, the properties, depend on the direction in which they are, tested. For example, rolled metals, which are, anisotropic, tend to develop a crystal orientation in the rolling direction. Thus rolled and, sheet-metal products have different mechanical properties in the two major directions., Also, extruded plastic film can have different, properties in the machine and transverse' directions. These materials are oriented biaxially and are anisotropic. (As reviewed above, under EXTRUSION, Orientation)., The designer must be aware that as the degree of anisotropy increases, the number of, constants or moduli required to describe the, material increases; with isotropic construction one could use the usual independent constants to describe the mechanical response, of materials, namely, Young's modulus and, Poisson's ratio (Chapter 2). With no prior, experience or available data for a particular, product design, uncertainty of material properties along with questionable applicability of, the simple analysis techniques generally used, require end use testing of molded products, before final approval of its performance is, determined., RPs are either constructed from a single, layer or built up from multiple layers., The properties of each layer are usually, orthotropic, which is a special case of, anisotropy. Fibers that remain straight in the, single layer are desired. However, with many, fabrics, they are woven into configurations, that kink the fiber bundles severely. Such fabric constructions may be very practical since, , they drape better over double-warped molds, than do fabrics that contain predominantly, straight fibers. To reduce the number of kinks, in a fabric and develop different form abilities, and properties, satin weave fabrics are used., They have different constructions such as, weaving a fiber over 9 fibers rather than, using the more conventional square weave., The square weave has one fiber over another., Fiber bundles in lower cost woven roving, are convoluted or kinked as the bulky rovings conform to the square weave pattern., Kinks produce repetitive variations in the direction of reinforcement with some sacrifice, in properties. Kinks can also induce high local stresses and early failure as the fibers try, to straighten within the matrix under a tensile load. Kinks also encourage local buckling, of fiber bundles in compression and reduce, compressive strength. These effects are particularly noticeable in tests with woven roving, in which the weave results in large scale, renforcement. Fiber content can be measured, in percent by weight of the fiber portion, (wt%). However, it is also reported in percent by volume (vol %) to reflect better the, structural role of the fibers, which is related, to volume (or area) rather than to weight., When content is only in percent, it usually, refers to wt %., The fiber content in mat or random fiber, RPs is usually somewhat lower than for an, isotropic laminate which is comprised of a, number of unidirectional plies. Both laminates may, for example, be planar-isotropic., The random criss-cross nature of chopped, fibers in a mat does not permit close packing of the bundles, and thus the fiber content, is usually lower. With a lay-up of unidirectional plies, the packing of fibers within a ply, may be very close, and the fiber content can, be very high. The higher fiber content made, from individual plies tends to make it stiffer, and stronger than the mat construction., There is a relationship between the way the, glass is arranged and the amount of glass that, can be packed in a given product. By placing continuous strands, such as round glass, fibers in a filament 'winding pattern, next to, each other in a parallel arrangement, more, glass can be placed in a given volume. Glass

Page 527 : 8 Plastic Processing, content can range from 65 to 95.6 wt% or up, to 90.8 vol%. When one-half of the strands, are placed at right angles to each half, glass, loadings range from 55 to 88.8 wt% or up to, 78.5 vol%., , Advanced Reinforced Plastic, An advanced RP (ARP) typically refers, to a plastic matrix reinforced with very high, strength, high modulus fibers and/or other, properties. Examples of these type fibers, include carbon, graphite, aramid, boron,, S-glass and ZenTron-glass. ARPs can provide the designer with specific properties or, characteristics such as strength, stiffness and, lower density used in different environments., They can be at least 50-times stronger and, 25 to 150-times stiffer than the matrix. As, an example ARPs can possess the desirable, properties of low density (1.4-2.7 g/cm3),, high strength (3-5 GPa) and high modulus, (60-550 GPa). With proper processing these, ARPs provide certain properties equal or exceeding those of most other materials., , Micromechanic, It is analyzing the mechanical behavior of, RPs by considering the properties, concentration, geometry, and packing of the individual, components. This contrasts with macromechanics by recognizing the inhomogeneous, nature of RP. By making various approximations of the packing geometry and stress, fields within an element of the matrix, the, average properties of the element may be, calculated (62)., , Material, Plastics offer the opportunity to optimize, RP design by focusing on material composition in conjunction with reinforcement orientation, as well as product structural geometry., This interrelation affects processing methods, product performances, and costs. This, action also gives the designer great flexibility and provides freedom not possible with, , 509, , most other materials. However, it requires a, greater understanding of the interrelations to, take full advantage of RPs., Certain plastics provide higher strength, and stiffness; a broad range of properties exit., Even though there are literally over 35,000, plastics available worldwide (for all plastic, fabricating processes) only a few hundred are, used in RPs. In turn only a few of those are, predominantly used in most of the RPs. The, thermoplastics (TPs) include principally nylons and polypropylenes, as well as polycarbonates, acetals and polyesters. Thermosets, (TSs) include predominantly polyesters as, well as epoxies, phenolics and urethanes., TSs and RTSs generally are more suitable, to meet the tighter tolerances. The crystalline, RTPs, particularly unreinforced TPs, can be, more complicated if the designer does not, understand their behavior. Crystalline plastics generally have significant different rates, of melt flow shrinkage, particularly during, injection molding, in the longitudinal melt, flow and transverse directions; less transversewise. With reinforcement and/or certain, fillers these differences can be reduced or, eliminated. With amorphous TPs basically no, difference occurs. Compensation for any potential undesirable differences can be made, during product and mold designs, reinforcement/filler selection and/or during processing, (Chapter 6)., Reinforcements are discrete (usually) inert inclusions used to significantly improve, the structural characteristics of a TP or TS, plastic. They can be in continuous forms, (fibers, filaments, woven or non-woven fabrics, tapes, etc.), chopped forms having different lengths (Fig. 8-58), or discontinuous in, form (whiskers, flakes, spheres, etc.). The reinforcements can allow the RP materials to be, tailored to the design, or the design tailored, to the material. The required approach often results in better designs for certain products and can be less complicated to fabricate., However when permitted, it is best to use, prepreg or molding compounds where the, plastic and reinforcement are prepared and, ready for fabricating into a product. These, materials include sheet molding compounds, (SMC), bulk molding compounds (BMC)

Page 528 : 8 Plastic Processing, , 510, Flexural modulus,, million p.', 4, , 1601/::::;, 3, , 01651, 01601, , (6010, , 0155), , (401 /::::;, , 2, , 1401, , Short-fiber, nylon, polyester, , o 140J, , 0, , Long-fiber compounds, 6PET oP8l ONylon, % Glass shawn in parentheses, , 2, , 3, , 4, , 5, , 6, , 7, , 8, , 9, , 10, , notched Izod Impact Strength, (ft-Ib/ln.), , Fig.8-58 Long glass fiber RP molding compounds have higher and more metal-like than conventional, shorter fiber compounds., , and stampable sheets. They can be prepared, and processed to meet different directional, properties or product performances., , Flexible RP These materials are used with, elastomeric materials providing special engineered products such as conveyor belts, mechanical belts, high temperature or chemical, resistant suits, wire and cable insulation, and, architectural designed shapes., Preimpregnation Also called prepreg. It, is the practice of mixing usually TS plastic, (hot melt or solvent system; also wet system without solvent) and reinforcement and, stored for use at a latter time or for shipping, to a molder. The reinforcement can be of any, style such as glass fiber mat or fabric. It is, partially cured (B-stage) ready-to-mold material in web form that may have a substrate, of glass fiber mat, fabric, roving, etc.; paper;, cotton cloth; etc. With proper storage condition of temperature, their shelf life can be, controlled lasting at least 6 months., , of the mixture used in sheet molding compound (SMC), except that it contains only, short fibers. IMMs are used with special screw, designs and some type of ramming system to, feed the screw (3)., , Sheet molding compound SMC is a, ready-to-mold glass fiber reinforced TS, polyester material primarily used in compression molding. SMC is usually TS polyester, plastic (generally cross-linked with styrene), with glass fibers and additives such as pigments, fillers, etc. that have been compounded and processed into sheet form to, facilitate handling in the molding operations., This B-stage material has a good shelf life, particularly when stored in a cool place., Different methods are used for manufacturing SMC. A few will be reviewed. Figure, 8-59 shows continuous glass-filament rovings, going through a chopper (where the length, ROVINGS, , RESIN, , PASTE, , Bulk molding compound BMC is also, called dough molding compound (DMC). It, is a molding compound (extruded log form), that is not produced in sheet form. It consists, , Fig. 8-59 SMC production line with chopped, glass fibers.

Page 529 : 511, , 8 Plastic Processing, , Surfacing reinforced mat It is a very thin, mat, usually 180 to 510 /Lm (7 to 20 mil) thick, of highly filamentized glass fiber. It is used, to produce a smooth surface on glass fiber, reinforced plastics., , ROVINGS, , Fig. 8-60 SMC production line incorporating, long fibers., , of the chopped fibers can be changed by, the location of the cutting blades). The belt, moves at a controlled rate and the plastic, paste compound is controlled by a doctor, blade that provides an opening for the paste, to move over the speed-controlled revolving, conveyor belt. Plastic carrier film (usually PE, that is not shown) placed on the SMC eliminates the sticking problem ofB-stage TS compounds, permit ease of handling for shipment,, cool room storage, and lay-up for fabrication., The films are removed prior to fabrication, lay-up., Figure 8-60 is a schematic that shows, the production of SMCs incorporating long,, high-performance fiber reinforcements oriented in either the machine direction or positioned in any direction desired, using single, or multiple fibers and rovings to obtain the, desired orientation and directional properties. Figure 8-61 shows a schematic of the offline production process used when required, to cut directional-type SMC to conform to a, specific mold contour to significantly reduce, or even eliminate unwanted wrinkles during, lay-up., , Gel coat In RP processing a gel coat on, the outer surface can be used to ensure a, smooth surface appearance and a tough surface. It could contain a thin synthetic fiber, veil to improve performance of the gel coat, and/or a surfacing mat. It is a quick setting, plastic and gelled prior to reinforcement layup. The gel coat becomes an integral part of, the finished RP product., RP cost Important to recognize that a, major cost in the production of RPs, going from the design concept to the finished, product, is materials of construction. They, can range from 40 to 90% of the total cost., Thus, it is important to understand how best, to use the materials based on the design, and processing requirements. It calls for the, ability to recognize situations in which certain approaches may be used and to develop, problem-solving methods to fit specific design, requirements., An important criteria is to understand and, properly apply the interrelations of design, requirements with materials of construction, and fabricating methods. RPs has some mechanical, formability, and other characteristics that differ from other materials (steel,, aluminum, wood, etc.). So what is new; all, materials have certain characteristics that, , Typical Charge, , Pattern, , - pierced 1st ply, - ' - pierced 2nd ply, , Typical Molding, :::: "windows" 1st ply, :::~"windows" 2nd ply, , SMC production line permits conforming to a molded shape.

Page 530 : 512, , 8 Plastic Processing, , differ from others. It is a fact that RPs have, not come near to realizing their great potential in a multitude of applications usually due, to cost limitations. An example of its growth, is its expanding use in automobile constructions. Cost to performance advantages definitely exist., , Process, Different fabricating processes are, employed to produce RP products that, represent about 5wt% of all plastic products, produced worldwide. They range in fabricating pressures from zero (contact), through, moderate, to relatively high, at temperatures, ranging from room to well over 100DC, (212°F). Equipment may be simple/low cost, to rather expensive specialized computer, control of the basic machine with auxiliary, equipment. Labor costs range from very high, to very low. Each process provide capabilities, such as meeting production quantity (small, to large), performance requirements, proper, ratio of reinforcement to matrix, fiber orientation, reliability/quality control, surface, finish( s), and so forth versus cost (equipment,, labor, utilities, etc.) (Tables 8-29 and 8-30)., Common processes are injection molding (1M), pultrusion, compression molding, (CM), contact molding methods (hand lay up,, spray, etc.), matched mold methods (modified 1M or CM, resin transfer, pressure bag,, etc.), spray up, and filament winding. Other, processes include autoclave molding; rotational molding, reaction 1M reinforced, continuous laminating, and centrifugal casting., The usual process for processing TP-short, glass fiber RPs is 1M consuming about 55wt%, of all RPs. Specially designed IMMs process, TS-RPs with materials such as BMCs (bulk, molding compounds). The other processes, primarily use TS plastic matrices., Selecting the optimum process encompasses a broad spectrum of possibilities, (shape, size, material used, quantity, tolerance, time schedule, cost, etc.). There are designs when only one process can be used but, there can be applications where different processes can be used. Each process, like each, material of construction have their capabil-, , ities (or limits). Material or product performances are frequently strongly influenced by, the process used (2, 10, 14,62,92)., , Autoclave molding Very high pressures, can be obtained for processing RPs enclosed, within a bag that initially contains a vacuum., Process mayor may not employ an initial, vacuum. When required vacuum is used to, improve RP performance such as reducing, or eliminating entrapped air/gas thus increasing mechanical properties, etc. Air or steam, pressures of 100-200 psi (690-1380 kPa) are, commonly achieved. If still higher pressures, are required, a hydroclave may be used, employing water pressures as high as 10,000 psi, (68.9 MPa). The bag must be well sealed, to prevent infiltration of high pressure air,, steam, or water into the molded product., Bag molding Process applies an impermeable tailored flexible bag (parting film,, elastomer, etc.) over an uncured thermoset, RP product located in a mold cavity (male, or female), sealing the edges (bagging), and, introducing a vacuum and/or compressed air, pressure (or water) and heat around the bag., It provides a means of evacuating air and, other gases as pressure is applied. Hand operated serrated rollers are usually used to, squeeze out voids, air, etc. This high labor, technique can produce compact structures, that meet tight thickness tolerance simulating, injection molded products. This technique is, also applied with other RP fabricating processes., Bag molding Hinterspritzen This patented process allows virgin or recycled TPs such, as PP, PClABS, etc. to thermally bond with, the backing of multilayer PP based fabrics, providing good elasticity. This one step molding technique provides a low cost approach, for in-mold fabric lamination that range from, simple to complex shapes., Contact molding Also called open molding or contact pressure molding. It is a process for molding RPs in which the reinforcement and plastic are placed in a mold, cavity. Cure is either at room temperature using a catalyst-promoter system or by heating

Page 531 : FRptspray metal, cast, aluminum: gusket seal,, air vents, self-sealing, injection port, Pressure feed pumping, equipment req'd:, mold halves clamped, (methods range from clamp, frame to pressure pod), , 'Courtesy Owners-Coming Corp., tFRP = Fiberglass reinforced plastics., , Generally expected 3,000, mold life (parts), , Part trim equipment, , Resin compounding High shear type, equipment, Continuous strand mat,, Reinforcement, preform, woven roving, , Cure system, , Pressure, , Mold construction, , Resin Transter Molding, , 1,000, , 3,000, , Continuous Chopped strand Continuous strand, roving, mat, woven, mat. preform,, roving, cloth, woven roving, Yes, , Not needed, , Room temperature, , Hydraulic: as high, as 2,000 psi, (138 MPa), , High grade steel;, shear edge, , Sheet Molding, Compound, , Continuous strand, Continuous roving, mat, preform,, (specific orientations, woven roving, for higher strength), With optimum shear edges, minor, trimining only, 1S0.000+, 1S0.000+, , Heated: normal, Heated: normal, range of 22S-32soF range of 27S-3S0°F, (107-163°C), (13S-177°C), High shear type, , Lows pressure press,, Hydraulic press,, capable of SO psi, normal range, (hydraulic or pneumatic of 100-S00 psi, mechanical); resin, (0.69-3.0S MPa), dispensing equipment, not req'd but, recommended, , None, , Metal, shear edge, , FRP, spray metal, cast, aluminum, pinch, (land), , Mat-Preform, , Compression Molding, , FRP, , Open Molding, Spray-up, Hand Lay-up, , Table 8-29 Process comparison of various RP manufacturing techniques, , 00, , ~, f..;.j, , ~., , ~, ~, , n, , :::1'., , So.,, , "tj

Page 532 : 514, , 8 Plastic Processing, Table 8-30, , Guide to the directional RP properties vs. processes, , VI, , Unidirectional, Fiber, Orientation, , (I), , VI, , C1l, , (I), , .~, , - c, , ai.Q, , Etii, r-------------~ (1)Bidirectional, Fiber, Orientation, , o~.~..., £~, ~il, , c.n-=, , C1l_, , 0,0, , ~~u, , r--------------i u., , o.~, , (1)"0, , Multidirectional, Fiber, Orientation, , 01.£, , j~, ~ ~, , a. iii, , in an oven without pressure or using very little (contact) pressure., Hand lay-up This is the oldest and in, many ways the simplest and most versatile, process for producing RP products. However,, it is slow and very labored intense. It consists, of hand tailoring and placing oflayers of (usually glass fiber) mat, fabric, or both on a onepiece mold cavity and simultaneously saturating the layers with a liquid plastic (usually, TS polyester). Depending on the plastic additives, the material in the mold can be cured, with or without heat, and commonly without pressure. An alternative is to use preimpregnated, B-stage TS polyester such as sheet, molding compound (SMC), but in this case, heat is applied with low pressure via a impermeable sheet over the material (Fig. 8-62)., Boat. By far the most important application of RP in marine structures, particularly, with respect to volume consumed, has been in, boat construction. This has occurred in both, civilian and military markets. Growth continues where it already dominates the small, boats with the larger boat market growing., The US. Navy pioneered in glass-TS, polyester RP (hand lay-up) large boat construction with the production of an 8.5 m, , REINFORCEMENT TYPES:, Filaments. Rovlngs, PROCESSES:, Pullruslon, Folament, Winding, RTM. RIM, , REINFORCEMENT TYPES:, Filaments, Rovings,, Woven FabriCS. Braiding, PROCESSES:, Filament Winding, Hand Layup., Compression Molding. In/ectlor., MOlding. Vacuum Bag. Stamping., COining, Pullruslon, REINFORCEMENT TYPES:, Chopped Strands,, Milled Fibers, Mats, PROCESSES:, Hand Layup. Compression,, InJection. Spray-Up, Vacuum Bag,, Autoclave. RTM, RtM, Rotational., Stamping, AutocaJve. Coining, , (28 ft) hull in 1947. RP Navy boats (in the, US. and other countries) range from 3.7 m, (12 ft) to over 30.5 m (100 ft)., In 1972, the British launched the world's, largest (at that time) RP ship. The H.M.S., Wilton was 46.7 m (153 ft). It became the, forerunner of a new class of mine hunters, that involved other countries (Netherlands,, Belgium, Germany, France, Italy, USA, and, others). The British program followed with, 45.8 to 61 m (100-200 ft) RP minesweepers., Untraditional hull design. The US. Navy, upgraded its minehunter fleet (1991) with a, successful ship design based on using glass, fiber-TS polyester. This "Osprey" class minehunter was designed and built by Interimarine S.P.A. of Sarzana, Italy (Fig. 8-63). Unlike traditional ships, the new minehunter, class does not have longitudinal or transverse, framing inside the hull. The design and material combine to provide enough strength, and resiliency to withstand underwater explosions. The unstiffened hull is engineered, to deform elastically as it absorbs the shock, waves of a detonated mine. Judicious design, simplifies inspection and maintenance from, within the structure., Basically, the hand lay-up molding process, was used, with 98wt% of the structure via

Page 533 : 8 Plastic Processing, , 515, , Fig.8-62 Example of hand lay-up using glass matt-TS polyester RP., , a semiautomated lay-up process. Each mat, layer was unrolled and sent through an impregnation liquid plastic bath. Up to six layers were laid-up, wet-on-wet, as a package., A crane laid the wet lay-up along a path in, the ship's huge female stainless steel mold., Decks, similarly fabricated, were form-fitted, to the hull and bolted in place. Not all the RPs, were hand lay-ups. Storage tanks for fuel and, water used the filament winding process, etc., The ship's RP hull was up to 17.8 cm (7 in), thick in the thickest sections. No core materials were used. The glass-to-plastic ratio was, 1:1. Final outfitting with gear and equipment, resulted in a 55 m (I 88 ft) long warship that, holds a crew of 44 people., In addition to their use in boat hull construction, RPs has been used in a variety of, shipboard structures (internal and external)., RPs was used generally to save weight and/or, , to eliminate corrosion problems inherent, in the use of aluminum and steel or other, metallic constructions. Applications included, masts, booms, spinnaker poles, deckhouses,, bridge housings, radio rooms, storage tanks, (potable water, fuel, etc.), ventilation ducts,, piping systems, reefer boxes, hatch covers,, sonar domes, radomes, floats, buoys, small, safety boats, and more. Much more history, exists on RP boats/ships in the literature., , Filament winding FW basically produces, high strength and light weight products that, consist of two reinforced plastic ingredients, that are the reinforcement and a plastic matrix. The process uses a continuous reinforcement (glass, carbon, graphite, Pp, wire,, and other materials in filament, yarn, tape,, etc. forms) either previously impregnated, (prepreg) or impregnated at the machine

Page 534 : Fig. 8·63, , After removal from the mold, work continued on the ship to which the super structure was added., , v,, , ~., , ~, , ("), , ~, , '"...., ;::;., , ~, , 00, , ........, 0\

Page 535 : 8 Plastic Processing, with a plastic matrix that is placed on a, revolving (removable) mandrel followed, with curing. Reinforcements have set pattern, lay-ups to meet performance requirements;, target is to have them uniformly stressed, (Chapter 4, RP PIPES, Filament Wound, Structure) (7, 10, 14,37,62)., Examples of different winding patterns are, shown in Table 8-31. The different patterns, meet different shape and performance requirements (37). Figure 8-64 shows the use, of an isotensoid pattern with only glass fibers, and also a view of the cured TS polyesterglass fiber RP structure that provides the, strongest product for this shape when compared to any other material (steel, etc.)., Figure 8-65 is a racetrack fabricating technique that was used to fabricate a very large, tank (rocket motor case) for NASA. This, 150,000 gallon tank was 12112 ft diameter by 21, ft long; used a 100 T steel mandrel; contained, about 156 million miles of glass fibers; and the, textile creel containing 60 spools traveled up, to 4% mph., Figure 8-66 RP (glass fiber-TS polyester, plastic) tank trailers are used for hauling corrosive and hazardous materials. In Canada, they meet code 312 to operate., , Injection molding The RTPs (reinforced, thermoplastics) are practically all injection, molded with very fast cycles using short, glass fiber producing highly automated and, high performance products. The TPs used, include nylons, acetals, polyethylenes, and, polypropylene. Of all the RP materials used,, about 55wt% represent these RTPs., Injection-compression molding See in, this chapter INJECTION MOLDING, Modified 1M Technique, Injection-compression, molding., Lost-wax Also called RP molding,, fusible-core. A bar (or any shape) of wax, is wrapped with RP. After the RP is cured, (bag molding, etc.) in a simplified restrict or, mold to keep the RP-wax shape, the wax is, removed by drilling a hole or removing the, end caps by applying a low temperature so, that the RP is not effected (review in this, chapter INJECTION MOLDING, Modified, , 517, , 1M Technique, Soluble core molding. This, process can produce high performance, products. It was used in fabricating the first, all-plastic airplane (Fig. 4-11)., , Marco process This process was popular, during the 1940s-1950s. Like resin transfer, molding (RTM) and bag molding, the reinforcements are laid up in any desired pattern. Low cost matched molds (wood, etc.), confine the reinforcement. A pool of liquid, catalyzed TS polyester surrounds the bottom, of the mold above its partially opened parting, line. From a central opening (hole) in one of, the mold halves a vacuum is applied so that, the plastic flows through the reinforcements., With proper melt flow, wet-out of fibers occurs and voids are eliminated. This method, when first used was the reverse of RTM. The, Marco method eventually incorporated pressure plugs at the parting line and also had a, push-pull action where pressure was applied, in the center hole similar to RTM and use, could also include intermittently the vacuum, pool action. Eventually only pressure was applied through the center hole; latter became, known as RTM., Pressure bag molding This is a take-of to, vacuum bag molding where the bag and mold, is placed in a closed system and is subjected, to pressure during the curing cycle., Pultrusion A continuous process for fabricating RPs that usually have a constant cross, sectional shape. The reinforcing fibers are, pulled through a plastic (usually TS) liquid, impregnation bath through rollers, etc. and, then through a shaping die followed with a, curing action. There are also systems where, no plastic bath is used and the plastic is impregnated in the die that is a take-off in extruding wire and cable providing controlled, impregnation., Resin transfer molding With vacuum, assisted RTM, this process can be called, infusion molding. RTM usually uses liquid, TS plastics that is transferred or injected into, an enclosed mold usually at low pressures of, about 60 psi (410 kPa) in which reinforcement

Page 536 : Multiple passes of carriage necessary to cover, mandrel. Programmed relationship between, carriage motion and mandrel rotation necessary., Reversal of carriage must be timed precisely, with mandrel rotation. Dwell at each end of, carriage stroke may be necessary to correctly, position fibers and prevent slippage., Fibers positioned around end of mandrel close, to support shaft. Characteristics of "helix, with narrow ribbon" apply. Fibers tend to go, slack and loop on reversal of carriage. Fibers, tend to group from ribbon into rope during, carriage reversal. Mandrel turns so slowly that, extremely long delay occurs at each end of, carriage stroke and speed-up of mandrel at, each end of carriage stroke is highly, desirable to shorten winding time., , Helix with low winding angle, , d:X2J=, , ~~\~], , duill, , Helix with wide ribbon, , IDmJ, , Helix with narrow ribbon and medium, or high angle, , Considerations, High winding angle. Complete coverage of, mandrel each pass of carriage. Reversal of, carriage can be made at any time without, affecting pattern., Complete coverage of mandrel each, pass of carriage. Reversal of carriage, can be made at any time without affecting, pattern., , Type of winding, , Examples of different winding patterns, , Hoop or circumferential, , Table 8-31, , Precise helical winding machine required. Ratio, of carriage motion to mandrel rotation must be, adjustable in very small increments. Relationship of, carriage to mandrel positions must be held in selected, program without error through carriage reversals, and dwells. Relationship between carriage position, and mandrel rotation must be progressive so that, pattern will progress., Similar machinery required as for "helix with narrow, ribbon." Take-up device for slack fibers is, necessary if cross-feed on carriage is not used., Cross-feed on carriage is required for very low, winding angles. Programmed rotating eye can be, used to keep ribbon in fiat band at carriage reversal., Mandrel speed-up device must be programmed, exactly with carriage motion or pattern will be lost., Polar wrap machine can be used for narrow, ribbons with winding angle below about 15°, without take-up device or mandrel speed-up, being required., , Simple equipment with provision for wide selection, of accurate ratios of carriage-to-mandrel speeds., Powerful machine and many spools of fiber required, for large mandrel., , Simple equipment. Even a lathe will suffice., , Machinery Required, , ~., , ~, , t"'l, , ~, , S....., "", 1=;., , "i:1, , 00, , 00, , ~

Page 537 : Polar wrap machine with swinging fiber delivery, arm desirable for high-speed winding. Helical, machine with programmed cross-feed will wind, polar wraps more slowly., Programmed non-linear carriage motion required., Other machine requirements same as for helical, winding., Sine wave motion of carriage is required for, carriage with no cross-feed. At low angles of wind,, cross-feed is necessary because carriage travel becomes, excessive. Polar wrap machine may be used if range, of axis inclination is large enough., Helical machine with programmed carriage or cross-fee., Polar wrap machine can be used where geodesic, (non-slipping) path is in a plane., , Special machine best approach. Otherwise complex, programming of all motions of helical machine, required., , Machine to reproduce motions of hand winding., Programmed motions in several axes may, be required., , General considerations same as for helical, winding except that carriage motion is, not uniform., Planar windings at a particular angle result in a, heavy build-up of fibers at ends of wrap. For, more uniform strength, successive windings, at higher angles are required., , Similar to simple spherical winding but with, different carriage or cross-feed motion., , Path of fibers programmed to give uniform wall, thickness and strength to all areas on sphere., , For successful filament winding, it must be possible, to hand-wind with no sideways slipping of fibers on, mandels surface., , True spherical, , Miscellaneous, , ~, , o, , Simple ovaloid, , .~, @, , Simple spherical, , 1b~, , Cone, , ~, , 0, , Low angle wrap. Fibers may be placed at, different distances from centers at each end, when geodesic (non-slipping) path does not, have to be followed., , ~, , Polar wrap, , {, , Precise mandrel indexing required. Simple two-position, cross feed on carriage sufficient. Vertical, mandrel machine and pressure follower for ribbon, sometimes required to preserve ribbon integrity., , Mandrel must remain motionless during pass of, carriage and then rotate a precise amount near, 180 while carriage dwells. Fibers must be held, close to support shaft during mandrel motion or, fibers will slip., , Zero or longitudinal, , v,, ........, , '0, , ~, , S·, , ~, , i, , ~, ....., (:;., , 00

Page 538 : 520, , 8 Plastic Processing, , (a), , (b), , Fig. 8-64 (a) FW layup shows isotensoid pattern of the reinforcing fibers and (b) plastic molded, isotensoid case/container., , has been placed. The reinforcement is usually, glass fiber woven, nonwoven, and/or knitted, fabric. Plastic flows through the reinforcement targeting to remove air through release ports and/or openings where its parting, , line exists. Cure can be with a heated mold, or catalyzed so that it develops its own, heat based on a prescribed time schedule, (Tables 8-32 to 8-34). See also above the, Marco process.

Page 539 : Fig. 8-65, , Racetrack fabricating technique produced a very large tank., , ~, ......., , ~., , §, , i, , ~~., , 00

Page 540 : 522, , 8 Plastic Processing, , Fig. 8-66, , RP tank trailer., , SCRIMP process This Seeman Composites Resin Infusion Process (SCRIMP) is, described as a gas-assist resin transfer molding process. As an example glass fiber fabrics/ thermoset vinyl ester polyester plastic, and polyurethane foam panels (for insulation) are placed in a segmented tool. A vacuum is pulled with a bag so that a huge, amount of plastic can be drawn into the mold, (Marco process approach). Its curved roof, is made separately and bonded to the box, with mechanical and adhesive fastening. It is, similar to various reinforced plastics molding, processes., Spray-up Popular system with reinforced, plastic production. An air spray gun includes, a roller cutter that chops usually glass fiber, rovings to a controlled short length before, being blown in a random pattern (manually, or automatically) onto a surface of the mold;, simultaneously the gun sprays catalyzed TS, polyester plastic. The chopped fibers are plastic coated as they exit the gun's nozzle. The, resulting, rather fluffy, RP mass is consolidated with serrated rollers to squeeze out air, and reduce or eliminate voids. A closed mold, , with appropriate temperature and pressure, produce products., Stamping In the stamping process, usually a reinforced TP sheet material is precut to the required sizes. The precut sheet, is preheated in an oven, the heat depending on the TP used (such as PP or nylon,, where the heat can range upward from 520, to 600°F). Dielectric heat is usually used to, ensure that the heat is quick and, most important, to provide uniform heating through the, thickness and across the sheet. After heating,, the sheet is quickly formed into the desired, shape in cooler matched-metal dies, that can, use conventional stamping presses or SMCtype compression presses., Stamping is a highly productive process capable of forming complex shapes with the, retention of the fiber orientation in particular locations as required. The process can be, adapted to a wide variety of configurations,, from small components to large box-shaped, housings and from flat panels to thick, heavily ribbed products. Reinforced TS plastic, B-stage sheet material can be used with its, required heating cycle. However the most, popular is to use TP sheets.

Page 541 : 523, , 8 Plastic Processing, Table 8-32 Comparison of resin transfer, compression, and injection molding RP processes, Process, SMC, Compression, , RTM, Process operation:, Production requirement,, annual units per press, Capital investment, Labor cost, Skill requirements, Finishing, Product:, Complexity, Size, Tolerance, Surface appearance, Voids/wrinkles, Reproducibility, Cores/inserts, Material usage:, Raw material, cost, Handling/applying, Waste, Scrap, Reinforcement, flexibility, Mold:, Initial cost, Cycle life, Preparation, Maintenance, , Injection, , 5,000-10,000, , 50,000, , 50,000, , Moderate, High, Considerable, Trim flash, etc., , High, Moderate, Very low, Very little, , High, Moderate, Lowest, Very little, , Very complex, Very large parts, Good, Gel coated, Occasional, Skill dependent, Possible, , Moderate, Big flat parts, Very good, Very good, Rarely, Very good, Very difficult, , Greatest, Moderate, Very good, Very good, Least, Excellent, Possible, , Lowest, Skill dependent, Up to 3 percent, Skill dependent, Yes, , Highest, Easy, Very low, Cuts reusable, No, , High, Automatic, Sprues, runners, Low, No, , Moderate, 3,000-4,000 parts, In factory, In factory, , Very high, Very high, Years, Years, Special mold-making shops, Special machine shops, , Vacuum bag molding Also called just, bag molding; see previous review on Bag, molding. RP can be prepared for TS plastic curing in an open mold with a flexible, membrane or bag over the RP. A vacuum is, drawn inside the enclosure [commonly resulting in atmospheric pressures of 10-14 psi (6997 kPa)] with or without heat (depending on, how the plastics was prepared). The result is, a molded product with a very smooth surface, against the mold surface. Figure 8-67 shows a, completely automated vacuum bag molding, process., RP Future, There is always a growing need in many, areas to find alternatives to heavy structures, , made from iron and steel. The modern lightweight RPs are being used in applications, where they provide savings in raw materials,, energy, and/or installation costs., Calendering, Basically the calendering process is used in, the production of plastic films and sheets. It, converts plastic into a melt and then passes, the pastelike mass through roll nips of a series of heated and rotating speed-controlled, rolls into webs of specific thickness and width., The web may be polished or embossed, either, rigid or flexible (9). One of its sheets major, worldwide markets is in credit cards. At the, low cost side these lines can start a $ million. A line, probably the largest in the world

Page 542 : 524, , 8 Plastic Processing, , Table 8-33, , Cost comparison of RTM vs. injection and SMC moldings, Process, RTM, , Process operation:, Production requirement,, annual units per press, Capital investment, Labor cost, Skill requirements, Finishing, Product:, Complexity, Size, Tolerance, Surface appearance, Voids/wrinkles, Reproducibility, Coreslinserts, Material usage:, Raw material, cost, Handling/applying, Waste, Scrap, Reinforcement flexibility, Mold:, Initial cost, Cycle life, Preparation, Maintenance, , Fig. 8-67, B-stage., , SMC Compression, , Injection, , 5,000-10,000, , 50,000, , 50,000, , Moderate, High, Considerable, Trim flash, etc., , High, Moderate, Very low, Very little, , High, Moderate, Lowest, Very little, , Very complex, Very large parts, Good, Gel coated, Occasional, Skill-dependent, Possible, , Moderate, Big flat parts, Very good, Very good, Rarely, Very good, Very difficult, , Greatest, Moderate, Very good, Very good, Least, Excellent, Possible, , Lowest, Skill dependent, Up to 3 percent, . Skill dependent, Yes, , Highest, Easy, Very low, Cuts reusable, No, , High, Automatic, Sprues, runners, Low, No, , Moderate, 3,000-4,000 parts, In factory, In factory, , Very high, Very high, Years, Years, Special mold-making shops, Special machine shops, , Automated-integrated RP vacuum lay-up process that use prepreg sheets that are in the

Page 543 : 8 Plastic Processing, Table 8-34, , 525, , Property comparison and design guidelines for RTM vs. other RP processes, , Design, Parameter, Minimum inside, radius, in. (mm), Molded-in holes, In-mold trimming, Core pull and slides, Undercuts, Minimum recommended, draft (deg.), Minimum practical, thickness, in. (mm), Maximum practical, thickness, in. (mm), Normal thickness, variation, in. (mm), Maximum thickness buildup,, heavy buildup (ratio), Corrugated sections, Metal inserts, Bosses, Ribs, Hat section, Raised numbers, Finished surfaces, , Sheet Molding, Resin -Transfer, Molding, Spray-up Hand Lay-up Mat/Preform Compound, 1/4, , (6.35), , 1/4, , (6.35), , 1/4, , (6.35), , 1/4, , (6.35), , 1/16, , (1.59), , No, No, Difficult, Difficult, 2 to 3, , Large, No, Difficult, Difficult, 0, , Large, No, Difficult, Difficult, 0, , 0.080, (2.0), 0.500, (12.7), ±0.010, (±0.25), 2:1, , 0.060, (1.5), No limit, , 0.060, (1.5), No limit, , ±0.020, (±0.50), Any, , ±0.020, (±0.50), Any, , Yes, Yes, Yes, Yes, No, Yes, No, Yes, % to 6-in. depth 1 to 3;, above 6-in. depth 3, or as, required, 0.030, 0.050, (0.76), (1.3), 0.500, 1, (12.7), (25.4), ±0.008, ±0.005, (±0.1), (±0.2), 2:1, Any, , Yes, Yes, Difficult, Difficult, Yes, Yes, 2, , Yes, Yes, Yes, No, Yes, Yes, 1, , Yes, Yes, Yes, No, Yes, Yes, 1, , Yes, Yes, Difficult, Yes, Difficult, Yes, 2, , processing PVC sheet, build by Kleinewefers, Kunststoffanlagen GmbH, Munich, Germany, cost $33 million (1999). It is a 5-roll, using L-type configuration. They have 3500, mm roll-face widths and 770 mm diameters, with an output rate at 4000 kg/h., The calender was developed over a century ago to produce natural rubber products., With the developments of TPs, these multimillion dollar extremely heavy calender lines, started using TPs and more recently process principally much more TP materials. The, calender consists essentially of a system of, large diameter heated precision rolls whose, function is to convert high viscosity plastic, melt into film, sheet, or coating substrates., The equipment can be arranged in a numberofways with different combinations available to provide different specific advantages, to meet different product requirements. Automatic web-thickness profile process control is used via computer, microprocessor, control., , Yes, Yes, Yes, Yes, No, Yes, 2, , The calendering configuration of rolls may, consist of two to at least seven rolls. The number of rolls and their arrangement characterizes them. Examples of the layout of the rolls, are the true "L", conventional inverted "L",, reverse fed inverted "L", "I", "Z", and so on., The most popular are the four-roll inverted, "L" and "Z" rolls. The "Z" calenders have, the advantage of lower heat loss in the film, or sheet because of the melts shorter travel, and the machines simpler construction. They, are simpler to construct because they need, less compensation for roll bending. This compensation occurs because there are no more, than two rolls in any vertical direction as opposed to three rolls in a four roll inverted "L", calender and so on., The nip is the radial distance or "V" formed, between rolls on a line of centers. In-going, safety devices in the nip areas are built into, these machines. They protect the hands of operators. An emergency stop device is placed, in an accessible location on the upstream side.

Page 544 : 526, , 8 Plastic Processing, , If a problem develops, the machines immedi-, , ately stop., Calendering in the manufacture and surface finishing of plastic products, such as nonwovens and woven fabrics, requires roll systems to meet stringent control of their nip, pressure requirements. In this respect, products of uniform quality and thickness, with, defined properties, call for an adjustable nip, and/or controllability of the nip pressure., Control across the full roll width is achieved, by various methods such as: suitable compensation of the deflection of a pair of rolls,, mechanical-geometrical compensation such, as roll bending, axis crossing and crowning, of the rolls, and hydraulic compensation systems. Bowl deflection can occur. It is the distortion suffered by calender rolls resulting, from the pressure of the plastic running between them. If nor corrected the deflection, produces a sheet or film thicker in the middle, than the edges., Variations in these multimillion dollar calender lines are dictated by the very high, forces exerted on the rolls to squeeze the, plastic melt into thin film or sheet web constructions. High forces at least up to 6000 psi, (41 MPa) could (if rolls were not properly, designed and installed) bend or deflect the, rolls, producing gauge variations such as a, web thicker in the middle than at the edges., During calendering, particularly film, rollseparating forces in the final nip may be, as high as 6000 psi. This potential problem is counteracted by different methods, that include the following: (1) crowned rolls,, which have a greater diameter in the middle, than the edged; (2) crossing the rolls slightly, (rather than having them truly parallel), thus, increasing the nip opening at both ends of, the roll; and (3) roll bending, where a bending moment is applied to the end of each roll, by having a second bearing on each roll neck,, which is then loaded by a hydraulic cylinder., Controls are used to perform any roll bending and crossing of the rolls., Compounding Material, Important to their success includes the, preparation of the material or compound., , It is usually done by computer controlled, electronic weighing scales that supply precise, amounts of each ingredient to a high intensity, mixer. The still-dry, free-flowing blend is then, charged to a feed hopper where it is screw fed, into a continuous mixer such as an extruder, and/or kneader. Under the action of a mixer's, reciprocating screw in the confined volume of, the mixer chamber, the blend begins to flux, or masticate into the required plastic state., Usually the next step is to force it out of, the barrel of the mixing chamber through a, die producing strands. The strands can exit as, a continuous rope or be chopped into small, baseball size buns. This hot plastic material, may be passed through a two-roll mill and/or, be directly conveyed to the top of the calender rolls. The (usual) parallel rolls have, extremely flat surfaces and rotate at possibly the same speed but usually at slightly different speeds depending on the plastic being, processed. Although plastic forming occurs, in the calender itself, down-stream precision, cooling rolls operating equipment are needed, to produce the TP film or sheet., , Coating, One special application of calendering is, the coating of paper, textile, and/or plastic., For one-sided coating a calender with three, rolls is usually sufficient, although four rolls, are frequently used for extremely thin coatings. Double-sided coating can either be done, simultaneously on both sides using a four-roll, or sequentially by two three-roll calenders., Frictional calendering is the process whereby, an elastomeric compound is forced into the, interces of woven or cord fabrics while passing through calender rolls., Calendering or Extrusion, Film and sheet can, in principal, be made by, calendering or by extrusion. Factors that govern the advantages and disadvantages (limitations) of each process can interact in a complex way. Factors to be considered include:, (1) type of material to be processed, (2) quantity of product to be produced, (3) thickness

Page 545 : 8 Plastic Processing, and uniformity required on film or sheet, and, (4) costs. The capital equipment and replacement parts in calendering lines are more expensive. The very small-unsophisticated lines, start about the million-dollar range compared to the much lower cost extrusion lines., In general, plastic materials such as PE, PP,, and PS film and sheet are usually produced, through the rather conventional extrusion, lines. To produce PVC film and sheet in large, quantities, calendering is almost always used, since the process is less likely to cause degradation than is extrusion as well as having, dimensional and cost advantages., A web thickness between 0.002 to 0.020, in (0.05 to 0.50 mm) is generally the kind, of plasticized film and sheeting produced by, calender lines. For extremely light gauges,, those under 0.001 in (0.02 mm), calendering could become impractical or damaging to, the equipment. The reasons include factors, such as for certain materials their exists poor, strength of the thin webs and also very high, forces developed on the matting heavy duty, rolls., For very heavy/thick gauges such as, sheeting over 0.020 in (0.50 mm), calendering may not be the optimum method of, production. Reason is that there may not, be enough shearing action that can be put, into the rolling banks to keep the compound, at uniform temperature. In addition, the, separating forces on the rolls get so low that, gauge variations could become prohibitive., It can be said that basically the up-stream, and down-stream procedures are similar, in production lines whether calenders or, extruders are used. For a given quantity, of output, it is usually necessary to have, more extruders than calenders. This situation makes the extrusion lines more flexible, and more able to handle relatively short production runs. The extrusion flexibility, when, compared to calendering, includes ease of, changing product thicknesses, widths, and, materials., Calenders are capable of higher production speeds. Thus, there are situations where, they provide a favorable situation for long, runs. For these long runs, cost advantages, exist. Tolerancewise the calender is easier, to produce products that can meet tighter, , 527, , minimum-to-maximum thicknesses on sheets, and films. Calendering also provides product uniformity. Constant in-process monitoring and continuous profile adjustments are, usually a significant advantage of calendering over other methods., Compression and Transfer Molding, , CM and TM are two methods used to, produce molded products from generally, thermoset (TS) plastics. CM was the major, method of processing plastics during the first, half of the last century because of the development and extensive use of phenolic plastics (TSs) in 1909. By the 1940s this situation, began to change with the development and, use of thermoplastics (TPs) in extrusion and, injection molding (1M) processes. CM originally processed about 70wt% of all plastics,, but by the 1950s its share of total production, was below 25 %, and now that figure is about, 3% of all plastic products produced worldwide. This change does not mean that eM is, not a viable process; it just does not provide, the much lower cost-to-performance benefit, of TPs, particularly at high production rates., In the early 1900s plastics were almost entirely TS (95wt%), but that proportion had, fallen to about 40% by the mid-1940s and, now is about 10%., TSs has experienced an extremely low total, growth rate, whereas TPs have expanded at, an unbelievably high rate. Regardless of the, present situation, eM and TM are still important, particularly in the production of certain, low-cost products as well as heat-resistant, and dimensionally precise products. CM and, TM are classified as high-pressure processes,, requiring 13.8-69 MPa (2,000 to 10,000, psi) molding pressures. Some TSs, however,, require only lower pressures of down to, 345 kPa (50 psi) or even just contact (zero, pressure)., eM is the most common method of molding TSs. In this process, material is compressed into the desired shape using a press, containing usually a two-part closed mold, and is cured with heat and pressure. This, process is not generally used with TPs. TM,, also called compression-transfer molding is a

Page 546 : 528, , 8 Plastic Processing, , method principally used with TS plastics. The, plastic is first softened by heat and pressure, in a transfer chamber (pot) and then forced, by the chamber ram at high pressure through, suitable sprues, runners, and/or gates into a, closed mold to produce the molded product or products using one or more cavities., Usually dielectrically preheated circular preforms are fed into the TM pot and also CM, cavity (2, 7, 9)., Reaction Injection Molding, , The RIM process involves the highpressure impingement mixing of two or more, reactive liquid components and injection, of the mixture into a closed mold at low, pressures. Large and thick products can be, molded using fast cycles with relatively lowcost materials. Its low energy requirements, with relatively low investment costs make, RIM attractive (9)., Different materials can be used such as, nylon, polyester (TS), and epoxy, but TS, polyurethane (PUR) is predominantly used., Almost no other plastic has the range of properties of PUR. Modulus of elasticity range, in bending is 200 to 1,400 MPa (29,000203,000 psi) and heat resistance from 90 to, over 200°C (122-392°F). The higher values, are for chopped glass-fiber-reinforced RIM, (RRIM)., RIM is very similar to RTM (see above, REINFORCED PLASTICS, Processes)., In the reinforced RIM (RRIM) process a dry, reinforcement preform is placed in a closed, mold. Next a reactive plastic system is mixed, under high pressure in a specially designed, mixing head. Upon mixing, the reacting liquid flows at low pressure through a runner, system to fill the mold cavity, impregnating, the reinforcement in the process. Once the, mold cavity is filled, the plastic quickly completes its reaction. The complete cycle time, required to produce a molded thick product, can be as little as one minute., The advantages of RRIM are similar to, those listed for RTM. However, RRIM uses, preforms that are less complex in construction and lower in reinforcement content than, , those used in RTM. The RRIM plastic systems currently available will build up viscosity rapidly, resulting in a higher average viscosity during mold filling. This action follows, the initial filling with a low-viscosity plastic., Liquid Injection Molding, , LIM has been in use longer than RIM;, the two processes are practically similar. The, advantages it offers in the automated lowpressure processing of (usually) TS plastics, is faster molding cycles, low labor cost, low, capital investment, energy saving, and space., LIM is very competitive to potting, encapsulating, compression transfer, and injection, molding, particularly when insert molding is, required., Rotational Molding, , RM is a simple, basic, four-step process, that uses a thin-walled mold with good heattransfer characteristics. Its closed mold requires an entrance for insertion of plastic, and, most important, the capability to be, "opened" so that solidified products can be, removed. These requirements are no problem. Liquid or dry-powder plastic equal to, the weight of the final product is put into, the mold cavity(s), which rotates simultaneously about two axes located perpendicular to each other (Fig. 8-68). These two, rotation speeds can be varied to permit more, , Fig. 8-68 Mold and its rotating mechanism is an, example of the RM process.

Page 547 : 8 Plastic Processing, evenly flow in a complex mold cavity. With, slow rotation about each axis, the material, inside the mold tumbles to the bottom, creating a continuous path that covers all mold, surfaces equally (9)., The next step involves heating the mold, while it is rotating. Molds can be heated by, a heated oven, a direct flame, a heat-transfer, liquid (either in a jacket around the mold or, sprayed over the mold), or electric-resistance, heaters placed around the mold. With uniform heat transfer through the mold, the plastic melts to build up a layer of molten plastic, on the molds inside surface., After the required heat-time cycle is completed, the mold is ready for cooling, which, is accomplished with the mold rotating continually. Cooling is usually done by air from a, high-velocity fan and/or by a fine water spray, over the mold. After cooling, the final step, is to remove the solid hallow product and, reload the mold with plastic., This process is capable of molding small, to large hollow items with relatively uniform wall thicknesses, using certain plastics., Its production rates, compared to those of, other processes, can be low. The total cost, of equipment and the production time for, moderate-sized and, especially, large products are also low. Large products range up, to at least 85,200 L (22,000 gal.) in size, with a, wall thickness of 3.8 cm (1.5 in.). One tank, used 2.4 t (5,300 Ib.) of XHDPE; the first, charge was about 1.5 t (3,300 lb.), followed, by 0.45 t (1,000 lb.), and finally another 0.45 t, (1,000 lb.)., Molds can be of any shape and can include, corrugated or rib constructions to increase, their stability and stiffness (large, flat walls, can be difficult if not impossible). The thickness of their walls is limited to allow heat, penetration., Encapsulation, , Also called conformal coating. It encloses, a product in a closed envelope of plastic, by immersing the product (solenoids, ornament, sensors, motor components, integrated, circuits, and other articles.) in an unheated or, , 529, , heated plastic. Different processes can be, used that range from casting to injection, molding., Casting permits applying different techniques. As an example half or part ofthe casting can gel. The product such as an ornament, is placed on the gelled plastic followed with, the final pouring of the plastic., The typical TP encapsulation process is an, insert injection molding or liquid injection, molding operation. The insert, a coil, or an, integrated circuit, for example, is placed in a, mold equipped with either fixed spider type, supports or retractable pins or other features, to support it when molten TP is injected., This technique with insert molding is a, clean, repeatable process that lends itself, to automation and cellular manufacturing,, and fits well with total quality management, (TOM). With off-the-shelf process controls, and systematic production methods, manufacturers can deliver repeatable, high-quality, products that come out of the tool ready for, assembly. The products generally do not require costly trimming or deflashing, as do, many TS encapsulated products when using, processes such as compression molding (136)., Although horizontal clamp injection molding equipment can be used for encapsulation,, vertical-clamp machines allow easier insert, placement and greater insert stability during, mold clarnping movement. For high-volume, production, a vertical machine with a shuttle, or rotary table is highly efficient. For example, a two-station table fitted with two lower, mold halves allows molding at one station, while an operator or robot unloads finished, products and loads inserts at the other shuttle, station., Casting, , Some TPs and TSs begin as liquids that, can be cast and polymerized into solids. In, the process various ornamental or utilitarian, objects can be embedded in the plastic. By, definition, casting applies to the formation, of an object by pouring a fluid plastic solution into an open mold where it completes its, solidification. Casting can also lead to the

Page 548 : 530, , 8 Plastic Processing, , formation of film or sheet, made by pouring, the liquid plastic onto a moving belt or by precipitation in a chemical bath. Casting differs, from many of the other techniques described, in this book in that it generally does not involve pressure or vacuum casting, although, certain materials and complex products may, require one or the other., Powder Coating, , Powder coating is a solventless coating system that is not dependent upon a sacrificial, medium such as a solvent, but is based on the, performance constituents of solid TP or TS, plastics. It can be a homogeneous blend of the, plastic with fillers and additives in the form, of a dry, fine-particle-size compound similar, to flour. The three basic methods are the fluidized bed, electrostatic spray, and electrostatic fluidized bed processes (9)., The advantages of the process include its, minimizing air pollution as well as water contamination, and increased product performance when coated, resulting in cost savings., This is basically a chemical coating, so it has, many of the same problems as solution painting. If not properly formulated, the coating, may sag at high thicknesses, show poor performance when not completely cured, reveal, imperfections such as craters and pinholes,, and have poor hiding, with low film thickness., It is extensively used to coat wire trays used in, dishwashing machines, protecting steel products subjected to salt water, etc., Textiles, paper, and other flexible substrates such as fusible interlining, interlinking drapery and upholstered fabric, and, carpets are examples of large volume applications. Another important market is with, metals and other rigid materials. Included are, plastics (pipes, tanks, screens, etc.) that can, provide protective coatings using its variety, of processing techniques., There are different coating techniques. The, woven and nonwoven fabrics normally involves three steps as it passes from the unwind roll to the rewind roll. Powder is metered onto the fabric, heated in an oven (gas, or electric) that are usually divided into several heating zones, and cooled by a chill roll., , Coating plastics, metals, etc. steps generally, involve surface preparation, preheating substrate, powder applications, and post-heating., Vinyl Dispersion, , Vinyl dispersions are fluid suspensions of, special fine-particle-size polyvinyl chloride, (PVC) plastics in plasticizing liquids. When, the PVC is heated to about 148 to 180°C (300, to 355°F), fusion or mutual solubilization of, the plastic and the plasticizer takes place. The, dispersion then turns into a homogeneous, hot melt. When the melt is cooled below 50, to 60°C (122 to 140°F), it becomes a tough, vinyl product. With vinyl dispersions the processor can use convenient liquid-handling, techniques such as spraying, pouring, spread, coating, and dipping. This system permits, products to be made that would otherwise, require costly and heavy melt-processing, equipment., The term plastisol is used to describe a, vinyl dispersion that contains no volatile thinners or diluents. Plastisols often contain stabilizers, fillers, and pigments, along with the, essential dispersion plastics and the liquid, plasticizer. All ingredients exhibit very low, volatility under processing and use conditions. Plastisols can be made into thick fused, sections with no concern for solvent or water, blistering, as with solution or latex systems, so, they are described as being 100 percent solids., It is convenient in some instances to extend the liquid phase of a dispersion with, organic volatiles, which are removed during, fusion. The term organosol applies to these, dispersions. Organosol are a suspension of, a finely divided vinyl plastic in a plasticizer, (diluent) together with a volatile organic liquid. The plastic does not dissolve appreciably, in the liquid at room temperature but does, at elevated temperatures at which time the, liquid evaporates. Upon cooling a homogeneous plastic mass is produced., Process Control, , Fabricating controls involve many facets, of the machine operation and the behavior

Page 549 : 531, , 8 Plastic Processing, , PROCESS, ANALYSIS, , FOLLOW·UP, PRESSURE PHASE, , FILLING PHASE, AND RATE, , MODEL, FORMING, , PRODUCT, , CHARACTER·, ISTICS, , PROCESS MODEL, , PROCESS, , ClOSED·LOOP, , PROCESS COMPUTER, MACHINE PARAMETER, CORRECTION, , SET POINT, , INTERFERENCE, , MAGNITUDES, , ACTUAL, , Fig. 8·69 Designing with a process control., , of the plastic. Most important is the interaction between the machine operation and plastic behavior. Basically the processing pressure and temperature vs. time determine the, quality of the molded product. The design, of the control system has to take into consideration the logical sequence of all these, basic functions and their ramifications. Basically developing a process control (PC) flow, diagram requires a combination of experience (at least familiarity) of the process and, a logical approach to meet the objective that, has specific target requirements. PCs range, from very simple/standard types to advance, complex types., Control of machines continually enters, new eras that dramatically improve ease of, machine setup, allow uninterrupted operation, simplify remote handling, reduce fabricating times, cut energy costs, boast part, quality, and so on. The process of making, a product has many dynamic fragments that, must come together properly for successful, results. Lack of sufficient PC over each of, these fragments will result in a less than desirable product. For success, there are three key, ingredients: sufficient dynamic performance,, sufficient repeatability, and very important is, the selection of proper control parameters. A, lack of these ingredients can result in unacceptable products, higher scrap rate, longer, cycles, higher part cost, etc. The control unit, , is composed of input, signal processing, and, power stages (Fig. 8-69)., PCs all have one thing in common. They, monitor the process variables, compare them, to values known to be acceptable, and make, appropriate corrections without operator intervention. The acceptable range of values, can be determined by using melt flow analysis software and/or trial and error when the, machine is first starting its production. Using, the software approach, the acceptable process values are known before the mold or die, is ever built. It should be noted that none of, the PC solutions address the problem of the, lack of skilled setup people. Most of the PC, systems available today are rather complex, and require skilled people to use them efficiently or at least start up the line., Adequate PC and its associated instrumentation are essential for product quality control. The goal in some cases is precise adherence to a single control point. In other, cases, maintaining the temperature within a, comparatively small range is all that is necessary. For effortless controller tuning and the, lowest initial cost, the processor should select the simplest controller (of temperature,, time, pressure, melt-flow, rate, etc.) that will, produce the desired results., Examples of the more sophisticated controls used with injection molding are seen, in Figs. 8-70 and 8-71. Based on the process

Page 551 : 533, , 8 Plastic Processing, Mold, , Design, , COSI., and, "-, , eve Ie Time, , ~ Parts flequlred, NumberDI, , '-,, , /~, , ·""\YP., , Maid, Cooling, Analysis, , "../, , Mold, , ~, , "".'", ----., , Tolo,ances •, , ~':; 2·Plol., , \~~t:!~~d, , ~, , Humber af Cavities, , ), , a:, , ),, .\ '\~", ., , ParlShape, , ~~ CamAclions, , .~ Care Pullers, , ------e, , Tool Llle, , Plastic, , Men Flow, , "--, , ----__..--..., _ Temperature, Men, , .',, ", ....., , ", , Runner Diameter, , Cavity localions, , """, , ",, , ~_., Type Bushl.., .... ".., Runner L~l'Igth, , """ _, , Inserts, Others, , Melt, , Others, , -- Pranu,., \, ., , MeltTlm., , Fig.8-71 Controls important to mold operation., , control settings, different behaviors of the, plastics will occur. Some examples of these, behaviors are shown in Figs. 8-25 for injection molding and 8-72 for extrusion., Processing Window, Regardless of the type of controls available, the processor setting up a machine uses, a systematic approach based on experience, or that should be outlined in the machine or, control manuals. Once the machine is operating, the processor methodically makes one, change at a time, to determine the result for, each change., Two basic examples are presented in Figs., 8-73 and 8-74 to show a logical approach to, evaluating the changes made with any processing machine that results in an operating, window. Within the area (Fig. 8-73) or volume, (Fig. 8-74) basically all products meet the performance requirements. However because of, machine and plastic variations, rejects can develop at their edges. As the injection-molding, machine is very complex with all the controls, required to set it up, these examples refer, to the injection-molding process. Note that, a major cause for problems with any process, is not of poor product design but instead that, the processes operated outside of their required operating window., The term process control is often used, when machine control is actually performed., As the knowledge base of the fundamentals, of the molding process continues to grow,, , the control approach is moving away from, press control and closer to real process control where material response is monitored, and then moderated or even managed. The, designer should note that changes in process, parameters, such as injection rate, can have, dramatic effects on moldings, especially mechanical properties, meeting tolerances, and, surface properties (Appendix A. PLASTICS, DESIGN TOOLBOX)., , Auxiliary Equipment, Even though modern primary processing, machines with all their ingenious molds/dies, and microprocessor control technology is in, principle suited to perform flexible tasks, it, nevertheless takes a whole series of peripheral auxiliary equipment to guarantee the, necessary degree of flexibility. Examples of, this action includes: (1) up stream material, supply systems; (2) mold or die transport, facilities; (3) mold or die preheating banks;, (4) mold or die changing devices that includes rapid clamping and coupling equipment; (5) plasticizer cylinder changing devices (screws, barriers, etc.); (6) molded or, extruded product handling equipment, particularly robots with interchangeable arms allowing adaptation to various types of production; and (7) transport systems for finished, products and handling equipment to pass, products on to subsequent production stages, (Figs. 8-75 and 8-76) (1-3,6-9,10,20,37).

Page 552 : 8 Plastic Processing, , 534, , t, , FILM, OPTICAL, PROPERTIES, , ------, , t, , HAZE, VALUE, , DIE TEMPERATURE _, , t, , DIE LAND LENGTH---...., , +, , FILM, IMRIICT, STRENGrH, , FILM, IMPACT, STRENGTH, , 8LCW UP RATIO _ _, , FREEZE LINE HEIGHT_, , t, , Fit.!.!, IMPACT, ST1lENGTH, , -------, , HIGH BLOW, UP RATIO, , ~BLOW, , t, , TENSILE, STRENGTH, , UP RATIO, , ~, DIRECTION, , CHINE, DIRECTION, , t, , FILM, TEAR, SllIENGiH, , COOLING RATE, , BLOW UP RATIO ----..., , ---...., , ~~~~, , +, , LOW BLOW UP, , _TO, , FILM, TEAR, STRENGTH, , MO, , IRECTION, , t5i"~~}~\(MD), BLOW UP RATIO - . . ., , -, , TO, -MD, HIGH BLOW UP, , FREEZE LINE HtlCiHT_, , Fig. 8-72 Examples of how extrusion settings affect certain properties of plastics., , Secondary Equipment, , Ideally, fabricating TP or TS products will, be finished as processed. For example many, types of texture or surface finish can be on, extruded products or molded into the product, as can almost any geometric shape, hole,, or projection. There are situations, however,, where it is not possible, practical, or economical to have every feature in the finish product., 'lYpical examples where machining might be, required are certain undercuts, complicated, side coring, flashing, or places where parting line irregularity is unacceptable. Another, common machining/finishing operation with, , plastics is the removal of the molded remnant, of the sprue or gate if it is in an appearance, area or critical tolerance region of the part., Many plastic products are decorated to, make them multi-colored, add distinctive logos, or allow them to imitate wood, metal, and other materials. Some plastic products, are painted since their as-molded appearance, is not satisfactory, as may be the case with, reinforced, filled or foamed plastics. Painting or coating is also for product protection., The following section will discuss some of the, secondary operations frequently used with, plastics. Since plastics vary widely in their, ability to be machined and to accept finishes,

Page 553 : 8 Plastic Processing, , '"':;, , Flash area, , .,~, , a., , .., , E, a:, , t, Short shot area, , - - . . . Mold temperature, , Fig.8·73 A 2-D molding area diagram (MAD), that plots injection pressure (ram pressure) vs., mold temperature., , this discussion will be general in nature, with, details left to other literature dealing with, specific plastics., , Machining and Prototyping, All plastics can be shaped and finished, with common equipment used for machining, , 535, , metals. In addition, many tools specifically, used for woodworking, such as routers,, shapers and sanders, are well suited for plastic, materials. Since many materials are available, in the form of sheets, blocks, slabs, rods, tubes, and other cast and extruded shapes, initial, prototypes (Chapter 3) are frequently made, entirely by machining. Also their may be a, requirement for only a few products making, it more economical to machine., The main problems encountered when machining plastics, particularly TPs, are due to, the heat built up by friction. As the plastic and, cutting tools begin to heat up, the plastic can, distort or melt. This can produce reduction in, performances, poor surface finish, tearing, localized melting, welding together of stacked, products, and jamming of cutters. It is important to prevent the product and cutting tool, from heating up to the point where significant, softening or melting takes place. There are, cutting tools specifically design to cut plastic, that eliminate or reduce the heating problem., Some plastic materials machine much easier, and faster than others due to their physical, and mechanical properties. Generally, a high, melting point, inherent lubricity, and good, hardness and rigidity are factors that improve, machinability., , Drilling and Reaming, , ..., , Q., , ~, , a., , ., , E, , II:, , t, , Fig.8·74 After a 3-D molding volume diagram, (MVD) is constructed, it can be analyzed to find, the optimum combination of melt temperature,, mold temperature, and injection or ram pressure., , In addition to the building of prototype, products, drilling and reaming are often required to enlarge, deepen, or remove the, draft from, as an example, a molded hole. In, some cases, secondary drilling is a more economical and precise solution than side cores, in a mold. Although specific requirements, will vary with material, the following guidelines apply to almost all TPs., 1. Standard drill presses, as well as other, drilling equipment used for metals and wood,, are appropriate for drilling and reaming thermoplastics. Speeds and feeds must be controlled to avoid heat build-up., 2. Wood and metal drill bits can usually be, used, but best results are obtained with commercially available bits designed for plastics.

Page 554 : 536, , 8 Plastic Processing, , Fig.8·75 Production line sequence going from upstream, through the fabricating machine, and downstream., , These special drills usually have one or two, highly polished or chrome plated fiutes, narrow lands, and large helix angles to quickly, expel chips and minimize frictional heating., , For holes in thin sections, circle cutters, or, drills which only cut the circumference and, eject a round thin plug of material, will often, be preferred for production., , Fig.8·76 Examples of auxiliary equipment in a production line that starts at the top right end through, to the bottom left end.

Page 555 : 8 Plastic Processing, 3. In practice the drill speed and feed rate, can be increased for maximum production, provided that there is no melting, burning,, discoloration or poor surface finish. For deep, drilling, frequent withdrawal of the drill may, be necessary for chip ejection., 4. Drill bits and reamers must be kept, sharp and cool for good results. For high, production, carbide tools are sometimes preferred, especially with glass reinforced materials. The first choice for cooling is clean, compressed air, since there is no contamination of, the product, and chip removal is improved. If, a liquid coolant/lubricant is required for deep, drilling, water or some aqueous solution can, be used. Metal cutting fluids and oils should, be avoided since they may degrade or attack, the plastic and create a cleaning problem., 5. Plastic products must be firmly held,, fixed or clamped during drilling and reaming operations to prevent dangerous grabbing and spinning of the work., , Thread Tapping, Many plastic products use self-tapping, screws, threaded metal inserts, molded-in, threads or other fastener systems. When a, machine thread must be added after molding, standard metal cutting taps and dies may, be used provided that the same precautions, regarding heat, chip removal, tool maintenance, and lubrication discussed for drilling, are observed. For high production or with, filled plastics, carbide taps are recommended., Drilled or molded holes should generally, be larger than those specified for steel, and, threads finer than 28 threads per inch should, be avoided., , Sawing, Milling, Turning, Grinding,, and Routing, These cutting operations are usually used, only for machined prototypes, or very low, volume production of simple shapes. High, speed routing is sometimes used for slotting or gate removal on injection molded, products. Standard end mills (two-flute), cir-, , 537, , cular cutters, tool bits, wood saw blades,, router bits, files, rasps, and sandpaper can, usually be used. As with drilling, tools must, be kept sharp and cool, and speeds and feeds, may be increased until overheating, gumming, or poor finish becomes a problem. All, machining operations should provide for dust, control, adequate ventilation, safety guards,, and eye protection. Inquire about machining, information for a specific plastic., Finishing and Decorating, , Since most fabricated products are attractive as well as inherently corrosion and rust, resistant when fabricated they usually do not, require any finishing or decoration. For others there are paints, coatings, and other surface treatments that usually are used mainly, to enhance eye appeal. Tables 8-35 to 8-37, provide some guidelines., Many reinforced and filled plastic products, as well as structural foam molded or, extruded products, emerge with an uneven, appearance, and paint may be necessary, in critical appearance applications. Common decorative finishes applied to plastic, are spray painting, vacuum metallizing, hot, stamping, silk screening, metal plating, printing and the application of self-adhesive labels, decals, and border stripping. In some, cases, the finish will give the product added, protection from heat, ultraviolet radiation,, chemicals, scratching, or abrasion., Some conductive coatings are applied to, the inside of the product for dissipation of, static electricity and/or provide electromagnetic shielding. These coatings are common, in computer and other products such as, electronic and medical equipment housings., With all coatings and finishes, a clean surface is essential for a good bond. Care must, be used to avoid contamination. Common, sources of contamination include oils, release, agents (particularly silicone), environment,, and handling. In addition to cleaning with solvents and detergents, some plastics require, primers, etching, sanding, or flame treatment, to enhance adhesion. The following is a brief, description of several widely used processes.

Page 556 : 8 Plastic Processing, , 538, Table 8-35, , Guide to decorating selection, PART TO BE DECORATED, , I, , I, , SURFACE PREPARATION, , I, , I, , FLASH, REMOVAL, , 1, TUMBLING, WHEELABRATOR, HAND FILING, MACHINING, , I, , I, I, , BONO, PREPARATION, , SURFACE, COATING, , INTEGRAL, COATING, , I, SANDSLAST, PLASMA ETCH, SOLVENT, ETCH, CHEMICAL, ETCH, , PAINTING, DYE Al'PLICATION, METALLIZATION, by VACUUM .nd, ELECTROPLATING, SILK SCREEN, TRANSFER, HOT STAMPING, Ind EMBOSSING, , COLOR CONCENTRATES, IN RESIN, LIQUID ADDEO AT, PRESS OR EXTRUDER, COLOR MIX IN TUMBLE, BARREL, , DECALS, , IN-MOLD DECORATION, , In-Mold Decoration, This term is used both to describe designs, that are etched or engraved in the mold surface and the process of inserting a printed film, into the mold, to be produced as an integral, component of the finished product. Etched, surfaces can be drawn both parallel and perpendicular to a parting line of molds or postforming in an extrusion line .. However, be, alert with molds to the fact that parallel to, the parting line additional draft is required., A wide selection of patterns is available and, new ones can be readily created., Engraved designs and lettering normally, have greater depth and fine detail. Parallel to, the parting line, a side action (to clear the engraving) will be required in most cases. Therefore, they should be used only when absolutely necessary. Recessed letters and designs, are to be avoided whenever possible. They, collect dirt and they are costly to put into the, tooling. Raised letters are less expensive to, make and to maintain. In either case, sharp, points, such as those found in the letters N,, M, and W, are prone to breaking out when, subjected to molding pressures over a period, of time., Hence, it is wise to place designs and lettering as an insert in the mold. This will create an, , outline around the lettering (which can hopefully be incorporated into the design) however it will make repairs and revisions far less, costly. Generally, one should avoid the use of, serif typefaces unless the letters are very large, indeed. Artwork is prepared for engraving in, the same manner as for printing. Regardless, of which finishing method is used, it is important to consider its design requirements, from the beginning. Many a designer, preoccupied with the mechanical requirements of, the product, postpones consideration of this, aspect until the very end of the project, only, to discover that major design revisions are, necessary in order to meet appearance requirements., Inserting printed film in a mold provides, the advantages gained in appearance, hiding, defects, and so on. In addition it can provide, increasing strength and other properties in, the plastic thus reducing the amount of plastics required. Required is compatibility with, the fabricated plastic material. The inserts, can range from flat to rather complex shapes., , Painting, Most plastics can be painted, though, some are a lot more difficult than others.

Page 557 : Screen Printing, , Roller coating, , Wiping, , Ink is applied to part through, a finely woven screen., Screen is masked in areas, that won't be painted., Economical means for, decorating flat or curved, surfaces, especially in, relatively short runs., , Paint's sprayed by air or, airless gun( s) for, functional or decorative, coatings. Especially good, for large areas, uneven, surfaces, or relief designs., Masking used to achieve, special effects., Charged particles are sprayed, on electronically conductive, parts; process gives high paint, utilization; more expensive, than conventional spray., Paint is applied, conventionally, then, paint is wiped off. Paint, is either totally removed,, remaining only in recessed, areas, or is partially removed, for special effects such, as woodgraining., Raised surfaces can be, painted without masking., Special effects like stripes., , Painting:, Conventional spray, , Electrostatic spray, , How It Works, , Printing and decorating systems, , The Process, , Table 8·36, , All plastics can be, decorated. Some work,, not much, being done, on powder coating of, plastics., Can be used for most, materials. Products, range from medical, containers to furniture., , Can be used for most, materials., , Spray gun, high-voltage power, supply; pumps; dryers., Pretreating station for parts, (coated or preheated to, make conductive)., Standard spray-paint setup, with a wipe station, following. For low, production, wipe can be, manual. Very highspeed, automated, equipment available., Roller applicator, either, manual or automatic., Special paint feed system, required for automatic, work. Dryers., Screens, fixture, squeegee,, conveyorized press, setup (for any kind of, volume). Dryers., Manual screen printing, possible, for very lowvolume items., , Most materials. Widely used, for bottles; also finds, big applications in areas, like TV and computer dials., diels., , Can be used on all materials, (some require surface, treatment)., , Applications, , Spray guns, spray booths,, mask washers often, required; conveying and, drying apparatus needed, for high production., , Equipment, , ( Continued), , Single or multiple colors, (one station per color)., , Generally one-color, painting, though, multicolor possible with, side-by-side rollers., , One color per pass;, multicolors achieved in, multistation units., , Generally for one-color,, overall coating., , Solids, multicolor, overall or, partial decoration,, special effects such as, woodgraining possible., , Effect, , \0, , ~, , OQ, , '", S·, , ~, , ("), , ~, , "1::1, , '"("), :::-., , "1::1, i:), , 00

Page 558 : Depositing, in a vacuum, a, thin layer of vaporized, metal (generally, aluminum) on a surface, prepared by a base, coat., , Uniform metallic coatings, using electrodes., , Deposition of a metallic, finish by chemical, reaction of water-based, solutions., , Cathode sputtering, , Spray, , Involves transferring coating, from a flexible foil to, the part by pressure and, heat. Impression is made, by metal or silicone, die. Process is dry., Similar to hot stamp but, preprinted coating (with, a releas e paper backing), is applied to part by, heat and pressure., Gives a functional metallic, finish (matte or shiny), via electrodeposition, process., , How It Works, , Metallizing: Vacuum, , Electroplating, , Heat Transfers, , Hot Stamping, , The Process, , Table 8-36 ( Continued), , Activator, water-clean and, applicator guns; spray, booths, top- and basecoating equipment if, required., , Discharge systems-to, by provide close control of, metal buildup., , Most plastics, especially PS,, acrylic, phenolics, PC, unplasticized PVc., Decorative finishes (e.g.,, on toys), or functional, (e.g., as a conductive, coating)., High-temperature materials., Uniform, precise, coatings for applications, like microminiature, circuits., Most plastics. For decorative, items., , Most thermoplastics can be, printed; some, thermosets. Handles, flat, concave, or convex, surfaces, including, round or tubular shapes., Can handle most, thermoplastics. A big, application area is, bottles. Flat, concave or, cylindrical surfaces., Can handle special plating, grades of ABS, PP,, polysulfone, filled, Noryl, filled polyesters,, some nylons., , Rotary or reciprocating hot, stamp press. Dies., High-speed equipment, handles up to 6,000, parts/hr., Ranges from relatively, simple to highly, automated with multiple, stations for, say, front, and back decoration., Preplate etch and rinse tanks;, Koroseal-lined tanks for, plating steps; preplating, and plating chemicals;, automated systems, available., Metallizer, base, and, topcoating equipment, (spray, dip or flow),, metallizing racks., , Applications, , Equipment, , Metallic (silver and, bronze)., , Metallic finish. Silver and, copper generally used., Also gold, platinum,, palladinm., , Metallic finish, generally, silver but can be others, (e.g., gold, copper)., , Very durable metallic, finishes., , Metallics, wood grains or, multicolor, depending, on foil. Foil can be, specially formulated, (e.g., chemical, resistance)., Multicolor or single color;, metallics (not as good, as hot stamp)., , Effect, , C)q, , ~S·, , '"t:l, ~, , ...ri'~, , ~, , 00, , ~

Page 559 : Labeling, , Valley Printing, , Offset Printing, , Uses embossing rollers to, print in depressed areas, of a product., From simple paper labels to, multi color decads and, new preprinted plastic, sleeve labels., , Film or foil inserted in mold, is transferred to molten, plastics as it enters the, mold. Decoration, becomes integral part of, product., Printing of a surface directly, from a rubber or other, synthetic plate., Roll-transfer method of, decrating. In most cases, less expensive than, other multi color, printing methods., , In-the-Mold, Decorating, , Flexography, , Special process using a soft, transfer pad to pick up, image from etched plate, and tamping it onto a, part., , Tamp Printing, , Ranges from low-cost hand, presses to very, expensive automated, units. Drying,, destaticizers, feeding, devices., Embosser with inking, attachment or special, package system., Equipment runs the gaunt, from hand dispensers to, relatively high-speed, machines., , Manual. Semi- or automatic, press, dryers., , Metal plate, squeegee to, remove excess ink,, conical-shaped transfer, pad, indexing device to, move parts into printing, area, dryers, depending, on type of operation., Automatic or manual feed, system for the transfers., Static charge may be, required to hold foil in, mold., , Used largely with PVC, PE, for such areas as floor, tiles, upholstery., Can be used on all plastics., Used mostly for, containers and for price, marking., , Most plastics, especially, polyolefims and, melamines. For parts, where decoration must, withstand extemely high, wear., Most plastics. Used on such, areas as coding pipe, and extruded profiles., Most plastics. Used in, applications like coding, pipe., , All plastics. Specially, recommended for oddshaped or delicate parts, (e.g., drinking cups,, dolls' eyes)., , All sorts of colors and, types., , Generally two-color, maximum., , Multicolor print or, decoration., , Single- or multicolor., , Single- or multicolor, decoration., , Single- or multicolor-one, printing station per, color., , ~, , OQ, , S·, , ~, , ("), , ~, , !=;., , ~, ....., , ~, , 00

Page 560 : Electrostate, , Applique, , Two-shot, molding, , Inserted, nameplates, , Unit cost: high, Labor cost: high, Investment:, moderate to, high, Unit cost: low to, moderate, Labor cost: low, Investment:, moderate to, high, , Unit cost: low, Labor cost: low, Investment:, moderate, Unit cost: high, Labor cost: high, Investment: none, to moderate, Unit cost: high, Labor cost: high, Investment:, moderate, Unit cost: high, Labor cost: high, Investment:, moderate to, high, , Economics, , Restricted, , Partially limited, , Limited, , Somewhat, limited, , Good durability, , Not critical, , Good durability, , Not critical, , Good durability, , Critical, , Good durability, , Not critical, , Chemistry, , Somewhat, restricted, , Moderate to, good durability, , Critical, , Good durability, , Done after Molding, Unrestricted, Not critical, , Somewhat restricted, , Somewhat, restricted, , Unlimited, , Limited, , Unrestricted, , Product Design, , Done in the Mold, , Limited, , Aesthetics, , Guide to plastic-decorating methods, , In-mold label, , Engraved, mold, , Table 8-37, , Hand operation, , Two molding, operations, , Longer molding, cycles, , Longer molding, cycles, , No extra, operations, , Manufacturing, , Dry process, no tool contact, with product., , Allows unusual effects., , Good where maximum, abrasion resistance, necessary., , Good for thermoplastics and, thermosets. Automatic, loading equipment, becoming available., Allows three-dimensional as, well as special effects., , Best for simple lettering, and texture., , Comments, , 'XI, , '", S·, , ~, , ("), , '"i:l, ~, , '"i:l, , S', '"....., ;:;., , 00, , ~, , v,

Page 561 : Spray, , Silk screening, , Offset, intaglio, , Heat transfer, , Hand painting, , Flexographic, , Unit cost: low, Labor cost: low, Investment:, moderate to, high, Unit cost: high, Labor cost: high, Investment: low, Unit cost: low, to moderate, Labor cost: low, to moderate, Investment: low, to moderate, Unit cost: low, Labor cost:, moderate, Investment:, moderate, Unit cost:, moderate, Labor cost:, moderate, Investment:, moderate, Unit cost:, moderate, Labor cost:, moderate, Investment:, moderate, to high, , Unrestricted, Somewhat, restricted, , Unrestricted, , Somewhat, restricted, , Unrestricted, , Unlimited, , Limited, , Somewhat, limited, , Limited, , Moderate, durability, , Restricted, , Somewhat, limited, , Somewhat, limited, , Good durability, , Critical, , Good durability, Requires much, floor space, , ( Continued), , Wet process, no tool, contact with product., , Wet process, tool contacts, product., , ~, , VI, , Qt), , '", S·, , ~, , ~, ("), , Flexible, operation, , ::l'., , '~", '", , 00, , Critical, , Wet process, tool contacts, product., New process., , Multicolor graphics., , Dry process, tool contacts, product., , Wet process, tool contacts, product., , Wet process, tool contacts, product. Sometimes, requires top coat., , ("), , Requires little, floor space, , Requires little, floor space, , Hand operation, , Automates well, , Moderate to, good durability, , Critical, , Good durability, , Good durability, Critical, , Critical, , Critical

Page 562 : Offset, , Nameplates, , Metallizing, , Labeling, , Hot stamping, , Somewhat, restricted, , Unlimited, , Somewhat, restricted, , Restricted, , Unlimited, , Unlimited, , Somewhat, restricted, , Somewhat, restricted, , Limited, , Limited, , Specialized, , Specialized, , Unit cost: high, Labor cost: high, Investment:, moderate, to high, Unit cost: low, Labor cost: low, to moderate, Investment: low, to moderate, Unit cost: low, to moderate, Labor cost: low, to moderate, Investment: low, to high, Unit cost:, moderate, to high, Labor cost:, moderate, to high, Investment: high, Unit cost: high, Labor cost:, moderate, to high, Investment: low, to moderate, Unit cost: low, Labor cost:, moderate, Investment: high, , Moderate to good durability, , Multicolor graphics., , Wet process, tool contacts, product., , Automates well, , Critical, , Produces bright metallics., Dry process, tool contacts, product., , Wet and dry process, no tool, contact with product., , Multicolor graphics., , Adaptable, to many, situations, , Requires special, technological, know-how, , Multicolor graphics., , Good durability, , Good durability, Less critical, , Moderate to, good durability, Critical, , Dry process, no tool contact, with product at times., , Adaptable to, many situations, , Less critical, , Dry process, tool contacts, product., , Wet process, tool contacts, products., , Comments, , Produces bright metalics., , Requires little, floor space, , Mostly hand, operated, , Manufacturing, , Good durability, , Critical, , Good durability, , Critical, , Chemistry, , Done after Molding, Product Design, , Aesthetics, , Economics, , ( Continued), , Woodgraining, , Table 8·37, , OQ, , "", S·, , ~, , ("), , \:I, , ..", , '"tI, , :::-., ""("), , ~, , 00, , ~, ~, , v.

Page 563 : 8 Plastic Processing, Materials such as polyethylene, polypropylene and acetal, which have waxy surfaces,, or other crystalline plastics that are very, solvent resistant, can be difficult to paint, and require special primers or pre-treatments, (flame, etc.) for satisfactory adhesion. Many, amorphous plastics easily accept a wide variety of paint coatings., Although rolling and dipping are sometimes used, power spray painting is the, usual method of paint application. Among, the coatings used are polyurethane, epoxy,, acrylic, alkyd and vinyl based paints. With, paints that are oven cured, products must, have sufficient heat resistance to survive, without distortion, etc., , 545, , lightweight replacements for die castings, and sheet metal in demanding applications such as automotive grilles and wheel, covers., , Flame Spray/Arc Spray, , In these processes, specialized equipment, actually deposits a fine spray of molten, metal on the plastic surface. The relatively, thick, rough surface is generally used in nonappearance internal surfaces for electromagnetic and radio frequency shielding, as well, as static electricity dissipation., Hot Stamping, , Vacuum Metallizing and Sputter Plating, , In these processes, a special base coat is applied to the surface of the plastic product to, be metallized. The product is then placed in, a vacuum chamber in which a metallic vapor, is created and deposited on the product. A, protective clear top coat is then applied over, the thin metal layer for abrasion and environmental resistance. The simplest vacuum, metallizing processes use resistance heating, to melt and vaporize the metal., These processes are generally limited to, pure metals; typically aluminum but also silver, copper and gold. There are vacuum metallizing process that uses an electron beam to, vaporize the metal. The sputter plating process uses a plasma to produce the metallic, vapor. Both the electron beam and plasma, heating methods can be used satisfactorily, with alloys such as brass. These are economical metallizing processes that can produce an, attractive high gloss finish. However, the adhesion is generally low., Electroplating, After special pretreatments, specific, grades of plastics can be put through electroplating processes similar to those used in, the plating of metals. Electroplated plastic, products are very durable and provide, , This is a one step economical process for selectively transferring a high quality image to, a plastic product. A heated die transfers the, pattern from selected transfer tape to a flat, plastic surface. Lettering or decorative designs can be transferred in pigmented, wood, grain, or metallic finishes., , Sublimation Printing, Sublimation (diffusion) printing is a textile process in which color patterns in dry die, crystals are transferred from a release film, to the fabric under high heat and pressure., The process has been adapted to plastics. The, equipment used is very similar to that used for, hot stamping. Under heat and pressure, the, dye crystals sublime (go directly to the vapor, phase from the solid phase without melting), and the vapor penetrates the plastic product., As a result, the decoration is very durable, and wear resistant. It is also cost competitive, against other processes such as two-step injection molding or silk screening., The process is generally limited to certain, plastics such as TP polyester and polyester, based alloys due to the availability of dye, technology from the textile industry. However, new dyes are under development and, the application of the process to more plastics is anticipated.

Page 564 : 546, , 8 Plastic Processing, , Printing, Lettering and decoration can be applied to, most materials using various printing methods. Offset printing, silk screening, and pad, printing are among the methods adapted to, plastics., Decal and Label, These are usually self-adhesive, precut,, printed patterns on a substrate that are simply, adhered to the surface of a product. Decals, generally use a transparent plastic film while, labels are usually on an opaque plastic, metallic and multilayer sandwich base. Labels of, sufficient thickness are useful for hiding unavoidable appearance problems such as gate, and sprue removal areas, sink marks, blushes,, splays, and weld lines., Surface Treatment, Different treatments are used to provide a, surface that is more receptive to inks, coatings, adhesives, etc. They include chemical, solvents and corona treatments. As an example the corona treatment is an effective and, efficient process that is commonly used to increase the surface tension of a wide variety of, products. Highly consistent and controllable,, the process is continually being adapted for, new applications using both standard and innovative techniques. When considering the, purchase of a corona treating system, one, should be certain to investigate the flexibility of the proposed unit as well as its overall efficiency. Selecting the proper system, will ensure that the equipment does not become the limiting factor in the event of future manufacturing changes such as an alteration in materials or increased production, rates., Joining And Assembly, , Different methods are used for joining, or fastening and assembling plastic products and plastic to other materials. It is im-, , portant to both designer and end-user that, the techniques, advantages, and limitations, of these methods are understood so that, intelligent choices can be made. As an example, different materials that include plasticto-plastic and plastic-to-metal could have different thermal expansions and could cause, failure of the assembly when the individual materials are not free to expand or, contract., Parts to be assembled for TP for high, volume production include solvent bonding,, adhesive bonding, ultrasonic welding, hot, tool welding, electromagnetic and induction, bonding, and dielectric heat welding. For low, volume TP assembly include gas welding, adhesive bonding, ultrasonic tool welding, hot, tool welding, and spin welding. TS plastics include for high volume production molded-in, inserts, mechanical fasteners, adhesive bonds,, and electromagnetic or induction heating of, adhesives; TS plastics include for low volume, production adhesive bonding and mechanical, fastening. Tables 8-38 to 8-43 provide some, guides., Troubleshooting, , With all types of plastic processes, troubleshooting guides are set up to take fast,, corrective action when products do not, meet their performance requirements. This, problem-solving approach fits into the overall fabricating-design interface. One brief example of troubleshooting an RP/composite is, in Table 8-44., A simplified approach to troubleshooting, is to develop a checklist that incorporates the, basic rules of problem solving such as (1) have, a plan, and keep updating it, based on the, experience gained; (2) watch the processing, conditions; (3) change only one condition or, control at a time; (4) allow sufficient time for, each change, keeping an accurate log of each;, (5) check housekeeping, storage areas, granulators, etc.; and (6) narrow the range of areas, in which the problem belongs-that is, primary, or secondary machines, molds or dies, operating controls, materials, part designs, and management (1-3, 6-9, 10, 20, 37).

Page 565 : 547, , 8 Plastic Processing, Table 8·38 Methods for part assembly, , I, I, , I, , I, HIGH VOLUME, , I, , I, 1, , I, , MOLDED-IN INSERTS, MECHANICAL FASTENERS, ELECTROMAGNETIC II<, INDUCTION HEATING, OF ADHESIVE, ADHESIVE BONDING, (DRIFILM II< WET), , I, , I, , I, , I, , THERMOSETS, , I, , I, , PARTTO BE ASSEMBLED, , THERMOPLASTICS, , I, LOW VOLUME, , I, , l, , I, , I, HIGH VOLUME, , I, , I, , J, , I, , SOLVENT BONDING, HOT TOOL WELDING, ULTRASONIC WELDING, ADHESIVE BONDING, ELECTROMAGNETIC, II< INDUCTION BONDING, SPRING & VIBRATION, WELDING, DIELECTRIC HEAT, SEALING, , ADHESIVE BONDING, MECH FASTENERS, , Safety And Processing, , I, I, , I, , LOW VOLUME, , I, , GAS WELDING, ADHESIVE ISONDING, ELECTRO·MAGNETIC, II< INDUCTION BONDING, ULTRASONIC, HOT TOOL WELDING, SPIN WELDING, , With plastics that decompose, there may, be hazards such as personal burns or wounds, and air contamination. Faulty controllers, andlor freeze-off can cause the overheating, situation from a burned out heater. Safety, devices should be used that alert the plant, when problems develop; people have to be, aware of these possible situations. Recognize that personnel injury in plants due to, machinery represents 10% of all accidents, (Fig. 8-77)., , All process equipment has procedures to, operate and meet safety requirements. They, include a checklist that includes preparation, (moving material, etc.), startup and shutdown procedures, tooling changes, and to, cleanup of all equipment. Most equipment, generates high heats and pressures. They are, built to run safely, but they must be treated, with "respect"., Table 8·39 Assembly methods guide, Thermoplastics, Polyimide, Polypropylenes, Propylene, copolymers, Polystyrenes, Polysulphone, Polyvinyl, chloride, Polyvinyl, chloride, copolymers, PVC-acrylic, compounds, PVC-ABS, compounds, Styrene acrylo, nitrile, Thermoplastic, polyesters, , Adhesive Dielectric Induction Mechanical Solvent, Spin, Thermal Ultrasonic, Bonding Welding Bonding Fastening Welding Welding Staking Welding Welding, , x, , X, X, X, , X, X, , X, X, , X, X, X, , X, X, , X, , X, X, X, , X, , X, , X, , X, , X, , X, , X, X, , X, X, , X, , X, X, , X, , X, X, , X, , X, , X, X, , X, , X, X, , X, X, , X, , X, , X, X, , X, , X, , X, , X, , X, , X, , X, , X, , X, , X, X

Page 566 : 548, , 8 Plastic Processing, , Table 8-40 Reference chart in selecting method of fastening TPs, , Thermoplastics, , Mechanical, Fasteners Adhesives, , Spin and, Vibration, Welding, , Thermal, Welding, , Ultrasonic, Welding, , Induction, Welding, , ABS, , G, , G, , G, , G, , G, , G, , Acetal, , E, , P, , G, , G, , G, , G, , Acrylic, , G, , G, , F-G, , G, , G, , G, , Nylon, Polycarbonate, Polyester TP, Polythylene, , G, G, G, P, , P, G, F, NR, , G, G, G, G, , G, G, G, G, , G, G, G, G-P, , G, G, G, G, , Polypropylene, , P, , P, , E, , G, , G-P, , G, , Polystyrene, , F, , G, , E, , G, , E-P, , G, , G, NR, G, F, , G, G, G, G, , G, NR, E, F, , E, NR, G, G, , E, NR, G, F, , G, G, G, G, , Polysulfone, Polyurethane TP, PPO modified, PVC rigid, , Remarks, Body type, adhesive, Recommended, Surface treatment, for adhesives, Body type, adhesive, Recommended, , Surface treatment, for adhesives, Surface treatment, for adhesives, Impact grades, difficult to bond, , E = Excellent, G = Good, F = Fair, P = Poor, NR = Not recommended., Processing equipment has standard procedures to operate and meet safety requirements. Safety information and standards are, available from various sources that include, the equipment suppliers, Society of Plastics, Industry (SPI), and American National Standards Institute (ANSI). For the past century, we have observed increasing activity on the, , Table 8-41, , part of equipment manufacturers to upgrade, safety; also fabricating plants., Examples of safety features are many and, differ for the different equipment in the lines., Safety interlocks ensure that equipment will, not operate until certain precautions have, been taken. Safety machine lockout procedures are set up for action to be taken in, , Reference chart in selecting method of fastening TSs, , Thermosets, , Spin and, Mechanical, Vibration Thermal Ultrasonic Induction, Fasteners Adhesives Welding Welding Welding Welding, , Alkyds, DAP, Epoxies, Melamine, , G, G, G, , G, G, , F, , G, , Phenolics, Polyester, Polyurethane, Silicones, Ureas, , G, G, G, , E, E, E, , F, F, , G, G, , E, , NR, NR, NR, NR, , NR, NR, NR, NR, , NR, NR, NR, NR, , NR, NR, NR, NR, , NR, NR, NR, NR, NR, , NR, NR, NR, NR, NR, , NR, NR, NR, NR, NR, , NR, NR, NR, NR, NR, , E = Excellent, G = Good, F = Fair, P = Poor, NR = Not recommended., , Remarks, , Material, notch sensitive, , Material, notch sensitive

Page 567 : 20--30, 65-80, 65-80, 50--70, 20--50, 50--70, 40--50, 60--80, 60--80, 20--50, 20--50, 60--70, 60--70, , 50--70, 65-80, 65-80, 50--70, 30--50, 50--70, 40-50, 70--90, 70--90, 30--60, 20-50, 50--70, 50--70, , 20--30, 60-75, 60--75, 50-70, 30--70, 50--70, 35-50, 60--80, 60--80, 20--50, 20--60, 60--70, 60--70, , 8,000--10,000, 2,400--8,500, 3,000--7,000, , 2,000--8,000, 8,000--11 ,000, 7,000--12,000, 8,000--9,500, 800--6,000, 3,000--6,000, 3,500--8,000, 8,000--11 ,000, 5,000--9,000, 3,000-5,000, , *To convert psi to Pascals, multiply by 6,895., , 50--70, , 50--70, , 10--15, , Hot-Plate, Welding, , 10--15, , Friction, Welding, , 50--70, , Hot-Air, Welding, , 2,400--9,000, , 7,000-13,000, 7,000--13,000, 6,000-9,000, 6,000-13,000, , Original Tensile, Strength (psi)*, , Percent tensile strength retention using welding techniques, , Thermosetting plastics, Epoxy, Melamine, Phenolic, Polyester, Thermoplastics, Acrylonitrile butadiene, styrene, Acetal, Cellulose acetate, Cellulose acetate, butyrate, Ethyl cellulose, Methyl methacrylate, Nylon, Polycarbonate, Polyethylene, Polypropylene, Polystyrene, Polystyrene acrylonitrile, Polyvinyl chloride, Saran, , Table 8·42, , 30--50, 60--70, 60--70, , 50--80, , Dielectric, Welding, , 25-50, 25-60, 50--70, 50--70, , 40--60, , 80--90, 40--60, , 90--100, 90--100, , 30--60, , Solvent, Welding, , 50--80, 40--60, 20-40, 5-15, 10--30, 20-40, 20--50, 20--50, 50--70, 50--70, , 50--60, 50--80, , 40--60, , 50--80, 50--80, 50--80, 50--80, , Adhesive, Bonding, , 60--90, , 60--100, 60--100, 60--100, 60--100, , Polymerization, Welding, , \0, , ~, , v,, , ~, , S·, , ~, , (""), , <::), , ~, ....., , (""), , '"~., , ~, , i2i", , 00

Page 568 : 8 Plastic Processing, , 550, Table 8-43, , Plastics' behavior with ultrasonic welding, , Material, , Percent of, Weld, Strength', , General-purpose plastics, ABS, 95-100+, Polystyrene unfilled, 95-100+, Structural foam (styrene), 90-1001, Rubber modified, 95-100, Glass filled (up to 30%), 95-100+, SAN, 95-100+, Engineering plastics, ABS, 95-100+, ABS/polycarbonate, 95-100+ 2, alloy (Cycoloy, 800), ABS/PVC alloy, 95-100+, (Cycovin), Acetal, 65-703, Acrylics, 95-100+ 4, Acrylic, 95-100, multipolymer, (XT-polymer), Acrylic/PVC alloy, 95-100+, (Kydex), ASA, 95-100+, Methylpentene, 90-100+, Modified phenylene, 95-100+, oxide (Noryl), Nylon, 90-100+2, Polyesters, 90-100+, (thermoplastic), Phenoxy, 90-100, Polyarylsulfone, 95-100+, Polycarbonate, 95-100+ 2, Polyimide, 80-90, Polyphenylene, 95-100+, oxide, Poiysuifone, 95-100+ 2, High-volume, low-cost applications, Butyrates, 90-100, CeUulosics, 90-100, Polyethylene, 90-100, Polypropylene, 90-100, Structural foam, 85-100, (polyolefin), Vinyls, 40-100, , Welding, Spot Weld, , Staking and, Inserting, , Swaging, , Near, Fieldt, , Far, Field t, , E, E, E, E, E, E, , E, E, E, E, E, E, , G, F, F, G, F, F, , E, E, G, E, E, E, , G, E, P, G-P, E, E, , E, E, , E, E, , G, G, , E, E, , G, G, , E, , E, , G, , G, , F, , G, G, E, , E, E, E, , P, P, G, , G, E, E, , G, G, G, , E, , E, , G, , G, , F, , E, E, E, , E, E, E, , G, G, F-P, , E, G, G, , G, F, E--G, , E, G, , E, G, , F-P, F, , G, G, , F, F, , G, G, E, F, E, , E, E, E, G, G, , G, G, G-F, P, F-P, , G, E, E, G, G, , G-F, G, E, F, G-F, , E, , E, , F, , G, , G-F, , G, G, E, E, E, , G-F, G-F, E, E, E, , G, G, G, G, F, , P, P, G-P, G-P, G, , P, P, F-P, F-P, F-P, , G, , G-F, , G, , F-P, , F-P, , Code: E = Excellent, G = Good, F = Fair, P = Poor., 'Weld strengths are based on destructive testing. 100 + % results indicate that parent material of plastic part gave, way while weld remained intact., tNear field welding refers to joint 1/4 in. or less from area of hom contact: far field welding to joint more than 1/4 in., from contact area., 1High-density foams weld best., 2Moisture will inhibit welds., 3Requires high energy and long ultrasonic exposure because of low coefficient of friction., 4Cast grades are more difficult to weld due to high molecular weight.

Page 569 : 551, , 8 Plastic Processing, Table 8-44 Troubleshooting RP processes, Problem, Nonfills, Excessive, thickness, variation, Blistering, Extended, curing, cycle, , Possible Cause, , Solution, , Air entrapment, Gel and/or resin timet too short, Improper, clamping, and/or lay-up, Demolded too soon, Improper catalytic action, , Additional air vents and/or vacuum required, Adjust resin mix to lengthen time cycle, Check weight and lay-up and/or check, clamping mechanisms such as, alignment of platens, Extend molding cycle, Check resin mix for accurate catalyst content, and dispersion, Check equipment, if used, for proper catalyst, metering, Remix resin and contents: agitate, mix to provide even dispersion, , Improper catalytic, action, , proper lockout of the machine's operation, such as electrical and mechanical circuits., There are preloaded pressure bolts around, dies, pressure rupture disks on barrels, turret winder emergency stops, coextrusion line, alarm if one extruder stops, drop bar between, platens (IMM, CMM, etc.), and so on. The, operating environment is continuously upgraded with reduced sound and noise in the, operating areas., To protect operating personnel from recognized hazards, American National Standards Institute (ANSI) voluntary standards, , have been prepared to assign responsibilities, to machine manufacturers, re-manufacturers,, modifiers, and employers to ensure safety, measures are taken. They are updated periodically. An SPI group (mid-1970s) that, included D. V. Rosato as a working member started these ANSI standards on different primary and auxiliary equipment. As of, 1992 OSHA adopted these standards making them mandatory. Revisions and up-dating, continually occurs., , EquipmentIProcessing Variable, 23%, , Manual handling, of oblects, , 14%, , 7%, Striking objects, , Fig. 8-77 National Safety Council, Chicago, IL, provides updates on where accidents occur in all, types of manufacturing plants., , In addition to material variables, as reviewed in Chapter 6, there are a number of, factors in equipment hardware and controls, that cause processing variabilities. They include factors such as accuracy of machining, component products, method and degree of, accuracy during the assembly of component, products, temperature and pressure control, capability particularly when interrelated with, time and heat transfer uniformity in metal, components such as those used in molds and, dies., These variables are controllable within, limits to produce useful products. What is, important to appreciate is that during the, past many decades' improvements in equipment have made exceptional strides in significantly reducing operating variabilities or limitations (Fig. 8-78). This action will continue

Page 570 : 552, , 8 Plastic Processing, Combining Variable, , Fig.8-78 You can not expect a 20 year old machine to compete with a machine built to today's, standards., , into the future since there is a rather endless, improvement in performance of steels and, other materials and methods of controlling, such as fuzzy controls. Growth is occurring in, applying fuzzy logic that in 1981 was based on, the idea to mimic the control actions of the, human operator (2, 3)., Unfortunately these variables and problems exist in all industries. As an example, a major situation occurred that was catastrophic in the aerospace industry. (Nothing, is perfect on earth.) The Challenger shuttle, spacecraft exploded 28 January 1986 above, Cape Canaveral, FL. (Fig. 8-79), , ---, , ow, , -~.', ., , ~-, , Fig.8-79 Challenger shuttle spacecraft exploded, 28 January 1986 above Cape Canaveral, FL.; photo, taken by D. V. R. from Route 95 Florida., , There are many different processing factors that could influence the repeatability of, meeting performance requirements such as, tolerances. Some products may require only, the compliance of one or two processing factors, but others will require many. Computer, programs have been developed to provide, the capability of integrating all the applicable, factors, thus replacing traditional trial-anderror methods. These programs improve with, time since providing improved controls is an, endless effort., Most computer-integrated systems have, been developed for injection molding, since, a much bigger market exists with 1M. Other, computer systems are available for the other, processes., Selecting Process, For any given product, the most important processing requirements should be determined based on the plastic to be processed,, the quantity, and the dimensions of size and, the tolerances. Process selection is a critical, step in product design. Failure to select a viable process (and material) during the initial, design stages can dramatically increase development costs and timing. It is important to, recognize that the process can have a significant effect on the performance of the finished, product. The following examples of the considerations in choosing a process are based, on what has been reviewed throughout this, book., 1. The nature of the process may have a, profound influence on a product's mechanical strength., 2. Excessive heat during processing can, consume sacrificial heat stabilizers for certain, plastics, rendering stabilization levels insufficient to ensure long life at elevated temperatures and/or outdoor weathering. Thermal, degradation usually results in embrittlement, (tests can be conducted to determine the remaining levels, Chapter 5) ., 3. The slow cooling of crystalline polymers, such as HDPE and PP, can allow large, crystal formations to develop. Such crystals

Page 571 : 8 Plastic Processing, embrittle the plastic and make it prone to, stress cracking., 4. The rapid cooling of certain plastic products can result in "frozen in" stresses and, strains (particularly with injection molding)., The stresses may decay with time in a viscoelastic manner. However, they will act like, any other sustained stress to aggravate cracking or crazing in the presence of aggressive media and hostile environments like UV, radiation., 5. Annealing at temperatures below the, Tg (glass transition temperature, Chapter 7), where material becomes leathery is not necessarily beneficial. For example, annealing a, PC greatly accelerates both its crazing and, rupture under sustained loading. In general,, the annealing of plastics results in lowering, its properties; however, its dimensional stability may be improved. Heating a material, to above its Tg, however, results in the relief, of internal stresses., 6. Knit or weld lines form where the melt, flow during processing meets after flowing, through separate gates in an injection mold, or after being parted by either "spiders" in an, extruder die or bosses in an injection mold., Because the material is not well mixed in the, zone of the knit or weld line, the seam thus, formed can be weak or brittle under longterm or impact loads. This problem can easily arise with fiber reinforced plastics, where, under ideal molding conditions 40 to 60% of, their strength can be lost, since fibers fail to, knit together at their seams., 7. In RPs, insufficient compaction and consolidation before plastic solidification or cure, will result in air pockets, incomplete wet-out, and encapsulation of the fibers, and/or insufficient fiber or uniform fiber content. These deficiencies lead to loss of strength and stiffness, and susceptibility to deterioration by water, and aggressive agents., These examples show the kinds of alterations that the processing of plastics can have, on the performance of the product. As discussed throughout this book, the many different plastics tend all to behave in different, patterns, so where a particular problem could, develop during processing with one mate-, , 553, , rial, it might have little or no effect on another, even if the base plastics are the same, but contain different additives or reinforcements. Regardless, the problems that might, arise should be eliminated at the outset., In some cases the designer will not have, the ability to choose freely from all the design, material, and process alternatives. For, example, a design is often heavily constrained, by the need to fit an existing assembly, and, the material and process may be determined, largely by the need to use existing processing facilities. However, to optimize results the, designer should establish the extent of any, design freedom early in the design process, and explore the design, material, and process alternatives within these bounds. Before, final selection of the process, the entire process of production should be considered, including such secondary operations as painting and decorating (Appendix A, PLASTICS, DESIGN TOOLBOX)., , Shape, Both shape and design details are heavily, process related. The ability to mold ribs, for, example, may depend on material flow during a process or on the flow ability of a plastic, reinforced with glass. The ability to produce, hollow shapes depends on the ability to use, removable cores, including air, fusible or soluble solids, and even sand. Hollow shapes can, also be produced using cores that remain in, the product, such as foam inserts in RTM or, metal inserts in 1M., The geometric symmetry of a product influences process selection. For example, an, axis of symmetry in a long, narrow product, may suggest selecting an extrusion or pultrusion process. Similarly, the need for hollow, sections in the product could suggest blow, molding or rotational molding. In order to, handle materials that melt, flow, and solidify, quickly, it may be necessary to use a mechanical process such as injection molding. It is a, process that could still be limited by the time, available with the particular inadequate machine in question to fill the mold cavity before the melt solidifies; thus, higher pressures, are required to increase the speed of mold, filling, etc.

Page 572 : Compression, , 1 Special mold required., 2Not recommended., 30nly flexible material., 40nly direction of extrusion., 5Possible with special techniques., 6Fusing premix/yes., 7Rated 1 to 5 (1 = very smooth. 5, , Major shape, characteristics, , = rough)., , Hollow Simple, Moldable, bodies, configurations, in one, plane, Equipment, Limiting size factor Material Material, Maximum thickness. > 0.25, None, 0.5, (12.7), in. (mm), (6.4), 0.01-{).125, Minimum inside, 0.125, 0.125, (0.25-3.18), (3.18), radius, in. (mm), (3.18), Minimum draft, 0-1, 0, >1, (deg.), Minimum thickness. 0.01, 0.01-0.125, 0.01-0.125, (0.25-3.18), in. (mm), (0.25), (0.25-3.18), Threads, Yes, Yes, Yes, Yes), NR2, Undercuts, Yes, Yes, Inserts, Yes, Yes, Built-in cores, Yes, No, Yes, Yes, Yes, Molded-in holes, Yes, Yes, Bosses, Yes, Yes, Yes, Fins or ribs, Yes, Yes, Molded in designs, Yes, Yes, Yes, and nos., 1-2, 2, 1-2, Surface finish7, Overall dimensional 0,01, 0.001, 0.001, tolerance (in'/in.,, plus or minus), , Blow, Molding Casting, Structure, with surfaces of, revolution, Equipment, 3, (76), 0.125, (3.18), 2-3, 0.015, (0.38), No, NR2, Yes, Yes, Yes, No, NoS, No, 5, 0.005, , Extrusion, Constant, cross section, profile, Material, 6, (150), 0.01-0.125, (0.25-3.18), NR2, 0.001, (0.02), No, Yes, Yes, Yes, Yes4, Yes, Yes, No, 1-2, 0.005, , Process, Filament, Winding, , Basic processing methods as a function of product design, , Part Design, , Table 8-45, , 1, 0.001, , 0.005, (0.1), Yes, Yes), Yes, Yes, Yes, Yes, Yes, Yes, 4-5, 0.005, , 0.03, (0.8), No, NR2, Yes, Yes, Yes, Yes, N0 6, Yes, , Few, Moldable, limitations, in one, plane, Equipment Equipment, 6, 2, (150), (51), 0.01-0.125, 0.06, (0.25-3.18), (1.5), <1, 1, , Injection, , 2-3, 0,01, , 0.02, (0.5), Yes, Yes3, Yes, Yes, Yes, Yes, Yes, Yes, , 1-3, 0.01, , 0.002, (0.05), No, Yes), NR2, Yes, No, Yes, Yes, Yes, , Moldable, in one, plane, Material, Material, 0.5, 3, (12.7), (76), 0.01-0.125 0.125, (0.25-3.18) (3.18), 1, 1, , Hollow, bodies, , Matched Die, TherrnoMolding, Rotational forming, , Wet lay-up, (Contact, Molding), , 1-2, 0.001, , 0.01-0.125, (0.25-3.18), Yes, NR2, Yes, Yes, Yes, Yes, Yes, Yes, , 4-5, 0.02, , 0.06, (1.5), No, Yes, Yes, Yes, Yes, Yes, Yes, Yes, , Simple, Moldable, contigurations, in one, plane, Equipment, Mold Size, 6, 0.5, (150), (12.7), 0.01-0.125, 0.25, (0.25-3.18), (6.4), 1, 0, , Transfer, Compression, , ()t), , "", S·, , ~, , "tI, ~, ('), , ('), , "", :::., , "tI, is', , 00, , ~, , v., v.

Page 573 : 8 Plastic Processing, Table 8·46, , 555, , Guide to compatibility of processes and RP materials, Thermosets, , Thermoplastics, Q), , "'""5", , Q), , "''K", , <;::::, , ..., , u, , u, , ..., , ~, , ;:;s, C/), , ;:;s, , .!l, , .!l, , !l, , Q), , Q), , Q), , '";>,, , "0, ~, , '";>,, , "0, ~, , '";>,, , "0, ~, , ~:l -a, "0 .c0 Q:lu, ;>,, 0.., , UJ, , ~, , u, , >., 0.., 80.., , "0, , "0, , "0, , iO, , ~, , -<, , \0, , c=, , 0, , >., Z, , >e., \0, c=, 0, , >., Z, , '", , c=, , 0, , .rJ, , til, , ;>,, , ~, , Q), , c=, Q), , ;>,, , ~, , 0, , Q), , c=, 2;>,, c=, Q), ..c:, , Q), , Q), , 0.., ;>,, , ~, , Q), , 5, , >., c=, ], , C/), , ~, , -<, , 0.., ;>,, , "0, ~, , Eo<, Q), , c=, ~, , c'", ;£, , ;>,, , ~, , ..., , ~, , .!l, , '";>,, Q), , "0, ~, , 53, ~, ..., , *, Q), , ;>,, , "0, ~, , Injection molding, Hand lay-up, Spray-up, Compression, molding, Preform molding, Filament winding, Pultrusion, Resin transfer, molding, Reinforced reaction, injection molding, , Each process has certain characteristics, that can be summarized by determining, whether (1) its ribs and bosses are feasible,, depending on whether one or both sides of, the product reproduce the tool (mold or die), surface; (2) the sequence of material injection, or some other process and tool closure allows, of having deep vertical sections in the surface wall; (3) the material's viscosity is high, enough to allow the use of slides and cores in, the tool without their being gummed up with, material flowing into the slide mechanism;, (4) hollow sections or containers are feasible;, and (5) whether hollow or foam-filled box, sections can be produced to increase section, stiffness (Appendix A: PLASTICS DESIGN, TOOLBOX)., , length of flow s it relates to residence time, and the material's reaction time. With most, labor-intensive methods, such as hand lay-up,, slow-reacting TSs can be used and there is virtually no limit on size., The functions and property characteristics, of a product will be largely determined by, the performance requirements and material, selected for fabrication. The basic requirement of the process is its capability of handling a suitable material. For example, if a, major function requirement is for resistance, to creep under high loads, it is probable that, a long-fiber RP will be necessary. Thus it, would immediately eliminate such processes, as blow molding and conventional injection, molding., , Size, , Thickness tolerance With some processes,, thickness is limited only by the size of the, equipment that is either available or can be, produced. A general guide to practical processing thickness limitations is (in inches): injection molding, 0.02 to 0.5; extrusion, 0.001, to 1.0; blow molding, 0.003 to 0.2; thermoforming, 0.002 to 1.0; compression molding,, 0.05 to 4.0; and foam injection molding of 0.1, to 5.0., , Product size is limited by the size of available equipment and a process's available, pressure such as melt and clamping pressure., The ability to achieve specific shape and design detail is dependent on the way the process operates. Generally, the lower the processing pressure, the larger the product that, can be produced. Other restrictions are the

Page 574 : ABS, Acetal, Acrylic, Allyl, ASA, Cellulosic, Epoxy, Fluoroplastic, Melamineformaldehyde, Nylon, Phenolformaldehyde, Poly (amide-imide), Polyarylether, Polybutadiene, Polycarbonate, Polyester (TP), Polyesterfiberglass (TS), Polyethylene, Polyimide, Polyphenylene, oxide, Polyphenylene, sulfide, Polypropylene, Polystyrene, Polysulfone, Polyurethane (TS), (TP), SAN, Silicone, Styrene butadiene, Urea formaldehyde, Vinyl, , Material, Family, , X, X, , X, X, X, X, , X, , X, , X, X, , X, , X, , X, , X, , X, X, , X, X, X, , X, , X, , X, , X, X, , X, X, X, X, X, , X, , X, X, , X, , X, X, X, , X, X, , X, X, X, , X, , X, , X, , X, , X, , X, X, X, , X, , X, , X, , X, X, , X, , X, , X, X, , X, , X, , X, X, , X, , X, , X, , X, , X, , X, X, , X, , X, , X, , X, X, X, X, , X, , X, X, X, X(TP), , X, X(TP), X, , X, X, X, X, X, X, , X, , X, X, , X, , X, , X, , X, , X, , X, X, X, , X, , X, , X, , X, , X, , X, X, , X, X, , X, X, , X, X, , X, , X, X, , X, X, X, , X, X, X, X, , X, X, , X, X, , X, , X, , X, X, X, X, , X, , X, , X, , X, X, , X, X, X, , X, , X, , X, , X, , X, , X, , X, , X, X, , X, , X, X, X, , X, , X, , X, X, X, , X, , X, , X, , X, X, , X, , X, , X, X, X, , X, , X, , X, , X, , RP, Dip, Structural, Cold, Sheet, Molding, and, Foam, Extrusion Laminating Forming, Injection Compression 1fansfer Casting Molding Coating, FRP, Filament Slush Blow Rotational, , Table 8·47 Molding processes guide to plastic materials, , O\l, , S·, , ~, , ("), , ~, , a, , ::to, ("), , [, , ~, , 00, , ~, , 0\

Page 575 : 8 Plastic Processing, Table 8-48, , General information relating processes to properties of plastics, , Thermosets, , Properties, , Polyesters, Properties shown, also apply to, some polyesters, formulated for, thermoplastic, processing by, injection molding, , Simplest, most versatile. economical and most, widely used family of resins, having good, electrical properties, good chemical, resistance, especially to acids, , Epoxies, , Excellent mechanical properties, dimensional, stability, chemical resistance (especially, alkalis), low water absorption, selfextinguishing (when halogenated), low, shrinkage, good abrasion resistance, very, good adhesion properties, Good acid resistance, good electrical properties, (except arc resistance), high heat resistance, Highest heat resistance, low water absorption,, excellent dielectric properties, high arc, resistance, Good heat resistance, high impact strength, Good electrical insulation, low water absorption, , Phenolics, Silicones, Melamines, Diallyl phthalate, Thermoplastics, Polystyrene, Nylon, Polycarbonate, Styrene-acrylo-nitrile, Acrylics, , Vinyls, , Acetals, , Polyethylene, , 557, , Low cost, moderate heat distortion, good, dimensional stability, good stiffness, impact, strength, High heat distortion, low water absorption, low, elongation, good impact strength, good tensile, and flexural strength, Self-extinguishing, high dielectric strength, high, mechanical properties, Good solvent resistance, good long-term strength,, good appearance, Good gloss, weather resistance, optical clarity, and, color; excellent electrical properties, Excellent weatherability, superior electrical, properties, excellent moisture and chemical, resistance, self-extinguishing, Very high tensile strength and stiffness,, exceptional dimensional stability, high, chemical and abrasion resistance, no known, room temperature solvent, Good toughness, light weight, low cost, good, flexibility, good chemical resistance; can be, "welded", , Processes, Compression molding, Filament winding, Hand lay-up, Mat molding, Pressure bag molding, Continuous pultrusion, Injection molding, Spray-up, Centrifugal casting, Cold molding, Comoform 1, Encapsulation, Compression molding, Filament winding, Hand lay-up, Continuous pultrusion, Encapsulation, Centrifugal casting, Compression molding, Continuous laminating, Compression molding, Injection molding, Encapsulation, Compression molding, Compression molding, Injection molding, Continuous laminating, Injection molding, Blow molding,, Rotational molding, Injection molding, Injection molding, Injection molding, Vacuum forming, Compression molding, Continuous laminating, Injection molding, Continuous laminating, Rotational molding, Injection molding, , Injection molding, Rotational molding, Blow molding, , (Continues)

Page 576 : 558, , 8 Plastic Processing, ( Continued), , Table 8-48, , Thermosets, , Properties, , Fluorocarbons, , Processes, , Very high heat and chemical resistance,, nonbuming, lowest coefficient of friction,, high dimensional stability, Very fough engineering plastic, superior, dimensional stability, low moisture, absorption, excellent chemical resistance, Excellent resistance to stress or flex cracking, very, light weight, hard, scrach-resistant surface,, can be electroplated: good chemical and heat, resistance: exceptional impact strength, good, optical qualities, Good transparency, high mechanical properties,, heat resistance, electrical properties at high, temperature, can be electroplated, , Polyphenylene oxide, modified, Polypropylene, , Polysulfone, , Another consideration is the ability of, a material to provide a surface that is, compatible with the requirements of the, application: a smooth finish for extruded, profiles, molded-in colors, textured surfaces,, etc. The compatibility of the major processes, with in-mold coating and other insertsurfacing materials, and their compatibility, with surface decoration secondary processes,, could also be important., , Injection molding, , Guide to process selection, , Table 8-49, , PART TO BE FORMED, , ~, OVER 25(J°F, THERMOSETS, , I, OVERlsqft, OVER 51b1, , I, , I I, , FILAMENT WINDING, COMPRESSMlN, HIGH.pRESSURE, LAMINATION, , ADHESIVE BOND, , I, UNDER 250°F, , THERMOPLASTICS, , I, LARGE AREA, , THERMOFORM, , FOAM, HEAT SEAL, WELD, ROTOFORM, BLOW MOLD, ADHESIVE BOND, STRUCT\JRAL, , FOAM, RIM, , I, , J, , I, LOW'-PRESSURE, LAMINATION, , I, , I, , LARGE PART, , I, , MACHINE, PULTRUSION, , Injection molding, Continuous laminating, Rotational molding, , It should be recognized that surface finish can be more than just a cosmetic standard. It also affects product quality, mold or, die cost, and delivery time of tools and/or, products. The surface can be used not only, to enhance clarity for the sake of appearance, but to hide surface defects such as sink and, parting marks. The Society of Plastics Engineers/Society of Plastics Industries standards, range from a No.1 mirror finish to a No.6 grit, blast finish. A mold finish comparison kit consisting of six hardened tool steel pieces and, , Surface Finish, , POST FORM, , Injection molding, Encapsulation, Continuous pUltrusion, Injection molding, , I, , I, , I, , I, , I, , LLONG LENGTHS J, , I, , I, EXTRUDE, , I, , OVER 2SOoF, THERMOSETS, , HIGH·VOLUME, , I, COMPRESSION, TRANSFER, , INJECTION, , LAMINATION, PULTRUSION, , I, , J, , LESS THAN 1 aq ft, LESS THAN 5 Jb, , I, , I, , I, , I, ~ALL PART, , I, , I, I, , I, LESS THAN 250°F, , THERMOPLASTICS, , I, , I, , LOW-VOLUME, , HIGH·VOLUME, , I, CASTING, MACHINING, LOWPRESSURE, , LAY-UP, POST FORM, SPRAY-UP, RESIN 'tRANSFER, , I, INJECTION, BLOW MOLD, THERMOFORM, EXTRUSION, ROTOFORM, RIM, , I, , I, I, , LOW·VOLUME, , I, MACHINE, THERMOfORM, COMPRESSION, CASTING, , ROTOFORM, FOAM, , ADHESIVE BOND

Page 577 : 8 Plastic Processing, Table 8-50, , 559, , Economic comparison of three different processes, , Production, Considerations, Typical minimum, number of parts a, vendor is likely to, quote on for a, single setup, , Relative tooling cost,, single cavity, , Average cycle times, for consistent part, reproduction, Is a multiple-cavity, tooling approach, possible to reduce, piece costs?, , Structural Foam, 250 (using multiple, nozzle equip. with, tools from other, sources designed, for the same, polymer and, ganged on the, platen), Lowest. Machined, aluminum may be, viable, depending, on quantity, required, 2 to 3 minutes, /4 in. nominal wall, thickness), Yes, , e, , Are secondary, operations, required except to, remove sprue?, , No, , Range of materials that, can be molded, , Similar to, thermoplastic, injection molding, , Finishing costs for, good cosmetic, appearance, , 40 to 60 cents per sq., ft. of surface, (depending on, surface-swirl, conditions), , associated molded pieces is available through, SPE/SPI., Various types of surface finishes are available for plastics and RP products, such as, smooth, textured, molded-in color, and inmold coating. A textured product surface can, be obtained through either a textured mold, cavity or a postmold paint process. The former method is the most commonly used. A, , Injection Molding, , Sheet Molding, Compound, , 1,000 to 1,500, , 500, , 20 percent more., Hardened-steel, tooling, , 20 percent to 25, percent more., Compressionmolding steel, tools, 11/z to 3 minutes, , 40 to 50 seconds, Yes. Depends on size, and configuration,, although rapid, cycle time may, eliminate the, need., No, , Unlimited; cost, depends on, performance, requirements, None, if integrally, colored; 10-20, cents per sq. ft. if, painted, , Not necessarily., Secondary operations, may be too costly, and material flow, too difficult, Yes, e.g., removing, material where a, "window" is, required (often, done within the, molding cycle), Limited; higher cost, , None, if secondary, operations such as, trimming are not, required., Otherwise 20 to, 30 cents per sq. ft., of surface, , wide variety of texture designs are available., The surface smoothness, and to some degree, the texture, of a plastic or RP is as dependent, on the materials used in it as on the surface, of the cavity. For example, certain chemically, etched textured surfaces can be obtained only, if the proper steel or metal is used in the mold, cavity. Also, with any mold or die the proper, cavity steel based onthe plastic processed will

Page 578 : 8 Plastic Processing, , 560, Table 8-51, , Design recommendations for choosing an RP process, Contact, Molding., Spray-up, , Minimum inside, radius, in., Molded-in holes, Trimmed-in mold, Built-in cores, Undercuts, Minimum practical, thickness, in., (mm), Maximum practical, thickness, in., (mm), Normal thickness, variation, in., (mm), Maximum buildup, of thickness, Corrugated, sections, Metal inserts, Surfacing mat, Limiting size, factor, Metal edge, stiffeners, Bosses, Fins, Molded-in labels, Raised numbers, Gel coat surface, Shape limitations, Translucency, Finished surfaces, Strength, orientation, Typical glass, percent by, weight, , Pressure, Bag, , Filament, Winding, , Continuous, Pultrusion, , Premix!, Molding, Compound, , Matched Die, Molding, with Preform, or Mat, , 1/4, , liz, , l/S, , N.A.', , 1/32, , l/S, , Large, No, Yes, Yes, 0.060, (1.5), , Large, No, Yes, Yes, 0.060, (1.5), , N.R.', Yes, Yes, No, O.OlD, (0.25), , N.A., Yes, N.A., No, 0.037, (0.94), , Yes, Yes, Yes, Yes, 0.060, (1.5), , Yes, Yes, Yes, No, 0.030, (0.76), , 0.50, (13), , 1, (25.4), , 3, (76.2), , 1, (25.4), , 1, (25.4), , 0.25, (6.4), , ±0.020, (±0.51), , ±0.020, (±0.51), , ±0.010, (±0.25), , ±0.005, (±0.1), , ±0.002, (±0.05), , ±0.008, (±0.2), , As desired, , As desired, , As desired, , N.A., , As desired, , Yes, , Yes, Yes, Yes, Bag size, , In longitudinal, direction, No, Yes, Pull capacity, , Yes, , Yes, Yes, Mold size, , Yes, No, Press, capacity, , Yes, Yes, Press, dimensions, , Yes, , N.R., , Circumferential, only, Yes, Yes, Lathe bed, length and, swing, Yes, , 2 to 1, maximum, Yes, , No, , Yes, , Yes, , Yes, Yes, Yes, Yes, Yes, None, , N.R., Yes, Yes, Yes, Yes, Flexibility, of the bag, Yes, One, Orientation, of ply, 45-60, , No, No, Yes, No, Yes, Surface of, revolution, Yes, One, Depends, on wind, 50-75, , No, N.R., Yes, No, No, Constant, cross-section, Yes, Two, Directional, , Yes, Yes, No, Yes, No, Moldable, , Yes, N.R., Yes, Yes, Yes, Moldable, , No, Two, Random, , Yes, Two, Random, , 30-60, , 25, , 30, , Yes, One, Random, , 30-45, , 'Note: N.A.: Not applicable., N.R.: Not recommended., , significantly reduce its wear and tear and extend its useful life., Cost, , The production flexibility of the fabrication process is often the single most, , important economic factor in a plastic product. The component's size, shape, complexity,, and required production rate can be primary determinants. As an example, small, numbers of large objects tend economically, to favor casting, as well as the RP's hand, lay-up or spray-up process, with a minimal tooling cost and maximum freedom for

Page 579 : MATCHED TOOL, , SPRAY·UP, , I, , I, , ~, , ~I, , I, , SPRAY·UP, , I, , MATCHED, TOOLING, , INJECTION, , I, , I, , COMPRESSION, , I, , MATCHED, TOOLING, , I, , VACUUM, BAG, , PREMIX, , I, , FABRIC, , PREP REGS, , I, , PREFORM, , I, , MAT, , PREFORM, , I, , VOLUME, , 5MC:dAT, PREFORM, , FABRIC, PREPREGS, , I, , CONTINUOUS, LAMINATION, , I, , PREFORMS, , I, , INJECTION, , COMPRESSION, , HI;Hn, , INJECTION, , I, , MATCH E 0 TOOL, , I, , c$J$$, , I, , COST PREDOMINANT, , MAT PREFORMS, , I C~;LEX I ~, , MATCHED, TOOL, , AUTOCLAVE, , BAG, , PRESSURE, , MAT, , I, , 1, , 5MALLPART, ,UNDER 3a 5 FTI, , FABRIC·, PREPREGS, , FILAMENT, wlNmNG, , I, , CONTACT, , I ~CW+EX I IL~W I, , I, , INJECTION, , I, , LAMINATION, , CONTINUOUS, , I, , S:-.ICUAT·, PREFORM, , SHAPE, , AUTOCLAVE, , I, , I, , MATCHED TOOL, , I, , RESIN, TRANSFER, , BMCII.PREMIX·, , I, , CONTACT, , I, , I, , RESIN, TRANSFER, , AUTOCLAVE, , I, , PRESSURE, BAG, , VOLUME, , PRESSURE, BAil, , WtNOING, , I, , BAil, , VACUUM, , CONTACT, , STRENGTH PREDOMINANT, , I, , PULTRUSION, , I, , SPRAY·UP, , I, , SHAPE, , PULTRU510N, , I, , I, , PRESSURE, BAG, , RESIN, TRANSFER, , I, , AUTOCLAVE, , I, , FILAMENT, WINDING, , CONTACT, , I, , VACUUM, BAG, , fiLAMENT, , 51+E, , PULTRUSION, , I, , SPRAV.UP, , c$J~-$, , I, , dP~~, , I, , COST PREDOMINANT, , STRENGTH PREDOMINANT, , LARGE PART, ,OVER 3.5 fTl, , REINfORCED PLAsncs PART TO BI PROCESSED ,THERMD$ETI, , Table 8-52 Guide to reinforced TS plastics' process selection, , is', , ~, , i)Q, , S·, , ~, , ~, , ~, , ...., '"c:;., , "'I:l, , 00

Page 580 : 8 Plastic Processing, , 562, , Table 8-53, , Comparison of structural foam with five other processes, Foam vs. Sheet Molding, , Foam vs. Sheet Melal, I. Fabrication economy:, , tess assembly time:, , ~, , ~, , -G, , <, , Foam, , V5., , Die Casting, , 1. Much lower tooling, costs, 2. Longer tool life. lower, , tighter dimensional, loler.U\c~s; increased, product integrity: less, , maintenance, 3. No trim dies required, , tinal producl.inspection, , 4. Lighter weight, , time, , 5. Higher impact, resistance, 6. Better sound damping, 7. Belter strength-to-, , 2. Fewer parts required, for assembly, 3. Dent resistance, 4. Elimination of oil, cilnning, , weight, 8. Bener impact resistance, , 5. Greater design freedom, 6. Better sound damping, 7. Reduced damage from, shipping, 8. Reduced tooling costs, for complex., configurations, I. Smaller variety of, , .~, , l!i, , ·s, :::;, , 2., , J., 4., S., , finishes available. such, as chrome or baked, enamel, No R.F.1. and, grounding capabilities, Harder to retrofit to, frame or skins, Thicker wall, Higher tool costs than, with brakeforming, , 50+*, , I. No heat sink, capabilities, 2. No R.F.1. and, grounding capabilities, J. Fewer available finishes, for cosmetic, appearance, 4. Higher finishing costs, 5. Thicker walls, 6. Possible internal voids, , Compound, , Foam vs. Hand Lay-up, Fibergl.", , Foam vs. Injection, Molding, , 1. Unifonn physical, , I. More consistent part, , (Many process similarities, , propenies throughout, the part, 2. Warping and sink, marks reduced or, eliminated, , reproductklO, 2. Lower labor, 3. Simplified assembly, , exist), I. Flexibility for, functional engineering, 2. Better low- 10 mediumvolume economics, J. Lower tooling costs, 4. Better large-pan, capability, S. Bener sound damping, 6. Lower internal stresses, 7. Sink marks redu(..-ed or, , 3. No resin-rich areas to, cause configuration, , 4. Better dimc:nsional, stability, S. More design freedom, 6. More unifonn physical, , problem., 4. Higher impact, resistance, S. Gre3ter inherent, structural capabilities, 6. Lower shipping costs, 7. Large paru more, economical, 8. Lower tooling costs, 9. Bener sound damping, , properties, 7. Better sound damping, , I. Increased finishing, costs (surface swirl), 2. Heat distortion, 3. Thicker wall, 4. Lov.'er physical, propenies, S. Possible internal voids, , I. More prone to heat, distortion, 2. Poorer economies of, , eliminated, 8. Inherent structurJI, strength, , pan size vs. quantity, J. Thicker waJls, 4. Higher tooling costs, , I. Poorer surface finish, , 2. Applica.tion or cosmetic, detail for appearance, part•, J. Longer cycle time, 4. Thicker walls, 5. Poorer high-volume, economics, 6. Less equipment, available for various, shot sizes, , IS to 30, , Up to 30, , .50+, , 1.5 to 20t, , -Even wilb limiCed quantifies., tDepcndiag 011 unil volume and pan size., , design changes. Many products favor injection and compression molding or long runs in, extruders, with their automation capabilities, to minimize labor costs. Often the shape dictates the process, such as centrifugal casting, or filament winding being used for cylindrical products, rotational molding for complex, hollow shapes or extremely large products,, and pultrusion for constant cross-sections requiring extremely high strength and stiffness., These general examples should be considered broadly, since individual processes can, all be designed for a specific product capability to meet performance requirements at the, lowest cost., A further important point is that major costs can be incurred in the operations required after fabricating: trimming, finishing, joining, attaching hardware, and so, on. Observing the following design practices, , will help reduce costs and improve processing and performance, whatever fabrication, method is selected: (1) strive for the simplest shape and form; (2) use the shape of the, product to provide stiffness, reducing its required number of stiffening ribs; (3) combine, the parts into single moldings or extrusions, as much as possible, to minimize assembly, time and eliminate designing fasteners and so, on; (4) use a uniform wall thickness wherever, possible, and make changes in thickness gradually, to reduce stress concentrations; (5) use, shape to satisfy functional needs like slots for, hoisting, hand grips, and pouring; (6) provide, the maximum radii that are consistent with, the functional requirements; and (7) keep, tolerances as liberal as possible, but once in, production aim for tighter tolerances, to save, plastic material and probably reduce production cost.

Page 581 : 8 Plastic Processing, , Minimizing cost is generally an overriding, goal in any application, whether a process, is being selected for a new product application or opportunities are being evaluated for, replacing existing materials and equipment., The major elements of cost include capital, equipment, tooling, labor, and inefficiencies, such as scrap, repairs, waste, and machine, downtime. Each element must be evaluated, before determining the most cost-effective, process from among the available alternatives. To a great extent, the selection of a, process for a new plastic or plastic composite, product will be dictated, or at least restricted,, by the limitations imposed by designs and, cost factors. These factors frequently coincide to indicate the preferred processes. Some, plastics will have a limited scope of processes, available, but others will be more flexible., And products for limited production or small, volumes may require processes with low, capital and tooling costs to make products, economical., In summary, when considering alternative processes for producing plastic and RP, products, the major concerns usually involve, (1) limitations that may be imposed by the, material, because not all materials can be, processed by all methods; (2) limitations imposed by the design, such as the size, singlepiece versus multiple-piece construction, a, closed or open shape, and the level of dimensional and tolerance accuracy required;, (3) the number of products required; and, (4) the available capital equipment in-house, or subcontracted. Certain equipment may be, available, although it may not necessarily be, the one needed for the lowest production, cost. There have always been designing companies that have in-house fabricating capability that discard their existing equipment in, favor of purchasing new equipment in order, to reduce costs. Their approach is to design, the product, put a mold or die around it, and, in turn put a machine around the mold or die, so that maximum cost-efficiency exist., Summary: Matching Process and Plastic, , As reviewed throughout this book it can be, said that there is a basic thought of designing., , 563, , It is that the plastic and the process selected, , profoundly affect the quality and appearance, of the product. For this reason, it is usually unwise to create a design first, and then decide, on material and process; at least consider all, three factors from the start. This seems obvious and logical, but it is frequently ignored in, practice, especially when converting a metal, design to a plastic material., As reviewed there is much to consider. Examples include cooling as the product sets up, results in different shrinkage rates for thicker, versus thinner sections in the different processes. This results in either external waviness, or sink marks, or warpage and internal voids,, as the product contracts. Flat surfaces are difficult to maintain but not impossible to attain, using certain processes. High speed of flow, to fill the cavity of the mold is impeded going, around square corners, so provision for radii, and fillets are important., Attempting to flow past thin sections to fill, wider sections is difficult or may be impossible, because the flow thickens enroute acts, like plaque forming along walls of a human, artery. Even if both of these ills are avoided,, the final result may still contain areas of high, shear stresses invisible to the eye but waiting in ambush to cause failure later under, extreme conditions previously thought to be, well within the material's specifications., However, when beginning to design a, product, it is often wiser to permit the creative mind to freewheel, especially in the initial concept phases. Undue concern for technical aspects may inhibit creativity. After this, initial conceptual stage, though, when ideas, have been set down graphically and as the, design begins to crystallize, it is wise to look, carefully and explore the total aspects determining the potential for the most well established bond of plastic and process., Preliminary consideration of candidate, materials, processes and tooling factors, configuration, thicknesses in section, ribs, bosses,, holes, surface characteristics, color, graphics,, decoration, and assembly methods will begin to impose some discipline on the product, design as it evolves. In the middle and latter phases of the design cycle, two or three, concepts should make their validity apparent to all involved. With luck (logic), one will

Page 582 : Al, , $TEEL, , FILLED, EPOXY, , I, I, , SPRAYED, METAL, , I, , L, , HI, , ELECTROFORM, , I, , PLASTIC, , AL, , I, , PLASTER, , ELECTRO FORM, , I, , AL, , I, , LOVOL, , MEHANITE, , EPOXY, , I, FILLED, , FIBERGLAS, , STEEL, IMACH, HOBBEOI, , I, , HI VOL, , I, , ELECTROFORM, • BACK UP, , BoCu, , I, , I, AL, I, PLASTER, I, EPOXY·, , LOVOl, , CASTAL, , I, , STEEL, , FILLEDIRIM, EPOXY, , I, , I, , I, , I, , STEEL, ) CAST AL, ( MACHINE, H0B8ED, ELE'=TRO MACH. AL, FORM., BACK·UP, KIRKSITE, , I, , HI VOL, , I, , HI VOL, , I, , HI VOL, , LOW VOL, , Table 8-54 Guide to tool to be made, , PLASTER, , I, , WOOD, , I, , LO, , ELECTROFORM, , I, , CASTAl, , I, , I, I, , I, , PLASTIC, , I, , SILICONE, , I, , I, , PLASTIC, ITP OR TSI, , DIP METAL, , elASTOMER, , I, ELASTOMER, , ELASTOMER, , I, , SPRAYED, METAL, , I, , I, , DIPPED METAL, , ELECTRO FORM, , STEEL, , WOOD, , AL, , PLASTIC, , I, , SPRAY METAL, , ELECTROFORMED, , ~..----'I, , SHEET, METAL, , I, , LOVOL, , FlOTO-FOR-;;'~, , I, HI VOL, I, , [, , ~., , '", , ~, , ('), , ~, , '"tl, , is'', '"....., 1=;., , 00, , v., ~

Page 583 : 565, , 8 Plastic Processing, Table 8-55, , Material guide to tool material selection, , ~, 'i>~, , ~.,,,, , ~e, , ro, , 'ro'", , ~e'", , ,;;e, , ~"'~.~, , r}e\, , R'I>, , .tte, , .r:-tfJ, 'S:-~~ r.:"o~ "o~, '\..'l;~, ~«,, ~~..., iJ~~, ~~<S" ....o",CS C,o\\O riP\~" ~e~ ....'<:'e\~ ,<0";;- ~i/>'I>, , f-, , Comments, , 5, , 1, , 3, , 1, , 5, , 1, , 1, , 51, , Prototype. shan run and structural, foam molding., , P·20, , 2, , 2, , 2, , 2, , 3, , 3, , 4, , 4, , Large cavities. cores· eliminate heat, treal process and associated warpage, and cracking., , H·13, , 3, , 2, , 4, , 2, , 3, , 5, , 4, , 4, , Thermallaligue resistance. pollsnatJility., Mostly chosen tor zinc. aluminum die, casting., , 4205.5., , 3, , 2, , 5, , 2, , 1, , 2, , 2, , 4, , Corrosion resistance (poor thermal, conductivity)., , P·6, , 4, , 4, , 2, , 2, , 3, , 3, , 4, , 4, , Easily machinable. Welds. repairs welt., Low carton steel. not dimensionally, stable in heat Irealment., , 0·1, , 3, , 2, , 2, , 2, , 3, , 2, , 3, , 3, , Oil hardening' pins. small insens. elc., , S·7, , 3, , 5, , 3, , 3, , 3, , 3, , 2, , 4, , Shock resisting sleel • long cores· where, subjected to mechanical loads, (slides. lifters), , A·2, , 3, , 4, , 4, , 4, , 3, , 2, , 4, , 1, , GoOd abrasion resistance. pOllshab,hly., Air hardentng • heat trea: siable., , 0·2, , 1, , 4, , 4, , 5, , 3, , 1, , 4, , 1, , Aluminum, , 1--', , --, , E~lreme abrasion resislance. Used as, gale insens. elc. for filled resin, app'icalions., , Range: 5 (best) to 1 (poorest), Table 8-56 Interrelating to the plastics machinery and equipment sector, cor~, , PONENTS, , Hydraulles jPUmII~v-...C)«Jxfe~"PIsfo"", , Nozzles, , Shutoff Valves, GiiS Injection Equipment, Quickmold..clamping Systems, , UPSTREAM AUXILIARY EQU!Ft.1ENT, , Bulk Material Processing, Loaders, Feeders, Blenders, Dryers, Kneaders, Magnetic Separators, Preformers, Preheaters (HIJII FNqIMnCr" SI:NW Type), , OTHER PRIMARY, MACHINERY, , Thennofonning, , Compression Molding, Transfer Presses, I, , DOWNSTRE"Ai1 AUXILIARY EQu!prI1ENT, , OFF LINE EQUIPMENT, COMPONENTS, , Process Measurement, Screws, 8lmetalilc Barrals & Liners, Instruments & Controls, Heaters & H••ting Elements, Motors & Drives, On-lIne Inspection Devices, , Weldet'1l, , ----, , Cleaning Ovens & Baths, Prindng & Stamping Equipment, Assembly Equipment, Testing &1nspectfon Equipment, , "'-', T_, , EIecbIcaI V.lIes, , SCAlP Rec:overy ... Granulators, Deflashers, , Gauge Inspection, Pelletlzera I Olcers, Cut off Equipment, Vacuum Sizing Equipment, Takeoff equipment, Slitters, , DOWNSTREAf1 AUXILIARY EQUIPr,1ENT, , Fihratlon, Gear Pumps, Dies, Feed Blocks, Static Mixers, Continuous Conveyors

Page 584 : 566, , 8 Plastic Processing, , then be so obviously right that it will stand, out without question. When seeking the best, choice among candidate materials and processes the possibilities can become numerous, and as time passes they will become even, more apparent., In narrowing the options and your experience has not developed, it is best to seek, advice from the appropriate people. When, choosing a fabricator, seek out those with experience close to the materials, end-use categories and sizes of your project. When pro-, , totype products are made, test them under, the worst possible conditions, and if possible, simulating a longer time frame than the, product is designed to withstand in normal, service., The processing information (as well as, material information) presented in this and, other chapters has provided a variety of useful selection guides (see INDEX, Selection, guide for guides throughout this book). Additional process selection guides are in the, following Tables 8-45 to 8-55.

Page 585 : 9, Cost Estimating, , Introduction, , The cost to produce products involves, many different categories such as materials, and equipment, method of purchasing materials and equipment, additives used, and fabricating costs (Fig. 9-1). All these factors have, a direct effect on a designed product even, though the designer is not involved in most, of them. However it could very easily influence the expected initial cost that the designer had to include in the design evaluation., As experience tells one, cost of material can, be very variable., Interesting is the fact that the actual time, and cost to design products may take less, than 5% of the total time and cost to fabricate products. Even though this is a relatively small percentage of the overall operation, it has a direct and important influence, performancewise and costwise on the success, or failure of fabricating products., A major cost advantage for fabricating products is their usual low processing cost. The, most expensive part of the product is the, cost of plastic materials. Since the material, value in a plastic product is roughly up to, one-half (possibly up to 80%) of its overall, cost, it becomes important to select a candidate material with extraordinary care particularly on long production runs. Cost to fabricate using most processes and particularly, , in long runs usually represents about 5 % of, total cost. Thus with the product to be fabricated in-house, it can be economically beneficial to replace existing equipment to meet a, lower product cost, as many do. The expensive equipment cost would be justifiable., In purchasing equipment consider what, John Ruskin (1819-1900) stated that it is unwise to pay too much, but it is unwise to pay, too little unless you know that the machine is, capable of meeting the requirements you set., It is a popular misconception that plastics, are cheap materials. There are low cost types, but there are also the more expensive types., Important that one recognizes that it is possible to process a more expensive plastic because it provides for a lower processing cost, (1-10,20,37,64)., To put plastics in its proper cost perspective, it is usually best to compare materials based on volume rather than the weight, used. On a weight basis most plastics can be, more expensive than steel, and only slightly, less than aluminum (Fig. 9-2). Examples of, other cost factors to consider are reviewed in, Figs. 9-3 to 9-5., Cost-effective production of high-quality, plastic products is the prime target of the plastic processor. As an example, the continually, growing pressure from the competition demands the choice of IMMs with the smallest, possible injection and clamping units in order

Page 586 : 9 Cost Estimating, , 568, , Sales, , Capacity, Cost of sales, Mot ....ation costs, Overhead, , ~, , Order, process, , -, , Capacity, Labor costs, Eqpl.lmatl. costs, Overhead, , Production, , Shipping/, receiving, , Capacity, Labor costs, MatI. costs, Maintenance costs, Motivation costs, Oual. assur. costs, Downtime history, Downtime costs, Eqpl. costs, OSHA costs, Overhead, , Capacity, Labor costs, Eqpt. costs, Motivation costs, OSHA costs, Inventory costs, Inspection costs, Overhead, , ""-, , Purchasing, , Capacity, Labor costs, Ordering costs, Motivation costs, Overhead, , Fig. 9-1, , Examples of cost factors., , to minimize the product costs by reducing investment and (important) operation costs. At, the same time, however, these savings must, not be made at the expense of product quality. This example is applicable to other processes such as extrusion, blow molding, and, thermoforming., To obtain the equipment needed a simple basic approach can be used. Design the, product determining the plastic material to, , be used. Next design and plan building the, mold or die to meet the product requirements. Now you are ready to determine the, fabricating equipment required. It will be, based on two factors: (1) the mold or die size, and movements it requires and (2) the plastic material processing requirements. Thus, the equipment purchased will only meet the, requirements it has to meet. Probably one, of the most difficult aspects of purchasing, Metals, , 4, , 3, Q), , Thermoplastics, , E, :I, , ;g, 'lii, , 2, , 8, '0, o, i, a:, , Thermosets, 1, , ~, « "", u; '" ", '"u '"e! ~, Ql, , is, "-, , o!!, , '"zci, , (]), , ..., , 0, , '?, (j), Ql, , U5, , b, N, , ", , Fig. 9-2, , A general plastic cost comparison, based on volume, for a general classification of materials.

Page 587 : 569, , 9 Cost Estimating, , t, , OJ, til, , ttl, , OJ, , ~, , U, C, , c, o, , :;::;, ttl, ....,, ~, , c, , OJ, , u, , c, , o, u, ~, , OJ, , Plastic material cost r i s e _, Fig. 9-3 Example why fillers become more attractive as plastic prices go up., , equipment is ensuring that the quotes solicit from different machine manufacturers, are comparable. With the preparation of, a complete detailed specification, particularly when unusual requirements exist on, what is required, the quotes will be more, compatible., , 6, , Size of container, Special, size, containers, , Bo)(, , Truck, , Rail car, , Premium rates over bulk railcar, 5, , $20 billion annual sales, used by over 22,000 plants, , v~, Ifrn, LLLJ, , Drum, , Bag, , When designing a plastic product, it is frequently desirable to compute an approximate, cost in order to determine whether the considered design is within desired economical, limits. Based on the preliminary design configuration and type of material to be used,, a determination has to be made regarding, the fabricating process to be used. Considerations used include the number of products to be made and probably a time schedule that has to be met. There may be options, where different plastics are being considered, and also different processes. Ideally if history, exists on similar products, available data can, be used as a guide to develop a cost analysis., If the designer is not familiar with fabricating plastic products, the usual practice is, to contact a reliable fabricator(s), obtain a, rough estimate(s), and proceed on the basis, of this information to either redesign or finish, the design on hand. This is time consuming,, and on many occasions even this step is neglected because of time not available. To be, efficient in designing products a qualified person should be included who is familiar with, the different processing techniques., , d, , 250 to, , 350lb, , Processing Number of, plants, , 65%, , "I', , 19%, , 7%, , 91%, , employee.s, 1 to 19, 20 to 49, 50 to 99, , 20%, , of, sales, , I-----~, 1-, , -rol0001b, , ~ 40,000 Ib, , 6':, , td, , 150,000 to, , ~ro;:!;:::===~b!J;=;I 200,OOOIb, , 9% of processing, plants (100 + employees), , Fig. 9-4 Estimated plastic dollar purchases by plant size and size of containers., , 80%, , of, sales

Page 588 : 9 Cost Estimating, , 570, , High Volume Parts, , Precision ·Parts, , Power 14%, Water 6%, Labor 2%, , Machine, Operation 24%, , Fig.9-5, , Cost example of injection molding high-volume and precision products., , What may be an inefficient approach to, costing a process is for the design group to, have a specific manufacturing operation inhouse. The companies target is to use their, equipment that includes certain sizes. Perhaps the only jobs they take can only fit in, their equipment which is OK. However, if, they imprevize there is the possibility that, a competitor will provide lower cost products using just the appropriate equipment. In, the past many decades for companies with, the big production products, they design the, products, the molds or dies are designed to, produce the products, and literally they design the manufacturing equipment around, the mold or die. In turn they order new, equipment to meet their specifications usually replacing in-house existing equipment., Many of these companies at that time, as at, present have better qualified people in designing equipment than certain equipment, producers., The following information concerns injection molding a product. It is a practical and, very simplified guide of costing. It covers, , the main and significant factors that include, 85-90% of product direct value and should, suffice for the requirements of a product designer when various designs are comparatively evaluated. The two basic ingredients, that determine the value of a plastic product, are the cost of the plastic material and the, cost of fabrication., Calculating the volume (in. 3 or cm3 ) of the, product and multiplying it by cost per the volume unit derives the cost of the plastic material content. Once the volumes of the product, are established, one will utilize these data as, the basis for obtaining the remainder of the, information., Cost of processing can start by taking the, thickest portion of the product that will determine the processing time required. With, a contemplated yearly activity and an ordering frequency of say every 45 days, one can, tentatively decide on the number of cavities, needed when molds are involved. The number of cavities should be such that it would, take the 45-day requirement to produce in, two hundred hours. Thus the number of

Page 589 : 9 Cost Estimating, cavities times the volume per cavity leads to, the machine size., There are many cases in which the volume, of material for all the cavities is small and, the projected areas of the cavities are large., In this example, the choice of machine size, is governed by the tonnage of the clamp required to keep the mold from opening during, the fabricating process (3)., As an example for most plastics the usual, is 2-5 tons/in. 2 . For certain plastics pressure, could go up to 15 tons/in. 2 . Both the material, volume and tonnage have to be satisfied while, deciding on a machine size and, therefore,, machine cost per hour. The larger press of, the two requirements should prevail. When, machine size in terms of volume and tonnage, is decided upon, the molding cost can now be, established. Molding cost per hour divided, by pieces per hour gives molding cost per, piece., During the checking of volume against the, press tonnage, only 70% of the machine volumetric capacity should be considered as the, useful volume. The reason for this downgrading is that the heating capacity is based, on polystyrene and most other materials require more energy for plasticating than does, polystyrene. If the calculated volume for a, product is more than 70% of rating, the selection calls for a higher tonnage press., When using other processes, such as extrusion, blow molding, rotational molding, etc.,, cost of fabrication is usually related to the size, of the product and output rate. Those familiar with any of these processes can easily and, quickly provide cost information. What exists and required is experience in the different, processes. For the designer not familiar with, processes relying on the best-cost analysis can, be a problem particularly if time does not, exist to contact different fabricators. Recognize that those providing you a cost includes, in their estimate factors such as their interest in obtaining the job, the odds of obtaining the job, how busy is their operation, are, they helping a competitor, etc. Final quoted, costs may differ from approximate cost estimates because quotations will include such, features as close tolerances and special performance requirements not previously listed., , 571, , We now have the means of obtaining the, material cost as well as the manufacturing, cost per piece. Consider the sum of these, two costs multiplied by 1.2 gives the complete cost. The 20% addition is to cover other, elements of expense (probably accidentally, not included) as well as a safety factor. The, description of the method of cost computing, may give the impression of a lengthy procedure; however, the actual performance ofthe, estimating will prove brief and will be worthwhile in doing. The described cost estimates, are intended for comparative design evaluation., Effective Control, , Properly training employees will help (and, even eliminate) variable costs. In addition to, other forms of training, such as shop floor, training, seminars, video, and reading, implementing an interactive in-house training program becomes an important cost-effective, form of educating the workforce. Effective, training is essential to the survival and growth, in today's world of plastics. Interactive training has proved to be the best way to provide, employees with skills and knowledge that ultimately creates a more confident and productive workforce. An example of this service is available through different schools, and organizations such as the University, of Massachusetts-Lowell or Penn State at, Behrend, PA., Technical Cost Modeling, , A wide range of processes, materials, and, economic consequences characterizes the, adoption of any technology for producing, manufactured products. Although considerable talent can be brought to bear on the, processing and designing aspects, economic, questions can remain. Cost problems are particularly acute when the technology that will, be employed is not fully understood, as much, of cost analysis is based on historical data,, past experience, and individual accounting, practices.

Page 590 : 572, , 9 Cost Estimating, , Historically, technologies have been introduced on the shop floor incrementally,, with their economic consequences measured, directly. Although incorporating technical, changes in the plant to test their viability, may have been appropriate in the past, it is, now economically infeasible to explore today's wide range of alternatives in this fashion. Technical cost modeling (TCM) has thus, been developed as a method for analyzing the, economics of alternative manufacturing processes without the prohibitive economic burden of trial-and-error innovation and process, optimization (3, 20)., TCM is an extension of conventional process modeling that particularly emphasizes, capturing the cost implications of process, variables and economic parameters. By coordinating cost estimates with processing, knowledge, critical assumptions (processing rates, energy used, materials consumed,, scrap, etc.) can be made to interact in a consistent, logical, and accurate framework of, economic analysis, producing cost estimates, under a wide range of conditions., For example, TCM can be used to determine the plastic process that is best for production without extensive expenditures of, capital and time. Not only can TCM be used, to establish direct comparisons between processes, but it can also determine the ultimate, performance of a particular process, as well, as identifying the limiting process steps and, parameters., TCM uses an approach to cost estimating in which each of the elements that contribute to the total cost is estimated individually. These individual estimates are derived, from basic principles and the manufacturing, process. This reduces the complex problem, of cost analysis to a series of simpler estimating problems and brings processing expertise, rather than intuition to bear on solving these, problems., In dividing cost into its contributing elements the first distinction to be made is that, some cost elements depend upon the number of products produced annually, whereas, others do not. For example, the cost contribution of the plastic is the same regardless, of the number of items produced, unless the, , material price is discounted because of high, volume. On the other hand, the per-piece, cost of tooling will vary with changes in production volume that is influenced by maintenance, wear, etc. These two types of cost elements, which are called the variable and fixed, costs, respectively, create a natural division of, the elements of manufacturing product cost., Basically the variable cost elements are, those elements of piece cost whose values, are dependent on the number of pieces produced. For most plastics fabrication processes, the principal variable cost elements are the, material, direct labor, and energy costs., Fixed costs are those elements of piece cost, that are a function of the annual production, volume. Fixed costs are called fixed because, they typically represent one-time capital investments (buildings, silos, processing machines, etc.) or annual expenses unaffected, by the number of products produced (building rent, engineering support, administrative, personnel, etc.). Typically, these costs are distributed over the total number of products, produced in a given period. For plastics processes the principal elements are main machine cost, auxiliary equipment cost, tooling, cost, building cost, overhead labor cost, maintenance cost, and the cost of capital., To demonstrate the use of such a comparative cost analysis, the production of a panel, was analyzed according to different processes, (Fig. 9-6). In these case studies the following conditions existed: (1) the panels measured 61 x 91 cm (24 x 36 in.) with the wall, thickness dictated by the process and part requirements so that the weights of the panels differed; (2) production was at a level of, 40,000/yr.; (3) the plastics for all panels were, of the same type, except that different grades, had to be used, based on the process requirements, so that costs changed; (4) each panel, received one coat of paint, except that the, structural foam also had a primer coating; and, (5) costs were allocated as needed to those, processes that required trimming and other, secondary operations., TCM can keep cost data current, based on, cost changes from day to day, region to region, and so on. Of course, the means of keeping these data updated require that those

Page 591 : 9 Cost Estimating, , dollars; use the best material for the application. There are molds that run a few, hundreds to many millions. Design and construction that relates to cost of a mold or die, depends on the lifetime required., An unwritten rule says that a mold or die, should cost almost half the cost of the basic, machine (injection, extrusion, blow molding,, etc.). If it does not then something is wrong, such as you probably have an oversized machine for the job for the lower cost mold or, die., , $ 35, $ 30, , §, , $10, , ~ $15 ~~'4:l, ii:, , $10, $5, , c::J, , Material, , c::J, Finishing, , 573, , E::J, Overhead, , IE], , Equipment, , IZ.W, , Labor, , Processes: Inj = Injection molding, Foam = Structural foam molding, T-Form = Thermoforming, Blow = Blow molding, , Fig.9-6 Cost comparison of panel production using TCM program that shows blow molding with, the lowest product cost., , costs be obtained on a regular basis and incorporated into the TCM., , MoldlDie Cost, , Cost breakdown of a high production mold, or die is approximately as follows: Material, cost used to about 12 to 20%, design about, 5 to 10%, mold building hours about 40 to, 60%, and profit at about 5 to 10%. In general they are very expensive with the major, cost principally in machine building labor., The proper choice of materials of construction for their different parts is paramount, to quality, performance, and longevity of a, mold/die. Add good machinability of component metal parts, material which will accept, the desired finish (polished, textured, etc.),, ability to transfer heat rapidly and evenly, capability of sustained production without constant maintenance, etc., Using low cost material to meet high, performance requirements will compromise, their integrity. As an example, the cost of a, mold cavity and core materials, for more than, 90% of the molds, is less than 5% of the total mold cost. Thus it does not make sense, to compromise mold integrity to save a few, , Cost Analysis Method, , Cost-Benefit Analysis, CBA is the economic analysis, such as with, design developments and research programs,, in which both the inputs to produce the intervention (or costs) and its consequences or, benefits are expressed in monetary terms of, net savings or a benefit-cost ratio. A positive net saving or a benefit-cost ration greater, than one indicates the intervention saves, money., , Direct and Indirect Cost, They are the operating quality costs of prevention and appraisal that are considered to, be controllable quality costs. Add that in year, 2000 the IRS decided to let companies deduct, ISO 9000 costs as a business expense. Also, there are the internal and external failure, costs. As the controllable cost of prevention, and appraisal increases, the uncontrollable, cost of internal and external failure decreases., At some point the cost of prevention and appraising defective product exceeds the cost of, correcting for the product failure. This point, is the optimum operating quality cost., In addition to the direct operating quality costs, the indirect quality costs and their, effect on the total cost curve must be considered. Indirect quality costs can be divided, into three categories: customer-incurred, quality costs, customer-dissatisfaction quality costs, and loss-of-reputation costs. These

Page 592 : 574, , 9 Cost Estimating, , intangible, indirect quality costs are difficult, to measure; however, they do effect the total quality cost curve. This influence is apparent when the indirect quality costs are added, to the direct cost curve. When the optimum, point increases, it indicates the need for a, lower product defect level. A lower product, defect level can be obtained by increasing the, prevention and appraisal costs, which subsequently lowers the external failure costs. A, lower external failure has a desirable influence on the direct costs. The measurement of, the actual indirect costs may be impossible., However, a knowledge that these costs exist, and their relationship to the direct costs can, aid in their control (3)., Cost Effectiveness, Minimizing costs is generally an overriding, goal in any application, whether designing a, product, selecting a material, or a process is, being selected for a new product or opportunities are being evaluated for replacing existing materials. The major elements of cost, are, equipment and material with those that could, be called inefficiencies such as scrap, repairs,, waste, and machine downtime. Even though, the scrap is recycled, it cost to granulate, handle, and possible slow down the line. Each of, these elements must be evaluated before determining the most cost-effective approach., Cost-Effectiveness Analysis, CEA is the economic analysis in which the, consequences or effects of intervention are, expressed in improvements such as fabricating successful products, years of service, etc., Cost Estimating, Estimating is a critical aspect that ranges, from designing to fabrication. Particularly in, fabrication it is often practiced with very little, logic. It is shrouded in mystery and rarely discussed by processors. Indeed, it is considered, among the dullest of topics. It is extraordinary, if one estimate in ten produces a successful, , bid. In other words, a 90% failure rate is terrific. No wonder estimating seems like some, bizarre sacrificial rite. That does not include, those estimates you just go through the motions of preparing because another company, is going through the motions of getting three, bids, and you have no chance at all of landing, the job. Or that company's supplier is overloaded or had an accident, so the customer, needs "temporary" help and you know it; in, which case provide the high end of the bid, (to be safe)., But what more directly represents the, heart of a fabricator's business than estimating? You are pulling together every facet of, your operation, distilling it, putting numbers, on it, and putting your company on the "line.", You are stating that this is what we can do, and, this is what we must charge to make a normal, profit. There are probably as many estimating, techniques as there are estimators., Cost Estimating Factor, Much contemporary estimating follows, very vague procedures. The number of factors assembled to reach the appropriate figures is sometimes alarmingly small. Some, may not consider scrap, coloring, setup time, with trial and error, and so on to mention, some of the more obvious omissions. Some, estimates, that can work, are simple creations such as determining the part volume, or weight, cost of plastic, and processing time;, scribbling down some numbers; and adding a, fudge factor (possible a little prayer). Some, companies do not even have their own standard forms whereby they could develop some, useful history. Of course what influences how, one estimates generally relates to the fact that, plastic processing is a highly competitive industry, so logically spend the time to prepare, quotes where a payoff has a possibility to, occur., Cost Reduction, When it is possible, observing the following usual practices for extrusion will help to, reduce costs (relate them to your process):

Page 593 : 9 Cost Estimating, , (1) strive for the simplest shape and form;, (2) combine parts into single extrusions or, use more than one die to extrude products/use multiple die heads and openings;, (3) make gradual changes in thickness to reduce frozen stress. (4) where bends occur,, use maximum permissible radii. (5) purchase, plastic material as economical as possible., (6) keep customers tolerance as liberal as possible, but once in production aim for tighter, tolerances to save material costs and also, probably reduce production costs., Cost Target, , The production flexibility of the plastics, fabrication processes is often the single most, important economic factor in producing a, product. The products size, shape, complexity, strength, orientation, etc. can be primary, determinants but not impossible to produce., Thus, processing takes on the task of doing, the "impossible" at the lowest cost (Fig. 9-7)., Economics can be improved by targeting, various factors. (1) reduction in the use of material by minimizing tolerances. (2) improvement in product quality in terms of strength, and/or other mechanical-physical characteristics, (3) reduction in setting-up times of, start-up aids and automation systems, and, (4) savings in electricity consumption by the, optimization of the plasticizing and the use of, efficient heating and cooling systems., Variable Cost, , Processing cost variations may be due to, one or more of the following factors: (1), , 575, , improper or unattainable performance requirements; (2) improper plastic selection;, (3) improper in-line and off-line hardware, and control selections; (4) improper selection, of the complete line; (5) improper collection, and/or handling at the end of the line; and, (6) improper setup for testing, quality control, and troubleshooting., Energy Cost, , Cost savings via energy conservation can, be considered from the viewpoints of machine operation, the plastic material, and the, finished product. Fabricating machines are, usually energy intensive. Thus it becomes, obvious to reduce the energy requirements, where it is possible starting with the purchase, of any equipment in the line that provides reducing energy consumption., Product Cost, , In a production line that has a relatively, long run, the cost for equipment in relationship to producing the product including, its financial amortization, usually is about, 5% with probably maximum of 10% Plastic, material cost could be at about 50% with, as high as 80% for high volume production., The other costs include power, water, labor,, overhead and taxes. With precision, short, runs, costs could be equipmentwise at 20 to, 30%, material 45 to 50%. Thus, as it is usually, stated, do not buy equipment just because it, cost less since more profit could occur with, the more expensive equipment; study what, is to be purchased. Of course the reverse, is possibly true. So, you the buyer, have to, know what you want and are ordering to a, specification properly determined based on, the designed product requirements., Designing Product, , Performance requirement _, , Fig. 9-7 Target to meet performance requirements at the lowest cost., , In product design there has always been, the desire to use less of any material, because, the result is usually a lower-cost product. On, the other side of the issue is the use of more

Page 594 : 9 Cost Estimating, , 576, , material to provide for a higher design safety, factor beyond what is required. Thus, unfortunately, there are designs using more material than needed. It is inexperience in designing with plastics that causes this problem., Many designers lack the knowledge of at, least relating a material's performance to the, processing variables that directly influence, safety factors and the amount of a plastic, to be used. With the flexibility that exists, in designing with plastics, there are different, approaches that may be used to reduce, product volume or weight, such as applying, different shapes like internal ribbing, corrugations, sandwich structures, and orienting or, prestretching., All this activity is aimed at producing products that use less in the way of materials and, in turn let less material enter the solid-waste, stream. Some designers have habitually listed, in product design specifications that specific, environmental requirements should be met., A designer sometimes has an opportunity to, use a material that provides no problem in the, solid-waste stream or to use a design that lets, lower-cost recycled plastics be used. In fact,, blends of virgin (not previously processed), plastics with recycled plastics could permit, the meeting of required product performance, and environmental requirements (Chapter 6,, RECYCLING)., This approach has been used for the past, century, but now there will be more use of, it, as more and more recycled plastics become available. However, the designer must, 10, , take into account the potential lower performances that could occur with recycled, plastics. Interesting that at times recycled, materials is more expensive than virgin plastics. They are used in many cases since there, is a regulation (government or industry), that states the product has to contain some, amount, such as 50 wt%, ofrecycled plastics., The recycled plastic will also have a degree, of different contaminants that would eliminate its use in certain devices or products,, such as in medicine, electronics, and food, packaging. However, within these market applications there are acceptable designs with, three-layer coextruded, coinjected, or laminated structures having the contaminated, plastic as the center layer, isolated by "clean", plastics around it and no migration occurring., Another method of reducing the quantity, of plastics that has been used in certain products is to use engineered plastics with higher, performance than the lower-cost commodity, plastics. When applicable, this approach permits using less material to compensate for its, higher cost. With a thinner-walled construction there could also be additional cost savings, since less processing heat, pressure, and, time cycle is required., Energy, To produce and process plastics requires, less energy than practically any other material (Fig'. 9-8). In contrast, glass requires much, more energy than any of the materials listed., , o, _, , Fig. 9-8, , Fuel, Feedstock, , Energy requirements for different materials.

Page 595 : 9 Cost Estimating, , 577, , 25,000 . . . . - - - - - - - -- - -- - - - - - - - - - - - - - -- - -------,, , 20,000, , :<>, §, , 15,000, , e>l-, , :;;'", c:, , w, , 10,000, , 5,000, , Wastes, , Wastes, waste, , Fig. 9·9, , Incineration and energy output., , Solid Waste, , rubbers, clarity film LLDPE vs. LDPE and, , Only about 7 wt% of the solid waste produced are plastics. Incinerating, recycling,, landfill, and other methods are used to handle the worldwide plastics (and other materials) waste problems. Incineration of plastics, produces a high energy content. For example, polystyrene has nearly twice the energy, content of coal, without its ensuing problems, of ash, acid rain pollution, or harmful emissions. Plastics are just one of many materials, that produce solid waste, and, as with other, materials, there are good and bad disposal solutions. As shown in Fig. 9-9, plastic scrap and, waste does provide cost savings when compared to other materials., , This action will continue and expand as, is evident by new plastics being developed., DuPont's iron and cobalt single-site catalyst system that makes HDPE with higher, melting points and performances such as, adhesion, barrier performances, etc. Other, examples include the expanding process techniques, and applications that are always, on the next horizon. Thus to help plastics expand, there has been and will continue to exist plastic-to-plastic competition, to meet all kinds of requirements, including high and safe performance in all kinds, of environments. Recognize that in the future different basic raw materials will be, used in addition to those already being, used., In general, companies in the plastics, industry can obtain patents upon the processes they use to manufacture new materials (Chapter4,DESIGNINGAND LEGAL, MATTER). However, since a processed, patent discloses a great deal of information that may be useful to competitors even, though they are not using or do not wish to, use the exact process as that described in the, patent. Some firms in the industry do not, , Competition, , For over a century plastics have successfully competed with other materials in, old and new applications providing costperformance advantages, etc. In fact within, the plastic industry there is extensive competition where one plastic competes with another plastic. Examples include many such, as thermoplastic elastomers vs. thermoset, , Pvc.

Page 596 : 578, , 9 Cost Estimating, , patent each new process (or material) in order to maintain strict secrecy. To prepare a, practical fool proof patent requires lots of, money., Plastic materials' manufacturing is primarily a large-volume, low-cost, low-unit, profit margin business with great overall, economies. The plastics generally compete, with each other on a "money value" basis, in which an economic analysis takes into account the differing densities of the various, plastics in order to judge them on a cost per, pound or volume basis., Conventionally, we think of competition as, being between essentially similar products on, a price, quality, and service basis. In plastics,, competition is much broader and often more, intense., Competition, at each stage in the plastics industry, is in their raw materials. Many, monomers can be made from alternate raw, materials such as polyvinyl chloride that may, begin with either ethylene or acetylene. Most, plastic products may be made from a variety of plastics such as pipe that may be extruded from PVC, polyethylene, ABS, and, so on., Competition is also within processes. Both, plastics and finished products may be made, by entirely different routes, requiring different procedures and different equipment. For, example, polyvinyl chloride may be made by, , three different processes and thermoplastic, sheets may be cast, injection molded, or extruded. Plastic competition is within the industry both locally and particularly international as well (210, 211). Plastics can compete, with the products of other industries for the, same application; for example, against wood,, metal, and concrete in construction application, against natural fibers for textiles, and, against animal glue in the adhesives field. In, addition, plastics is an international business, with growing industries in other countries vying with USA firms for markets both abroad, and at home., An example of the way in which process competition works in the manufacture, of plastics is the story of acrylonitrile. The, first process for the production of this plastic was based upon the reaction between hydrogen cyanide and acetylene, both hard to, handle, poisonous, and explosive chemicals., The raw material costs were relatively low as, compared to materials for other monomers,, but the plant investment and manufacturing, costs were too high. As a result, originally, acrylonitrile monomer (1950s) sold for about, 30 cents per pound and the future of the material looked dim as other plastics such as, polyethylene became available at much lower, prices due to their lower production costs., During the late 1950's, chemists at the, Standard Oil Company of Ohio worked, , I, , Sales volume, , "5, o, Q), , ~, $, , !, , Time- +, , Fig.9·10 Example of factors to consider in marketing a product.

Page 597 : 9 Cost Estimating, , 579, , Fig. 9-13, profit., , Any other operation not showing a, , TiME _ _, , Fig.9-11, , Example for the life of a product., , on the development of a new process for, the manufacture of acrylonitrile. In 1961,, SOHIO built the first plant using their new, process to produce acrylonitrile from propylene and ammonia, both materials being, readily available and easy to handle. This new, process used more expensive raw materials, than the old one, but required only one production operation to produce the acrylonitrile monomer. This meant lower plant investment and lower manufacturing costs, and the, price of the monomer went down to around, 14 cents per pound., This new lower price changed the comparative economic advantages of some of the, newer plastics and led to a search for new uses, of acrylonitrile and its polymers and copolymers. A new route to Dacron was developed by du Pont using this lower priced acrylonitrile and the use of acrylic fabrics grew, rapidly. There was also an increase in uses of, ABS and acrylonitrile production capacity., On the other side of costs, the higher priced, plastics continue to be marketable since they, meet required performances for certain products. As an example polyaryletherketone, Debugging, Phase, , 3, ~, , 0::, , ~, , :>, , ~, , u.., , Wear Our, Phase, , Chance Failure, Phase, , I', , I', Time It), , Fig.9-12 Life-history curve., , (PAEK) plastic that cost $40/lb was being, market in dental implants, bone replacement, joints, and components for the hip, elbow,, finger, knee, spine, and other body products., And so all these type of actions continue in, the plastic industry worldwide., Quotation, , Document quote that states the selling, price and other sales conditions of a material,, product, etc. has different meanings. Did, you know that by law if someone reports, that verbally the vender made statements, such as "buy this injection molding machine, and all you have to do is push a button to, make good/acceptable products" the vender, is legally in trouble. Even if that person wins, the case (rare), it will be very expensive to, pay for the court case., Market, , Throughout this book reviews have been, made on products that literally are used in, many different markets. This action fits the, usual statement that "this is the World of, Plastics" Important with all the cost analysis, is that profits have to be included. Influencing, factors that involve profits are summarized, in Figs. 9-10 to 9-13. The life-history curve,, Fig. 9-11, shows the basic format of a typical, product cycle for an infinite number of products. It is also called a "bathtub" curve.

Page 598 : 10 _ _ __, Summary, , Overview, , Design is essentially an exercise in predicting performance. The designer of plastic products must therefore be knowledgeable in such behavioral responses of plastics, as those to mechanical and environmental, stresses. This book presented important basic, concepts of plastics that define their range of, design behaviors. It provides the background, needed to understand performance analysis, and the design methods available to the performing designer, as well as for those less, familiar with conventional design and engineering practices. Products made of plastics, can then be designed using the logical approach that also applies to such other materials as steel, wood, glass, and concrete,, which have their own specific techniques of, behaviors and analysis. The design approach, includes factors such as the proper product, evaluation (Table 10-1) to the release of the, product (Table 10-2)., Many plastic products seen in everyday life, are not required to undergo sophisticated design analysis because they are not required, to withstand high static and dynamic loads, (Chapter 2). Examples include containers,, cups, toys (Fig. 10-1), boxes, housings for, computers, radios, televisions and the like,, electric iron (Fig. 10-2), recreational products (Figs. 10-3 and 10-4) and nonstructural, , or secondary structural products of various, kinds like the interiors in buildings, automobiles, and aircraft. In fact many of these only, require a practical approach (Fig. 1-4)., Designing is, to a high degree, intuitive, and creative, but at the same time empirical and technically influenced. An inspired, idea alone will not result in a successful design; experience plays an important part, that, can easily be developed. An understanding, of one's materials and a ready acquaintance, with the relevant processing technologies are, essential for converting an idea to an actual, product. In addition, certain basic tools are, needed, such as those for computation and, measurement to testing of prototypes and/or, fabricated products to ensure that product, performance requirements are met., For these reasons design is spoken as having to be appropriate to the materials of, its construction, its methods of manufacture, and the product performances involved., Where all these aspects can be closely interwoven, plastics are able to solve design problems efficiently in ways that are economically, advantageous., Design Success, , Plastics provide the designer with many, different materials and processes useful

Page 599 : 581, , 10 Summary, Table 10-1, , Product evaluation, , toward meeting many of the varying types, of product requirements. They are also capable of producing from simple to complex, shapes and are economically beneficial. They, can be made to have a long life, they resist, corrosive environments, and are recyclable,, degradable, and can meet practically any performance requirements. They also permit the, fabrication of products whose manufacturing, would be difficult if not impossible in other, materials. Different design approaches are, used such as those described in Figs. 10-5, to 10-8., However, designers must routinely keep, up to date on developments with the more, useful plastics and acquire additional inforTable 10-2, , Product release evaluation, , IPRODUCT RELEASE I, I, , I, , ENSURE, MEETING, ALL PRODUCT, FUNCTIONS, , I, SET, UP VALUE, ANALYSIS (VA), , I, AFTER START OF, PRODUCTION, ANALVZE, COMPLETE DESIGN (AGAIN), TO CHANGE, DESIGN/PRODUCTION/SAFETY, FACTORS IN ORDER TO, REDUCE COSTS, , Fig. 10·1, , Toys all around us., , mation on how the plastics behave during, processing. The emphasis throughout this, book has been that it is not difficult to design, with plastics and to produce many different, sizes and shapes of thermoplastic and thermoset commodities and engineering plastics,, whether unreinforced or reinforced., Some plastics can be worked by many different processes, but others require a specific, process (Fig. 10-9). Process selection can take, place before material selection, when a range, of materials may be available, or made first, to meet performance requirements and only, then have the applicable process or processes, chosen. (Chapter 7, SELECTING PLASTIC, and Chapter 8, SELECTING PROCESS), Usually, in the latter situation only one special process can be used to provide the best, performance-to-cost advantages. A particular design group may have its own processing, capabilities. Unfortunately, some operations, use just whatever equipment is available., This situation could either be very unprofitable, limit profitability, or restrict product

Page 600 : 582, , 10 Summary, , Fig. 10-2 View of an electric iron showing their use of different plastics that use different fabricating, processes., , performance. It is important to recognize that, the fabrication process can markedly influence all aspects of product performance, including cost., Compared to other material-based industries, plastics have enjoyed an impressive, growth rate over a century since their inception, but particularly since about 1940., The product-design community was quick, to recognize the design freedom and great, versatility that plastics' materials and pro-, , Fig. 10-3, , cessing techniques afforded. Recognizing a, growing marketing opportunity worldwide,, international plastics material suppliers, started an endless cycle of developing new, and improved materials to meet continually new design needs. Processing machinery, builders worldwide respond with improved, equipment and even totally new processes,, as conventional tool shops everywhere expanded their capabilities to include mold and, die manufacturing for the plastics industry., , Practical all glass fiber-TS polyester RP (hand layup) recreational vehicle.

Page 601 : 10 Summary, , 583, , Fig. 10·4 Examples of recreational plastic products (paddles, surface boards, inflatable boat, etc.)., , Important for the reader to recognize is, that new plastic material data as well as plastic fabricated product data is endless because, of what can be done in the production of plastic materials as well as fabricating equipment., Thus the importance of keeping up to date, , on this information tends to be an endless, project. However when designing with plastics, the basics will remain rather constant as, reviewed in this book. Just keep up to date on, plastic behavior (Appendix A, PLASTICS, DESIGN TOOLBOX)., , Port design, , •, , Material selection, , I, , Simulation of rundionality, I, , Does design meet end-use, .pecifications within, economic constroints?, I Yes, Port specificotions, , No, , Revise design, ondlor moleriol sel..crion, , Mold design, I, , Selection of mochine, ond molding conditions, I, Process simulotions, t, , Were quolity ond cost, specificotions met~, I Yes, Production specificotions, , Fig. 10·5, , No, , Modify mold design, and/or processing conditions, , A decision tree diagram for integral designing.

Page 602 : No, , Basic, , No, , !lis, , Yes, , ~NO, 7, ' -,, , Fig. 10-6 Decision tree to help designers develop environmentally friendly packaging., , Requirements, , Functional, , ~, , I::), , ~, ~, , ~, , ~, , ......, , ~

Page 603 : 585, , 10 Summary, , .., , Startinz Point, , Fig.10·7 Example of a typical toxicology study for a plastic for industrial us, non-food contact., , New device is compared to, marketed device, Do the differences alter the, intended therapeutic/diagnostic/etc., Yes, °7nSd~c:~o:~~~~e~~~t:;me ~, effect (in deciding, may, consider impact on safety and, Yes, effectiveness)?, , D, , Descriptive information, about new or marketed, device requested, as needed, , d, , ., , h, , N, , New device has same intended, use and may be "substantially ....., . . . - - - - - - - - ', equivalent", , Does new device have same, technological characteristics, (e.g., design, materials, etc.)?, , rNo, , r, , No, , Performance, data, required, , No, , Could the new, , No, , ~ characteristics, , affect safety, or effectiveness?, , Yes, , New device has new, intended use, , Yes, ~, , Do the new characteristics, raise new types of safety or, effectiveness questions?, , !", , No, , ------Are the descriptive, characteristics reeise enough, to ensure equivalence?, p., , Do accepted scientific methods, exist for assessing effects of, the new characteristics?, , !, , Are performance data available - - - - ,, to assess effects of new, No, characteristics?, Performance, Yes, data, required, , +, , Yes, , Do performance data demonstrate, equivalence?, , LDO performance data demonstrate Yes, equivalence?, , I, , No, , No, , T00, , Fig. 10-8, , No, , Yes, , Yes, , Are performance data available, to assess equivalence?, , "Not substantially, equivalent", determination, , "Substantially equivalent", determination, To, , Flow pattern for designing medical device., , ----J

Page 604 : 586, , 10 Summary, STRUCTURAL PLASTICS, , Fig. 10-9 Interrelation among the methods of plastic applications and processing for the family of, plastic materials., , Challenge, , There is always a challenge to utilize advanced techniques without overlooking the, understanding of its.lJasic operation. They include: (1) the different plastic melt flow behaviors, (2) operational monitoring and process control systems, (3) importance of the, different molds or dies and auxiliary equipment, (4) fundamentals of product designs,, (5) design features that influence mold or die, designs and product performances, (6) testing and quality controls, (7) statistical analysis, (8) setting up troubleshooting and main-, , tenance guides, (9) detail cost factors that, influence products final costs, and (10), analyze competition (both those in the plastic business and those using other materials)., Knowledge of this type information ensures the elimination or significant reduction, of potential problems. This type of understanding is required in order to be successful in the design-through-prototype-throughmanufacture-to-profitable sales of the many, different, marketable, plastic products worldwide., The reputation of plastics periodically has, been harmed a great deal by the fact that in

Page 605 : 10 Summary, certain cases designers and engineers have,, after deciding tentatively to try to introduce, plastics, lavishly copied the material (metal,, aluminum, etc.) used in a product it was suppose to replace. Too much emphasis can not, be laid down upon the general principle that, if plastics are to be used with maximum advantage and with minimum risk of failure, it is, essential for the unfamiliar or limited knowledge designer in working with plastics to do, some homework and become familiar and, keep up to date with the plastic processes and, materials., Challenge Requires Creativity, In order to find unique, creative solutions, to difficult challenges that were not resolved, by past tried and true techniques, one must, get away from the conventional state of mind, that is often unimaginative, frustrating, repetitive, and negative. Examples of this type, challenge exist all around us (Fig. 10-10)., The nature of some problems tends to invite unimaginative suggestions and attempts, only to use past approaches. Problem solving in designing and producing products, as in, business and personal problems, generally requires taking a systematic approach. If practical, make rather small changes and allot time, to monitor the reaction of result. With whatever time is available, patience and persistence are required., However, when a problem is particularly, difficult or only limited time exists, consider, a new and imaginative approach with techniques that previously generated creative, ideas. First generate as many ideas as possible that may be even remotely related to the, problem. During the idea-generating phase it, is of critical importance to be totally positive:, no ideas are bad. Evaluation comes later, so, do not attempt to provide creativity and evaluation at the same time; it could be damaging, to your creativity. Look for quantity of ideas,, not quality, at this point. Now all ideas are, good; the best will become obvious later., If possible, relate the problem to another, situation and look for a similar solution. This, , 587, , approach can stimulate creative thinking toward other ideas. Try humor; do not be afraid, to joke about a problem. The next step is to, evaluate all the ideas. Consider categorizing, the list, then add new thoughts, select the best,, and try them., After all this action, if nothing satisfactory, occurs, rather than give up look for that really, creative solution because it is out there. You, may be too close to the problem. Get away, from the trees and look at the forest. Climb, up one of the trees and look at things from a, different perspective., Use your creative talents but be positive., You have now creatively worked through, the frustration and negativism that problems, seem to generate. Your increasingly creative, input will generate future opportunities., Now let us take the thoughts above and improve on them. In doing so let us avoid saying, in effect "My mind is made up-do not give, me the facts." Rather, let us use the approach, that there is always room for improvement, and resolving the problem., Value Added!Analysis, Well designed products have the value, added approach that results in customer satisfaction and profit gains. Value is an amount, regarded as a fair equivalent for something,, that which is desirable or worthy of esteem,, or product of quality having intrinsic worth., Aside from technology developments,, there is always a major emphasis on value, added services. It includes the design concept to fabricator that continually tries to find, ways to augment or reduce steps during manufacture with the target of reducing costs., While there are many definitions of value, analysis, the most basic is the following formula where VA = (function of product) / (cost, of the product). Immediately after the product goes into production, the next step that, should be considered is to use the value, design approach and the FALLO approach, (Fig. 1-3). These approaches are to produce, products to meet the same performance, requirements but produced at a lower cost.

Page 606 : 588, , 10 Summary, , ~ '~, , ., ,, , , .., , ', , 1. Lens implant, 2. ContaC1 lens, 3. In vivo artificial, 4., 5., 6., 7~, , hearing system, DenIal struclures, External prothesis, Artiliciallaryn~, , Artificial skin, , 8. Heart valves, 9. Artificial heart, , , O . Kidney-dialysis, system, 11. Artifici al blood, (synlt1etic o~ygen, carriers), 12. InlTaeortic balloon, 13. Angioplasly calt1eter, 14. Vascular grafts, 15. Sutures, 16. Postmasteclomy, reconstruC1ion, 17. Artificial hip, knee, 18. Artificial finger., loe joints, 19. Tom ligaments, 20. Natural·aC1ion, Seattle Foot, 21 . Aorta, , ;, , :, , ., c~, , !,, I', , Fig. 10-10 Application of plastics in the human body continues to be a challenge in order to meet, performance and biocompatibility requirements., , If you do not take this approach, then your, , Plastic Industry Size, , competitor will take the cost reduction approach. VA is not exclusively a cost-cutting, discipline. With VA you literally can do, "it all" that includes reduce cost, enhance, quality, and/or boost productivity., , 4th, , Plastic product industry is ranked as the, largest USA manufacturing industry and, growing 3 to 4 times that of the total national products (Fig. 1-5). Motor vehicles are

Page 607 : 10 Summary, in 1st place, petroleum refining in 2ed place,, and automotive parts in 3ed place. Plastic is, followed by computers and their peripherals,, meat products, drugs, aircraft and parts, industrial organic chemicals, blast furnace and, basic steel products, beverages, communications equipment, commercial printing, fabricated structural metal products, grain mill, products, and dairy products (in 15th place)., At the end of the industry listings are plastic materials and synthetics in 24th place and, ending in the 25 th ranking are the paper mills., Worldwide total sales for the category of, plastic products and plastic materials is now, well over $275 billion/year. Machinery sales, (primary, auxiliary, secondary, etc.) in the, plastic industry are estimated to be above, $7.5 billion/year (1995)., Recognize that the USA economy has, been changing from a manufacturing society, to an information and service society (as first, reported during 1939 by a college professor, who stated it actually started during the start, of the 20th century). In 1998 the US Department of Labor reported that about 93 million, people are no longer in manufacturing but, are in an information and services. Considering this situation the USA plastic fabricating, industry continues to grow., , 589, , material with their processing capabilities can, be made to accomplish a unique result. Ingenuity in the application of materials has been, the thrust of the plastics industry, and it will, present new opportunities in the future., The versatility of the plastic materials permits them to be varied to perform special, functions. By applying ingenuity to these, amazingly adaptable materials, we can produce products that add to the worldwide survival capability of life under severe environments and improve the quality of life under, normal environments. The designer's role in, fitting the possibilities to the needs is one that, is increasingly important., , Research and Development, , In USA the yearly man-hours employment, producing all plastic products by all processes, is estimated at 650 million, second to motor vehicles at 845 million. Following plastic, products (in millions) are aircraft at 570, commercial printing at 560, newspapers at 475,, meat at 460, metal structural products at 350,, and computers at 325. The USA plastics Industry is growing and creatingjobs faster than, the other manufacturing sectors., , The extent to which plastics are used in any, industry in the future will depend in part upon, the continued total R&D activity carried on, by materials producers, processors, fabricators, and users in their desire to broaden, the scope of plastic applications. An R&D, example is the rail car hopper, called the, Grasshopper (10,14). It is literally all plastic, that provides improved load and operating, performances over metals (Fig. 10-11)., The bulk of such research expenditure is, done by the materials producers themselves, and the rest by the additive and equipment industries who do more than the processors and, fabricators whose share is very small. Important to plastic growth have been government, projects in basic research and new applications, particularly the military. Their work in, turn expands into the industrial industry., The project of communicating new technology to processors and users is the subject, of much discussion in the industry. The lag, time from laboratory discovery to end user, benefits is generally three years or more., , Future, , Theoretical vs. Actual Value, , In addition to many of the major present, markets expanding, the design opportunities, for plastics materials in the future will be in, such areas where the special properties of the, , Through the laws of physics, chemistry, and, mechanics, in 1944 theoretical data was determined for different materials (42). These, are compared to the present actual values, , Fabricating Employment

Page 608 : 590, , 10 Summary

Page 609 : 591, , 10 Summary, , Comparison of theoretically possible and actual experimental values for modulus of elasticity and tensile strength of various materials, , Table 10-3, , Modulus of Elasticity, , Tensile Strength, , Experimental, , 'JYpe of Material, Polyethylene, , Experimental, Normal, Polymer, , Theoretical,, , Fiber,, , Normal, Polymer,, , N/mm2, , N/mm2, , N/mm2, , N/mm2, , N/mm2, , (kpsi), , (kpsi), , (kpsi), , (kpsi), , (kpsi), , (kpsi), , 300,0000, , 100,000, (33%), (14,500), , 1,000, (0.33%), (145), 1,600, (3.2%), (232), 2,000, (1.3%), (290), 70,000, (87.5%), (10,100), , 27,000, , 1,500, (5.5%), (218), 1,300, (8.1 %), (189), 1,700, (6.3%), (246), 4,000, (36%), (580), 4,000, (19%), (580), 800, (10.5%), (116), , 30, (0.1 %), (4.4), 38, (0.24%), (5.5), 50, (0.18%), (7.2), 55, (0.5%), (8.0), 1,400, (6.67%), (203), 600, (7.89%), (87), , Polypropylene, , (43,500), 50,000, , Polyamide 66, , (7,250), 160,000, , Glass, , (23,200), 80,000, , Steel, , (11,600), 210,000, , Aluminum, , (30,400), 76,000, (11,000), , 20,000, (40%), (2,900), 5,000, (3%), (725), 80,000, (100%), (11,600), 210,000, (100%), (30,400), 76,000, (100%), (11,000), , 210,000, (100%), (30,400), 76,000, (100%), (11,000), , Theoretical,, , (3,900), 16,000, (2,300), 27,000, (3,900), 11,000, (1,600), 21,000, (3,050), 7,600, (1,100), , Fiber,, , N/mm2, , For the experimental values the percentage of the theoretically calculated values is given in parenthesis, as (47)., , in Table 10-3. With steel, aluminum, and, glass the theoretical and actual experimental values are practically the same, whereas, for polyethylene, polypropylene, nylon, and, other plastics they are far apart, and have the, important potential of reaching values that, are far superior to the present values., When polyethylene was first produced in, the early 1940s, physicists in England, USA,, and Germany predicted a tremendous potential for it. At that time the properties of PEs, were much lower than those presently available. Out of that original general-purpose, PE, have been developed specific PEs in this, polyolefin family of plastics such as LDPE,, HDPE, UHMWPE, and so on. In turn their, different properties, as well as other plastics,, continually increase and their variables continue to be reduced and/or easier to process, to tighter tolerances., , Design Demand, It can be said that the challenge of design is, to make existing products obsolete or at least, offer significant improvements. Despite this, level of activity there are always new fields, of industry to explore. Plastics will continue, to change the shape of business rapidly. Today's plastics tend to do more and cost less,, which is why in many cases they came into, the picture in the first place. Tomorrow's requirements will be still more demanding, but, with sound design plastics will satisfy those, demands, resulting not only in new processes, and materials but improvements in existing, processing and materials., Research will no doubt become even more, adept at manipulating molecules to the extent that the range of materials offered, to industry will continue to present new

Page 610 : 592, , 10 Summary, , Load, , or, , Enviroment, , Fig. 10-12 Product performances in its simplest, form relates to this 3-D plot., , opportunities and allow existing businesses, to enjoy profitable growth. Also ahead are, the different raw material sources to produce, plastics that involve biotechnology (186). A, reading of the literature and patents being, issued indicates that there is a great deal of, commercially oriented research being aimed, at further improvement and modification into, the plastic family. However recognize that the, basic analysis for designing plastic products, continues to be related to temperature-timeload or environment (Fig. 10-12)., Unfortunately sometimes a new design, concept is not accepted or may simply be, ahead of its time. In 1483 Leonardo da Vinci, designed what he called a spiral screw flying, machine. In 1942 Igor Sikorsky developed the, , R4B helicopter processes (included plastics, parts). One could say in a joking manner taking 459 years to bring a designed product to, market seams a failure in materials or perhaps the interoffice communication., Alexander Graham Bell believed the photophone, not the telephone, was his greatest, invention. His photophone carried the spoken voice by reflected sunbeams instead of, wire, but did not find any practical application a century ago. Because light has 20,000, times shorter frequency than microwaves, it, can carry 20,000 time more information. Only, since the onset of ("plastic") computers has, this ability been needed. It would seem that, Alex Bell was ahead of his time., Fortunately designers did not have to design the human body. The human body is the, most complex structure ever "designed" with, its so-called 2,000 parts (with certain parts being replaced with plastics). As an example the, heart recirculates all the blood in the body, every 20 minutes, pumping it through 60,000, miles of blood vessels. Can one image designing the human body. Even with our extensive, technology, it would be a total disaster., The past events in designing plastic products have been nothing short of major worldly, achievements. Designers' innovations and visionary provides the required high level of sophistication that is applied to problems that, exist with solutions that follow. Ahead is a, continuation of meeting new challenges with, these innovations and idealism that continues to make plastics a dynamic and visionary industry. The statement that we are in the, World of Plastics is definitely true. In fact one, can say that plastic products has made life, easier for all worldwide.

Page 611 : Appendix A, Plastics Design Toolbox, , Here are examples in the selection of the, many resources available to the plastics designer and other plastics users; also review, references 3, 6, 10, 14, 20, 29, 31, 36, 37, 39,, 43 to 125., Contents, 1., 2., 3., 4., 5., 6., 7., 8., 9., 10., , Plastics databases, electronic, Hard-copy data sources, Process simulation software, Plastics design books, Design education, Trade publications, Trade associations, Industry conferences, Key related websites, Key corporate web sites, , 1., , Plastics Databases, Electronic, , The optimum selection of materials is becoming increasingly important for cost controls and innovation in engineering design., The following databases are tools of choice to, help the designer and others meet this need., , 1.1, , IDES INC., , Tel: 800-788-4668/307-742-9227, Fax: 307-745-9339, (http://www.idesinc.com/Products_1.htm), , 1.1.1 Prospector web Prospector Web is, an interactive database used to find and compare plastic materials. You can specify your, application requirements to search a catalog of nearly all North American plastics, and increasing amounts of plastics data from, European and Pacific Rim material suppliers., Materials can be searched by any of 200+, properties, reviewed, sorted, and compared, to determine the material best fitted to your, needs. Test data is available in both English, or Metric units and ASTM or ISO format., Both Prospector Web and its sister product, Prospector Desktop come with IDES's exclusive Plastics Materials Hotline to help with, questions that may arise., 1.1.2 Prospector, desktop Prospector, Desktop is a disk-based version of the popular Prospector Web. Prospector Desktop also, contains multi point data graphs. (Available, on CD-ROM or diskette for Windows and, Macintosh)., 1.1.3 Electronic product catalog Electronic Product Catalog is a sales tool available to material producers and distributors., Potential customers looking for materials can, be directed to a website through direct links, from datasheets accessed by customers on, Prospector Web.

Page 612 : 594, , Appendix A: Plastics Design Toolbox, , 1.1.4 FreeMDS, http://www.freemds.com, FreeMDS from IDES (http://www.idesinc., comlProducts_l.htm) is a no-charge service, that provides Plastic Material Data Sheets., This growing database contains over 35,000, Material Data Sheets from North America,, Europe, and the Pacific Rim., 1.2 PLASPEC Materials Selection, Database, http://www.plaspec.com (Tel: 212-592-6570), There are now 12775 grades of plastic materials in the PLASPEC Materials Selection, Database. Searches may be conducted for, materials using:, •, •, •, •, •, •, •, •, •, •, , Supplier Name, Generic Family, General information, Processing/Physical Characteristics, Mechanical Properties, Thermal Properties, Electrical Properties, Optical Properties, Pricing Information, Features/Characteristics, , 1.3 CenBase Materials on WWW, http://www.centor.comlcbmat/CenBASE/, Materials on WWW is a searchable document base on over 35,000 thermoplastics, thermosets, elastomers, and rubbers,, composites and fibers, ceramics and metals from over 300 manufacturers product, catalogs worldwide. In addition to complete, property data, it includes application data,, chemical resistance, MSDS and advanced, engineering graphs. The database is also, available on CD-ROM, and contains the, equivalent of over 150,000 pages of data., Engineers, scientists and purchasing professionals use it for competitive analysis, materials selection, materials research, vendor, selection and materials engineering education., , 1.4 CAMPUS®, The Plastics Database®, registered trademark of CWFG GmbH,, Frankfurt/Main, 1991, http://www.CAMPUSplastics.com, , 1.4.1 CAMPUS, the plastics database, CAMPUS is an internationally known, database software for plastic materials, developed by close cooperation with leading plastics producing companies. It is, available worldwide from leading material suppliers. More than 50 plastics, producers are participants of CAMPUS., Information about the latest list of participants and distribution addresses can, be found at the CAMPUS homepage:, http://www.CAMPUSplastics.com/.This web, site also includes extensive information about, the data content of CAMPUS and links to, the participants' web sites. It is important to, emphasize that only CAMPUS participants, distribute CAMPUS diskettes. Each plastic, producer distributes his own diskette to his, customers without charge., The plastics properties catalogue includes, single-point data, multi-point data, processing data, product description texts and customer service information. You can select, plastic products for your specific application, by using the query options. The main feature, of the CAMPUS philosophy is comparable, data. The properties are based on the international standards ISO 10350 for Single-Point, data and ISO 11403-1,-2for Multi-Point data., CAMPUS is available in English, German,, Spanish, French and Japanese., CAMPUS uses a uniform database structure and uniform interface for all participating suppliers, with frequent updates of, the property data. It allows preselection or, screening of materials, suitable for specific, applications, from a worldwide range of commercial plastics, while continuously being, developed further with respect to its properties base. CAMPUS is based on two international standards for comparable data,, that use meaningful properties based on, unambiguous selection of specimen types

Page 613 : Appendix A:, , Plastics Design Toolbox, , and conditions for processing and testing,, (ISO 10350 [Single-point data] and ISO, 11403 [Multi-point data]). Interfaces between CAMPUS and other systems, especially CAE systems are possible via MCBase,, the CAMPUS merge program, which is available from M-Base Engineering + Software, GmbH, Aachen., , 1.4.2 MCBase, the CAMPUS merge, database distributed by: M-Base Engineering + Software GmbH,, Dennewartstr. 27 D-52068 Aachen, Germany, Tel: +492419631450, Fax: +49 241 963 1469, http://www.m-base.de, MCBase is distributed by:, USA-The Madison Group,, 505 S. Rosa Rd., Madison, WI, USA 53719-1257, Tel: 608231-1907, Fax: 608 231-2694, E-mail: [email protected], Germany-KI, Kunststoff Information, Verlagsgesellschaft GmbH, Bad, Homburg, Germany, France-SYSTIA Plasturgie,, Centre Hermes, 48, Rue des Grives, F-38920, CROLLES, MCBase offers the possibility to load the, original CAMPUS data of different suppliers from version 3.0 and higher into one, database, which allows direct comparison. It, has been developed in close cooperation with, the CAMPUS consortium. For more information see: http://www.m-base.de/. MCBase, is user friendly and offers extremely efficient, handling of material data. All CAMPUS options are available: define search profiles; define and sort tables; print tables and data, sheets; curve overlay; scatter plots. In addition MCBase 4.1 offers search in curves;, search for comparable grades; text search;, update via Internet; calculation of simulation, parameters. A French version of MCBase, is available from the distribution agent in, France., , 1.5, , 595, , Plastics and Rubbers Data Collection, , Plastics Design Library (PDL), William, Andrew Inc., http://www.williamandrew.com, The PDL Electronic Databooks (also available in hardcopy) provide properties of, thermoplastics, elastomers, and rubbers. The, world's largest collection of phenomenological data, information is provided as concise, textual discussions, tables, graphs and images, on chemical resistance, creep, stress strain,, fatigue, tribology, the effects of UV light and, weather, sterilization methods, permeability,, film properties, thermal aging, effects of temperature. The Databooks are available on a, single CD-ROM as a complete set (the Plastics and Rubbers Data Collection) or as individual topics. They are updated annually., Features of the complete set include:, • information and data for 180+ material families-thermoplastics, elastomers, alloys and rubbers, 5,000 chemical reagents, and exposure media, 175,000 material and, reagent combinations, • difficult-to-find information, • search, sort and compare across the entire, database, • customize charts, tables and curves to compare performance characteristics, • print out or export to your favorite word, processor, spreadsheet or database, • 6,000 curves that enable you to display the, coordinates of a chosen point, fit curves to, • data points, do a trend analysis, export data, points and images, • 100,000 tables-search by key-words, numerical ranges and indices completely, source referenced, Collections and individual Databooks are, available for the following topics:, • Polymer Degradation Collection, • Chemical Resistance of Plastics and Elastomers, Volumes I and II, • Effects of Sterilization Methods on Plastics, and Elastomers, • Effect ofUV Light and Weather on Plastics, and Elastomers

Page 614 : 596, , Appendix A: Plastics Design Toolbox, , • Performance Properties of Plastics, Collection, • The Effect of Creep and Other Time Related Factors on Plastics, • Permeability and Other Film Properties of, Plastics and Elastomers, • The Effect of Temperature and Other Factors on Plastics, • Fatigue and Tribological Properties of PI astics and Elastomers, • Dynamical Mechanical Analysis for Practical Engineering, , 1.5.1 PDLCOM. Available, through, NACE., http://www.nace.org/naceframes/, Store/pdlindex.htm, Published by the Plastics Design Library,, PDLCOM is an exhaustive reference source, of how exposure environments influence, the physical characteristics of plastics. Data, include resistance to thousands of chemicals, weathering and UV exposure (i.e. color, change after accelerated weathering or outdoor exposure); sterilization (radiation, ethylene oxide, steam, etc.); thermal air and water aging; environmental stress cracking and, much more., Description of samples tested, specific test, methods used, exposure medium notes, solubility parameters, and other important details are provided. Emphasis is on providing, all relevant information so the most informed, conclusions and decisions can be made by, the user. Over 60,000 individual entries (specific tests) are covered in the database., Classes of materials covered include thermosets, thermosetting elastomers, thermoplastics, and thermoplastic elastomers. Approximately 700 different trade name and, grade combinations representing over 130, families of materials are included. Over 3300, exposure environments are represented., Records can quickly be grouped by generic, family, exposure medium or trade name and, grade. In addition, records can be searched,, sorted and displayed by exposure temperature, exposure time, exposure medium concentration, and supplier or using the PDL, resistance rating. Complete information can, then be viewed on any individual record., , 1.6 Plascams Computer-Aided Materials, Selector, (Access is regulated by user ID and password)., RAPRA Technology Ltd. Shawbury,, Shrewsbury, Shropshire SY4 4NR, UK., Tel: +44-1939-250-383, Fax: +44-1939-251-118, http://www.rapra.net, The system works interactively with the user, to select the best material for the specified, application, educating the novice and informing the expert. Users can access definitions, of materials, their advantages and disadvantages, compare graphs of flexural modulus vs., temperature, review data sheets and explore, materials selection examples. The system is, also hyper-linked to complete material supplier information and online help., The first interactive electronic encyclopedia for users of plastics, materials selection, is carried out using 3 search routines. The, "Chemical Resistance Search" eliminates, materials that cannot meet user specified, chemical resistance requirements. The other, search routines ("Elimination" and "Combined Weighting") eliminate candidate materials based on 72 properties, falling within one, of the following groups: General and Electrical, Mechanical, Cost Factors, Production, Methods and Post Processing. All data is evaluated and based on independent tests conducted in RAPRA's laboratories., , 1.7 POLYMAT, FIZ CHEMIE BERLIN, Postfach 12 03 37, D-10593 Berlin, Tel: +49 (0)30/39977-0, Fax: +49 (0)30/39977-134, E-mail: [email protected], http://www.fiz-chemie.de/en/katalog/, , 1.7.1 POLYMAT materials data for, plastics POLYMAT Materials Data for, Plastics contains property values, e.g., mechanical, thermal, electrical, optical, rheological properties and text fields, e.g. special

Page 615 : Appendix A:, , Plastics Design Toolbox, , characteristics, preferred applications, preferred processing techniques, additives., In all, 109 numeric and 19 text fields are, available. The properties are retrieved in, tabular form. The long term behavior of, plastics is represented in diagrams, which, may also be used in searches. An editor is, also available for customizing the database, with the user's own data., • Type: in-house numerical database with, editor for the construction of a customized, database, • Field: thermoplastics, thermoplastics elastomers, thermosetting resins, • Product form: in-house database with editor function, • Language: German or English, • Content: approximately 12,000 materials, from 140 manufacturers, approximately 40, measured properties for each material, approximately 15 product class values per, material in the absence of experimental, values, • Updates: semi-annually, • Source materials: manufacturers' technical, bulletins, handbooks, other specialized literature, FIZ, CHEMIE, • Producers/suppliers:, BERLIN and TDS Herrlich GmbH, • Host: at the beginning of 2000, online available at TDS Herrlich GmbH, (www.polybase.com), • Operating systems: MS/DOS 3.1 or higher,, WINDOWS 3.1 or higher, • Remarks: also available-POLYMAT light, as a version with less data for less costs with, direct access to the full version via internet, • Editor: 50 numeric properties and 15 text, fields are available, light POLYMAT, 1.7.2 POLYMAT, light Materials Data for Plastics is a manufacturer independent, materials database, for plastics and contains properties of thermoplastics, thermoplastic elastomers and, blends. In total, data from approximately, 13,000 commercial products of 170 manufacturers are available; products and data, can be retrieved via searching in 35 different, numerical properties and 15 text fields., , 597, , POLYMAT light can be used for: time saving, and comprehensive selection of materials, according to a customer's application profile;, employment of reasonably priced alternative, materials with comparable properties in plastics manufacture; searching for alternative, manufacturers in case of delivery problems;, comparison of different plastics materials for, a single production task; market analyses,, e.g. a search for manufacturers producing, PA 6 with a content of 30% carbon fibers., • Type: in-house numerical database, • Field: thermoplastics, thermoplastic elastomers, blends, • Product form: in-house database, CDROM, • Language: German, • Content: approx. 13,000 materials of 170, manufacturers, • Updates: semi-annually, • Source materials: manufacturers' technical, bulletins, handbooks, other specialized literature, FIZ, CHEMIE, • Producers/Suppliers:, BERLIN and TDS Herrlich GmbH, • Operating system: WINDOWS 3.1 or, higher, • User aids: handbook, help functions, 1.8 SOFINE.· Grade Specific Selection of, Plastics Materials, TIMPAS OY Kauppakatu 34, Fin-80100 Joensuu Finland, Tel: 358-(0)500-780011, Fax: 358-(0)50-8532 7850, E-mail: [email protected], http://www.plasticsselection.com/, Distributed:, UK, worldwide by RAPRA Technology Ltd.,, Shawbury, Shrewsbury, Shropshire, SY4, 4NR,UK, Tel: +44 (0) 1939 250 383, Fax: +44 (0) 1939251118, E-mail: [email protected], http://www.rapra.net, Italy, by EUROCAD., Via Bottola 3,33070 POLCENIGO (PN) ,, Italy

Page 616 : 598, , Appendix A: Plastics Design Toolbox, , Tel: +390434749609, Fax: +390434749921, E-mail: [email protected], France, by CERAP S.A., 27, bd du 11 Novembre 1918, BP2132, 69603, Villeurbanne Cedex, France, Tel: +33 (0) 4.72.69.58.30, Fax: +33 (0) 4.78.93.15.56, E-mail: [email protected], http://www.cerap-ingenierie.com, Spain, by Diego Ramon Larios S.L., Plastics and Consulting., Avda Montevideo, 68, 08340 Vilassar de Mar,, Barcelona, Spain., Tel: +34 93 750 21 90, Fax: +34937502370, E-mail: [email protected], http://www.cambrabcn.es/drl-plastics, Sweden, by Plamako Ab, gatan 13, 33421 ANDERSTORp, Sweden, Tel: +46 (0)371 58 82 80, Fax: +46 (0)371185 85, E-mail: [email protected], The Netherlands, Germany, by Schouenberg, & Partners v.o.F., Burg. Stolklaan 16, 4002 WJ Tiel, The, Netherlands, Tel: +31 (0) 344616 161, Fax: +31 (0) 344 631 014, E-mail: [email protected], SOFINE includes detailed technical information of more than 11,000 plastics (thermoplastics and elastomers); plastic materials, from over 100 producers; continuous updating of the program; operates in 7 languages., SOFINE versions available include:, , 1.8.1 Standard version Search of plastics by name, with technical limitations, price, level, producer, processing method etc., and, search of/comparison of equivalent materials:, • Compares different plastic materials on the, screen., • Language: Gives the possibility of choosing the working language for the software (English, French, German, Spanish,, Italian, Finnish or Swedish)., , • Country: Gives the possibility of choosing the country for which the program, gives the contact information of the producer/distributor., • Currency: Gives the possibility of choosing, the currency., • Gives the possibility of transferring files, from SOFINE to ACCESS and EXCEL., • Search: by name, technical limitations, or, equivalent material., , 1.8.2 Interactive version Includes the, possibility of adding and modifying all information:, • Properties: Gives the possibility of modifying, adding or deleting plastic data., • Agency: Gives the possibility of modifying the list of producers and/or distributors with their addresses, telephone and fax, numbers., • Personal properties: Gives the possibility, of adding own properties., , 1.8.3 Tailor-made version Made according to the needs and demands of the customer:, • Versions are produced for customers with, customized possibilities and specific data,, which can also be updated at agreed, intervals., • Links to customer's own database on, request., , 1.9 RUBSCAMS, RUBSCAMS Computer-aided Materials, Selector for Elastomers, RAPRA Technology Ltd. Shawbury,, Shrewsbury, Shropshire SY4 4NR, UK., Tel: +44-1939250383, Fax: +44-1939251118, http://www.rapra.net, Rubacams is a computer aided materials, selection routine for elastomeric materials., Covering 99 generic types of rubber, each, material is cross referenced with over 190, chemical agents and materials property data, including physical, chemical mechanical and, process related properties. Search results

Page 617 : Appendix A: Plastics Design Toolbox, identify the most suitable materials, a detailed description of the elastomer and supplier details., , 2., 2.1, , Hard-Copy Data Sources, Polymers and Elastomers, , Polymer and elastomer data are typically, producer-specific. Sources therefore tend to, be scattered and incomplete. While no single hard-copy source is all encompassing, the, following are worth consulting., 2.1.1 "Modern plastics world encyclopedia", A Chemical Week Associates Publication (800-525-5003) updated annually. Includes primer type descriptions and a global, listing of key plastic resin and compound, properties for a wide range of material grades, based on filler and additive content plus primary processing method and supplier; auxiliary equipment and components, fabricating, and finishing also covered. Extensive Buyer's, Guide included., 2.1.2 "Handbook of Plastics Materials, and Technology", Irvin I. Rubin; John, Wiley & Sons; (1990); ISBN: 0471096342., Essential information from acetal to XT, polymer. This single source comprises 119, chapters of in-depth basic information about, plastic materials, properties, processing, assembly, decorating and industry practices-all, presented in a readily accessible and consistent format. Also features a wealth of useful, auxiliary information and tables., 2.1.3 "Plastics technology manufacturing, handbook and buyers guide", Bill Communications (212-592-6570). Updated annually., The Handbook and Buyers' Guide is a comprehensive tool for locating suppliers of primary machinery, materials (thermoplastics, and thermosets), auxiliary and secondary, equipment and controls, chemicals and additives, and a variety of specialized services., Contains extensive equipment and materials, specifications., , 599, , 2.1.4 "Performance of plastics", W., Brostow; Hanser Gardner PubIs; (1999);, ISBN: 1569902771. Comprehensively covers the behavior of the most important, polymer materials. Subject areas range, from Computer Simulations of Mechanical, Behavior to Reliability and Durability of, aircraft structures made of fiber-reinforced, hydrocarbons., 2.1.5 "Saechtling international plastics, handbook: for the technologist, engineer &, user", 3rd edition, Dr. Hansjurgen Saechtling; Hanser Gardner PubIs; (1995); ISBN:, 1569901821. Very comprehensive hard-copy, data-sources for polymers. Covers key facts, about the plastics industry, from basic materials and theoretical concepts to manufacturing, with detailed descriptions of individual plastics, their properties and applications., Contains more than 100 tables of plastics, properties and plastics data in ASTM, ISO, and DIN standards. Also includes a buyer's, guide., 2.1.6 "Plastics for engineers: materials, properties, applications", Hans Domininghaus; Hanser Gardner PubIs; (1993);, ISBN: 1569900116. Provides a comprehensive overview in text, tables and graphs, of, properties and applications for all plastics of, current technical and commercial interest., 2.1. 7 "The, plastics, compendiumvolumes 1 and 2", ISBN: 18599570585, , • "Volume 1: Key Properties and Sources",, M.e. Hough, & R. Dolbey; Rapra Technology Ltd.; (1995). Volume 1 contains, data on 351 generic and modified material, types. Information provided includes property and commercial data sheets covering:, advantages and disadvantages; typical applications; materials data listing values of, 24 key properties; and source data listing, suppliers and their trade names in the USA, and Europe., • "Volume 2: Comparative Materials Selection Data", M.e. Hough, S.l Allan,, & R. Dolbey; (1999). Volume 2 provides, comparative materials selection data for

Page 618 : 600, , Appendix A:, , Plastics Design Toolbox, , the 351 thermoplastic and thermosetting, materials covered in volume 1. Each material has been assigned one of six ranking values for each of 62 properties, ranging from excellent to not applicable., The information is based upon the numerical rankings contained within Rapra's, PLASCAMS (see 1.6)., , function and properties requirements, size,, shape and design detail considerations, and, surface requirements; properties modification by polymer/polymer mixtures and use, of additives; and properties of thermoplastic structural foam. Structural Analysis, and Design covers the use of engineering, formulas., , 2.1.8 "Handbook of plastics, elastomers, and composites", 3 rd edition, Charles A., Harper; McGraw-Hill; (1996); ISBN:, 007026693X. This comprehensive source, of at-a-glance plastics design data includes, property and performance data; application guidelines; costs; joining techniques;, fabrication method trade-offs; processing, procedures for laminates and reinforced, plastic materials; protective and decorative, coatings; advanced composite materials;, liquid and low-pressure resin systems;, thermoplastic elastomers. Treatment of the, chemical, mechanical, and electrical properties of plastics, elastomers, and composites;, gives complete coverage of plastic compositions and optimizations of plastic product, design; advances in thermoplastic elastomers; new developments in applying and, processing advanced composite materials;, plastics and elastomers for high-volume,, high-performance automotive and packaging, applications; important factors in the recycling of plastics., , 2.1.10 "International plastics selector",, 9th edition, Int. Plastics Selector, San Diego,, CA; (1987). Thermoplastics, thermosets, elastomers, and key property areas critical to, plastics are extensively specification defined., , 2.1.9 "ASM engineered materials handbook", Vol 2. engineering plastics, ASM;, (1988); ISBN: 0871702800. ASM International, 9639 Kinsman Rd. Materials Park,, Ohio 44073-0002 (www.asm-intl.org). Engineering Plastics is designed and written for, working engineers. The book opens with, general design considerations. The volume's, Guide to Engineering Plastics Families describes 40 major engineering plastics families, 29 thermoplastics and 11 thermosets., Content includes typical costs, major applications, competitive materials, significant, characteristics, performance properties, design and processing considerations, and major suppliers. Other sections include manufacturing process considerations, such as, , 2.1.11 "Pocket specs for injection molding", 4th edition, (IDES) (http://www., idesinc.com/Products_1.htm). Quick reference processing guide. Released in January, 1999, this newest edition has the most, current processing information available in, a book. Pocket Specs covers 13,000 injection, moldable materials and 15 key processing, properties and provide a compact guide, for the injection molding of thermoplastic, and thermoset materials. Data is provided, for individual grades of molding materials, from more than 130 manufacturers. The, data, provided in tabular from, gives basic, information for determining regrind levels,, material drying temperatures and times, and, initial machine settings for injection pressure, barrel heats, and mold temperature., Additional physical property data includes, specific gravity, shrink data, melt flow, and, processing temperature ranges., 2.1.12 "Pocket performance specs for, thermoplastics", 1st edition, (IDES) (http://, www.idesinc.com/Products_1.htm)., Over, 13,000 thermoplastic materials from more, than 100 manufacturers with 15 different engineering properties make this book the ideal, "take anywhere" partner for the plastics, industry. This book contains the information, needed for quick, accurate, and convenient, design and materials information, providing, a basic guide to selecting thermoplastic, materials. The information in the tables is intended to give you the basic information for, determining the general performance

Page 619 : Appendix A: Plastics Design Toolbox, characteristics of a plastic material in order, to screen for candidate plastic materials., 2.1.13 "Handbook of elastomers", A.K., Bhowmick and H.L. Stephens; Marcel, Dekker; (1988); Series: Plastics Engineering,, Volume 19; ISBN: 0824778006. This handbook systematically addresses the manufacturing techniques, properties, processing, and, applications of rubbers and rubber-like materials. The Handbook of Elastomers provides, authoritative information on natural rubbers, synthetic rubbers, liquid rubbers, powdered rubbers, rubber blends, thermoplastic, elastomers, and rubber-based compositesoffering solutions to many practical problems, encountered with rubber materials., , 2.1.14 "Technical, data, sheets",, Malaysian Rubber Producers Research, Association, Tun Abdul Razak Laboratory,, Brickendonbury, Herts. SG13 8NL (1995)., Data sheets for various blends of natural, rubber., 2.2 All Materials, The five hard-copy data-sources listed below attempt in different ways to span the full, spectrum of materials and properties., 2.2.1 ''ASM engineered materials reference book", 2nd edition, Michael L. Bauccio., ASM International; (1994); ISBN:, 0871705028; (www. asm-intl.org). Compact, compilation of numeric data for metals, polymers, ceramics and composites. This is an, excellent reference for persons involved in, nonmetallic materials selection, design, and, manufacturing. Sections include:, • Composites (fibers, fillers, and reinforcements, design, tooling and manufacturing), • Ceramics (single and mixed oxides, carbides, nitrides, borides, glasses, and traditional ceramics), • Plastics (thermoplastics, thermosets, and, production and machining), • Electronic Materials (properties devices, and manufacturing methods), , 601, , 2.2.2 The "CRC-Elsevier materials selector", 2nd edition, NA. Waterman, and, M.E Ashby; CRC Press; (1996); ISBN:, 0412615509. (Now, also available on CDROM). Basic reference work. Three-volume, compilation of data for all materials; includes, selection and design guide. The Materials Selector is the most comprehensive and up-todate comparative information system on engineering materials and related methods of, component manufacture. It contains information on the properties, performance and, process ability of metals, plastics, ceramics,, composites, surface treatments and the characteristics and comparative economics of the, manufacturing routes which convert these, materials into engineering components and, products., • Volume 1 addresses the initial stages in, solving a materials selection problem, provides the background to all aspects of materials behavior, and discusses manufacturing processes., • Volume 2 details the performance of metals and ceramics., • Volume 3 covers the performance of polymers, thermosets, elastomers, and composites., , 2.2.3 "Handbook of industrial materials", 2nd edition, I. Purvis, Elsevier; (1992);, ISBN: 0946395837. A very broad compilation of data for metals, ceramics, polymers,, composites, fibers, sandwich structures, and, leather. Contents include:, • Ferrous Metals: Cast iron, carbon steel,, BS970, replacing en steel, alloy steel, spring, steel, and casting steel., • Non-ferrous Metals and Alloys: Diaphragm material, metal composite,, refractory metal., • Non-metallic Materials: Carbides, carbon,, ceramic fiber, ceramic, cermet, composite, cork, elastomer, felt, fiber, glass,, glycerin, non-metallic bearing material,, rubber (natural), rubber (synthetic), silicone, wood, leather., • Thermoplastics: ABS, acetal and polyacetal, acrylic (methyl methacrylate), cellulose plastic, EVA, fluorocarbon, PTFE,

Page 620 : 602, , Appendix A: Plastics Design Toolbox, , lonomer, methylpentene, (TPX) , PBA,, PETB, polyisobutylene (PIB), nylon, (polyamides), polyethylene, polyethersulphone, polypropylene oxide (PBO),, polystyrene, PVC, polyvinylcarbazole,, SAN, PBT (thermoplastic polyester),, polycarbonate, polymers, polypropylene,, POM., • Thermoset Plastics: Alkyd, amino resin,, thermosetting acrylic resin, casein, epoxy,, phenolic, polyester, polyamide, silicone., • Other: Laminated plastic (industrial laminate), sandwich molding, 'filled' plastic, cellular plastic, glass reinforced plastic (GRP), carbon fiber reinforced plastic, (CFRP)., 2.2.4 "Materials Handbook", 14th edition, George S. Brady, Henry R. Clauser, and John Vaccari; McGraw Hill; (1996);, ISBN: 0070070849. Covers metals, ceramics,, polymers, composites, fibers, sandwich structures, leather. This one-volume encyclopedia, of materials, known simply as "Brady's" and, published since 1929, is now in its 14th edition. This unique tool provides a one-stop, source of comprehensive information on virtually every material and substance used in, industry and engineering., The Fourteenth Edition gives you:, • A-to-Z organization for easy access;, • Coverage of more than 13,000 materials;, • Details on chemicals, metals, minerals,, fuels, plastics, textiles, finishes, woods, elastomers, ceramics, coatings, composites, industrial substances, and natural plant & animal substances;, • Entries on new materials, including recyclate plastics, fullerenes, hard-surfaced, polymers, dendrimers, transflective materials, rapid prototyping materials, silicone, nitride, supercritical fluids, bulk molding, compounds, conversion coatings, folic acid,, replacements for chloro-fluorocarbons;, • Properties and characteristics of materials,, including composition, production methods, uses, and commercial designation or, trade names, 2.2.5 Materials selector", Materials Engineering, (now Advanced Materials and, , Processes), (ASM), Special Issue; Penton, Publishing; (1994). Basic reference work-up, dated annually. Tables of data for a broad, range of metals, ceramics, polymers and composites., 3. Process Simulation Software, 3.1, , Moldflow (and C-Mold, a Division of, Moldflow), , Moldflow Corporation, 91 Hartwell Avenue,, Lexington, MA 02421 USA, Phone: +1-781-674-0085, Fax: +1-781-674-0267, http://www.moldflow.com, http://www.cmold.com!, 3.1.1 Dr. C-Mold Molding intelligence, for plastic professionals. Easy to use for quick, and dynamic evaluation of critical design and, manufacturing variables. Evaluate part and, mold design, processing conditions, and material options. No CAD model, meshing, or, special training is necessary., 3.1.2 C-MOLD advanced solutions CMOLD Advanced Solutions are designed, for dedicated simulation users who need indepth predictions for all phases of design,, manufacturing, and resulting part quality., Advanced simulation products cover a wide, range of thermoplastic and reactive molding processes, including injection molding,, gas-assisted injection molding, co-injection,, injection-compression molding, rubber injection molding, reaction injection molding, structural reaction injection molding, (SRIM), resin transfer molding (RTM), and, microchip encapsulation. Advanced Solutions address all aspects of product and mold, design, molding process conditions, and part, quality. Evaluate part thickness, part size,, gate placement, cooling system placement, and efficiency, optimize process conditions,, evaluate resulting part size, shape, and structural integrity., 3.1.3 Desktop, products C-MOLD, Desktop Products are designed to meet the, needs of design, tooling, manufacturing, and

Page 621 : Appendix A: Plastics Design Toolbox, process engineers who may not have access, to advanced simulation capabilities or who, want to get simulation feedback with high, accuracy, but without the time requirements, to run an advanced simulation., • Desktop tools address design and manufacturing concerns such as gate placement,, injection time/rate, injection pressure, melt, and mold temperatures, packing time and, pressure, cooling time requirements, and, machine size requirements., • Project Engineer uses numerical input values of maximum flow length, nominal wall, thickness, and projected area to describe, the part geometry., • 3D QuickFilI uses STL-format, solidmodel geometry to show geometry-specific, simulation results on the solid part model., , 3.1.4 Moldflow plastics advisers Moldflow Plastics Advisers are used in the early, stages of part and mold design when the cost, of change is minimal and allows the designer, to take control of early part and mold design optimization to eliminate potential manufacturing problems downstream. Injection, molded plastics parts can be designed for, "manufacturability" at the same time as form,, fit and function. Part Advisor provides automated tools to help the designer optimize a, part before the mold is cut. Mold Adviser allows mold designers to easily layout and optimize the gate and runner systems for single cavity, multi-cavity or family molds as, well as predict clamp tonnage, shot size and, cycle time requirements-all during preliminary design and before the part geometry is, finalized. Companies that identify and eliminate problems at early or conceptual stages of, design, achieve significant benefits, via time, and cost savings and the capture of timely, market opportunities., 3.1.5 Plastics insight (In-depth analysis, of plastics part and mold designs) To, undertake in-depth validation of part and, mold designs prior to manufacture. Plastics, Insight is an integrated suite of CAE analysis, software that makes it possible for plastics, part design, mold design, and machine, processing conditions to be optimized during, , 603, , the design stage, saving time and money., Plastics Insight solves complicated injection, molding problems for all geometry types,, thin or thick, simple or complex, that are, encountered during filling, packing and cooling, as well as warpage problems. Moldflow, Plastics Insight works with all CAD model, geometry types including wire frame and, surface models, thin-walled solids and thick, or difficult-to-midplane solids. Moldflow, Plastics Insight products can simulate plastics, flow, mold cooling, part warpage, stiffness, and shrinkage, and the behavior of fiberreinforced materials in plastics. In addition,, MPI includes products that simulate the gas, and thermoset injection molding processes., 3.1.6 Moldflow plastics xpert Moldflow, Plastics Xpert injection molding simulation, enables process engineers and molders to, quickly optimize machine set-up, reduce cycle times, and monitor and correct molding processes during production by providing, shop-floor solutions to the problems associated with injection molding machine setup,, process optimization and production part, quality. While no combination of software, and hardware can transform a bad design, into good parts, Plastics Xpert quickly differentiates between process-related problems, and inherent design problems. Integrated, with the molding machine's controller, MPX, provides real-time process optimization and, feedback that help remedy the production, problems. Plastics Xpert also has a remote, control capability that allows process optimization and monitoring to be done away, from the actual molding machine., Plastics Xpert is comprised of three Xpert, Systems:, • The Setup Xpert: Provides an intuitive,, systematic, and documentable method for, establishing the combination of process parameters that produce good molded parts., • The Optimization Xpert: Automated design of experiments that builds on the, foundation established in Setup Xpert and, allows users to further optimize the combination of processing parameters to determine a robust "good parts" processing, window.

Page 622 : 604, , Appendix A:, , Plastics Design Toolbox, , • The Production Xpert: A comprehensive, production monitoring and control system, that will maintain the optimized processing conditions determined with MPX's automated design of experiments., , 3.2, , MSC.Mvision, , 900 Chelmsford Street, Lowell, MA 018518103, Tel: 800642-7437/978453-5310 x 2551, Fax: 978 454-9555, http://www.mechsolutions.com/products/, mvision/index.html, MSCMvision provides materials information for predictive engineering, ensuring, consistent data for engineers evaluating new, designs and reducing cycle time by integrating materials data directly into CAD/CAE., The software enables MSC customers to integrate internal materials test information, and published materials data directly with, their processes. With MSCMvision, companies automate the flow of materials data from, test through design and analysis, maintaining, clear audit trails, thereby ensuring:, • Increased efficiency in the design process, • Reduction in product development and, support costs, • Faster and more innovative designs, • More representative analyses, • Consistent usage of materials data, • Reduced materials testing requirements, • Increased confidence in use of materials, data, • Fewer inappropriate materials selections,, and thus, • Fewer redesigns and warranty recalls, MSCMvision provides integrated access, to materials information from within the, MSCPatran and Pro/ENGINEER environments, and generates formatted input data for, MSCNastran and other analysis programs., Customers can also integrate MSCMvision, readily within their proprietary computer, aided engineering environments. MSC provides "off the shelf" materials databanks developed and maintained with authoritative, Partners including:, , • Battelle Memorial Institute, • University of Dayton Research Institute, • Plastics Design Library, from William, Andrew, Inc., • Materials Sciences Corporation, • GE Plastics, • Penton Publishing, • Information Handling Services, Inc., • ASM International, 3.3, , The Madison Group, , 505 S. Rosa Rd., Suite 124; Madison, WI, 53719-1257, Tel: 608-231-1907, Fax: 608-231-2694, E-mail: [email protected], http://www.madisongroup.com/Products/, products.html, The Madison Group: Polymer Processing, Research Corporation was incorporated in, 1993 by University of Wisconsin-Madison, researchers to permit technology transfer, from academia to industry. Several simulation packages for the polymer processing industry have been developed to help various, industry design plastic parts and solve processing problems. The Madison Group offers, a wide range of software solutions from commercially available packages to custom software development., , 3.3.1 Cadpress-SMC (Thermoset compression molding simulation) CadpressSMC is a general purpose finite element, compression molding simulation program, which calculates the mold filling, pressure, and velocity distributions, fiber orientation,, anisotropic material properties, curing, behavior, and the shrinkage and warpage, of the final part. Cadpress, developed over, the past two decades, is a finite element, based simulation package that has become, the standard for the compression molding, industry. The software simulates the entire, molding process for fiber reinforced thermoset compression molding, from mold, filling to prediction of residual stresses and, warpage of the final part. Through accounting for fiber orientation, it also predicts

Page 623 : Appendix A:, , Plastics Design Toolbox, , the anisotropic material properties of the, final part and can be interfaced to other, simulation packages, e.g. ANSYS. Cadpress, allows engineers to design parts for optimal strength with minimal shrinkage and, warpage., 3.3.2 Cadpress-BMC (injection/compression molding simulation) Cadpress-BMC,, purchased as an add-on module to the basic, Cadpress molding software, was developed, to simulate the multiphases of the injection/compression molding process of thermoset molding. With this module, the injection/compression molding process of Bulk, Molding Compound (BMC) or vinyl esters, can be simulated. The software can calculate the mold filling during the injection phase,, the initial fiber orientation after injection,, the filling during the subsequent compression phase, and the final fiber orientation as, well as shrinkage and warpage ofthe finished, part. The add-on BMC module allows the injection phase of flow to be calculated, and, also predicts the initial fiber orientation in, the part before compression. Differences between the standard Cadpress and the addon BMC module are mainly contained in, the calculation routines, with minimum userperceivable changes to the front end of Cadpress. Except for the additional injection inputs, the user interface remains identical to, Cadpress., 3.3.3 Cadpress-GMT (Glass-mat thermoplastic compression molding simulation), Cadpress-GMT (Glass-Mat Thermoplastic, Simulation Package) developed at the IKV, (EXPRESS) simulates the complete compression molding process for fiber reinforced, thermoplastic compounds. Using CadpressGMT during the design process helps to, reduce costs, shorten development times,, minimize changes on the final mold and to, incorporate design improvements at a very, early stage. Express is based on the FiniteElement Method. It is embedded in the CAE, design process and offers interfaces to a variety of familiar CAE pre- and postprocessors,, including I-DEAS, Patran, and COSMOS., , 605, , 3.3.4 FiberScan (In situ fiber detection, system) Fiber orientation caused during, processing of composites has a significant, influence on final mechanical properties of a, reinforced part. Though simulation programs, can predict fiber orientation in a molded, part, it is much more difficult to determine, the actual fiber orientation experimentally., Traditional burn-out tests can show low fiber, content regions or knitlines but the actual, fiber orientation is nearly impossible to, determine. FiberScan provides a quick, efficient method to experimentally determine, the fiber orientation field in a molded part., With any of the following inputs, FiberScan, can determine the resulting fiber orientation, field from an as-molded part: X-ray of, the specimen; photograph of transparent, samples; photographs of burnt samples., FiberScan uses image processing technology, to analyze the digital input and determine, the distribution of fibers in a sample. Using, algorithms to increase contrast, x-rays may, be analyzed without the need to use lead, impregnated fibers. It is also possible to use, FiberScan for in situ measurement during, production for quality assurance purposes., 3.3.5 DSCfit, (Differential, scanning, calorimetry curve fitting software) For, simulation programs to correctly describe, the behavior of thermoset polymers during, processing, the curing process must be well, understood and described in a manner, consistent with numerical methods. Programs such as Cadpress and Cure3D (see, 3.3.9) characterize curing behavior using, empirically based models that relate heat, release to degree of cure. To use such models,, experimentally obtained DSC data must be, properly fit with a rigorous model. DSCfit is, a utility program developed to provide the, capability of fitting experimental data with, the appropriate numerical model., Because most thermoset composites cure, by a thermally activated reaction, a complicated heat transfer process occurs during solidification, the result of an exothermic cross, linking reaction in the resin. The complications of thermoset resin curing are compounded by the competing mechanisms of

Page 624 : 606, , Appendix A:, , Plastics Design Toolbox, , chemical kinetics and molecular diffusion. A, further complication is the fact that numerous reactive processes occur as the SMC cure, process involves free radical chain growth, with the 3 stages of initiation, propagation,, and termination. While this chemical process, has been well studied and characterized, taking into account the functions of initiators, inhibitors and monomers in SMC, the resulting, models are too complex for practical applications. A more convenient method relies upon, empirical kinetic models based on the work, of Kamal and Sourour who developed an autocatalytic model to represent the exothermic reaction of various molding compounds., The six constant model can directly fit to DSC, data for a particular resin formulation., 3.3.6 Application, database, (custom, database applications; Controlling data for, design decisions) In the plastics industry,, material selection is usually made by very, experienced engineers. These specialists use, their expertise to make material selections, in a heuristic and unstructured manner., This knowledge is fixed to the individual, person and is lost when that person leaves, the company. A more reliable method is to, make the relevant data available in a unified,, structured application that is useable by, many decision makers. Such an application, databank encompasses the critical design, information from previous applications, along with pertinent material properties., Information describing the functionality, of the application, abstractions that relate, application properties and useful graphics, can be combined in an integrated and, searchable way to be useful to the designer, or engineer., The material data base CAMPUS has led, to reliable and comparable quantitative values for material selection and design, making the design process more systematic and, objective. However, it is still necessary to, use application experience in design decisions, particularly when considering material, properties that cannot be easily quantified., Among these, is the impact strength of a component relative to the geometry, load conditions, and material properties. While impact, , strength of a material is measurable and readily available, using this property in design of a, new component is not readily accomplished., In addition, end-use properties such as surface quality and optical properties, not linked, to a specific material property, cause further, problems for systematic design., The Madison Group and its European, partner, M-Base, have developed, based on, years of research and experience with material data systems, the concepts and software for the management of such application databases. This application database is, searchable by part and application. Capability for general component information, multiple classifications, images and text and links, to material properties is included., Many successful projects have shown that, application information can be divided into, the following four categories: Terminology,, Special Characteristics, Abstract Functions,, and Graphics. Although these categories are, the basis for the searchable application data, base, each project requires a conceptual, phase to define how to focus., • Terminology: Components and applications must be handled with consistent, and correct names in order to allocate, and search through them in a repeatable, manner., • Special Characteristics: Information that, describes the functionality of the application needs to be handled in a specific, manner. This information can include such, properties as size, weight, geometric form,, special functional elements, processing, and assembly methods, and other product, specific information., • Abstract Functions: An important aspect of, an application database is to support the, user in finding analogies between old, well, known cases and new design ideas. To make, these analogies independent of the imagination and experience of a single user,, an abstract description of all functions is, recommended. In this case, elemental functions, as they are known from design theory, should be used. Based on such abstract, descriptions, the software can help find relations between applications.

Page 625 : Appendix A:, , Plastics Design Toolbox, , • Graphics: In most cases a graphical presentation of each application is necessary., Here, it is possible to store photographs,, sketches, CAD drawings, computer simulation results, and experimental results for, use in the database., The function of the database can be further, enhanced by the inclusion of links to actual, material data for the component. Using such, existing material database tools as MCBase,, the user can quickly look-up the material, properties of a component with the simple, click of a button., , 3.3.7 BEMflow, (boundary, element, simulation-extrusion mixing) BEMflow, is a boundary element simulation package, for designing, optimizing, and analyzing, polymer processes and equipment. The, boundary-only approach of the boundary element method (BEM) makes it attractive for, modeling flows in extruders, mixing heads,, extrusion dies, internal batch mixers, among, others. The boundary element method is, founded on rigorous mathematical theory, that reduces the dimensionality of the, problem. Now optimization can be done on, complex 3-dimensional geometries in a, realistic time frame on desktop computers., 3.3.8 MiniFlow (the essential tool for injection molding) MiniFlow is a tool used to, simulate the mold filling stage of injection, molding. Using material models to fully describe the flow and heat transfer during mold, filling, MiniFlow is capable of predicting the, flow length and cooling for thermoplastics., This aids the designer/engineer during the, critical first steps of material and machine, selection in the design stage. This software, provides for the selection of polymers, machines, or molding conditions. Generic polymers, specified by manufacturer, or user, defined, can be selected. The material parameters for the selected polymer are automatically used for any calculation. Pressure, and flow parameters are automatically used, for calculations based on injection molding, machine selection from a manufacturer data, bank or other injection molding machines, added into a user defined data bank., , 607, , 3.3.9 3-D curing (3D thermoset molding simulation) When molding with thermoset resins, there often arise problems with, cycle times or excessive residual stress in the, final part. These parts can have non-uniform, temperature distributions due to the heat, generated during curing, which lead to nonuniform curing and unacceptable residual, stress fields. Traditional methods of experimentally modifying molding conditions to, yield an acceptable part, are time consuming, and expensive. Additionally, the acceptable, molding conditions may lead to unacceptably, long cycle times., Cure3D is used to alleviate many of the, problems with molding thick sections out, of thermoset materials. Through the use of, the finite element method, a new design can, be evaluated for problems during processing, and then modified as appropriate to give both, good material properties and improved processability. As three dimensional geometry, of the part is considered, accurate solutions, for the temperature, cure, and residual stress, field are obtained from the simulation model., Typical thermoset polymeric reactions are, exothermic in nature and can release a great, deal of heat during cure. The relatively low, thermal conductivity of the polymer causes, heat to be stored in the polymer and for the, bulk temperature to rise. Since most systems, are also temperature dependent, the added, heat causes an increase in the rate of reaction and a compounding effect on the temperature. The process is further exacerbated, in thick sections, where the heat rise can actually exceed the degradation temperature, of the polymer system and cause dramatic, decreases in the mechanical performance of, the material. The problem is further compounded because the evolution of mechanical properties is directly dependent upon the, degree of cure of the material. As the material cures, residual stress begins to be formed, and built into the structure. If the cure does, not progress in a uniform manner, gradients, in the stress can result and lead to gross deformation of the finished part. Cure3D solves, the coupled equations of energy and stress to, accurately determine the temperatures, degree of cure, residual stress, and deformed

Page 626 : 608, , Appendix A:, , Plastics Design Toolbox, , shape of the component during the molding, process., , training, and support to help facilitate engineering processes., , 3.4, , 3.4.7 Aerospace center ofexcellence The, SDRC Aerospace Center of Excellence,, based in SDRC's San Diego, California, facility includes over 30 engineers with expertise in aerospace product development methods. The Center offers customers a process, for enabling significant gains in efficiency,, productivity, reliability, and overall quality in, their product development operations., , SDRC Solutions, , SDRC World Headquarters, 2000 Eastman, Drive, Milford, OH 45150-2400, Tel: 513-576-2400, http://www.sdrc.com/, 3.4.1 I-DEAS® master series SDRC's, mechanical design automation (MDA) software, used by manufacturers for the design, analysis, testing, and manufacturing of, mechanical products., 3.4.2 Metaphase® Metaphase offers a, Web-centric information infrastructure that, harnesses its customers' intellectual capital, to drive product innovation and manage the, complete product life cycle., 3.4.3 Imageware Imageware is SDRC's, advanced 3D surface modeling and verification technology for the automotive,, aerospace, and consumer products industries., 3.4.4 FEMAP and VisQ With FEMAP,, users can define analysis models, integrate the, appropriate solver technologies and review,, interpret and document their results quickly, and efficiently. VisQ speeds and automates, the batch solution process by integrating remote computer servers across networks and, the Internet with FEMAP on the engineer's, desktop., 3.4.5 Product catalog Organized to help, you find the mechanical engineering and, data management software tools you need, to boost the productivity of individual designers, drafters, analysts, test engineers, and, manufacturing engineers, as well as the entire, product development team., 3.4.6 Experteam(SM) services SDRC's, ExperTeam services-a world-class engineering organization-provides integration,, customization and implementation services,, , 3.5, , Finite Element Analysis Software, , 3.5.1 ANSYS, Inc., Southpointe, 275 Technology Drive, Canonsburg, PA 15317, E-mail: [email protected], http://www.ansys.com, Tel: 724. 746.3304/800937-3321, Fax: 724.514.9494, Toll Free Mexico: 95.800.9373321, ANSYS, Inc. has developed two product lines, that allow you to make the most of your investment. DesignSpace® gives you access to, CAD models through an intuitive, consistent, interface while ANSYS® provides the functionality you need to create state-of-the-art,, high quality products and the flexibility to, work with other CAD software. These two, product lines allow users to choose which, product works best in their environment., Combining the power of ANSYS analysis, with DesignSpace CAD integration establishes a truly collaborative engineering environment for companies to optimize their, product designs and internal processes., 3.5.2 Algor, Inc., 150 Beta Drive, Pittsburgh, PA 15238-2932, Phone: +1 (412) 967-2700, Fax: +1 (412) 967-2781, Europe (UK): +44 (1784) 442246, Algor Publishing Division phone number:, (1-800-482-5467), Information: to learn more about Algor's, complete line of CAD/CAE interoperability,

Page 627 : Appendix A: Plastics Design Toolbox, finite element modeling, FEA and Mechanical Event Simulation products, E-mail:, [email protected] for further information on, Algor or any of Algor's products., Tel: +1 (412) 967-2700, Fax: +1 (412) 967-2781, Europe (UK): +44 (1784) 442 246, Algor Publishing Division phone number:, (1-800-482-5467), Algor Finite Element Analysis and, other training through Live Webcasts., For webcast schedules see website page, http://www.algor.com/webcast/training.htm, , 3.5.3 Noran Engineering, Inc., NE/NASTRAN, , 5182 Katella Ave., Suite 201, Los Alamitos, CA 90720., Tel: (714) 895-5857, E-mail: [email protected], Web address: www.nenastran.com, , 3.5.4 FEAMAP, Free FEMAP 300-Node Demo software from, Enterprise Software Products, Inc., By downloading the basic FEAMAP with, Parasolid and ACIS add-ons, the demo license FEAMAP is enabled as a full FEMAP, Professional., http://sai-mtab.com/software/download.htm, 3.5.5 STARDYNE, Research Engineers, Inc., 22700 Savi Ranch Pkwy, Yorba Linda, CA 92887, General Inquiries, Email: [email protected], Ftp Site: ftp.reiusa.com, Phone: (714) 974-2500, Fax: (714) 974-4771, http://www.reiworld.com/, http://www.reiusa.com/sdyn/sdynO.htm, As the world's first commercially available Finite Element Analysis software,, STARDYNE has been at the forefront of, technology since 1967. Its comprehensive, array of Finite Element capabilities allows, the engineer to perform in a wide variety, of fields-from space vehicles to missiles to, nuclear power plants to sophisticated ma-, , 609, , chinery. Extremely reliable and easy-to-use,, STARDYNE offers Linear/Nonlinear Static,, Dynamic, Seismic, Buckling, Heat transfer,, Fatigue, Fracture analysis; efficient graphical, modeling and result verification., , 3.5.6 Structural research & analysis corporation, Developers of COSMOSI™ Applications, U.S. Headquarters 12121 Wilshire Blvd. 7th, Floor, Los Angeles, CA 90025, Phone: 310.207-2800, Fax: 310.207-2774, E-mail: [email protected], http://www.cosmosm.com, Eastern Regional Office, Developers of COSMOSI™ Applications, 5000 McKnight Road, Suite 402, Pittsburgh, PA 15237, Phone: 412.635-5100, Fax: 412.635-5115, E-mail: [email protected], European Headquaters, Developers of COSMOSI™ Applications, PO Box 98 Ashford, Kent TN24 9WZ, England, Phone: +44-0-1233 642104, Fax: +44-0-1233 642106, E-mail: [email protected], 3.5.7 FEMur: Finite element method universal resource Introduction to FEMur, Learning Modules for the Finite Element, Method (FEMur-LAM), Interactive Learning Tools for Finite Element Method (FEMur-CAL), Finite Element Resources on WWW, FEMur Developers, Financial, Hardware, and Software Supporters, http://femur.wpi.edu/main--Illenu.html, 3.5.8 Internet finite element resources, Lists public domain and shareware programs, a selection of pointers to commercial packages, and other finite element, resources., http://www.engr.usask.ca/..-.macphed/finite/, fe_resources/feJesources. html

Page 628 : 610, 3.6, , Appendix A: Plastics Design Toolbox, Other Plastics Design Computer, Software, , 3.6.1 "Computer aided analysis of, stress/strain behavior of high polymers",, 2nd edition, Technomic PubIs. The Book, provides a review of the fundamentals of, polymer viscoelasticity, the measurement of, viscoelastic properties, and the use of these, measurements in a constitutive model. The, ~odel is incorporated into the Computer, SImulator for predicting the behavior and, perfor~ance of polymeric materials during, processmg. Examples of the use of the, Computer Simulator in specific applications, are included. The software provides for the, creation of rheology models from dynamic, modulus data to simulate real polymer, processing situations. The book and software, provide the link between fundamentals, and practical applications in the design of, polymer manufacturing processes as well as, for insight into the enduse performance of, polymer products. See http://www.4spe.org, for availability., 3.6.2 "Computer program for formed, material cost comparisons ", developed by, ~ohm & Haas Co., and distribution rights, gIVen to the Thermoforming Div. SPE. This, program provides a direct cost comparison, of up to 5 resins (ABS, HDPE, HIPS, PETG, and PP). Three programs are included· the, ', 1st computes costs for thermoformed parts, n, d, ·, t h e 2 adds extrusIOn to the cost compari-', son. The 3rd program is a metric version of, the thermoforming/extrusion program. See, http://www.4spe.org for availability., 3.6.3 Design of foam-filled structures, (with PC Disk)", 2nd edition, John A., Hartsock; Technomic PubIs; (1991); ISBN:, 0877627452. A comprehensive guide and reference for the structural design of foam filled, panel systems. Combines the theory and the, calculations to enable an engineer to design, the foam filled building panels used for their, thermal insulation, load carrying ability, and, ease of erection. Also briefly considers other, foam filled products. The second edition has, been expanded to include information on, multiple spans and design values. The PC disk, , is pro.vided to save reader time in solving, equatIOns developed in the text., , 3.7 Internet Collaboration Tools, (Software designed specifically for collaborating online), , 3.7.1 CollabWare GS-Design, is, a, solids modeling 3D CAD system specifically designed to work over the Internet., Collabware™ is web based software for, the Coll~borative Engineering and Design, commumty. Software provides design, teams around the world with the ability, to design and manage product development using custom tools accessed through, the familiar internet browser interface., http://www.collabware.com, 3.7.12 Viewcad.com A free CAD sharing site allows users to share CAD drawings securely with anyone in the world. The, ~ite provides a simple method for publishmg and sharing CAD drawings on the Internet. The site is made available by Arnona, Internet Software, provider of Internet solutions for the CAD market. A standard account includes space for 5 drawings and the, CADViewer Light viewer is free. Account, access is restricted by password protection., http://www.viewcad.com, 3.7.3 Parametric technology corporationwindchill Windchill provides a collaborative environment for the sharing and visualization of product and process knowledge., Information can be accessed through a Web, browser and used to identify, visualize, and, markup models, providing engineers fast and, accurate responses to inquiries. http://www., ptc.com/products/windchilllindex.htm, 4., , 4.1, , Plastics Design Books, , Plastics Design Reference Books, , 4.1.1 "Designing with plastics: based on, material & process behaviors", Donald V., Rosato, Marlene G. Rosato, and Dominick V., Rosato, Kluwer Academic Publishers (2000).

Page 629 : Appendix A: Plastics Design Toolbox, This book provides a simplified and practical approach to designing with plastics that, fundamentally relates to the load, temperature, time, and environment subjected to a, product. It will provide the basic behaviors, in what to consider when designing plastic, products to meet performance and cost requirements. Important aspects are presented, such as understanding the advantages of different shapes and how they influence designs., Important are behaviors associated and, interrelated with plastic materials (thermoplastics, thermosets, elastomers, reinforced plastics, etc.) and fabricating processes, (extrusion, injection molding, blow molding,, forming, foaming, reaction injection molding,, etc.). They are presented so that the technicalor non-technical reader can readily understand the interrelationships., The data included provides examples of, what are available. As an example static properties (tensile, flexural, etc.) and dynamic, properties (creep, fatigue, impact, etc.) can, range from near zero too extremely high values. They can be applied in different environments from below the surface of the earth, to, over the earth, and into space., This comprehensive resource recognizes, that effective design is an interdisciplinary, process involving the ability to match application situations with techniques and to, develop problem-solving methods to fit the, specific design requirements. Detailed chapters' cover processing methods available for, manufacture and effective techniques for, evaluating plastic properties and applying, quality control. Coverage of the complete design cycle also explores:, • Unique plastic performance capabilities, and adaptabilities, • Selecting the right plastic or composite for, the end use product, • Optimizing material performance during, processing, • Maximizing product cost performance with, flexible production procedures, • Effective problem analysis to minimize, production difficulties, , 4.1.2 "Injection molding handbook, third, edition", Donald V. Rosato, Marlene G., , 6/1, , Rosato, and Dominick V. Rosato, Kluwer, Academic Publishers (2000). This third edition has been written to thoroughly update the subject of the Complete Injection, Molding Operation in the World of Plastics. By updating the book, there have been, changes with extensive additions to over 50%, of the 2nd Edition content. Many examples, are provided of processing different plastics and relating them to critical factors, that, range from product designs-to-meeting performance requirements-to-reducing costs-tozero defect targets. Changes have not been, made that concern what is basic to injection, molding (1M). However, more basic information has been added concerning present and, future developments, resulting in the book, being more useful for a long time to come., Detailed explanations and interpretation of, individual subject matters (1500 plus) are, provided using a total of 914 figures and 209, tables. Throughout the book there is extensive information on problems and solutions, as well as extensive cross-referencing on its, many different subjects., This book represents the ENCYCLOPEDIA on 1M, as is evident from its extensive, and detailed text that follows from its lengthy, Table of CONTENTS and INDEX with over, 5200 entries. Even though the worldwide industry literally encompasses many hundreds, of beneficial computer software, plastic related programs, this book explains with a, brief list these numerous beneficial programs, (ranging from operational training to product design to molding to marketing); no one, or series of software programs can provide, the details obtained and the extent of information contained in this single source-book., , 4.1.3 "Designing with reinforced composites: Technology, performance, economics",, Dominick V. Rosato; Hanser Gardner, PubIs; (1997); ISBN: 1569902119. This book, presents essential information on how to, succeed in meeting product performance, requirements while simultaneously producing at the lowest cost with zero defects., The information presented ranges from basic design principles to designs of different, sized molded parts produced by different RP, processes.

Page 630 : 612, , Appendix A: Plastics Design Toolbox, , 4.1.4 "Design data for reinforced plastics:, A guide for engineers and designers", Neil, L. Hancox, Rayner M. Mayer; Chapman &, Hall (Kluwer Academic Publishers); (1994);, ISBN: 0412493209. In this book, the authors, have assembled a systematic set of design, parameters describing short and long term, mechanical, thermal, electrical, fire and environmental performance, etc. for composites, based primarily on continuous glass, aramid, and carbon fibers in thermosetting and thermoplastic matrices., 4.1.5 "Design data for plastics engineers",, Natti S. Rao, Keith T. O'Brien; Hanser, Gardner PubIs; (1998); ISBN: 156990264X., Whether working on product design or process optimization, engineers need a multitude, of polymer property values. This book provides a quick reference on basic design data, for resins, machines, parts, and processes, and, shows how to apply these data to solve practical problems., 4.1.6 "Design formulas for plastics engineers", Natti S. Rao; Hanser Gardner PubIs;, (1991); ISBN: 1569900841. The formulas in, this book are classified for specific areas, including rheology, thermodynamic properties,, heat transfer, plastic and part type., 4.1. 7 "Flow analysis of injection molds",, Peter Kennedy; Hanser Gardner PubIs;, (1995); ISBN: 1569901813. For mechanical, engineers, polymer engineers, and applied, mathematicians who want to increase their, understanding of flow analysis technology,, this book is a thorough introduction to, computer simulation of the injection molding process, including MOLDFLOW. Provides mechanical and polymer engineers with, the theoretical background and hundreds of, equations for using the many software packages now available that apply flow analysis, to the design of plastic parts to be manufactured by injection molding. Among the topics, are material properties, governing equations, of fluid flow, mathematical models, finite element formulations, and numerical solutions., , 4.1.8 "Designing with plastics", G.W., Ehrenstein, G. Erhard; Hanser PubIs; (1984);, ISBN: 0029487706. Key book sections include (1) design influencing factors, (2) environmental effects on plastics, (3) life cycle, assessment and prediction, (4) cost estimation and (5) design guidelines., 4.2, , Fabricated Plastic Product Design, Books, , 4.2.1 "Designing with plastics: based on, material & process behaviors", Donald V., Rosato, Marlene G. Rosato, and Dominick V., Rosato, Kluwer Academic Publishers (2000)., This book provides a simplified and practical approach to designing plastic products, that fundamentally relates to the load, temperature, time, and environment subjected, to a product. It will provide the basic behaviors in what to consider when designing, plastic products to meet performance and, cost requirements. Important aspects are presented such as understanding the advantages, of different shapes and how they influence, designs., Important are behaviors associated and, interrelated with plastic materials (thermoplastics, thermosets, elastomers, reinforced, plastics, etc.) and fabricating processes (extrusion, injection molding, blow molding,, forming, foaming, reaction injection molding,, etc.). They are presented so that the technicalor non-technical reader can readily understand the interrelationships., The data included provides examples of, what are available. As an example static properties (tensile, flexural, etc. ) and dynamic, properties (creep, fatigue, impact, etc.) can, range from near zero too extremely high values. They can be applied in different environments from below the surface of the earth, to, over the earth, and into space., 4.2.2 "Injection molding handbook, third, edition ", Donald V. Rosato, Marlene G., Rosato, and Dominick V. Rosato, Kluwer, Academic Publishers (2000). This third edition has been written to thoroughly update the subject of the Complete Injection

Page 631 : Appendix A: Plastics Design Toolbox, Molding Operation in the World of Plastics. By updating the book, there have been, changes with extensive additions to over 50%, of the 2nd Edition content. Many examples, are provided of processing different plastics and relating them to critical factors, that, range from product designs-to-meeting performance requirements-to-reducing costs-tozero defect targets. Changes have not been, made that concern what is basic to injection, molding (1M). However, more basicinformation has been added concerning present and, future developments, resulting in the book, being more useful for a long time to come., Detailed explanations and interpretation of, individual subject matters (1500 plus) are, provided using a total of 914 figures and 209, tables. Throughout the book there is extensive information on problems and solutions, as well as extensive cross-referencing on its, many different subjects., This book represents the ENCYCLOPEDIA on 1M, as is evident from its extensive, and detailed text that follows from its lengthy, Table of CONTENTS and INDEX with over, 5200 entries. Even though the worldwide industry literally encompasses many hundreds, of beneficial computer software, plastic related programs, this book explains with a, brief list these numerous beneficial programs, (ranging from operational training to product design to molding to marketing); no one, or series of software programs can provide, the details obtained and the extent of information contained in this single source-book., , 4.2.3 "Blow molding handbook", Donald V. Rosato and Dominick V. Rosato, Hanser Gardner PubIs; (1989)., 4.2.4 "Plastic part design for lnjection, molding: An introduction", Robert A. Malloy; Hanser Gardner PubIs; (1994); ISBN:, 1569901295. This reference reflects the common problems an engineer faces while designing a plastic part and assists the designer, in the development of parts that are functional, reliable, manufacturable, and aesthetically pleasing. With wide use of injection, molding in the manufacture of plastic parts,, understanding the integrated design process, , 613, , is essential to achieving economical and functional design., , 4.2.5 "Injection molding alternatives: A, guide for designers and product engineers",, Jack Avery; Hanser Gardner PubIs; (1998);, ISBN: 1569902518. This guide covers a wide, range of processes, variations of injection, molding techniques, and low volume production techniques used for proto typing and, pre-production. The fit, advantages, disadvantages, materials used, and design, application and tooling considerations are reviewed, for each process covered. Innovations such, as deep-draw blow molding, multi-live feed, molding, gas-assisted injection molding and, in-mold decoration are discussed. Includes, process comparison charts., 4.2.6 "Blow molding design guide",, Norman C. Lee; Hanser Gardner PubIs;, (1998); ISBN: 1569902275. This book provides an understanding of plastic blow, molded parts, materials, and processes. It, also compares the benefits and limitations, of various processes, mold engineering,, decoration, assembly techniques, and other, topics. Issues relating to manufacturability, and cost are emphasized., 4.2.7 "Handbook of package engineering", 3 rd edition, IF. Hanlon, R.I Kelsey,, H.E. Forcinio; Technomic PubIs; (1998);, ISBN: 1566763061. The standard industry, reference on packaging materials and engineering, the 3rd edition includes development of environmentally-sensitive packaging. This reference work presents the basic, engineering aspects of packaging: materials, package designs, function and performance, production and graphics, machinery, and equipment and standards and regulation., Text also introduces the increasing web of, laws and regulations controlling virtually all, packaged products in efforts to reduce the, impact of packaging disposal on landfill., 4.2.8 "Rotational molding: Design, materials & processing", Glenn Beall; Hanser, Gardner PubIs; (1998); ISBN: 1569902607. A, highly versatile process, rotational molding

Page 632 : 614, , Appendix A:, , Plastics Design Toolbox, , allows for incredible design flexibility with, the added benefit of low production costs., This guide to the rotational molding process, explains how to make full use of the capabilities of this manufacturing technique. Emphasis is on when to specify rotational molding, and how to design and develop hollow plastic products that can be efficiently produced., The book also reviews the origins of the process, its present status, and future prospects,, and discusses design considerations, materials, and molds., , 4.3, , Industrial Design Reference Books, , 4.3.1 "Joining of plastics: Handbook, for designers and engineers", Jordan I., Rotheiser; Hanser Gardner PubIs; (1999);, ISBN US: 1569902534; German: 3446174184., This book takes the joining of plastics to a, new level by dealing with the special considerations necessary to apply the principal assembly methods to parts manufactured by the 22, maj or processing methods and made of the 34, most commonly used plastics. This handbook, emphasizes the relationship between the assembly methods, materials, and the manufacturing process. In addition, the subjects of, design for disassembly, recycling, cost reduction, and the complete elimination of joining, operations are addressed. The book provides, a chapter for a description of each of the 14, principle fastening and joining methods used, to assemble plastics today. The advantages, and disadvantages of each method are listed, and rapid guidelines for joining of plastics, are also provided. The author has gone to, considerable lengths to make information retrieval quick and effective. The book is extensively indexed and contains a detailed table of, contents., 4.3.2 "American plastic: A cultural history", Jeffrey L. Meikle; Rutgers Univ, Press; (1997); ISBN: 0813522358. Meikle, traces the course of plastics from 19thcentury celluloid and the first wholly synthetic bakelite, in 1907, through twentiethcentury science, technology, manufacturing,, marketing, design, architecture, consumer, , culture and the proliferation of compounds, (vinyls, acrylics, nylon, etc.) to recent ecological concerns. Winner of the 1996 Dexter Prize, from the Society for the History of Technology. 70 illustrations., , 4.3.3 "1950s plastics design: Everyday, elegance", 2nd edition, Holly Wahlberg;, Schiffer Publishing, Ltd.; (1999); ISBN:, 0764307835. This book presents a factual, discussion of the wide variety of colorful, and popular plastics housewares made between 1945 and 1960. Advertisements that, announced to the world what new designs, were possible with this experimental material are shown. Many color photographs, of today's highly collectible plastics objects, demonstrate the variety of colors and useful forms that were manufactured. Vinyl,, Lucite, Melamine and Formica, to name but a, few, have become common household names, since their introduction in this era. Here, are chairs, tables, dishes, cups, radios, lampshades, draperies, cooking containers, car interiors, floors and more-all made of plastics., A very useful Guide, providing information, about all the major manufacturers and trade, names, is organized by product types for easy, reference., 4.3.4 "Designing with plastics", P.R., Lewis; RAPRA Review Report, No 64;, (1993); ISBN: 0902348752. Dr. Lewis surveys, the current state of the art in designing with, plastics, in terms of materials properties and, processing technologies. He also considers, the legal implications of intellectual property, and product liability, as well as ergonomic, and aesthetic design, parts consolidation and, recyclability., 4.3.5 "Product design with plastics, A, practical manual", Joseph B. Dyn; Industrial Press Inc.; (1983); ISBN: 0831111410. A, classic, applied, practical plastic design book., Topics covered include: (1) introduction to, the application of plastics, (2) description and, derivation of short term and long term properties, (3) polymer formation, variation, and, characteristics, (4) product design features,, (5) designing the plastic product, (6) joining

Page 633 : Appendix A: Plastics Design Toolbox, or assembly techniques, (7) description of, processing plastics, and (8) cost estimating of, plastic parts for product designers., 4.3.6 "Plastic product design", 2 nd Edition, Ronald D. Beck; Van Nostrand Reinhold, (Kluwer Academic Publishers); (1980);, ASIN: 0442206321. This book serves very, well as a basic guide to the study and application of plastic product design. The main topics, discussed are: mold design for part requirements; molded holes and undercuts; threads;, inserts; fastening and joining plastics; decorating plastics; extrusion design and processing; reinforced plastics; and tests and identification of plastics., 4.3.7 "Plastics product design engineering handbook", Sidney Levy and T., Harry DuBois; Van Nostrand Reinhold,, (Kluwer Academic Publishers); (1977);, ASIN 0412005115. A classic design course, converted to book format that provides a, very good introduction to a multitude of, basic design features and environments, focused on specific examples and end use, application areas., , 4.4 Plastic Design Reference Books:, Special Topics, 4.4.1, , Plastics mold design, , • "Injection Molds 108 Proven Designs",, Hans Gastrow, E. Lindner (Editor), P., Unger (Editor); Hanser Gardner PubIs;, (1993); ISBN: 1569900280. This classic belongs on the desk of everyone involved, in designing or building injection molds., Invaluable for the working engineer, this, book demonstrates problem solving in, toolmaking for injection molding and contains a wealth of information, practical tips, and proven shortcuts., • "Injection Molds and Molding: A Practical Manual", 2nd Edition, Joseph B Dym;, Kluwer Academic Publishers; (1987);, ISBN: 0442217854. Highlights include, a description of CAD/CAM potential, and process control capabilities, and a, , 615, , method of mold maintenance that prolongs the period of operation. Also features a guide for cooling time that can be, used for comparing mold cooling performance., • "Mold-Making Handbook for the Plastics, Engineer, 2nd Edition, Klaus Stoeckhert,, Gunter Mennig (Editor); Hanser Gardner PubIs; (1998); ISBN: 1569902615., Stoeckhert's classic provides all of the, fundamental and engineering aspects of, mold construction and manufacturing., Designed to permit a direct comparison of, different molds used in plastics processing,, this comprehensive review covers molds, for various processing methods (injection,, compression and transfer molds, etc.);, mold materials (steel, bronzes, aluminum, and zinc alloys, materials for prototype, molds); and manufacturing and machining, processes (including computer-integrated, manufacturing and electroforming). Other, topics include mold maintenance and the, latest developments in CAD and rapid, prototyping technology., • "How to Make Injection Molds", 2nd Edition, G. Menges, P. Mchren; Hanser Gardner PubIs.; (1993); ISBN: 1569900820. This, is a comprehensive, classic handbook for, the design and manufacture of injection, molds. It covers all practical aspects involved such as material selection, fabricating cavities and cores, general mold design,, hot runner systems, venting, mechanical/dimensional/thermal design, demolding techniques and devices, maintenance of, injection molds, standard elements, hardware, and design/construction procedures., Geared to the applied industrial technologist and academic. Practical problem solutions illustrated throughout the text., 4.4.2, , Plastics failure analysis, , • "Plastics Failure Guide: Cause and Prevention", Myer Ezrin; Hanser Gardner PubIs;, (1996); ISBN: 1569901848. The focus of this, book is on actual field and product failures. This comprehensive volume emphasizes cause and prevention and illustrates, how and why a variety of plastic products

Page 634 : 616, , Appendix A: Plastics Design Toolbox, , fail due to fracture, appearance change,, loss of adhesion, and many other problems., Topics include the nature, causes, and consequences of plastics failure; fundamental materials variables affecting processing, and product performance or failure; failure related to design and material selection; processing-related factors in failure;, failure related to service conditions; failure, analysis and test procedures; quality control; legal aspects of failure., • "Failure Of Plastics", Witold Brostow,, Roger D. Corneliussen; Hanser Gardner, PubIs; (1986); ISBN: 1569900086. Complete reference on the mechanical failure of, plastics. Covering theory and practice, this, book describes an expert knowledge base, and provides directions for future work toward elimination of mechanical failure of, plastics under varied conditions., , 4.4.3 "Handbook of plastics testing, technology", 2nd edition, Vishu Shah; John, Wiley & Sons; (1998); ISBN: 0471182028., This handbook is the most complete compilation of the tests currently used in the plastics, industry. It provides descriptions and diagrams of testing procedures, and explains the, significance and advantages and limitations, of the tests. Properties that can be tested, by the methods described include mechanical, thermal, electrical, weathering, optical,, chemical, and flammability. In addition, chapters also discuss conditioning procedures,, identification of plastics, characterization, and analysis, testing of foam plastics, quality, control, professional and testing organization, product liabilities, failure analysis, and, uniform global testing standards., 4.4.4 "Designing plastic parts for assembly, 3Td Edition, Paul A Tres; Hanser, Gardner PubIs; (1998); ISBN: 1569902437., This practical design book facilitates costeffective design decisions and helps to ensure, that the plastic parts and products designed, stand up under use. The book describes good, joint design and joint purpose, the geometry, and nature of the component parts, the types, of loads involved and other basic information, important in plastic part assembly., , 4.4.5 "Guide to short fiber reinforced, plastics", Roger F. Jones with Mitchell R., Jones and Donald V. Rosato; Hanser Gardner PubIs; (1998); ISBN: 1569902445. Written from the perspective of the product, design engineer, the emphasis is on practical aspects of basic design considerations in, the selection, use, and automated fabrication of short fiber reinforced thermoplastics, and thermoset materials. This book examines, the principles characteristics of these materials and their strengths and weaknesses in, practical terms for design engineers. It examines the strengths and limitations of these, growth industry materials valued at over 1.5, billion dollars (US, 1997). Includes illustrations, suppliers, applications, and references, with a more theoretical bent., 4.4.6 "Molded thermosets: A handbook, for plastics engineers, molders, and designers", Ralph E. Wright; Hanser Gardner, PubIs; (1991); ISBN: 1569901120. This handbook provides in-depth coverage of every important family of thermoset polymer systems, and their molding-from the raw material, through the finished molded part., 4.4.7 "Composites-design, manual",, Jim Quinn; Jim Quinn Associates Ltd;, (1996); available from SPE. A concise handbook of composites related information that, engineers, designers and specifiers will find, valuable. Contents include specifications for, a wide range of reinforcements, and overview, of initiators, and other product information,, properties, processes, construction analysis,, property prediction, and design., 5. Design Education, , 5.1, , Design Education Books, , 5.1.1 "Concise encyclopedia of plastics:, Fabrication & industry", Donald V. Rosato,, Marlene G. Rosato, and Dominick V. Rosato,, Kluwer Academic Publishers (2000). This, practical and comprehensive book reviews, virtually the "A-to-Z" of the plastics industry by using over 20,000 entries. Each of

Page 635 : Appendix A:, , Plastics Design Toolbox, , the major subjects (entries) could represent, a separate book. Where common information exists, they are cross-referenced. There, is extensive cross-referencing where one subject is defined and related to many other, subjects, thus significantly reducing the size, of the book. Its brief and concise format, goes from understanding basic factors such, as a plastic's melt flow behavior during processing to designing and fabricating products, targeted to meet performance and cost requirements with zero defects. This type of, understanding is required in order to initially design, prototype fabricate, and volume, manufacture the many different marketable, products reviewed in this book and that exist, worldwide., More importantly, this extensive crossreferencing provides information on how the, many subjects interrelate. All pertinent information for a subject is included in the definition and/or its cross- referenced component., They are searchable under their own headings based on the reader's needs. In order to, cover the needs of different individual interests, many of the subjects have very extensive cross-referencing. Thus, the readers can, cross-reference those subjects that meet their, needs. This approach simplifies understanding any single subject and, most importantly,, shows very vividly the many common similarities and interactions that exist between the, subjects in the World of Plastics., , 5.1.2 "Plastic injection molding: Material, selection and product design fundamentals",, Douglas Bryce; Society of Manufacturing, Engineers; (1997); ISBN: 0872634884. Shows, how to identify the optimum material for a, particular product based on the product's design, manufacturing, and end-use parameters., Available from Injection Molding Magazine, Bookclub (See 6.2), or Society of Manufacturing Engineers., 5.1.3 "Plastic injection molding: Mold, design & construction fundamentals",, Douglas Bryce; Society of Manufacturing, Engineers; (1998); ISBN: 0872634957. Shows, how to design and build injection molds;, specifically, how to design gate location,, , 617, , shape, and size, as well as how to use venting, properly. A mold design checklist is also, included. Available from Injection Molding, Magazine Bookclub (See 6.2), or Society of, Manufacturing Engineers (see 7.5)., , 5.1.4 "Plastics: Product design and process engineering", Harold Belofsky; Hanser, Gardner PubIs; (1995); ISBN: 156990179l., This textbook, designed for undergraduate, mechanical engineering courses, integrates, product design with a study of mechanical, and physical properties, processing machinery and tooling, and materials and process, selection. The focus is on applications rather, than training for academic research. Many illustrative examples and quantitative homework problems are included., 5.1.5 "Understanding Product design injection molding", Herbert Rees; Hanser, Gardner PubIs, (Hanser Understanding, Books); (1996); ISBN: 1569902100. This book, highlights many of the questions and decisions engineers will face while designing, products. The designer using this book will, have a better understanding of process and, material selection, and how to design an injected mold product that will work as expected and be produced efficiently., 5.1.6 "Computer modeling for polymer processing: Fundamentals", Charles L., Tucker III (Series Editor: Ernest C. Bernhardt); Hanser Gardner PubIs; (1989); ISBN:, 1569901015. Computer simulations have become an important tool for the engineering of polymer processing operations. This, book looks inside this important technology,, showing how to use computers and numerical methods to simulate flow, heat transfer, and structure development in polymer processing operations., 5.1. 7 "Plastics engineering handbook of, the society of the plastics industry, inc. ",, 5th edition, Michael L. Berins (Editor);, Chapman & Hall (Kluwer Academic Publishers); (1991); ISBN: 0412991810. Since, 1947, the most comprehensive reference, available on plastics processing methods,

Page 636 : 618, , Appendix A: Plastics Design Toolbox, , equipment, and materials. Sponsored by the, Society of the Plastics Industry, Inc., the, revised and updated fifth edition incorporates all major advances in the plastics industry. It covers the state of the art in, both materials-high-temperature thermoplastics, liquid crystal polymers, and thermoplastic composites-and processing-resin, transfer molding, structural reaction injection molding, gas-assisted injection molding,, stretch blow molding, automation, and process control., , 5.2 Plastics Design Training (Seminars and, Interactive CD-Roms), 5.2.1 Glenn Beall plastics technology seminars, Glen Beall Plastics, LTD., 32981 North River Road,, Libertyville, Illinois 60048, Tel: 413 733-8588, Fax: 413 733-9325, http://www.pcn.org/Beall.htm, Glenn L. Beall, a Kunststoffe, and IMM contributing editor, has been intimately involved, with both plastics product design and injection molding for 40 years. He has been, doing preproduction engineering of plastics, components since 1957 and today is a recognized authority in this area. Glenn Beall, Plastics Ltd., concentrates on product design,, consulting and plastics technology seminars., Mr. Beall holds more that 35 patents in, the plastics area and works extensively as a, designer, consultant and expert witness on, projects involving plastics technology., 5.2.2 Paulson training programs, Inc.,, 15 No. Main St., P.o. Box 366,, Chester, CT 06412 USA, Phone: 860-526-3099, Fax: 860-526-3454, E-mail: [email protected], http://www.paulson-training.com, 5.2.3 A. Routsis associates, Inc., 275 Donohue Road, Suite 14, Dracut, MA 01826 USA, Phone: 978-957-0700, Fax: 978-957-1860, , E-mail @netway.com, http://www.plastics-training.com, , 5.2.4 Society of plastics engineers (SPE), PO Box 403, Brookfield, CT 06804-0403, Series of SPE sponsored seminars and workshops are held in various locations throughout the year. Subjects range from "Die Design Principles to Plastic Part Design for, Economical Injection Molding. A full range, of seminars are also conducted in conjunction with SPE's annual technical conference, (ANTEC)., http://www.4spe.org, 5.2.5 RAPRA training courses, Raspra Technology Ltd., Shawbury, Shrewsbury, Shropshire SY44NR,, , u.K., , Tel: +44-1939-250383,, Fax: +44-1939-251118), http://www.rapra.net, Rapra Training Courses are held at Rapra, or on-site and may also be developed to, meet clients' specific requirements. Popular, courses include: Plastics Materials and Products; Designing and Engineering with Rubber; Testing and Specification of Polymer, Products; Plastics in Packaging., , 5.2.6 Hanser gardner CD-ROM training, for plastics, Hanser Gardner Publications, 6915 Valley Avenue, Cincinnati, OH 45244-3029, http://www.hansergardner.com, Plastic Part Design Series: Based on, Dr. Robert Malloy's book, Plastic Part Design for Injection Molding, this new design, series consists of six CDs: Product Development and Prototype Process; Mechanical Behavior of Polymers; Mold Filling, Gating, and, Weld Lines; Shrinkage,Warpage, and Ejection; Mechanical Fasteners, Press and Snap, Fits; Welding and Adhesive Bonding Technology., 5.2.7 IMM Book Club-Training CDROMs, Paulson Training Programs, A. Routsis Associates Training Programs

Page 637 : Appendix A: Plastics Design Toolbox, Desktop Dimension International Training, Programs, http://www.immbookclub.com/store/, training.html, , 5.2.8 GE plastics e-seminars, GE Plastics virtual conference center., e-Seminars offers "live" online conferences., e-Seminar examples include:, Material Selection, Materials for Single-Use Microwave Food, Packaging, http://www.geplastics.com/resins/, designsolution/seminar/, 5.2.9 Nypro online (NYPRO Inc.), 101 Union Street, Clinton, Massachusetts, 01510, Tel: 978-365-9721, Fax: 978-368-0236, E-mail: [email protected], http://www.nypro.com, Nypro Online is a strategic training lllltiative of Nypro Inc., the largest multinational custom injection molder in the world., Nypro Online is the first global plastics education provider offering college education, and focused plastics training over the internet, jointly with its academic partners, the University of Massachusetts at Lowell, and Paulson, Training Programs., 6., , 6.1, , KunststoJfe, , Carl Hanser Verlag, KolbergerstraBe 22, 81679 Miinchen, Tel: 089-99830 621, Fax: 089-99830 625, E-mail: [email protected], http://www.hanser.deizeitschriften/KU/, index.htm, , 6.4, , Design News, , 275 Washington Street,, Newton, Massachusetts, 02458-1630, Tel: 617-558-4660, Fax: 617-558-4402., http://www.manufacturing.net/magazine/dn/, maginfo/aboutdn.html, Design News, in print for over 50 years, has, a circulation of over 180,000. It covers the, latest tools, components, and materials used, in mechanical and electromechanical design, of a broad range of products. Articles feature successful engineering projects and new, technologies that will spark ideas and assist, readers in the design of new products. All articles are written by the DN staff of editors,, many of whom are engineers themselves. Design News online provides readers with an ask, the Expert feature. Questions are normally, answered within 48 hours during the workweek., , Trade Publications, , Plastics Technology, , 355 Park Avenue, South; New York, NY, 10010-1789, Tel: 212 592-6570, http://www.plasticstechnology.com, , 6.2, , 6.3, , 619, , 6.5, , Global Design News, , Global Design News, sister publication of Design News magazine in the U.S., was launched, in response to the demands of European design engineers for technology from around, the world., http://www.manufacturing.net/magazine/gdnJ, , Injection Molding Magazine, , 59 Madison Ave., Suite 770; Denver, CO, 80206, Tel: 303 321-2322, http://www.immnet.com, Injection Molding Bookclub, http://www.immbookclub.com, , 6.6, , Design & Materials, , (Biweekly Newsletter, plastics focus), Market Search Inc., 2727 Holland Road, Suite A, Toledo, OH 43615, Tel: 415 535-7899

Page 638 : 620, , Appendix A:, , Plastics Design Toolbox, , 6.7 Product Design and Development, Product Solutions for Design Engineers, © 2000 Cahners Business Information, a division of Reed Elsevier Inc.,, 8773 S. Ridgeline Boulevard,, Highlands Ranch, CO 80126., Fax: 1-303-470-4546, E-mail: [email protected], http://www.pddnet.com/, Product Design & Development is a monthly, magazine with 170,000 design engineers and, engineering management readers in the original equipment market. Design engineers, read the magazine to keep up to date on the, components, materials and systems they need, to design high-quality end products., , 6.S, , Desktop Engineering Magazine, , Helmers Publishing, Inc, 174 Concord Street, PO Box 874, Peterborough NH 03458 USA, Tel: 603-924-9631, Fax: 603-924-6746, , 6.9, , Machine Design, , Penton Media, Inc., 1100 Superior Avenue,, Cleveland, Ohio 44114 USA, http://www.machinedesign.com/, , 6.10, , Computer-Aided ENGINEERING, , 1100 Superior Avenue, Cleveland, OH 44114-2543, USA, Tel: 216.696.7000, Fax: 216.696.1267, http://www.caenet.com, , 6.11, , ANSYS Solutions, , ANSYS, Inc., Southpointe, 275 Technology Drive, Canonsburg, PA 15317, http://www.ansys.com, ANSYS Solutions is a quarterly pUblication, , focused on software applications for mechanical simulation and engineering processes. Its, goal is to provide objective and authoritative, information to help readers understand and, apply finite element analysis and other technology developed and supported by ANSYS,, Inc. Its readers include designers and engineering managers, in addition to a wide variety of industry analysts and partners. The editorial director for ANSYS Solutions is John, Krouse, a well-known and respected writer in, the CAD/CAM field. John previously served, as CAD/CAM editor for Machine Design, magazine, Editor-In-Chief and Publisher of, Computer-Aided Engineering magazine, and, has written several books in the field including, "What Every Engineer Should Know, About CAD/CAM.", , 6.12, , CAD User Magazine, , BTC Ltd. CAD User, 24 High Street, Beckenham,, Kent, BR3 lAY, Tel: +44 (0) 181 663 3818, Fax: +44 (0) 181 663 6776, cad. [email protected], The Premium CAD Magazine for the UK and, Ireland. CAD User magazine covers the technical aspects of integrating CAD in a multidiscipline, multi-product environment. With, indepth reviews of new products, case studies, and technical tips, CAD User magazine and, its online version, CADUser.Com, are useful, for CAD information., , 6.13, , Materialpriifung, , Verschaffen Sie sich den Einblick: Das, aktuelle Heft, Ihr Ansprechpartner in der Redaktion von, Materialpriifung:, Carl Hanser Verlag, Frauke Zbikowski, KolbergerstraBe 22, 81679 Miinchen, Tel: 089-99830 614, Fax: 089-99830 623, [email protected], http://www.hanser.delzei tschriften/MP/, index.htm

Page 639 : Appendix A: Plastics Design Toolbox, 6.14 Medical Device & Diagnostic Industry, , 3340 Ocean Park Blvd., Suite 1000, Santa Monica, CA 90405, Tel: (310) 392-5509, 6.15, , Reinforced Plastics, , Garrard House, 2-6 Homesdale Rd., Bromley, BR2 9WL, UK, Fax: +44 (0) 2084028383, 6.16, , World Plastics & Rubber Technology, , Essex House, Regent St., Cambridge CB2 3AB, England., , 7. Trade Associations, 7.1, , Industrial Designers Society of America, , 1142 Walker Rd., Great Falls, VA 22066, Tel: 703.759.0100, Fax: 703.759.7679, E-mail: [email protected], http://www.isda.org, • IDSA is dedicated to communicating the, value of industrial design to society, business and government, • Publishes Innovation, the professional, journal of industrial design practice and education in America, • Organizes a national conference each year,, the largest gathering of industrial designers, educators and business executives in, the US, • Conducts the annual Industrial Design Excellence Awards (IDEA) under the sponsorship of Business Week magazine, • Organizes five annual District Conferences, in concert with the education community, • Publishes the annual Directory of Industrial Designers, • Supports a network of 25 active chapters, located in cities across the US, • Distributes Design Perspectives, the, monthly newsletter to members, • Performs as a vital member of the International Council of Societies of Industrial, Design (ICSID), , 7.2, , 621, , International Council of Societies of, Industrial Design, , ICSID Secretariat oversees the daily activities of the council; it has been in Helsinki,, Finland since 1985, Kaarina Pohto, Secretary General, ICSID Secretariat, Erottajankatu 11 A-18, 00130 Helsinki, Finland, Tel: +358 9 696 22 90, Fax: +358969622910, E-mail: [email protected], http:www.icsid.org, ICSID members are professional organizations, promotional societies, educational, institutions, government bodies, companies, and institutions which aim to contribute to, the development of the profession of industrial design. Today ICSID consists of, 149 Member Societies, representing 52 countries from all continents (except Antarctica!)., These Societies collaborate to establish an international platform through which design institutions worldwide can stay in touch, share, common interests and new experiences, and, be heard as a powerful voice., 7.3, , Color Marketing Group (CMG), , 5904 Richmond Highway,, Suite 408, Alexandria, VA 22303 USA, Tel: 703 329-8500, FAX: 703 329-0155, E-mail: [email protected], http://www.colormarketing.org/, Color Marketing Group, is the premier International Association that forecasts colors, for manufactured products. Founded in 1962,, this not-for-profit, international Association, of 1,600 Color Designers is involved in the use, of color as it applies to the profitable marketing of goods and services. CMG provides a, forum for the exchange of non-competitive, information on all phases of color marketing: color trends and combinations; design, influences; merchandising and sales; and education and industry contacts. CMG members are highly qualified Color Designers who, interpret, create, forecast and select colors, in order to enhance the function, saleability

Page 640 : 622, , Appendix A: Plastics Design Toolbox, , and/or quality of a product. Two International Conferences are held each year during which CMG members forecast Color, Directions® one to three years in advance, for all industries, manufactured products and, services., , 7.4 Society of Plastics Engineers (SPE), PO Box 403 Brookfield, CT 06804-0403 USA, Tel: 203 775-0471, Fax: 203 775-8490, E-mail: [email protected], http://www.4spe.org, SPE is the recognized medium of communication amongst scientists and engineers engaged in the development, conversion and, applications of plastics. An international Society, with many of its 35,000 members residing outside the United States, The SPE, mission is to provide and promote the knowledge and education of plastics and polymers, worldwide., , 7.5 Society of Manufacturing Engineers, (SME), One SME Drive, P.o. Box 930, Dearborn MI, 48121-0930, Tel: 313271-1500/800733-4763, http://www.sme.org, SME, headquartered in Michigan is the, world's leading professional society serving the manufacturing industry. Founded in, 1932, SME has some 60,000 members in 70, countries and supports a network of chapters worldwide. Through publications, expositions, professional development resources, and member programs, SME influences more, than 500,000 manufacturing executives, managers and engineers., , ASM International is a society whose mission is to gather, process and disseminate, technical information. ASM fosters the understanding and application of engineered, materials and their research, design, reliable, manufacture, use and economic and social, benefits. This is accomplished via a unique, global information-sharing network of interaction among members in forums and meetings, education programs, and through publications (i.e., Advanced Materials & Processes) and electronic media., , 7.7 Composites Fabricators Association, Composites Fabricators Association, 1655 N. Fort Myer Dr., Suite 510, Arlington, VA 22209, Tel: 703·525·0511, Fax: 703·525·0743, E-mail: [email protected], http://www.cfa-hq.org, (CFA) is the world's largest trade association serving the composites industry. Formed, in 1979 to provide education and support, for composites fabricators in the successful, operation of their businesses, CFA continues to offer leading-edge services that are, instrumental in regulatory compliance and, formulation, education and training, management, and market expansion. With approximately 800 members including open and, closed molders, suppliers, distributors, consultants, academics, and others with a vested, interest in the composites market, CFA has, earned a reputation as the voice of the, industry., , 8. Industry Conferences, , 7.6 ASM International, 8.1, 9639 Kinsman Rd., Materials Park, Ohio 44073-0002 USA, (440) 338-5151, 1-800-336-5152/1-888-336-5152, http://www.asm-intl.org, , National Design Engineering Show, , March, McCormick Place Complex, Chicago, Illinois USA, http://www.manufacturingweek.com!

Page 641 : Appendix A: Plastics Design Toolbox, 8.2, , Rapid Prototyping & Manufacturing, Conference & Exhibition, , April, Rosemont, Ill., Contact Society of Manufacturing Engineers, Customer Service,, (800) 733-4763, or (313) 271-1500, Ext. 1600;, fax: (313) 271-2861, , 8.3, , Materials Week, International Congress, on Advanced Materials, their Processes, and Applications, , September, Munich, Germany, Werkstoffwoche-Partnerschaft GBRmbH,, Hamburger Allee 26, 60486, Frankfurt, Germany, Phone: +496979 17 747, Fax: +49 69 79 17 733, E-mail: [email protected], http://www.materialsweek.org, , 8.4, , IEEEIACM International Conference, on Computer Aided Design, , November, Phone: 303 530-4562, Founded in 1982, ICCAD is an annual, show focusing on information technology for, computer-aided design professionals and engineers., , 8.5, , IDSA International Design Conference, , September, Organized by Industrial Designers Society of, America (IDSA), USA, Tel: +1 703 759 01 00, Fax: +1 703 759 76 79, [email protected], , 8.6, , Materials Solutions 2000, , October, Conference and exhibition organized by, ASM International, , 623, , St. Louis, Missouri, USA, Fax: +1 440 338 46 34, , 8.7 ICSID Congress and General, Assembly (Biannual), September/October, Congress and exhibition, General Assembly,, Tel: +82 2 708 20 52, Fax: +8223672 59 71, , 9., , Key Related Websites, , 9.1, , IBM Patents Website, , http://www.patents.IBM.com, The IBM Intellectual Property Network, (IPN) has evolved into a premier Website for, searching, viewing, and analyzing patent documents. The IPN provides you with free access to a wide variety of data collections and, patent information including:, • United States patents, • European patents and patent applications, • PCT application data from the World Intellectual Property Office, • Patent Abstracts of Japan, • IBM Technical Disclosure Bulletins, Searching is fast and easy. Along with a simple keyword search, IPN offers alternative, searches by patent number, boolean text,, and advanced text that allows for multiple, field searching. Browsing provides an organized approach to searching for patents., Through a review of specific classifications, you can identify topics and patents of, interest., , 9.2, , Federal Web Locator, , http://www.infoctr.edu/fwl/, The Federal Web Locator is a service provided by the Center for Information Law, and Policy and is intended to be the one, stop shopping point for federal government, information on the World Wide Web. This, site is hosted by the Information Center at

Page 642 : 624, , Appendix A: Plastics Design Toolbox, , Chicago-Kent College of Law, Illinois Institute of Technology., , 9.3 Maack Business Services, A Maack & Scheidl Partnership, CH-8804 Au/near Zurich, Switzerland, Tel: +41-1-781 3040, Fax: +41-1-781 1569, http://www.MBSpolymer.com, Plastics technology and marketing business, service, which organizes global conferences,, and edits a range of reports and studies,, which focus on important worldwide aspects, of polymer research, development, production, and end uses. Provides updates on plastic costs, pricing, forecast, supply/demand,, and analysis. Identified early in the cycle are, trends in production, products and market, segments., , 9.4 Material Safety Data Sheets (MSDS), 9.4.1 MSDSSEARCH.COM, Inc., http://www.msdssearch.com/, MSDSSEARCH.COM, Inc., is a National, MSDS Repository, providing FREE access to, over 1,000,000 Material Safety Data Sheetsthe largest centralized reference source available on the Internet. MSDSSEARCH.COM, is dedicated to providing the most comprehensive single source of information related to the document known as a Material Safety Data Sheet (MSDS). MSDS, SEARCH serves as the conduit between, users of MSDSs and any reliable supplier., MSDSSEARCH.COM provides access to, 350 K MSDSs from over 1600 manufacturers,, 700 K MSDSs from public access databases,, links to MSDS software, services, training, and product providers, links to Government, MSDS information, an MSDS discussion forum where you can ask questions, and supplies MSDSs directly from manufacturers via, search engine., 9.4.2 The canadian center for occupationalhealthandsafety (CCOHS) Promotes, a safe and healthy working environment by, , providing information and advice about occupational health and safety, 250 Main Street East, Hamilton ON L8N 1H6 Canada, Tel: 1-800-263-8466 (Toll free in Canada, only)/1-905-572-4400, Fax: 1-905-572-4500, http://www.ccohs.ca/products/databases/, msds.html, Search MSDS on CCINFOWeb. All, databases on CCINFOWeb may be searched, for free. The MSDSs are contributed by, North American sources, many that are, multi-national companies marketing chemical products worldwide. This database meets, a growing international requirement for, health and safety information on specific, chemical products. It helps thousands of users, worldwide manage their responsibilities under workplace, environmental imd other, right-to-know legislation. The MSDS database can be searched quickly and easily for, product names and other product identifications, manufacturer or supplier names, dates, of MSDSs, or any term used in the text of, the MSDS itself., MSDS records contain information such as:, •, •, •, •, •, •, •, , Chemical and Physical Properties, Health Hazards, First Aid Recommendations, Personal Protection, Fire and Reactivity Data, Spill and Disposal Procedures, Storage and Handling, , 10. Key Corporate Websites, 10.1, , GE Plastics, , http://www.geplastics.com, GE Plastics provides customers with, access to a full range of technical services and solutions information available from its webpage Design Solutions, Center, (http://www.geplastics.com/resins/, designsolution/). These include:, , 10.1.1 GE, workspaces: (http://www., geplastics.com/resins/designsolution/, workspace/) An internet-based project

Page 643 : Appendix A:, , Plastics Design Toolbox, , collaboration tool. It allows customers to, communicate, share, and organize information with GE Plastics project teams in a, virtual, secured environment., , 10.1.2 GE, E-seminars: (http://www., ge-plastics.com/resins/designsolution/, seminar/) GE's virtual conference center offers the ability to interact with GE, Plastics real-time in "live" on-line conferences. E-Seminar examples include Material, Selection, which provides the attendee with, the knowledge, skills and competencies to, determine how application requirements, influence the material specification process, and Materials for Single-Use Microwave, Food Packaging, which reviews trends in, the growing Freezer-to-Microwave Food, Packaging industry., 10.1.3 GE design tools: (http://www., geplastics.com/resins/designsolution/tools/, index.html), • Datasheets: Provides password access to, GE Plastics product data., • Material Selector: Access to: (1) GE Select,, a comprehensive database in Microsoft, Windows format of the family of GE polymers which allows users to sort for the, GE product families and grades of materials that will best meet the specified property ranges, and (2) CAMPUS, a worldwide, database for plastic materials with uniform, global protocol for acquiring and comparing data on competitive plastic materials., • Color Selector: GE Plastics customer color, services includes (1) ColorXpress Services,, dedicated to custom color matching and, small lot custom color compounding. This, online color match and ordering center includes an extensive online color library and, purchasing system. Customers can identify, the product and color of choice and fill in, an order form. Standards will be shipped, in less than 48 hours. Other ColorXpress, services offered range from custom color, matching to color standards development, and maintenance. (2) MicrolotXpress, the, small lot order center which allows customers to order small quantities of GE, , 625, , resins (down to 10 pounds) using a standard credit card. Material is shipped in 4, business days., • Calculator: An interactive process wizard, that provides quick, effective material, design, processing, and cost solutions. This, Engineering Calculator's capabilities include (1) Material, to select from a variety, of GE Plastics materials; (2) Design, which, calculates minimum part thickness based, upon allowable deflection; (3) Processing,, which calculates pressure to fill and clamp, force; and (4) Cost, which calculates estimated material and processing costs for the, intended part., , 10.1.4 Technical design library: Online, Technical Guide Library, provides access, to Design Guides, Processing Guides, Secondary Operations Information and Product, Literature. Examples include:, • GE Engineering Structural Foam Design, and Processing Guide, • Injection Molding Design, • Specific Industry Design Considerations, • Product Design, • Material Selection Guide Table, , 10.2, , Bayer Plastics, , http://www.plastics.bayer.com, Application Technology Information (ATIs), from Bayer (http://www.plastics.bayer.com/, englishlfiit.htm) can be downloaded as pdf, files. Examples of Bayer literature available, for download include:, • Self-tapping screws for thermoplastics;, • Metallized plastics housings to ensure electromagnetic compatibility;, • The mechanical layout of molded parts and, molds-ways of achieving optimum results, with the Finite Element Method (FEM);, • Data transfer of CAD geometries., CAMPUS®, the database of Bayer plastic, properties can also be downloaded from this, web page.

Page 644 : 626, , Appendix A: Plastics Design Toolbox, , 10.3 AlliedSignal-Honeywell, Honeywell Engineered Applications & Solutions, http://www.honeywell-eas.com/, Honeywell Engineered Applications & Solutions is a Honeywell business enterprise that, teams Engineering Plastics, Specialty Films, and Metal Injection Molding technologies to, provide a source for engineered solutions., Honeywell's EAS website supplies a range of, technical services and solutions information, helpful to the plastics designer., , 10.3.1 Troubleshooting tips, http://www.honeywell-plastics.com/, techinfo/tech-support/trouble.html, A comprehensive guide to symptoms, probable causes and corrections, examples of troubleshooting tips include:, •, •, •, •, •, •, •, , Extruder Related Problems, Cast Film Problems, Tubular Film Problems, Purging Procedures, Moisture Considerations, Drying of "Wet" Nylon 6, Processing Quality Checklist, , 10.3.2 Real-time processing tips and tutorials, http://www.honeywell-plastics.com/techinfo/, audiotips.html, These tips are also available in text only; examples include:, • Snap-Fit Design Applications, • General Snap-Fit Design Guidelines, • Capron Nylon Troubleshooting Guide for, Injection Molding, • CAD/CAE Capabilities, • Design Considerations for Injection, Molded Parts (Parting lines, draft angles,, wall thickness, fillets and radii, bosses, ribs,, opening formations, shrinkage, gating,, vents, potential knit lines), , 10.3.3 The literature shop http://www., honeywell-plastics.comltechinfo/litshop/, litshop.html, , View or Download Honeywell Literature, such as:, • Product and Technical Support Literature, • Industry Specific Literature, • Rotational Molding with Capron® Nylon, Resins, • Injection Molding Processing Guide for, Capron® Nylon, • Design Solutions Guide, • Snap-Fit Design Manual, • 1998 Automotive Specifications Guide, , 10.3.4 Tech information case histories, http://www.honeywell-plastics.comltechinfo/, snapshot/snapshot.html, 10.3.5 Material data Also accessible through http://www.honeywell-plastics.com are:, • Product Locator: A product-specific search, engine which provides datasheets/MSDS, sheets., • CAMPUS® 4.0: A downloadable database, program to search for specific resins., , 10.4 Montell, Formed, in, 1995, from, Royal, Dutch/Shell, Montedison polyolefin operations, and Himont polypropylene., http://www.montell.comlmontelllabout/, company.htrnl, To maximise the value of its products to its, customers business, Montell has developed, a series of services that allow customers to, develop products faster and more effectively., These include:, • Co-design-(http://www.montell.com/, montell/products/p-codesign.html) active, involvement in product design to optimise, the use of material and manufacturing, resources., • CAD and CAE (http://www.montell.com/, montell/products/p-cad.html) computer, modelling of product performance and, manufacturing, processes., Montell's, technical centres routinely use sophisticated CAD/CAE systems for customers

Page 645 : Appendix A: Plastics Design Toolbox, developing new applications, achieving often dramatic savings in time and costs by reducing time-consuming prototyping. Using, similar techniques to model the future, behaviour of the molten polymer while, it flows into the mould, Montell can, optimise mold design and achieve material, economies, as well as reduce development, times., • Piloting (http://www.montell.com/montell/, products/p-pilo.html) Montell is able to, test new materials and combinations in, dedicated laboratory facilities. Montell's, development facilities allow testing of new, solutions without committing full scale industrial resources., • Compliance testing (http://www.montell., comlmontell/products/p-compil.html), Montell will, on request, provide documentation certifying that the specific, Montell polymers to be used by the, converter meet the necessary requirements,.ensuring conformity to national, and international norms., , 10.5 Nypro Inc., http://www.nypro.com, , 10.5.1 Nypro Institute:. Nypro Institute, is the corporate university of Nypro Inc.,, providing educational opportunities to employees, customers, and the general public., Nypro Institute's headquarters are located in, Clinton, Massachusetts, and feature a stateof-the-science computer laboratory, a training resource library, and individual multimedia learning centers., 10.5.2 Nypro Online:. Plastics Education Online Nypro Online is a strategic, training initiative of Nypro Inc., the largest, multinational custom injection molder in, the world. Nypro Online is the first global, plastics education provider offering college education and focused plastics training, over the internet jointly with its academic, partners., , 627, , 10.6 Equipment Suppliers, 10.6.1 Milacron (Milacron Plastics Technologies Group), http://www.milacron.com/, http://www.milacron.comlPL/PLdefault.html, Milacron is a global leader in plastic, processing and metalworking technologies., Milacron's Plastics Technologies Group has, the world's broadest line producer of machines, systems, tooling and supplies for the, plastics processing industry, with manufacturing facilites in the U.S., Germany and India., The Milacon Group is vertically integrated, to produce machines for injection, extrusion, and blow molding of plastics and through, its D-M-E company, Milacron is also the, world's largest manufacturer of basic tooling for the plastics injection molding and, die casting industries. D-M-E products include: pre-engineered mold bases, mold design software, mold components, electronic, control systems, special tooling and supplies, for moldmaking. Other business units of the, Milacon Plastics Technologies Group are the, Specialty Equipment Group and Contract, Services Business Units. SEB is a systems integrator, capable of providing complete processing systems from rail car material unloading to robotic part handling. The CSB Group, retrofits, rebuilds, remanufactures and sells, used plastics machinery and also creates custom training programs., , 10.6.2 Husky, http://www.husky.ca/, Husky is a global supplier of injection molding systems to the plastics industry. Husky, designs and manufactures injection molding, machines-from 60 to 8000 tonnes, robots,, hot runners for a variety of applications,, molds for PET preforms, and complete, preform molding systems. Customers use, Husky's equipment to manufacture a wide, range of products in the packaging, automotive and technical industries. The company, serves customers in over 100 countries from, more than 40 service and sales offices around, the world.

Page 647 : Appendix A: Plastics Design Toolbox, Registered users count on PlasticsNet., Com for their range of procurement needs., With key strategic alliances including the, General Polymers Division of Ashland Distribution and MSC Industrial-PlasticsNet., Com is the one-stop resource for top brandname resins, machinery and equipment., , 629, , In the plastics industry, Commerx delivers, e-volved solutions including:, , • Procurent solutions for direct and indirect, materials, • Supply chain efficiencies, • Web-enabled services

Page 648 : Appendix B, Terminology, , A-basis Also called A-allowable. It is the, value above which at least 99% of the population of values is expected to fall with a, confidence of 95 %. See B-basis; population, confidence interval; S-basis; typical basis., A-B-C-stages These letters identify the various stages of cure when processing thermoset, (TS) plastic that has been treated with a catalyst; basically A-stage is uncured, B-stage, is partially cured, and C-stage is fully cured., Typical B-stage are TS molding compounds, and prep regs which in turn are processed to, produce C-stage fully cured plastic material, products; they are relatively insoluble and, infusible., Abscissa The horizontal direction in a diagram., Accelerator Also called promoter or cocatalyst. It is a chemical substance that accelerates chemical, photochemical, biochemical,, etc. reaction during processing, such as crosslinking or degradation of plastics. Action is, triggered and/or sustained by another substance, such as a curing agent or catalyst, or, environmental condition such as heat, radiation, or a microorganism. It can be used, to hasten a chemical reaction with a catalyzed TP or TS plastic. It can be used to, reduce the time required for a TS plastic to, , cure or harden. Often used in room temperature cures. During processing, it undergoes, a chemical change., Additive, slip An additive modifier that acts, as an internal lubricant which exudes to the, surface of the plastic during and immediately after processing providing the necessary lubricity to reduce or eliminate coefficient of friction in molded parts, film, etc., products., Adiabatic It is a change in pressure or volume without gain or loss in heat. Describes a, process or transformation in which no heat, is added to or allowed to escape from the, system., Adiabatic calorimeter Instrument used to, study chemical reactions which have a minimum loss of heat., Adiabatic flame temperature The highest, possible temperature of combustion obtained under the conditions that the burning occurs in an adiabatic vessel, that it, is complete, and that dissociation does not, occur., Algebra, transfinite A branch of higher, mathematics dealing with the algebra of, infinity.

Page 649 : Appendix B:, Algorithm Also known as a flow chart., It is an abstract description of a procedure, , or a program. A specified, step-by-step procedure for performing a task that will lead to, a correct answer or solving a problem., Algorithm and artificial intelligence AI programs rely less on algorithms than do conventional programs. Instead they use a procedure, which does not guarantee a correct answer., Algorithm, generic These are a class of, machine-learning techniques that gain their, name from a similarity to certain processes, that occur in the interactions of natural,, biological genes. Thus, GA is a method of, finding a good answer to a problem, based, on feedback received from its repeated attempts to a solution. Each attempt is called a, gene., Algorithm, recognition, Computer programs or instruction sets for the recognition, of specific phenomena from a processing, of data acquired for the system from some, external source., Aluminum foil Al foil is a solid sheet of, an appropriate Al alloy, cold rolled very, thin, varying from a minimum thickness of, about 0.0017 in. (0.00432 mm) to a maximum of about 0.0059 in. (0.1499 mm). In, the Al industry, thickness of at least 0.006 in., (0.1524 mm) is sheet material (sheet). After, (oil) cold rolling, the foil is annealed to restore its workability. From the standpoint of, packaging as well as other applications, one of, its most important characteristics is its impermeability to water vapor or gases. Bare foil, 1.5 mil (0.0015 in. or 0.0038 mm) and thicker, is completely impermeable and used in plastic coating and packaging process systems., Antioxidant agent Also called aging retardants. AOAs are of major importance to the, plastic industry because they extend the plastic's (that are effected by oxygen) useful temperature range and service life during processing and/or product use. The variety of, AOAs available and their specific uses are, extensive., , Terminology, , 631, , Arithmetic It is a branch of mathematics, that deals with real numbers and computations with these numbers., Arrhenius equation Refers to the rates of, reaction vs. temperature. It is a rate equation, followed by many chemical reactions., Arrhenius plot A linear Arrhenius plot is, extrapolated from the Arrhenius equation to, predict the temperature at which failure is, to be expected at an arbitrary time that depends on the plastic's heat aging behavior., It is usually 11,000 hours, with a minimum of, 5,000 hours. This is the relative thermal index, (RTI)., Asbestos It is not the name of a distinct, mineral species but is a commercial term, applied to fibrous varieties of several silicate minerals such as amosite and crocidolite. These extremely fine fibers are useful, as fillers and/or reinforcements in plastics., Property performances include withstanding, wear and high temperatures, chemical resistance, and strengths with high modulus, of elasticity. When not properly handled or, used, like other fibrous materials, they can be, hazardous., Aspect ratio It is the ratio of length to diameter of a material such as a rod or fiber; also, the ratio of the major to minor axis lengths, of a material such as a product., A-stage See A-B-C-stages., Asymmetric The opposite to symmetrical., It is irregular to form. Of such form or shape, , that no point, line, or plane exists about which, opposite portions are exactly similar., Asymptote A straight line connected with a, curve such that as a point moves an infinite, distance along the curve from the point to, the line approaches zero and the slope of the, curve at the point approaches the slope of the, line., Attenuation It is the diminution of vibrations or energy over time or distance; it is a

Page 650 : 632, , Appendix B:, , decrease in the strength of a signal between, two points or between two frequencies., Bamboo A grass or plant native to Southeast Asia having rather extremely high performance and having a rather high cellulose, content. Use includes specialty papers, light, fixtures, fishing rods, building scaffolds, etc., The development of the composite system, can be said to be based on the idea of utilizing the growth concept of the natural composite bamboo (which is still being used as, a building material in the Asian area). Bamboo stalks receive their high specific strength, and modulus of elasticity from unidirectional, oriented cellulose fibers that are embedded, in a matrix of lignin and silicic acid. A similar, situation exists in wood. However, whereas, the fibers in wood are usually 1 mm long, in, bamboo they reach up to 10 mm. The hallow bamboo stalks are stabilized by evenly, spaced fiat, strong nodes rectangular to the, longitudinal axes., Barrier plastic Also called barrier layer., They are materials such as plastic films,, sheets, etc. with low or no permeability to different products., B-basis The B mechanical property value is, the value above which at least 90% of the, population of values is expected to fall, with, a confidence level of 95%. See A-basis; population confidence interval; S-basis; typical, basis., Black-box A phrase used to describe a device whose method of working is ill-defined, or not understood., British thermal unit Btu is the energy, needed to raise the temperature of lIb of water 1°F (0.6°C) at sea level. As an example,, one lb of solid waste usually contains 4500 to, 5000 Btu. Plastic waste contains greater Btu, than other materials of waste., B-stage See A-B-C-stages., Calcnlns It is the mathematical tool used to, analyze changes in physical quantities, comprising differential and integral calculations., , Terminology, It was developed during the 17th century, to study four major classes of scientific and, mathematical problems of that time. (1) Find, the maximum and minimum value of a quantity, such as the distance of a planet from the, sun. (2) Given a formula for the distance traveled by a body in any specified amount of, time, find the velocity and acceleration of the, body at any instant. (3) Find the tangent to a, curve at a point. (4) Find the length of a curve,, the area of a region, and the volume of a solid., These problems were resolved by the greatest, minds of the 17th century, culminating in the, crowning achievements of Gottfried Wilhelm, (Germany 1646-1727) and Isaac Newton, (English 1642-1727). Their information provided useful information for today's space, travel., , Cap layer It is a plastic product that is topped, or capped with another plastic., Catalyst Basically a phenomenon in which, a relatively small amount of substance augments the rate of a chemical reaction without, itself being consumed; recovered unaltered in, form and amount at the end of the reaction., It generally accelerates the chemical change., The materials ordinarily used to aid the polymerization of most plastics are not catalysts, in the strict sense of the word (they are consumed), but common usage during the past, century has applied this name to them., Catalyst, metallocene Also called single, site, Me and m. Metallocene catalysts achieve, creativity and exceptional control in polymerization and product design permitting penetration of new markets and expand on of, present markets., Chromatography A technique for separating a sample material into constituent components and then measuring or identifying the, compounds by other methods. As an example separation, especially of closely related, compounds, is caused by allowing a solution, or mixture to seep through an absorbent such, as clay, gel, or paper. Result is that each compound becomes adsorbed in a separate, often, colored layer.

Page 651 : Appendix B:, Cold flow It is creep at room temperature., Colorimeter Also called color comparator, or photoelectric color comparator. An instrument for matching colors with results, about the same as those of visual inspection, but more consistent. Basically the sample is illuminated by light from the three, primary color filters and scanned by an electronic detecting system. It is sometimes used, in conjunction with a spectrophotometer,, which is used for close control of color in, production., Combination mold A mold which has, both positive portions or ridges, and cavity, portions., Computer acceptability Information produced via CAD, CAM, CAE, etc. that may, require a password., Computer science and algebra The symbolic, system of mathematical logic called Boolean, algebra represents relationships between entities; either ideas or objects. George Boole, of England formulated the basic rules of the, system in 1847. The Boolean algebra eventually became a cornerstone of computer, SCIence., Concentricity Term to describe two circles, or cylindrical shapes having a common center and common axis, such as the inside or, outside diameters of a barrel or outside diameters of the surface and bearing surfaces, of a screw. Deviation from concentricity is, referred to as runout. Also refers to the relationship of all inside dimensions to all outside, dimensions usually expressed in thousands of, inch or millimeter FIM (full indicator movement). Deviation from concentricity is usually referred to as a runout. The concentricity, should allow for the maximum part tolerance., The geometry of the part should help indicate, the tolerance applied., Corian DuPont's trade-name for their mineral filled acrylic continuous cast sheet material. This wear resistant and attractive material is used for consumer's kitchen counter, , Terminology, , 633, , tops, bathroom surfaces, fast-food restaurant, surfaces, health-care surfaces, etc., Crystallinity and orientation When crystallites already exist in the amorphous matrix,, orientation will make these crystallites parallel. If a plastic crystallizes too far in the melt,, it may not contain enough amorphous matrix, to permit orientation, and will break during, stretching. (Most partially crystalline plastics, can be drawn 4 to 5 times.) The degree of, crystallinity is influenced by the rate at which, the melt is cooled. This is utilized in the fabrication operations to help control the degree, of crystallinity. The balance of properties can, be slightly altered in this manner, allowing, some control over such parameters as container volume, stiffness, warpage, and brittleness. Nucleating agents are available that can, promote more rapid crystallization resulting, in faster cycle times., Crystallization The formation of crystallites, or groups of plastic molecules in an ordered, structure within the plastic as the plastic is, cooled from its amorphous state to a temperature below its crystallization temperature., C-stage See A-H-C-stages., Curing Refers to TS plastics that undergo, chemical change (cross-linking) during processing to become permanently insoluble and, infusible plastics. TPs do not go through a curing cycle, they go through a cycle of repeatedly softening when heated and hardening, when cooled. At times TPs are referred to, as curing even though it does not go through, a curing stage as in TSs. The term cure was, extensively used from the start of the 20 th century because practically the only plastics used, were phenolics. They are TSs that cure. So the, term was an incorrect carryover when TPs became popular. See Vulcanization., Damping The loss of energy, as dissipated, heat, that results when a material or material, system is subjected to an oscillatory load or, displacement. Perfectly elastic materials have, no mechanical damping. Damping reduces, vibrations (mechanical and acoustical) and

Page 652 : 634, , Appendix B:, , prevents resonance vibrations from building, up to dangerous amplitudes. However, high, damping is generally an indication of reduced, dimensional stability, which can be very undesirable in structures carrying loads for long, time periods. Many other mechanical properties are intimately related to damping; these, include fatigue life, toughness and impact,, wear and coefficient of friction, etc., Deformation Any part of the total deformation of a body that occurs immediately when, the load is applied but that remains permanently when the load is removed., Denier See Fiber denier, Density, apparent The weight in air of a unit, volume of material including voids usually inherent in the material. Also used is the term, bulk density that is commonly used for materials such as molding powders., Density, bulk Ratio of weight to volume of a, solid material including voids but more often, refers to loose form (bulk) material such as, pellets, powders, flakes, compounded molding material, etc., Design allowable Statistically defined material property allowable strengths, usually referring to stress and/or strain., Design motion control, mechanical and electronic effects Selecting a control system is, not something that can, or should, be done, without proper consideration. Your decision, should be guided by a number of parameters.1t basically depends on: (1) whether you, need a brand-new system or a retrofit, (2) one, that is 100% computer controlled or covers, select functions, (3) one with leading edge, technologies or with just enough high technology to get you up and running, (4) one, that designed in-house or by automation specialists, or (5) something in between these, choices. It all depends on your specific requirements. In motion controls there are different operating mechanical devices such as, actuators that convert the rotation of a motor into linear motion, linear guides, linear, , Terminology, bearings, properly deigned machine structure, to ensure rigidity and proper mounting installation, mechanical dampers to isolate the, motion system from its environment, ensure, control of inertia when components move, or cause friction, avoid resonance problems,, protect against dirt, etc., These are a few of the mechanical factors, that have much more effect on the electronic, design of motion control systems. The electronic engineer must understand the mechanics of motion that are encountered in order, for the electronic system to be successful. To, decide on electronic and software requirements, it is important factors have to be considered such as product flow and throughput, operator requirements, and maintenance, issues., Deviation Variation from the a specified, dimension or design requirement, usually, defining the upper and lower limits. The mean, deviation (MD) is the average deviation of a, series of numbers from their mean. In averaging the deviations, no account is taken of, signs, and all deviations whether plus or minus, are treated as positive. The MD is also, called the mean absolute deviation (MAD), or average deviation (AD)., Deviation, root-mean-square RMS is a, measure of the average size of any measurable item (length of bar, film thickness, pipe, thickness, coiled molecule, etc.) that relates, to the degree of accuracy per standard deviation measurement., Differential scanning calorimetry DSC is, a method in which the energy absorbed or, produced is measured by monitoring the, difference in energy input (energy changes), into the material and a reference material as, a function of temperature. Absorption of energy produces an endothermic reaction; production of energy results in an exothermic, reaction. Its use includes studying processing, behavior of the melting action, degree of, crystallization, degree of cure, applied to, processes involving a change in heat capacity, such as the glass transition, loss of solvents,, etc.

Page 653 : Appendix B:, Dilatant Basically a material with the ability to increase the volume when its shape is, changed. A rheological flow characteristic evidenced by an increase in viscosity with increasing rate of shear. The dilatant fluid, or, inverted pseudoplastic, is one whose apparent viscosity increases simultaneously with, increasing rate of shear; for example, the act, of stirring creates instantly an increase in resistance to stirring., Dilatometer Basically it is a pyrometer, equipped with instruments to study density, as a function of temperature andlor time. It, can measure the thermal expansion or contraction of solids or liquids. They also study, polymerization reactions; it can measure the, contraction in volume of unsaturated compounds. It basically is a technique in which, a dimension of a material under negligible, load is measured as a function of temperature, while it is subjected to a controlled temperature program., EI theory In all materials (plastics, metals, wood, etc.) elementary mechanical theory demonstrates that some shapes resist, deformation from external loads. This phenomenon stems from the basic physical fact, that deformation in beam or sheet sections, depends upon the mathematical product of, the modulus of elasticity (E) and the moment of inertia (I), commonly expressed as, EI. This theory has been applied to many, different constructions including sandwich, panels., Elastic-plastic transition It is the changes, from recoverable elastic behavior to nonrecoverable plastic strain which occurs on, stressing a material beyond its yield point., Endotherm A process or change that, takes place with absorption of heat and, requires high temperature for initiation, and maintenance as with using heat to melt, plastics and then remove heat; as opposed to, endothermic., Endothermic Also called endoergic. Pertaining to a reaction which absorbs heat., , Terminology, , 635, , Endothermic process Processes that absorb, heat from the surroundings., Energy Basically, it is the capacity for doing work or producing change. This term is, both general and specific. Generally it refers, to the energy absorbed by any material subjected to loading. Specifically it is a measure, of toughness or impact strength of a material;, as an example, the energy needed to fracture, a specimen in an impact test. It is the difference in kinetic energy of the striker before and after impact, expressed as total energy per inch of notch of the test specimen, for plastic and electrical insulating material, [in-Ib (Jim»). Higher energy absorption indicates a greater toughness. For notched specimens, energy absorption is an indication of, the effect of internal multi-axial stress distribution on fracture behavior of the material., It is merely a qualitative index and cannot be, used directly in design., Energy absorption A term that is both general and specific. Generally I refers to the, energy absorbed by any material subjected to, loading. Specifically it is a measure of toughness or impact strength of a material; the energy needed to fracture a specimen in an impact test., Energy activation An excess energy that, must be added to an atomic or molecular system to allow a process, such as diffusion or, chemical reaction, to proceed., Energy and bottle An interesting historical, (1950s) example is the small injection blow, molded whiskey bottles that were substituted, for glass blown bottles in commercial aircraft; continues to be used in all worldwide, flying aircraft. At that time, just in USA,, over 500 x 1012 Btu or the amount of energy, equivalent to over 80 x 106 barrels of oil was, reduced., Energy and plastic Numerous studies have, shown; (1) plastics consume less energy to, produce and fabricate products than other, materials with glass being the major consumer of energy; (2) their use as a product

Page 654 : 636, , Appendix B:, , reduces energy consumption; and (3) more, energy can be produced when products are, incinerated. Without plastic insulation, major appliances such as refrigerators would use, up to 30% more energy. Improvements made, in energy efficiency made through the use, of plastics in the last decade save more than, 53 billion kilowatt-hours of electricity annually in USA. This saves consumers more than, $4 billion each year., Energy conservation 1. Much less energy, is used to in the production of plastics then, probably any other commercial material. In, comparing the ratio of polyethylene (PE), plastic with others, steel requires about three, times as much, copper at 18, and aluminum, at almost 10. 2. When examining energy consumption or lost, the equipment used in the, complete production line as well as the use, of plastic products is involved, plastic requires less particularly when compared to, glass. Plastics are major contributors to saving energy such as building insulation, reduce, weight in automobiles, etc. Upon incineration, plastic provides much more energy that, can be put to work., Energy consnmption The plastics industry, consumes about 3% of U.S. total annual oil, and gas consumption. This use is more than, offset by the savings that plastic products, create. Many different studies have substantiated this fact. Worldwide there are areas, where the consumption may be lower and, possibly greater reaching up to 4 %., Eutectic It is a mixture of two or more substances that solidifies as a whole when cooled, from the liquid state, without changing composition. It is the composition within any system of two or more crystalline phases that, melts completely at the minimum temperature., Eutectic arrest In a cooling (or heating), curve an approximately exothermal segment, corresponding to the time interval during, which the heat of transformation from the, liquid phase of two or more conjugate solid, phases is being evolved (or conversely)., , Terminology, Eutectic composition It has a mInImUm, melting temperature when two or more, liquid solubility curves interact., Eutectic deformation The composition, within a system of two or more components,, which on heating under specified conditions,, develops sufficient liquid to cause deformation at the minimum temperature., Eutectic divorced Structure where the components of a eutectic mixture appear to be, entirely separate., Eutectic mixture It is the composition within, any system of two or more crystalline phases, that melts completely at a relatively low temperature and can be repeatedly solidified, and melted. Two or more substances solidify, (such as zinc-aluminum, tin, bismuth, etc.) as, a whole when cooled from the liquid state, without changing composition. They have, been used rather extensively since at least the, 1940s during certain plastic processing techniques such as injection molding, casting; reinforced plastic bag molding, and compression molding., Eutectic temperature Melting temperature, of an alloy with a eutectic mixture; it is at the, interaction of two or more liquid solubility, curves., Exotherm It is the temperature vs. time, curve of a chemical reaction or a phase, change giving off heat, particularly the polymerization of thermoset plastics. Maximum, temperature occurs at peak exotherm. Some, plastics such as room temperature curing, TS polyesters and epoxies will exotherm, severely with damaging results if processed incorrectly. As an example, if too, much methyl ethyl ketone peroxide (MEK, peroxide) catalyst is added to polyester, plastic that contains cobolt naphthenate, (promoter), the mix can get hot enough, to smoke and even catch fire. Thus, an, exotherm can be a help or hindrance, depending on the application such as during casting,, potting, etc.

Page 655 : Appendix B:, Exotherm curve Temperature vs. time curves during a curing cycle. Peak exotherm is, the point of highest temperature of a plastic, during the cure., Exotherm heat It is heat given off during a polymerization reaction by the chemical ingredients as they react and the plastic, cures., Exothermic reaction The temperature rise, resulting from the liberation of heat by a, chemical reaction. It is the opposite of endothermic reaction., Extensometer An extenso meter is an instrument to monitor strain in the linear dimension of a test specimen while a load or force, is applied to it. The automatic plotting of load, with strain produces stress-strain curves., Extrndate It is the plastic hot melt as it, emerges/discharges/exits from the extruder, die's orifice into a desired product form such, as film, sheet, etc., Fabric Any woven, knitted, felted, bonded,, knotted, etc., textile material. There are woven and nonwoven fabrics., Fabric woven, eight-harness satin It is a, seven-by-one weave where a filling thread, floats over seven warp threads and then under one. Like a crowfoot weave, it looks different on one side than the other side. This, weave is more pliable than others and is especially adaptable to forming around the more, complex shapes., Fiber denier It is a unit of weight expressing the size or coarseness but particularly, the fineness of a continuous fiber or yarn., The weight in grams of 9000 m (30,000 ft), is one denier. The lower the denier, the finer, the fiber, yarn, etc. One denier equals about, 40 micron. Sheer women's hosiery usually, runs 10 to 15 denier. Commercial work, 12 to 15 denier fiber is generated., Flash It is defined as that portion of the material that flows from or is extruded from the, , Terminology, , 637, , mold [usually where two separate sections, (parting line) of the mold meet] during the, molding process. When this excess is trimmed, off the finished piece, there will usually be a, noticeable line around the edge of the product that mayor may not distract from the appearance of the finished product. This problem can be avoided by properly designing the, product or the molds so as to eliminate the, flash problem or place the flash lines where, they will not be seen., , Flocked Usually provides a velvet-like layer, for decorative products., Fuzzy logic control Although fuzzy logic, control (FLC) may sound exotic, it has been, used to control many conveniences of modern life (from elevators to dishwashers) and, more recently into industrial process control that include plastic processing such as, temperature and pressure. FLC actually outperforms conventional controls because it, completely avoids overshooting process limits and dramatically improves the speed of, response to process upsets. These controllers, accomplish both goals simultaneously, rather, than trading one against another as done with, proportional-integral-derivative (PID) control. However, FLC is not a cure-all because, not all FLCs are not equal; no more than, PIDs. FL is not needed in all applications;, in fact FLCs used allow them to be switched, off so that traditional PID control takes, over., Geomembrane These liners chiefly provide, impermeable barriers. They can be characterized as: (1) solid waste containment: hazardous landfill, landfill capping, and sanitary landfill; (2) liquid containment: canal,, chemical/brine pond, earthen dam, fish farm,, river/coastal bank, waste-water, and recreation; (3) mining, leach pad and tailing ponds;, and (4) specialties: floating reservoir caps,, secondary containment, tunnel, erosion, vapor barrier, and water purification. Plastics, used include medium to very low density, PE, PVC, and chlorosulfonated PE (CSPE)., (The Romans used in their land and road constructions what we call geomembrane.)

Page 656 : 638, , Appendix B:, , Terminology, , Geometric steradian The solid angle which,, having its vertex in the center of a sphere, cuts, off an area of the surface of the sphere equal, to that of a square with sides of length equal, to the radius of the sphere., , producing parts that absorb and dissipate energy, usually from impact., , Glassy state In amorphous plastics, below the T g , cooperative molecular chain, motions are "frozen", so that only limited local motions are possible. Material behaves mainly elastically since stress causes, only limited bond angle deformations and, stretching. Thus, it is hard, rigid, and often, brittle., , Kinetic theory A theory of matter based, on the mathematical description of the relationship between pressures, volumes, and, temperatures of gases (PVT phenomena)., This relationship is summarized in the laws, of Boyle's law, Charle's law, and Avogadro's, law., , Good manufacturing practice See Quality, system regulation., Gough-Joule effect When an elastomer/, rubber is stretched adiabatically (without, heat entering or leaving the system), heat is, evolved. This effect was first reported discovered by Gough in 1805 and rediscovered by, Joule in 1859., , Kinetic friction It is the friction developed, between two bodies in motion., , Latex Also called emulsion. It is an aqueous dispersion of natural or synthetic elastome ric rubbers and plastics (dispersions of, plastic particles in water)., Load The term load means mass or force, depending on its use. As an example, a load, that produces a vertically downward force because of gravity acting on a mass may be expressed in mass units. Any other load is expressed in force units., , Heat sink A device for the absorption or, transfer of heat away from a critical element, or part. Bulk graphite is often used as a heat, sink., , Load amplitude One-half of the algebraic, difference between the maximum and minimum loads in the load cycle., , Hooke's Law It is the ratio of normal stress, to corresponding strain (straight line) for, stresses below the proportional limit of the, material., , Logarithm The exponent that indicates the, power to which a number is raised to produce, a given number. Thus, as an example, 1000 to, the base of 10 is 3. This type of mathematics, is used extensively in computer software., , Inlay or overlay They can be applied to, plastic fabricating processes such as moldings, during or after molding., Isothermal 1. Relating to or marked by, changes of volume or pressure under conditions of constant temperature. 2. Relating, to or marked by constant or equality of, temperature., Kinetic A branch of dynamics concerned, with the relations between the movement of, bodies and the forces acting upon them., Kinetic energy dissipated Different plastics, provide different degrees and excellencies for, , Lubricity Refers to the load-bearing characteristics of a plastic under conditions of relative motion. Those with good lubricity tend, to have low coefficients of friction either with, themselves or other materials and have no, tendency to gall., Mathematical dimensional eccentricity The, ratio of the difference between maximum and, minimum dimensions on a part, such as wall, thickness. It is expressed as a percentage to, the maximum., Mathematician Galois Evariste Galois, now, recognized as one of the greatest 19th century, mathematicians, twice failed the entry exam

Page 657 : Appendix B:, for the Ecole Poly technique and a paper he, submitted to the French Academy of Sciences, was rejected as "incomprehensible." Embittered he turned to political activism and spent, six years in prison. In 1832, at the age of 20, he, was killed in a duel, reported to have arisen, from a lover's quarrel, although their were, those who believed that an/agent provocateur of the police was involved., Mean Arithmetical average of a set of numbers. It provides a value that lies between a, range of values and is determined according, to a prescribe law., Mean absolute deviation MAD is a statistical measure of the mean (average) difference, between a product's forecast and actual usage (demand). The deviations (differences), are included without regard to whether the, forecast was higher than actual or lower., Mean and standard deviation The statistical normal curve shows a definite relationship among the mean, the standard deviation,, and normal curve. The normal curve is fully, defined by the mean, that locates the normal curve, and the standard deviation that, describes the shape of the normal curve. A, relationship exists between the standard deviation and the area under the curve., Mean, arithmetic More simply called the, mean, it is the sum of the values in a distribution divided by the number of values. It, is the most common measure of central tendency. The three different techniques commonly used are the raw material or ungrouped, grouped data with a calculator, and, grouped data with pencil and paper., , Terminology, , 639, , Motion control system MeSs are the major, user of electrical power. As with plastic, equipment, they can be found in practically, every aspect of our lives, performing the task, of converting electrical energy to mechanical, energy in a series of controlled motion activities such as those in fabricating equipment., There are constant speed, variable speed,, and positioning motion control systems. Although there are many good tuning methods, and self-tuning algorithms available to properly tune a motor, most of them are keyed to, specific brands of motion controllers or specific types of operations. A very popular style, of gain algorithm in use is the proportionalintegral-derivative., Necking Also called neck-down or neck-in., (1) It is the localized reduction in cross section that occurs in a material under tensile, or compression stress during thermoforming., (2) During fabrication of products necking, occurs such as extruding film where the width, of extrudate leaving the die is necked-in as it, moves downstream., Non-resonant forced and vibration technique, A technique for performing dynamic mechanical measurements in which the sample is oscillated mechanically at a fixed frequency. Storage modulus and damping are, calculated from the applied strain and the resultant stress and shift in phase angle., Oil-canning The property of a panel that, flexes past a theoretical equilibrium point,, and then returns to the original position. This, motion is analogous to the bottom of a metal, oilcan when pressed and released. Part flexing can cause stress, fracturing, or undesirable, melting of thin-sectioned, flat parts., , Metallocene See catalyst, metallocene., Mohr's circle A graphical representation of, the stresses acting on the various planes at a, given point., , Operator's station That position where an, operator normally stands to operate or observe the machine., Ordinate The vertical direction in a diagram., , Moment of inertia It is the ratio of torque, applied to a rigid body free to rotate about, a given axis to the angular acceleration thus, produced about that axis., , Orientation and glassy state An important, transition occurs in the structure of both crystalline and non-crystalline plastics. This is

Page 658 : 640, , Appendix B:, , the point at which they transition out of the, so-called glassy state. Rigidity and brittleness characterize the glassy state. This is because the molecules are too close together, to allow extensive slipping motion between, each other. When the glass transition (Tg), is above the range of the normal temperatures to which the product is expected to be, subjected, it is possible to blend in materials, that can produce the Tg of the desired mix., This action yields more flexible and tougher, plastics., Orientation and heat-shrinkability There, are oriented heat heat-shrinkable plastic, products found in flat, tubular film, and tubular sheet. The usual orientation is terminated (frozen) downstream of a stretching, operation when a cold enough temperature, is achieved. Reversing this operation occurs, when the product is subjected to a sufficient, high temperature. This reheating results in, the product shrinking. Use for these products includes part assemblies, tubular or flat, communication cable wraps, furniture webbing, medical devices, wire and pipe fitting, connections or joints, and so on., Orientation and mobility Orientation requires considerable mobility of large segments of the plastic molecules. It cannot, occur below the glass transition temperature, (Tg). The plastic temperature is taken just, above T g •, Orientation, cold stretching Plastics may be, oriented by the so-called cold stretching; that, is below its glass transition temperature (Tg)., There has to be sufficient internal friction to, convert mechanical into thermal energy, thus, producing local heating above T g . This occurs characteristically in the necking of fibers, during cold drawing., Orientation, thermal characteristic These, oriented plastics are considered permanent,, heat stable materials. However, the stretching decreases dimensional stability at higher, temperatures. This situation is not a problem, since these type materials are not exposed to, the higher temperatures in service. For the, , Terminology, heat-shrink applications, the high heat provides the shrinkage capability., Orientation, wet stretching For plastics, whose glass transition temperature (Tg) is, above their decomposition temperature, orientation can be accomplished by swelling, them temporarily with plasticizing liquids to, lower their T g of the total mass, particularly, in solution processing. As an example, cellulose viscous films can be drawn during coagulation. Final removal of the solvent makes, the orientation permanent., Plasticator A very important component, in a melting process is the plasticator with, its usual specialty designed screw and barrel used that is used in different machines, (extruders, injection molding, blow molding,, etc.). If the proper screw design is not used, products may not meet or maximize their, performance and meet their cost requirements. The hard steel shaft screws have helical flights, which rotates within a barrel to mechanically process and advance (pump) the, plastic. There are general purposes and dedicated screws used. The type of screw used is, dependent on the plastic material to be processed., Plasticize It is the mixing action to soften, a plastic and make it processable usually, through the use of heat., Plasticizer They are materials that may be, added to thermoplastics to increase toughness and flexibility and/or to increase the ease, of fabrication. These materials are usually, more volatile than the plastics to which they, are added., Plastic, virgin A plastic material in the form, of pellets, granules, powder, flock, liquid, etc., that has not been subjected to use or processing other than what was required for its initial, manufacture. It is not recycled plastics., Population confidence interval The limits, on either side of a mean value of a group, of observations which will, in a stated fraction or percent of the cases, include the

Page 659 : Appendix B:, expected value. Thus the 95% confidence limits are the layers between which the population mean will be situated in 95 out 100 cases., See A-basis; B-basis; S-basis; typical basis., Positive mold A projecting mold over which, the product is formed, usually referred to as, a male mold., Polyolefins Plastics such as polyethylene, (PE), polypropylene (PP), and polybutylene, (PB) that are derived from unsaturated hydrocarbons (also called olefins)., Primary structure Mainframe of a product, is the primary structure, Examples include, aircraft main supports, building main beams,, and automobile frames. If the primary structure fails, it would be damaging or catastrophic to the product and/or people. See, Secondary structure., Processing intelligent What is needed is to, cut inefficiency, such as the variables, and in, turn cut the costs associated with them. One, approach that can overcome these difficulties, is called intelligent processing (IP) of materials. This technology utilizes new sensors, expert systems, and process models that control, processing conditions as materials are produced and processed without the need for human control or monitoring. Sensors and expert systems are not new in themselves., What is novel is the manner in which they, are tied together. In IP, new nondestructive, evaluation sensors are used to monitor the, development of a materials microstructure as, it evolves during production in real time., These sensors can indicate whether the microstructure is developing properly. Poor microstructure will lead to defects in materials., In essence, the sensors are inspecting the material on-line before the product is produced., Processing, intelligent communication The, information these sensors gather is communicated, along with data from conventional, sensors that monitor temperature, pressure,, and other variables, to a computerized decision making system. This decision-maker, includes an expert system and a mathemat-, , Terminology, , 641, , ical model of the process. The system then, makes any changes necessary in the production process to ensure the material's structure is forming properly. These might include, changing temperature or pressure, or altering, other variables that will lead to a defect-free, end product., Processing, intelligent systematic There are, a number of benefits that can be derived from, intelligent processing. There is, for instance,, a marked improvement in overall product, quality and a reduction in the number of, rejected parts. And the automation concept, that is behind intelligent processing is consistent with the broad, systematic approaches, to planning and implementation being undertaken by industries to improve quality. It, is important to note that intelligent processing involves building in quality rather than, attempting to obtain it by inspecting a product after it is manufactured. Thus, industry, can expect to reduce post-manufacturing inspection costs and time. Being able to change, manufacturing processes or the types of material being produced is another potential, benefit of the technique., Processing line, downstream The plastic, discharge end of the fabricating equipment, such as the auxiliary equipment in an extrusion pipe line after the extruder., Processing line downtime Refers to equipment that cannot be operate when it should, be operating. Reason for downtime could be, equipment being inoperative, shortage of material, electric power problem, operators not, available, and so on. Regardless of reason,, downtime is costly., Processing line, upstream Refers to material movement and auxiliary equipment, (dryer, mixer/blender, storage bins, etc.) that, exist prior to plastic entering the main fabricating machine such as the extruder., Qualified products list QPL is a list of commercial products that have been pretested, and found to meet the requirements of a specification.

Page 660 : 642, , Appendix B:, , Quality system regulation The past good, manufacturing practice (GMP) and process, validation (PV) was renamed to quality system regulation (QSR). It is important for the, medical device industry (that uses an extensive amount of plastics) and also in other, product industries where they want to follow, strict processing procedures. It sets up an important procedure for many plastic fabricators to consider that targets to ensure meeting zero defects., The originator FDA (Food & Drug Administration) defined GMP and PV as a, documented program providing a high degree of assurance that a specific process will, consistently produce a product meeting its, predetermined specifications and quality attributes. Elements of validation are product specification, processing equipment, and, process revalidation and documentation. The, GMP regulation became effective during, 1978. As of October 7,1996 GMP was revised, incorporating many changes; it was renamed, to quality system regulation (QSR). The, GMP focused almost exclusively on production practices requiring very detailed manufacturing procedures and extremely very detailed documentation., The QSR major new requirements are in, the areas of design, management responsibility, purchasing, and servicing. It encompasses, quality system requirements that apply to the, entire life cycle of a device., Radome Also called radiation dome. It, is a cover for a microwave antenna used, to protect the antenna from the environment on the ground, underwater, and in the, air (aircraft nose cone, etc.). The dome is, basically transparent to electromagnetic radiation and structurally strong. Different materials have been used such as wood, rubbercoated air-supported fabric, etc. The most, popular is the use of glass fiber-TS polyester, RPs. The shape of the dome, that is usually, spherical, is designed not to interfere with the, radiation., Relative thermal index Section UL 746B, provides a basis for selecting high temperature plastics and provides a long-term, , Terminology, thermal aging index called the relative thermal index (RTI)., Reynold's number It is a dimensionless, number that is significant in the design of, any system in which the effect of viscosity, is important in controlling the velocities or, the flow pattern of a fluid. It is equal to the, density of a fluid, times its velocity, times a, characteristic length, divided by the fluid viscosity. This value or ratio is used to determine, whether the flow of a fluid through a channel or passage, such as in a mold, is laminar, (streamlined) or turbulent., Root-mean-square See Deviation, rootmean-square., Roving The term roving is used to designate a collection of bundles of continuous filaments/fibers, usually glass fibers, either untwisted strands or twisted yarns. Rovings can, be lightly twisted; their degree of twisting and, format depends on their use. As an example for filament winding they are generally, wound as bands or tapes with little twist as, possible., Safety device All machines are equipped, (or should be equipped) with applicable electrical, hydraulic, and/or mechanical safety devices. Some of them, such as injection molding machines, have all three modes for safety, operations., Safety interlock A safety device designed to, ensure that equipment will not operate until, certain precautions are taken and set on the, equipment., Secondary structure A structure that is not, critical to the survival of the primary structure. Examples are in aircraft and aerospace, vehicles that are not critical to safety of operations such as the interior decorative paneling. See Primary structure., Shrinkage block jig A metal, wood, plastic,, etc. shaped block against which parts are held, under light or no pressure while cooling to, reduce warpage and distortion.

Page 661 : Appendix B:, Specific gravity, apparent The ratio of the, weight in air of a given volume of the impregnable portion of a permeable material, (that is the solid matter including its permeable pores or voids) to the weight in air of, an equal volume of distilled water at a stated, temperature., Specific gravity, bulk The weight in air of, a given volume of a permeable material, (including both permeable and impermeable, voids normal to the material) to the weight, in air of an equal volume of distilled water at, a stated temperature., Specific heat It is the amount of heat in BTU, required to raise one pound of any material, one degree Fahrenheit (BTU/lb, lOF)., Stabilizer These are agents or materials, present in or added into practically all different plastics to improve their performances, that range in the many different requirements, needed in the fabricated product to meet, performance requirements. They basically inhibit chemical reactions that bring about undesirable chemical degradation., Standard industrial classification The SIC, system published by the u.s. Department of, Commerce classifies all manufacturing industries and services produced in USA (transportation, communication, electronic, plastic, etc.). Their digital numbering system, follows a pattern that provides input/output, detailed information data. Basically the 110, program determines what each of about 470, product level industries consumes from each, of the other 370 industries. The manufacturing segments of the plastics industry are in, the major group numbers 28 (chemicals and, allied products) and 30 (rubber and miscellaneous plastics products). In four-digit listings, such as the SIC 2821 (plastics materials), SIC, 3081 (unsupported plastics film and sheet),, SIC 3084 (plastics bottles), SIC 3086 (plastics, foam products), SIC 3088 (plastics plumbing, fixtures), and so on., Statistical benefit Using statistical methods, in the design of experiments and data analy-, , Terminology, , 643, , sis allows designers, etc. to attain benefits that, would otherwise be considered unachievable., Benefits include a 20 to 70% reduction in, problem solving time; a minimum 50% reduction in costs due to testing, machine processing time, labor, and materials; and a 200, to 300% increase in value, quality, and reliability of the information generated., Supercooling The rapid cooling of a normally crystalline plastic through its crystallization temperature, so it does not get a, chance to crystallize and it remains in the, amorphous state., Synergism Arrangement or mixture of substances in which the total resulting performance is greater than the sum of the, effects taken independently such as with alloying/blending., Thermodynamic It is the scientific principle, that deals with the inter-conversion of heat, and other forms of energy. Thermodynamics, (thermo = heat and dynamic = changes) is, the study of these energy transfers. The law, of conservation of energy is called the first, law of thermodynamics., Thermodynamic, first law Energy can be, converted from one form to another but it, cannot be created or destroyed., Thermodynamic phase transformation In, thermodynamic equilibrium a system may be, composed of one or several physically distinct macroscopic homogeneous parts called, phases, which are separated from one another by well defined interfaces. These phases, are determined by several parameters such, as temperature, pressure, and electric and, magnetic fields. By continuously varying the, parameters it is possible to induce the transformation of the system from one phase to, another., Thermodynamic property With the heat, exchange that occurs during heat processing, thermodynamics becomes important and, useful. It is the heat content of the melts, (about 100 cal/g) combined with the low rate

Page 662 : 644, , Appendix B:, , of thermal diffusion (10- 3 cm 2 /s) that limits, the cycle time of many processes. Also important are density changes, which for crystalline plastics may exceed 25 % as melts cool., Melts are highly compressible; a 10% volume, change for 10,000 psi (69 MPa) force is typical. Surface tension of about 20 g/cm may, be typical for film and fiber processing when, there is a large surface-to-volume ratio., Thermodynamic properties provide a, means of working out the flow of energy from, one system to another. Any substance of, specified chemical composition. perpetually, in electrical, magnetic, and gravitational, fields, have five fundamental thermodynamic, properties, namely pressure, temperature,, volume, internal energy, and entropy. All, changes in these properties must fulfill the requirements of the first and second law of thermodynamics. The third law provides a reference point, the absolute zero temperature, for, all these properties although such a reference, state is unattainable. The proper modes of, applying these laws to the above five fundamental properties of an isolated system constitute the well-established subject of thermodynamics., Thermodynamic, second law The entropy of, the universe increases in a spontaneous process and remains unchanged in a reversible, process. It can never decrease., Thermodynamic, statistical This discipline, tries to compute macroscopic properties of, materials from more basic structures of matter. These properties are not necessarily static, properties as in conventional mechanics. The, problems in statistical thermodynamics fall, into two categories. First it involves the study, of the structure of phenomenological frameworks and the interrelations among observable macroscopic quantities. The secondary, category involves the calculations of the actual values of phenomenology parameters, such as viscosity or phase transition temperatures from more microscopic parameters., With this technique, understanding general, relations requires only a model specified by, fairly broad and abstract conditions. Realistically detailed models are not needed to un-, , Terminology, derstand general properties of a class of materials. Understanding more specific relations, requires microscopically detailed models., Thixotropic A property of a plastic that is a, gel at rest but liquefies upon agitation and losing viscosity under stress. Liquids containing, suspended solids are likely to be thixotropic., They have high static shear strength with low, dynamic shear strength at the same time. As, an example, these materials provide the capability to be applied on a vertical wall and, through quick curing action remain in its position during curing., Tolerance, full indicator movement FIM is a, term used to identify tolerance with respect to, concentricity. Terms used in the past were full, indicator reading (FIR) and total indicator, reading (TIR)., Tooling Tools include dies, molds, mandrel,, jigs, fixtures, punch dies, etc. for shaping and, fabricating parts., Turnkey operation A complete fabrication, line or system, such as an extruder with a, thermoformer line with upstream and downstream equipment. Controls interface all the, equipment in-line from material delivery to, the end of the line handling the product for, in-plant storage or shipment out of the plant., Typical-basis The, an average value., is associated with, B-basis; C-basis;, interval., , typical property value is, No statistical assurance, this basis. See A-basis;, population confidence, , Vacuum pressure Gauge pressure in psi, (gpsi) is the amount by which pressure exceeds the atmospheric pressure of 14 psi, (negative in the case of vacuum). The absolute pressure (psia) is measured with respect to zero absolute vacuum [29.92 in., (101 kPa) Hg]. In a vacuum system it is equal, to the negative gage pressure subtracted from, the atmospheric pressure. (Gauge pressure +, atmospheric pressure = absolute pressure), (1 in. Hg = 0.4912 psi of atmosphere on a, product) (1 psi = 2.036 in. Hg).

Page 663 : Appendix B:, Variable A quantity to which any of the values in a given set may be assigned., Variable, deviation The difference between, dependent variable and steady state value., Variable, independent An experimental, factor that can be controlled (temperature,, pressure, order of test, etc.) or independently, measured (hours of sunshine, specimen thickness, etc.). Independent variables may be, qualitative (such as a qualitative difference, in operating technique) or quantitative (such, as temperature, pressure, or duration). Thus,, if variable A is a function of variable B, than, B is the independent variable., Variance The mean square of deviations,, or errors, of a set of observations; the sum, of square deviations, or errors, of individual, observations with respect to their arithmetic, mean divided by the number of observations, less one (degree of freedom); the square of, the standard deviation, or standard error., Virgin plastic See Plastic, virgin., Viscoelasticity A combination of viscous, and elastic properties in a plastic with the relative contribution of each being dependent, on time, temperature, stress, and strain rate., It relates to the mechanical behavior of plastics in which there is a time and temperature, dependent relationship between stress and, strain. A material having this property is considered to combine the features of a perfectly, elastic solid and a perfect fluid., Viscoelasticity of metal This subject provides an introduction on the viscoelasticity, of metals that has no bearing or relationship, with viscoelastic properties of plastic materials. The aim is to have the reader recognize that the complex thermodynamic foundations of the theory of viscoplasticity exist, with metals. There have been developments, in the thermodynamic approach to combined, treatment of rheologic and plastic phenomena and to construct a thermodynamic theory, non-linear viscoplastic material that may be, used to describe the behavior of metals under, dynamic loads., , Terminology, , 645, , It has been shown that the thermodynamic, foundations of plasticity may be considered, within the framework of the continuum mechanics of materials with memory. A nonlinear material with memory is defined by, a system of constitutive equations in which, some state functions such as the stress tension or the internal energy, the heat flux, etc.,, are determined as functionals of a function, which represents the time history of the local, configuration of a material particle., As a result of simultaneous introduction of, elastic, viscous and plastic properties of a material, a description of the actual state functions involves the history of the local configuration expressed as a function of the time and, of the path. The restrictions, which impose, the second law of thermodynamics and the, principle of material objectivity, have been, analyzed. Among others, a viscoplastic material of the rate type and a strain-rate sensitive, material have been examined., There are three different approaches to, a thermodynamic theory of continuum that, can be distinguished. These approaches differ, from each other by the fundamental postulates on which the theory is based. All of them, are characterized by the same fundamental, requirement that the results should be obtained without having recourse to statistical, or kinetic theories. None of these approaches, is concerned with the atomic structure of the, material. Therefore, they represent a pure, phenomenological approach. The principal, postulates of the first approach, usually called, the classical thermodynamics of irreversible, processes, are documented. The principle of, local state is assumed to be valid. The equation of entropy balance is assumed to involve a term expressing the entropy production which can be represented as a sum of, products of fluxes and forces. This term is, zero for a state of equilibrium and positive for, an irreversible process. The fluxes are function of forces, not necessarily linear. However, the reciprocity relations concern only, coefficients of the linear terms of the series, expansions. Using methods of this approach,, a thermodynamic description of elastic, rheologic and plastic materials was obtained., The second approach, called the thermodynamic theory of materials with memory.

Page 664 : 646, , Appendix B:, , The fundamental postulates of this approach, are as follows: (1) The temperature and entropy functions are assumed, to exist for nonequilibrium states, (2) The principal restriction imposed on the constitutive equations, is inequality, and (3) The notion of the thermodynamic state is modified by assuming, that the state of a given particle is characterized, in general, by the time history of the, local configuration of that particle. It should, be emphasized, however, that in particular, cases the history of the local configuration, of a particle can be determined by giving, the actual values of this configuration and, its time derivatives. No limitations are introduced for the processes considered. The constitutive equations are in general nonlinear., Within the framework of this approach, thermodynamic foundations of rheologic materials were established. The same was done for, plastic materials., The third approach is called the thermodynamic theory of passive systems. It is based on, the following postulates: (1) The introduction, of the notion of entropy is avoided for nonequilibrium states and the principle of local, state is not assumed, (2) The inequality is, replaced by an inequality expressing the fundamental property of passivity. This inequality follows from the second law of thermodynamics and the condition of thermodynamic, stability. Further the inequality is known to, have sense only for states of equilibrium,, (3) The temperature is assumed to exist for, non-equilibrium states, (4) As a consequence, of the fundamental inequality the class of processes under consideration is limited to processes in which deviations from the equilibrium conditions are small. This enables full, linearization of the constitutive equations., An important feature of this approach is the, clear physical interpretation of all the quantities introduced., Each of the three approaches above has its, weaknesses and none is commonly accepted., The first is subject to excessive limitations, in the form of the assumptions. Its present, development does not appear to be promising for the overcoming of the difficulties that, are encountered in nonlinear mechanics. The, second approach is criticized principally from, the point of view of physical foundations. The, , Terminology, problem of physical interpretation of quantities such as the temperature or entropy has, not found a detailed treatment within the, framework of this approach. The advantages, of the first approach are the mathematical, foundations that are very well developed and, offer a possibility of analysis of many interesting processes. They can also be used for, the description of nonlinear materials., The theories of elastic and viscoelastic materials can be obtained as particular cases of, the theory of materials with memory. This, theory enables the description of many important mechanical phenomena, such as elastic instability and phenomena accompanying wave propagation. The applicability of, the methods of the third approach is, on the, other hand, limited to linear problems. It, does not seem likely that further generalization to nonlinear problems is possible within, the framework of the assumptions of this approach. The results obtained concern problems of linear viscoelasticity., Viscosity Basically it is the property of the, resistance of flow exhibited within a body of, material. Ordinary viscosity is the internal, friction or resistance of a plastic to flow. It, is the constant ratio of shearing stress to the, rate of shear. Shearing is the motion of a fluid,, layer by layer, like a deck of cards. When plastics flow through straight tubes or channels, they are sheared and the viscosity expresses, their resistance. The melt index (MI) or melt, flow index (MFI) is an inverse measure of viscosity. High MI implies low viscosity and low, MI means high viscosity. Plastics are shear, thinning, which means that their resistance, to flow decreases as the shear rate increases., This is due to molecular alignments in the direction of flow and disentanglements., Viscosity is usually understood to mean, Newtonian viscosity in which case the ratio of, shearing stress to the shearing strain is constant. In non-Newtonian behavior, which is, the usual case for plastics, the ratio varies, with the shearing stress. Such ratios are often, called the apparent viscosities at the corresponding shearing stresses. Viscosity is measured in terms of flow in Pa·s (P), with water, as the base standard (value of 1.0). The higher, the number, the less flow.

Page 665 : Appendix B:, , Terminology, , 647, , Viscosity, apparent Defined as the ratio between shear stress and shear rate over a narrow range for a plastic melt. It is a constant, for Newtonian materials but a variable for, plastics that are non-Newtonian materials., , duced surface tackiness, increased elasticity,, much greater tensile strength, and considerably less solubility. Similar cross-linking, action occurs with thermoset plastics. See, Curing., , Viscosity, intrinsic Also called limiting viscosity number. For a plastic, it is the limiting, value of an infinite dilution. It is the ratio of, the specific viscosity of the plastic solution to, its concentration in moles per liter., , X-axis The axis in the plane of a material, used as 0° reference; thus the y-axes is the, axes in the plane of the material perpendicular to the x-axis; thus the z-axes is the reference axis normal to the x-y plane. The term, plane or direction is also used in place of, axis., , Vulcanization A process in which rubber or, TS plastic (elastomer) undergoes a change, in its chemical structure brought about by, the irreversible process of reacting the materials with sulfur and/or other suitable agents., These cross-linking action results in property, changes such as decreased plastic flow, re-, , Y-axis A line perpendicular to two opposite, parallel faces., Z-axis The reference axis perpendicular to, x and y axes.

Page 670 : 652, JSPS, JSR, JSW, JUSE, JWTE, K, K, , K, K, KB, kB, KBE, kc, kcal, KE, kg, KISS, KISS, KISS, KK, Km, KM, kmlh, KO, kPa, KRF, ksi, kV, , Appendix C: Abbreviation, , Japan Society for Promotion of, Science, Japanese SBR, Japan Steel Works, Japanese Union of Science, & Engineering, Japan Weathering Test, Center, bulk modulus of elasticity, coefficient of thermal, conductivity, Kelvin, Kunststoffe (plastic in German), kilobyte (1000 bytes), knowledge-based, knowledge-based engineering, kilocycle, kilogram calorie, kinetic energy, kilogram, keep it short & simple, keep it simple & safe, keep it simple stupid, thousand, kilometer, Kubelka-Munk theory, kilometer per hour, knockout, kilopascal, Korea (South) Research, Foundation, thousand pounds per square inch, (psi x 103 ), kilovolt, , length, litre (USA liter), pound, pound-force, liquid chromatography, length-to-diameter (ratio), low density polyethylene (also, PE-LD), LDM, light depolarization microscopy, LEED, low energy electron diffraction, LIM, liquid impingement molding, (now called RIM), LIM, liquid injection molding, LLDPE linear low density polyethylene, (also PE-LLD), , I, L, lb, lbf, LC, LID, LDPE, , LMDPE, , linear medium density, polyethylene, , matrix, metallocene (catalyst), meter, milligram, micromillimeter; millicron;, m/-L, 0.000001 mm, micrometer, /-Lm, M, mega, M, million, bending moment, Mb, MAD, molding area diagram, MD, machine direction, mean deviation, MD, MD&DI Medical Device & Diagnostic, Industry, MDD, Medical Devices Directory, Me, metallocene catalyst, mg, milligram, mHDPE metallocene HDPE (different, m/plastics such as mPS, mPp,, etc.), mi, mile, MI, melt index (see MFI), microinch (10- 6 in.), mike, mil, one thousand of inch, (10- 6 in.), min, minute, min., minimum, MIPS, medium impact polystyrene, ml, milliliter, mLLDPE metallocene catalyst LLDPE, MM, billion, MRPMA Malaysian Rubber Products, Manufacturers' Assoc., Msi, million pounds per square inch, (psi x 106 ), MVD, molding volume diagram, MVT, moisture vapor transmission, MW, molecular weight, MWD, molecular weight distribution, MWR, molding with rotation, Mylar, polyethylene glycol, terephthalate, m, , m, m, mg, , N, N, N, , Nano (10- 9), Newton (force), number of cycles

Page 671 : Appendix C:, North America Assoc. for, Environmental Education, NAAQS National Ambient Air Quality, Standards, National Assoc. of Corrosion, NACE, Engineers, National Assoc. of CAD/CAM, NACO, Operation, NAGS, North America Geosynthetics, Society, National Bureau of Standards, NBS, (since 1980s renamed National, Institute of Standards, & Technology or NIST), NCGA, National Computer Graphics, Assoc., NCP, National Certification in Plastics, NCRC, National Container Recycling, Coalition, NDE, nondestructive evaluation, NDI, nondestructive inspection, nondestructive testing, NDT, NEAT, nothing else added to it, NEMA, National Electrical, Manufacturers Assoc., NEN, Dutch standard, NFE, non-linear finite element, Dutch Plastics Federation, NFK, NFPA, National Fire Protection Assoc., NFPA, National Food Processors Assoc., nm, nanometer, not otherwise specified, NOS, nuisance odor solution evaluator, NOSE, NPCM, National Plastics Center, & Museum, NPE, National Plastics Exhibition, (SPI), NPFC, National Publications & Forms, Center (US gov't), NPII, National Printing Ink Institute, NPRC, National Polystyrene Recycling, Co., NQR, nuclear quadruple resonance, NTMA, National Tool & Machining, Assoc., NWPCA National Wooden Pallet, & Container Assoc., nylon, (see PA), NAAEE, , O2, , 03, , oxygen, ozone, , 653, , Abbreviation, OD, OEM, OPET, OSHA, oz, %vol, , outside diameter, original equipment, manufacturer, oriented polyethylene, terephthalate, Occupational Safety, & Health Administration, ounce, , percentage by volume (prefer, vol%), %wt, percentage by weight (prefer, wt%), load, P, P, pOIse, pressure, P, Pascal, Pa, polyamide (nylon), PA, polymer analysis, PASS, & simulation software, physical blowing agent, PBA, permeability coefficient, PC, personal computer, PC, plastic composite, PC, plastic compounding, PC, PC, plastic-concrete, polycarbonate, PC, printed circuit, PC, process control, PC, programmable circuit, PC, PC, programmable controller, pounds per cubic foot, pcf, PDFM, Plastics Distributors, & Fabricators Magazine, PE, plastics engineer, PE, polyethylene (UK polythene), PE, professional engineer, PEl, polyethylene isophthalate, polyethylene naphthalate, PEN, PET, polyethylene terephthalate, PETG, polyethylene terephthalate, glycol, PETS, plastics evaluation, & troubleshooting system, PE-UHMW ultra-high molecular weight, polyethylene (or UHMWPE), PFA, perfiuoroalkoxy alkane, phr, parts per hundred, pi, ][ = 3.141593, PI, polyimide, proportional integral, PI

Page 673 : Appendix C: Abbreviation, SRI, , Standards Research Institute, (ASTM), stress-strain, Special Technical Publication, (ASTM), standard temperature & pressure, , ULDPE, , V, V, V, VA, VCM, VDA, , torr, TP, TPE, TPO, TPU, TOC, TOM, TR, TS, TSC, TSE, two-D, TX, Tx, , thickness, temperature, time, torque (or T t ), glass transition temperature, melt temperature, tensile strength, test & evaluation, thermocouple, technical cost modeling, transverse direction, thermoforming, see PTFE, thermogravimetric analysis, thermogravimetric index, 3-dimensional (3-D), tooling indicator runout, total indicator reading, thermomechanical analysis, Tooling & Manufacturing Assoc., (formerly TDI), mm mercury (mmHg), thermoplastic, thermoplastic elastomer, thermoplastic olefin (TPE-O), thermoplastic polyurethane, total quality control, total quality management, torque rheometer, thermoset, thermal stress cracking, thermoset elastomer, 2-dimensional (2-D), thixotropic, toxic, , UA, UD, UHMW, UL, , urea, unsaturated, unidirectional, ultrahigh molecular weight, Underwriter's Laboratories, , S-S, STP, STP, t, T, T, T, , Tg, Tm, , t, , T&E, TIC, , TCM, TD, TF, TFE, TGA, TGI, three-D, TIR, TIR, TMA, TMA, , UR, USA, UV, , VOC, vol, vol%, vs., , 655, ultra low density polyethylene, (orPE-ULD), urethane (also PUR, PU), United States of America, (also USA), ultraviolet, vacuum, velocity, volt, value analysis, vinyl chloride monomer, Assoc. of the Automotive, Industry (Germany), volatile organic compound, volume, percentage by volume, versus, , width, watt, World Plastics & Rubber, Technology magazine, WPC, wood-plastic composite, WPC, world product code, wt%, percentage by weight, WVT, water vapor transmission, WVTR, water vapor transmission, rate, WYSIWYG what you see is what you get, w, W, WP&RT, , X, X-axis, XL, XLPE, XPS, Y-axis, YPE, Z-axis, ZDP, ZST, Z-twist, , arithmetic mean, axis in plane used as 0°, reference, cross-linked, cross-linked polyethylene, expandable polystyrene, axis in the plane, perpendicular to X -axis, yield point elongation, axis normal to the plane of, the X-Y axes, zero defect product, zero-strength time, twisting fiber direction

Page 674 : Appendix D, Conversion, , The following data uses the decimal point, (that is, a dot, as used in the USA) rather than, , 3., , a comma (as widely used in the rest of the, world, and eventually to be used in the USA)., , Alphabetical list of units, Convert from, , acre (43560 square US survey feet), atmosphere, standard, bar, British thermal unit (Btu) (Int'l Table), British thermal unit (Btu) (thermochem.), Btu per cubic foot (Btu/ft 3 ), Btu per degree Fahrenheit (BtuIOF), Btu per hour (Btu/h), Btu per pound (Btullb), centimeter of water, centipoise, chain (66 USA survey feet), circular mil, cubic foot (ft3), cubic foot per second (ft 3 /s), cubic inch (in3 ), cubic mile, cubic yard (yd3), day (mean solar), degree, degree Celsius (0C) (interval), degree Celsius (0C) (temperature), degree Centigrade (interval), degree Centigrade (temperature), , To, , Multiply by, , square meter (m2), pascal (Pa), kilopascal (kPa), pascal (Pa), kilopascal (kPa), joule (J), joule (J), joule per cubic meter (J/m 3), joule per kelvin (J/K), watt (W), joule per kilogram (J/kg), pascal (Pa), pascal second (Pa·s), meter (m), square millimeter (mm2 ), cubic meter (m3), cubic meter per second (m 3 /s), cubic meter (m3), cubic meter (m 3), cubic kilometer (km3 ), cubic meter (m 3 ), second (s), radian (rad), kelvin (K), kelvin (K), degree Celsius caC), degree Celsius (aC), , 4046.873, 1.013 25 x 105, 101.325, 1.0 x 105, 100, 1055.056, 1054.350, 3.7259 x 104, 1899.101, 0.2930711, 2326, 98.0665, 0.001, 20.11684, 5.067 x 10- 4, 0.028317, 0.028317, 1.638 706 x 10- 5, 4.168182 x 109, 4.168182, 0.764555, 8.64 x 104, 0.017453, 1.0, toe + 273.15, 1.0, ~tccntigrade

Page 675 : Appendix D:, 3., , Conversion, , 657, , (Continued), Convert from, , degree Fahrenheit caF) (interval), degree Fahrenheit caF) (temperature), degree Fahrenheit hour per Btu (OF. h/Btu), degree Rankine (OR) (interval), degree Rankine COR) (temperature), denier, dyne, dyne centimeter, faraday, fathom, fermi, foot, foot, USA survey, foot of water, foot pound-force (ft·lbf) (torque), foot pound-force (ft·lbf) (energy), gallon (Imperial), gallon (USA) (231 in3 ), gallon (USA) per day, gallon (USA) per minute (gpm), gallon (USA) per horsepower hour, gamma, hectare, horsepower (550 ft· Ibf/s), horsepower (boiler) (~33470 Btu/h), horsepower (electric), horsepower (metric), horsepower (water), hour, hour (sidereal), hundredweight, long (1121b), hundredweight, short (100 Ib), inch, inch of mercury, inch of water, kelvin (K) (temperature), kilogram-force, kilometer per hour, knot (nautical mile per hour), light year, liter, , To, , Multiply by, , kelvin (K), degree Celsius (0e), kelvin (K), degree Celsius cae), kelvin per watt (K/W), kelvin (K), kelvin (K), kilogram per meter (kg/m), newton (N), newton meter (N . m), coulomb (e), meter (m), meter (m), femtometer (fm), meter (m), meter (m), pascal (Pa), kilopascal (kPa), newton meter (N . m), joule (J), cubic meter (m3 ), liter (L), cubic meter (m 3 ), liter (L), cubic meter per second (m3/s), liter per second (Lis), cubic meter per second (m3/s), liter per second (Lis), cubic meter per joule (m3/J), tesla (T), square meter (m 2 ), watt (W), watt (W), watt (W), watt (W), watt (W), second (s), second (s), kilogram (kg), kilogram (kg), meter (m), pascal (Pa), kilopascal (Pa), pascal (Pa), degree Celsius (0e), newton (N), meter per second (m/s), meter per second (m/s), meter (m), cubic meter (m3 ), , 0.5555556, 0.5555556, (tOF + 459.67)/1.8, (t oF - 32)/1.8, 1.895634, 0.5555556, Ta R /1.8, 1.111 x 10-7, 1.0 X 10-5, 1.0 X 10-7, 9.649 X 104, 1.8288, 1.0 x 10- 15, 1.0, 0.3048, 0.3048006, 2989.07, 2.98907, 1.355818, 1.355818, 4.546 09 x 10-3, 4.54609, 3.785412 x 10- 3, 3.785412, 4.381 264 x 10-8, 4.381 264 x 10- 5, 6.309 020 x 10- 5, 0.06309020, 1.410 089 x 10- 9, 1.0 X 10-9, 1.0 X 104, 745.6999, 9809.50, 746, 735.4988, 746.Q43, 3600, 3590.170, 50.80235, 45.35924, 0.0254, 3386.39, 3.38639, 249.089, TK - 273.15, 9.80665, 0.278, 0.5144444, 9.46053 x 1015, 0.001

Page 676 : 658, a., , Appendix D:, , Conversion, , (Continued), Convert from, , microinch, micron, mil (0.001 in), mil (angle), mile, international (5280 ft), mile, nautical, mile, USA statute, mile per gallon (US) (mpg), mile per hour, mile per minute, millimeter of mercury, minute (arc), minute, minute (sidereal), ounce (avoirdupois), ounce (Imperial fluid), ounce (troy or apothecary), ounce (USA fluid), ounce-force, pica (computer) (116 in), pica (printer's), pint (Imperial), pint (USA dry), pint (USA liquid), point (computer) (1172 in), point (printer's), poise, pound (avoirdupois), pound (troy or apothecary), pound-force, pound-force foot (lbf . ft) (torque), pound-force per foot (lbf/ft), pound-force per pound (lbf/lb), pound-force per square inch (lbflin2) (psi), pound per cubic foot (lb/ft 3 ), pound per cubic inch (lblin 3 ), pound per cubic yard (lb/yd 3 ), pound per foot (lb/ft), , To, , Multiply by, , meter (m), micrometer (Mm), meter (m), micrometer (Mm), meter (m), millimeter (mm), radian (rad), degree (0), meter (m), meter (m), meter (m), meter per cubic meter (mlm 3 ), kilometer per liter (kmlL), meter per second (m/s), kilometer per hour (km/h), meter per second (m/s), pascal (Pa), radian (rad), second (s), second (s), kilogram (kg), gram (g), cubic meter (m3 ), milliliter (mL), kilogram, gram (g), cubic meter (m3 ), milliliter (mL), newton (N), millimeter (mm), millimeter (mm), cubic meter (m3 ), liter (L), cubic meter (m3 ), liter (L), cubic meter (m3 ), liter (L), millimeter (mm), millimeter (mm), pascal second (Pa·s), kilogram (kg), kilogram (kg), newton (N), newton meter (N . m), newton per meter (N/m), newton per kilogram (N/kg), pascal (Pa), kilopascal (kPa), kilogram per cubic meter (kg/m3), kilogram per cubic meter (kg/m3), kilogram per cubic meter (kg/m3), kilogram per meter (kg/m), , 2.54 X 10-8, 0.0254, 1.0 x 10- 6, 1.0, 2.54 X 10-5, 0.0254, 9.8175 x 10-4, 0.05625, 1609.344, 1852, 1609.347, 4.2514 x 105, 0.4251437, 0.44704, 1.609344, 26.8224, 133.3224, 2.9089 x 10- 4, 60, 59.83617, 0.02834952, 28.34952, 2.84131 x 10-5, 28.4131, 0.0311348, 31.103 48, 2.957 35 x 10- 5, 29.5735, 0.2780139, 4.233333, 4.2175, 5.6826 x 10-4, 0.56826, 5.5061 x 10-4, 0.55061, 4.731 76 x 10-4, 0.473176, 0.3527778, 0.35146, 0.1, 0.45359237, 0.3732417, 4.448222, 1.355818, 14.59390, 9.8066, 6894.757, 6.894757, 16.01846, 2.767990 x 104, 0.5932764, 1.488164

Page 677 : Appendix D:, a., , Conversion, , 659, , ( Continued), Convert from, , pound per gallon (US) (lb/gal), quart (USA dry), quart (USA liquid), rad (absorbed dose), ream (printing paper), revolution, revolution per minute (rpm), rod (16.5 USA survey feet), second (angle), second (sidereal), square inch (in2), square mile, square yard (yd 2), stokes, tex, therm (EEC), therm (USA), ton, assay, ton, long (2240 lb), ton, metric, tonne, ton, register, ton, short (2000 lb), ton of refrigeration (12000 Btu/h), ton (long) per cubic yard, ton (short) per cubic yard, torr, watt, watt hour, watt second, yard, year of 365 days, year (sidereal), year (tropical), , To, , Multiply by, , kilogram per cubic meter (kg/m3), kilogram per liter (kg/L), cubic meter (m3), liter (L), cubic meter (m3), liter (L), gray (Gy), sheets, radian (rad), radian per second (rad/s), meter (m), radian (rad), second (s), square meter (m2), square meter (m2), square meter (m2), square meter per second (m2/s), kilogram per meter (kg/m), joule (J), joule (J), gram (g), kilogram (kg), kilogram (kg), kilogram (kg), cubic meter (m3), kilogram (kg), watt (W), kilogram per cubic meter (kg/m3), kilogram per cubic meter (kg/m3), pascal (Pa), ergs per second, joule (J), joule (J), meter (m), second (s), second (s), second (s), , 119.8264, 0.1198264, 0.001101 221, 1.101221, 9.463 529 x 10-4, 0.9463529, 0.01, 500, 6.283185, 0.1047198, 5.029210, 4.8482 x 10- 6, 0.9972696, 6.4516 x 10-4, 2.589 99 x 106, 0.8361274, 1.0 x 10-4, 1.0 X 10-6, 1.0551 X 108, 1.0548 X 108, 29.16667, 1016.047, 1000, 1000, 2.831685, 907.1847, 3516.853, 1328.939, 1186.553, 133.322, 1 x 107, 3600, 1.0, 0.9144, 3.1536 x 107, 3.1558 X 107, 3.1558 X 107

Page 678 : -IU, , - 10, - 10, , - 62., - 56., , -10, , 14, 82, , 13, , 12, , II, , - 8.3, , -8.8, , - 8.11, , -·'1:, , 24, , 25, , "".0, , T3.4, '1$.2, , 89.8, '11.6, , 23, , - Ul 11, - 6.66 ZI, , - i:QC, , 6&.2, 68.0, , la 6U, , 112.6, , 60.8, , 53.6, $5.(, 5'l.2, 59.0, , 61.8, , 42.8, 44.6, 48.4, C8.2, 60.0, , 41.0, , 39.2, , 3U, , 3U, , 38.8, , F., , It, 20, , -'1.'1, , 17, , l', , -10.0 14, - 9.44 IS, , - . -..~:~, , - 68, - 40, - 22, , -'16, , -84, , •, , 10, , 7, 8, , •, , 5, , J, 2, 3, 4, , F., , '1.'f8, 8.13, 8.119, 9.44, 10.0, , $.00, 11.1\6, 6.11, 6.61, '1.22, , 2.22, 2.'18, 3.33, 3.89, 4.44, , - 0.66, 0, 0.1i6, 1.11, 1.81, , • 1.6'1, - 1.11, , C., , SO, , 4', , 4&, , 47, , 4', , 4S, , Cl, 42, 43, 44, , 40, , 37, 3., 3., , u, , 34, 35, , 33, , 31, S2, , 2t, 30, , F., , e.OI, , n.t, , 118.4, 120.2, 122.0, , 114.8, , lIG.6, , 109.4, 111.2, 118.0, , IOU, , 106.8, , 74, , 23.9, , 15, , 73, , 11, , 23.9, , 22,2, , 22.8, , 7t, , 10, , "11sa, ", , .4, IS, , 13, , .1, .2, , 10, , It, , 57, , "sa, , 55, , 54, , 53, , 11, 52, , P., , C;OI, , F., , "C -, , ·F •, , 169.1, IGI.6, 163.4, IIi&.!, 16'1.0, , 150.8, 152.8, 15U, 156.2, 158.0, , 143.6, 145••, lC'1.2, 149.0, , 141.8, , 140.0, , 138.2, , 116.C, , 1S2.8, 134.6, , 123.8, 125.', 12'1.4, 129.2, 131.0, , 61 to T6, , II.', , 18.9, 19.4, 20.0, 20.6, 21.1, , 1'1.8, 18.3, , 100.4, , IOU, 104.0, , l'l.I, , 18.3, 13.9, 14,4, 15.0, 111.11, , Ul.2, 12.1, , Jl.'1, , lU, , C., , 18.8, , 9G.8, , 81.4, 83.2, 95.0, , 89.&, , 1'1.8, , 116.0, , 81.4, 8402, , T8.8, 80.6, , F., , 111.1, 16.'1, , 28 to &0, , - US 2., - 2.'18 27, • 11.22 2t, , -, , ..., , 18, , II, 87, , IS, , "12U, , 10, , ,., 77, 78, , 71, , Icp~, , It, , t1, H, , ", , .1, , f4, , tl, , .2, , JO, , t1, , 212.0, , 210.2, , 204.1, 20U, 201.4, , 191••, 199.4, 201.2, 203.0, , 1911.8, , J94.0, , In.t, , 188.8, 188.8, 110.4, , 1'19.11, 181.4, 183.2, 185.0, , In.., , 1'f4.2, 11'.0, , 112.4, , i (·F - 82), , II, , F., 10.., 1'10.8., , !Ii ("C) + 3Z, , 3'1.8 100, , au, , 36.1, , 85.11, 38.1, , 86.0, , 33.8, 3404, , 82.8, 33.3, , 32,2, , 81.1 It, , 80.0, 80.6, 81.1, , 19.4, , 2U, , 2'1.8, 2U, , 27.1, , 28.'1, , tu, , 25.1, , IU, 25,0, , C., , 11 to 100, , TEMPERATURE CONVERSION, , NOT.:: --111... numbe... In bold Ieee typa rerer to thtl tempnature eIther In, deKnow C"ntlrrade or )'"hn'hh~i\ which It It! d""irt:d tn C(.n .."rt inw lhe oth..r, Ic:al~. It r.vnnrtinc lrom Fahrt-nhelt decl"1!t!l to Centicrede d"CI"IIN lh" "qui ...., lent temper., ure will be found In tbe 1"ll column. whllt II converl.inc Irom, decr~ C.nlirrade to derr_ Fahreuhelt, the anawer will be round iD tbe, column on the richt., , - 2~~ - 10, 0, - 11.1, , - :14.4 - 30, - 28.I - 20, , - 4~.~ - 40, , - 51. 1 - '0, - 45:~ - so, , - 67., , -ll.J, -to.6, , - '3., , -148, -130, -112, , -II.', , -lG8, , -12.2, , ·184, , -110, -100, , - '111., , - 9$.~ -140, - 90.~ -130, - 84.~ -120, , -13.', -12.8, , -IU, -13.1, , -1$.8, -15.0, , .-2$6, , ·2'14, , ·m, , -238, -220, -202, , -110, , -no, , -180, , -tU, , -ItO -310, , -US, , -1T.1, , -84', , -ZOO, , C., , -150, , -10'1, -101, , -123, -1\8, -IlZ, , -129, , -210, , -1M, , F., , 1c._01, , F., , C. Of, , C., , !to IS, , -210 to 0, , b. Temperature conversions, , 154, , 171, , \66, , 160, , 149, , 121, 12'f, 132, 138, 143, , U8, , 110, , 104, , 100, , 'I, , 18, .3, , '1', 77, , 82, , 340, , 300, 110, 310, 330, , 210, ZtO, , no, , uo, , 250, , 240, , uo, , %20, , 212, , ItO, , 180, 110, 200, , 1'10, , 33A, , G28, 6U, , 6110, 6011, , 6'1., , 482, 500, 1118, 1186, 654, , 484, , 446, , 410, 413, 428, , 814, lI9t, , 8S8, , 320, , 2", 302, , 130, , F., , 120 2'1, 130 188, , 110, , F., , C.GI, , u:, " "0, N, .0, , 43, 49, , C., , 101 to .40, , 1196, , 1142, 860, 11'18, , 80G, 824, , 1811, , 7&2, .,.,0, , TIll, '134, , H2, 680, 8911, , F., , 4to 914, , (SO, 410, .,0, 410, , (10, 420, 430, 440, , (00, , 310, , 380, , 3SG, HO, 370, , P., , C.GI, , "'., , '60, , 700, 710, 720, 730, 740, 750, , 399, , 690, , no, ao, , 6SO, , 100, 510, '20, '30, "0, , 5SO, 510, 5'10, 580, &to, , &20, 530, 540, , SID, , 500, , C.OI, , 371, 377, 3112, 3811, 393, , 360, 366, , 354, , 343, , 34', , 316, a21, 321, B32, 338, , 304, 810, , 299, , 288, 293, , 282, , 2'11, , 2'11, , 2811, , 260, , C., , 1:\0\&, , 1382, , 136~, , 1292, I:JIO, 1328, , 12112, 1220, 12:18, 1256, 1214, , llJ2, 1130, 1148, 1166, 1184, , JOiti, J1)9.(, , J02'~, , lo.tO, 1058, , 932, 950, 9611, 9116, 1004, , F., , 491 to 7:'0, , 0.56, 1.11, 1.67, 2.Zl!, 2.78, , C., 2, 3, , 4, I, , 1, , 9.0, , 5.4, 7.t, , 3.6, , C., 3.33, 3.89, 4.44, 6.00, 6.66, , F., J.8, , t, 10, , a, , 7, , ,, , 18.0, , 12.6, 14.4, Iti.2, , IO.M, , F., , lNTl':nrot.ATION FACT()R.q, , 2&4, , 20, , 238, le3, , IlIZ, , 221, 221, , 218, , 20.&, 110, , 199, , 193, , 188, , 182, , 117, , C., , 841 to 490, , ~, ~, , C·, , ~, , n:., , ~, , ~, , ~, , ~., , ~, , >:l..., , :g~, , ~

Page 679 : Appendix D:, c., , Conversion, , 661, , SI prefixes, Multiplication factor, , Prefix, , 1000000000 000 000 000 = lOIS, 1000000 000 000 000 = 1015, 1 000 000 000 000 = 1012, 1 000 000 000 = 109, 1 000000 = 106, 1000= UP, 100 = 102, 10 = 101, 0.1 = 10- 1, 0.01 = 10-2, 0.001 = 10-3, 0.000 001 = 10-6, 0.000 000 001 = 10- 9, 0.000 000 000 001 = 10-12, 0.000 000 000 000 001 = 10- 15, 0.000000000 000 000 001 = 1O-1S, , exa, peta, tera, giga, mega, kilo, hecto, deka, deci, centi, milli, micro, nano, pico, femto, aUo, , f, a, , Unit, , Symbol, , Definition, , Minute, Hour, Day, Week, month, etc., Degree, Minute, , min, h, d, , Second, , ", , Litre, Metric ton, Hectare, , L, , d., , E, , P, T, G, , M, k, h, da, d, c, m, JL, 1'/, P, , Units in use with SI, Quantity, , Time, , Plane angle, , Volume, Mass, Area, , e., , Symbol, , 0, , ha, , 1min=60s, 1h = 60 min = 3600 s, 1d =24h=S6400s, 1°, l', , =, =, =, 1", =, =, 1L =, =, 1t, 1 ha =, , (Jl' /lS0) rad, (1/60)°, (Jl' /10 SOO) rad, (1/60)', (Jl'/64S000)rad, 1 dm3 = 10-3 m3, 103kg, 1 hm2 = 104 m2, , Recommended pronunciation, , Prefix, , Pronunciation (USA)!, , Selected units, , Pronunciation, , exa, peta, tera, giga, mega, kilo, hecko, deka, deci, centi, milli, micro, nano, pico, femto, aUo, , ex' a (a as in about), pet' a (e as in pet, a as in about), as in terra firma, jig' a (i as in jig, a as in about), as in megaphone, kill' oh, heck' toe, deck' a (a as in about), as in decimal, as in centipede, as in military, as in microphone, nan' oh (an as in ant), peek'oh, fem' toe (fem as in feminine), as in anatomy, , candela, joule, kilometer, pascal, siemens, , candell' a, rhyme with tool, kill' oh meter, rhyme with rascal, same as seamen's, , The first syllable of every prefix is accented to assure that the prefix will retain its identity., Pronunciation of kilometer places the accent on the first syllable, not the second.

Page 680 : Appendix E, Mathematical Symbol, and Abbreviation, , +, , ±, x, --;-, /, , ~~, , >, <, >, , <, , -I, ex:, , 00, , II, , *, , D, , 0, , ", , plus (addition), minus (subtraction), plus or minus, times, by (multiplication), divided by, is to (ratio), equals, as, so is, therefore, equals, approximately equals, greater than, less than, greater than or equals, less than or equals, not equal to, varies as, infinity, parallel to, square root, square, circle, degrees (arc or thermometer), minutes or feet, seconds or inches, , ai, a", ai, a2, , a-prime, a-second, a-sub one, a-sub two, O,[],{} parentheses, brackets, braces, angle, perpendicular to, L,1a 2, a3, a-square, a-cube, a-I, a- 2 1/a,1/a2, sin-I a, the angle whose sine is, n, pi = 3.141593+, microns, = .001 millimeter, fL, micromillimeter, = .OOOOOL, mfL, summation, of, L, 8, e, base of hyperbolic, natural or, Napierian logs = 2.71828+, t:,., difference, acceleration due to gravity, g, (32.16 feet/sec. Per sec.), coefficient of elasticity, E, velocity, v, coefficient of friction, f, P, pressure of load, HP, horsepower, revolutions per minute, RPM, , GREEK ALPHABET, A, Ci, , B,,B, r,y, , ~,8, , E,8, Z, £,, , Alpha, Beta, Gamma, Delta, Epsilon, Zeta, , H,1), , e,e, , I,, , t, , K,K, , A,A, , M, fL, , Eta, Theta, Iota, Kappa, Lambda, Mu, , N,v, S,~, , 0,0, TI,n, p'p, ~,cr, , Nu, Xi, Omicron, Pi, Rho, Sigma, , T, r, Y,v, <1>,, , qJ, , X,X, \}I,ljr, Q,w, , Tau, Upsilon, Phi, Chi, Psi, Omega

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Page 688 : Index, , A, ablation, 121-122, 123, abrasion resistance, 330-331, 433, abrasion tests, 297, ABS. See acrylonitrile-butadiene-styrene (ABS), absolute pressure method, 241, acceptable risk, 276-277, accident reports, 286-287, acetal. See polyacetal (POM), acetate, 174, 175, acknowledgements, 287, acoustical emission tests, 303, acrylics, 11, 53, 54, 57, 161, 198,230,236,261,314,, 382-385,390,426, acrylonitrile, 579, acrylonitrile-butadiene-styrene (ABS), 11,53,54,57,, 80,161,198,252,314,382-385,427,444,478, additives, 348-353, adhesive tests, 297-298, advanced RP (ARP), 509, advantages of plastic, 16, 21-22, 335-337, aerospace, plastics in, 34, 108-109, 119-122, aging of plastic, 115-116, molecular weight and, 115, thermal, 323-324,399-400, aircraft, 255-259, alkyds, 386-388, 430, allowable working stress, 39, 79-81, 310, alloyed plastics, 345-347, allyl diglycol carbonate (CR-39), 236, 331, allyls,430, American Plastics Council (APe), 373, American Society for Testing and Materials (ASTM),, 83,107,286,301-302,382,386, aminos,430, amorphous plastics, 342-343, analysis method, 133-137, anisotropic construction, 153,506-507,508, , annealing, 126-127, 170,553, apparent creep modulus, 64, 65, 71-72, 77, 317, appliance products, 34-35, arc resistance, 327, 432, arc spray, 545, Arrhenius plot theory, 115-118,324, artificial weathering, 331-332, aseptic packaging, 237, assembly methods, 269--274, 546, autoclave molding, 512, automobiles, 34, 253-255, , B, backlash, 220, bag-in-box (BIB) packaging, 237, bag molding, 512, 523, bag molding Hinterspritzen, 512, bags,grocer~239, , balanced construction, 507, bankruptcy laws, 287, Barcol hardness, 315, 411, beam bending, 145-147, beam construction, 144-145, bearing design, 217-219, bearing strength tests, 298, bell-and-spigot joints, 217, biaxial load, 507, biaxially oriented, 455, bidirectional construction, 507, binders, structural, 228-229, biological substance packaging, 237, bioplastics, 259, bioriented (BO), 455, bioscience products, 259-260, biotechnology, 373, blind holes, 187, 188, blister (carded) packaging, 237

Page 689 : 672, , Index, , blowing agents, 174,499, blow molding (BM), 195-198, 284, 435, 440, 485-493, boats, process for, 514-515, Boltzmann's Law and Principle, 41, 42, 75, bosses, 187, Brewster's Constant law, 303, Brinell hardness, 315, brittleness, 52, 81, brittleness temperature, 322-323, bubble packs, 237, building materials, 33, 242-250, bulk molding compounds (BMC), 430, 509, 510, , c, CAD Plus SOLID EDGE, 31, calendering, 435, 440, 523-527, CAMPUS Database software, 31, 414, 594-595, cans, beverage, 237, cantilever beam method, 58, cantilever springs, 146, capacitors, 228, carcinogenicity tests, 298-299, CASSIS, 289, casting, 284-285, 440, 529-530, catalytic degradation, 117, cavitation erosion, 97-98, cellulose acetate (CA), 382-385, 427, cellulose triacetate, 175, cellulosics, 382-385, 427, 469, chairs, 250-253, Chapter 11 actions, 287, chemical blowing agents (CBAs), 499, chemical changes, 453-454, chemical resistance, 406-410, 424, 433, chlorinated polyether, 382-385, 427, 433, chlorinated polyethylene (CPE), 427, chlorinated polyethylene terephthalate (CPET), 496, clasps, 237-238, coatings, 176-177, 435, calendaring, 526, extrusion, 481, gel, 511, intumescent, 124-125,400, powder, 530, coefficient of linear thermal expansion (CLTE), 98-99,, 321-322,398-399, coextrusion, 195,477-481,491, coining, 154,472, coinjection molding, 470-471, 491, coin tap test, 304, cold working, 154, 180, colorants, 352-353, color filters, 235, color of plastic, 16, 432, combined action, theory of, 358-359, commodity plastics, 361, competition within industry, 577-579, composites. See reinforced plastics (RPs), compounded plastics, 345-353, 526, , compression molding (CM), 435, 440, 527-528, compression stretch-blow molding (CSBM), 492-493, compressive property, 59, 311, compressive stress, 94, computer-aided design (CAD), 25, 28-29,127,, 135,447, computer-aided design drafting (CADD), 29, computer-aided manufacturing (CAM), 29, computer-aided testing (CAT), 29, computer-integrated manufacturing (CIM), 27, 29, computers, use of, 25-31, conditioning, 107, 332, conductivity, thermal, 397, conflicts of interest, 287, connectors, power, 225-227, constant deflection amplitude fatigue testing, 84, constant strain amplitude, 84, constant stress amplitude, 84, Consumer Product Safety Act (CPSA), 287, contact molding, 512-514, containers, collapsible, 148-149,492, continuous loading, 20, contour packaging, 238, contraction, thermal, 98-101, 168, contracts, 288, controlled-atmospheric packaging (CAP), 238, copolymers, 345, copyright law, 287, coring, 187-188, corners, sharp, 180-181, 182-185, corotation, 201, corrosion resistance, 401-404, cost-benefit analysis (CBA), 573, cost-effectiveness analysis (CEA), 574, cost of plastics, 1,560-563, analysis of, 573-575, control over, 571, effectiveness, 574, estimating, 567-579, mold/die cost, 573, reduction in, 574-575, reinforced plastics, 511-512, rotational molding, 201, target, 575, tight tolerances and, 173-174, variable, 575, crazing, 52, 70,104-106,284, creep modulus, 64, 65, 71-72, 77, 317, creep property, 63-64, 65-82, creep rupture, 68-69, 70, 81, 86, definition of, 113, definition of creep, 67, designing for, 77-79, in foam cushioning, 502-503, modeling for, 66-67, performance data for, 67-68, stress relaxation and, 114, 316-318, creep tests, 317-318, cross-head rate, 53-55, cross-linked polyethylene (XLPE), 428, cross-linking, 117, 318-319, 340, 377

Page 690 : Index, crystalline plastics, 70, 72, 74, 75, 93, 126, 132, 168, 169,, 220,308,342-343,397, crystallinity, 318, cushioning, 502-503, cyclic fatigue, 86, cyclic loading, 82, 84-85, , D, Dalgren test, 299, damping, 44, 101, DAP. See diallyl phthalate (DAP), databases,28,31,412-416,593-599, decals, 546, decomposition temperature, 399, deflection load, 211-212, deflection temperature under load (DTUL), 319-321, deformation, creep, 81, 115, elastic, 45, toughness and, 377-380, underload,316, degradation, biological and microbial, 262-263, catalytic, 117, oxidative, 117, dental products, 261, design, analysis of, 132-138, 140,203, approach to, 23-24, computer assisted, 25-31, concepts in, 138-158, cost estimation, 575-576, definition of, 15-18, ethics in, 36, featuresin,24-25,158-177, performance and, 18-21, 179-202, plastic basics, 22-23, process for, 4-10, 204-208, protection of, 290, reinforced plastics, 357-359, safety and, 275-276, successin,35,580-588, designers, responsibility of, 35-36, 296-297, types of, 16-18, design technology, 16, design verification (DV), 274-275, destructive testing, 297-302, DFMA,31, diallyl phthalate (DAP), 111, 386-388, 390, 430, dichroic polarizer, 234, dielectric constant/loss, 223, 224-225, 328, dielectric strength, 223, 327-328, dies, 460-463, 573, diffusivity of plastic, 240-241, 398, dimensional stability. See stability of design, direct costs, 573-574, directional property, 152-153,210,457,504-509, directly applied loads, 138, , 673, , direct shear strength, 61, disadvantages of plastic, 21-22, dissipation factor, 328, distortion, 282, draft angle, 1M, 185, drilling, 535-537, drying plastics, 400-401, dual-ovenable trays (DOT), 238, ductility, 52, 81, Durometer hardness, 315, dyes, 353, dynamic loading, 38, 43, 44-45, 99, dynamic load isolator, 263-264, , E, e-commerce, 415-416, 141-142, elastic deformation, 45, elasticity, modulus of, 47-50,132,141, flexural,55-56,311, shear (G), 60, 61, 62, tensile (E), 61, 62, 72, 310, elasticity of plastic, 52, 431, 450-451, elastic limit, 47, 52, 310, elastomers, 93, 96, 100,270,359-361,391,599-601, electrets, 228, electrical eddy current test, 303-304, electrical products, 222-229, electrical property, 223-225, 327-328, 381-382, 433, electrical resistance test, 327, electromagnetic compatibility (EMC), 382-389, electromagnetic interference (EM1), 383, electromagnetic tests, 304, electronic products, 33, 222-229, 238, electro-optic products, 229, electroplating, 545, elongation, 47, employee invention assignment, 287, encapsulation, 529, endurance limit, 84-85, energy, control of, 100-101, energy costs, 575, 576-577, engineering designers, 17, engineering plastics, 361, environment, for building materials, 244-246, chairs and, 252-253, for electrical products, 227-228, for medical products, 261, ocean, 109-113,266, space, 34, 108-109, 119-122, epoxies, 226,237,325,386-388,390,430, equipment, auxiliary, 533, E1theor~62,, , secondar~534-537, , equipment variables, 551-552, erosion loading, 97-98, ethylene-propylene copolymers, 365, ethylene-vinyl acetate (EVA), 427

Page 691 : 674, expandable plastic foam (EPF), 500, expandable polystyrene (EPS), 427, 500, expansion, thermal, 98-101,168, expert witnesses, 287-288, extruded BM (EBM), 485, 489, 492, extrusion, 474-485, 526-527, design features, 192-195, modified techniques for, 477-481, plastic interaction with, 281-283, use of, 435, 440, , F, Fadeometer,331-332, failure, 82, of business, 295, of design, 203, 293-294, managing, 294-295, failure stress and strain, 52, FALLO approach, 4, 457, fatigue property, 81, 82-88, fatigue strength, 83, 316, fiber optics, 233, Fick's First and Second Laws of Diffusion, 241, filament winding (FW), 210-211, 515-517, fillers, 348-353, film, 174-175,526-527, breathable, 238, peelable, 239, filters, color, 235, gas, 266, water, 264-266, finite element analysis (FEA), 32,127-129,274,294,, 608-609, fire tests, 332-333, fixed support structures, 138, flame resistance, 431, flame spray, 545, flammability, 123-125, 332, flaw detection, 303-304, flexible packaging, 240, flexible RP, 510, flexural modulus of elasticity, 56, 311, flexural property, 55-58, 311, flexural strength, 55-56, 311, flow of plastic, 463, defects in, 452-453, direction of, 171-173, elasticity and, 450-451, extrusion, 282, injection molding, 185, 279, molecular weight distribution and, 448-449, performance, 451-452, rheology and, 448, viscosity and, 449, fluorinated ethylene propylene (FEP), 382-385, 427, fluorocarbons, 365, 368, 390, fluoroplastic (FP), 427, foamed plastics, 363-367, 496-503, foam reservoir molding, 503, , Index, folded structures, 147-150, food packaging, 238-239, fracture, 81, fracture mechanics theory, 85-86, free (unsupported) structures, 138, Fresnel lens, 231-232, friction, 410, frictional loading, 94-96, frictional spinning, 273, frozen-in stress, 279-280, 553, function of product, 204, , G, games, plastics in, 229, gas-assist injection molding (GAIM), 471, gas filters, 266, gasket design, 221, gate area, 1M, 185, 280, gear design, 219-220, gel coat, 511, glass-reinforced plastics (GRPs), 86, 104, 135, 136,343,, 355,412,417,514, glass-transition temperature Tg, 395-397, grafting, 346, 348, graphic designers, 17, Griffith theory, 293, grinding, 537, grocery bags, 239, grommet design, 221-222, GRP. See glass-reinforced plastics (GRPs), , H, hand lay-up, 514-515, hardness, 313-316, 411, haze, 328-329, HDPE. See high density polyethylene (HDPE), head forming, 270, heat capacity, 397-398, heat distortion temperature (HDT), 319-321, heat generation, 85, 126, heterogeneous construction, 508, high density polyethylene (HDPE), 11, 162, 165, 237,, 382-385,407,428,444,469,489, high impact polystyrene (HIPS), 377, 382-385, high speed property, 88-98, high-temperature plastics, 118-125, 325-326, hinges, blown, 195-197, integral, 153-154, homogeneous construction, 508, Hooke's Law, 42, 47, 48, 358, hoop stress, 94, hot fill, 239, hot stamping, 545, House of the Future, 246-248, human engineering, 17, huminous transmittance, 328-329, hydrostatic loading, 96-97

Page 692 : Index, hyperenvironment, 120, hypersonic atmospheric flight, 119-122, hysteresis effect, 50, 99-100, 219-220, , I, 1M. See injection molding (1M), impact loading, 90--92, 174,312-313, impact strength, 313, 431-432, impulse loading, 92-93, indirect costs, 573-574, industrial designers (IDs), 16-17, inertia, moment of (I), 62,141, infringement, patent, 288-289, injection BM (IBM), 485-486, 489, 492, injection-compression molding (ICM), 154 472, injection molding (1M), 95, 463-474, ', cost estimation for, 570-571, design features for, 181-192,278-281,468-469, modified techniques for, 469-474, plastic interaction with, 278-281, productivity of, 469, reinforced plastic production, 517, residual stress in, 180, 279-280, shrinkage allowance estimation for, 170--173, thermoforming compared, 496, use of, 435, 440, venting, 281, weld lines, 185-186, 281, in-line postforming, 481, in-mold decoration, 441, 538, innovative designers, 17-18, inserts, molded-in, 183, 190-191,269-270, insulation, electrical, 223, 224, 227, thermal, 397, insulation resistance, 327, !nsurance Risk Retention Act (IRRA), 288, mtegral hinges, 153-154, intermittent loading, 20, 73-74,139, International Electrotechnical Commission (lEe),, 286,382, interpenetrating networks (IPNs), 346, 347-348, intumescence coatings, 124-125,400, inventions, 288, ionomers, 382-385, 427, isochronous graph, 81, isometric graph, 80--81, isostatic method, 241, isotropic construction, 152-153, 507, isotropic transverse construction, 507, Izod impact tester, 91, 312, , J, jetting, 280--281, joining methods, 269-274, 546, joints, pipe, 217, joints, snap, 155, , 675, , K, knit lines. See weld lines, Knoop hardness, 315, , L, labels, 149-150, 546, laser lighting, 235, laser tooling, 178, laws, applicable, 286-291, LDPE. See low density polyethylene (LDPE), leaf springs, 146, leakage resistance, 224, lenses, 231-232, lenticulars, 232, light pipe, 232-233, I~near low density polyethylene (LLDPE), 11, 237, 428, lmear viscoelasticity theory, 113-114, liners, plastic, 266, liquid crystal polymer (LCP), 229, 343-345, liquid injection molding, 528, litigation, 287, 289, living hinges, 153, LLDPE. See linear low density polyethylene (LLDPE), load-bearing products, 139-140, loads, 20, 138-139, dynamic, 38, 43, 44-45, 99, erosion, 97-98, frictional, 94-96, hydrostatic, 96-97, long-term behavior, 63-88, mechanical, 43-44, puncture, 93-94, short-term behavior, 45-63, long-term load behavior, 63-88, loose fill, 239, lost-wax molding, 472-473, 517, low density polyethylene (LDPE), 11, 162,237,, 382-385,428,489, lubricants, 352, luminous reflectance, 329-330, Luscher & Hoeg formula, 212, , M, machine conditions, 20, machining, 535, Marco process, 517, markets for plastics, 579, mar resistance, 330--331, material optimization designers, 18, materials, behavior of, 38-41, 45, 442, 447-454, characteristics of, 137-138, process interaction with, 74-75, 277-285, properties of, 374-434, for reinforced plastics, 509-512, selection of, 205-206, material variables, 368-369

Page 693 : 676, maximum diametrical interference designers, 18, Maxwell fluid model, 66, mechanical load, 43-44, mechanical properties, 45, 309-319, 375-380,, 396-397,419, medical device designers, 18, medical products, 33-34, 259-262, medium density polyethylene (MDPE),, 382-385,428, melamine, 386-388, 430, meld lines, 176, melt flow. See flow of plastic, melt flow index (MF1), 449, melt flow rate (MFR), 449-450, melt index (M1), 449, melt index test, 449-450, melt temperature T m, 395, membranes, plastic, 265-266, membrane technology, 389, memor~367-368,401,454, , extrusion, 282, thermoforming, 283-284, metals, plastics compared, 136, microtoming optical analysis test, 304, milling, 537, modified atmosphere packaging (MAT), 239, modulus, apparentcreep,64,65, 71-72, 77,317, of elasticity. See elasticity, modulus of, relaxation, 42, Mohr's circle, 140, Mohs hardness, 315, Moire fringe analysis, 303, moisture, 401, 432-433, absorption of, 306, vapor permeability, 307-308, vapor transmission, 306-307, molded-in inserts, 183, 190-191, 269-270, MOLDEST,31, molding, 278. See also specific processes, Molding & Cost Optimization (MCO), 442, molds, 200-201, 457-460, 573, molecular weight distribution (MWD), 21,, 448-449, molecular weight (MW), 115, 448, moment of inertia (I), 62, 141, monocoque structures, 153, Monsanto House of the Future, 246-248, motion, control of, 100-101, , N, neat plastic, 363, necking, 89, Newtonian flow, 449, Newtonian response, 42, nonaxisymmetric blow molding, 490, nondestructive testing (NDT), 32, 274, 297-304, nonisotropic construction, 507, nonlaminar flows, 452-453, , Index, non-Newtonian flow, 449, nonplastication, 453, nylon. See polyamide (nylon) (PA), , o, ocean, plastics in, 109-113,266, odor of plastic, 431, opacity, 330, optical products, 229-237, optical property, 230-231, 328-331, organosol, 530, orientation, 368, 454-457, in extrusion, 481-485, of reinforcements, 504-507, thermoforming and, 284, original equipment manufacturer (OEM), 291, orthotropic construction, 507, oscillatory rheometer, 60, outdoor weathering, 331, over-molding, 473-474, oxifluorination, 242, Oxygenindex,332-333, oxygen scavenger packaging, 239, , p, PA. See polyamide (nylon) (PA), packaging, 33,237-242, medical, 262, misrepresentation on, 240, permeability of, 240-242, types of, 237-240, 242, PACT (prevention, assessment, corrective action, and, training), 18, painting, 538-545, paper, plastic compared, 267-268, Paradigm, 254, parting lines (PLs), 185, parylene, 427-428, patent law, 288-289, 291, Patent Term Extension (PTE), 289, Pc. See polycarbonate (PC), PE. See polyethylene (PE), pendulum test method, 91, performance of product, 31-32, design affecting, 18-22, predicting, 32-33, 274-275, process and, 435-447, permeability of plastic, 240-242, 306-308, 425, 433, PET. See polyethylene terephthalate (PET), PETG,149, phenol-formaldehyde (PF), 169,430, phenolics, 53, 54, 57, 228, 314, 325, 386-388,, 389,391, phenylene ether copolymer, 53, 54, 57, 314, phenylene oxide (PPO), 428, photopolymerization, 178-179, physical blowing agents (PBAs), 499

Page 694 : Index, physical properties, 305-309, pigments, 353, pipe design, 208-217, anisotropic behavior, 213, buckling, 212-213, deflection load, 211-212, directional property, 210, filament wound structure, 210-211, load testing, 209-210, Poisson's ratio, 214-215, stiffness, 211, 212-213, strength, 211, stress-strain curve, 213-214, weep point, 214, pipe joints, 217, piping light, 232-233, plastic, definition of, 337-338, plasticizers, 352, plastics industry, 1, 12, 588-589, plastisol, 530, PMMA. See polymethyl methacrylate (PMMA), point of first crack, 214, Poisson's ratio (v), 50-52, 61, 214-215, polarized lighting, 233-235, polyacetal (PC>M), 11, 161,343,382-385,426, acetal copolymer, 53, 54, 57, 314, 444, acetal homopolymer, 53, 54, 57, 314, polyamide (nylon) (PA), 11, 161, 168, 182, 184, 198,, 306,343,375,427, nylon-66, 455-457, Nylon 6, 46, 77, 375, 382-385, 418, 444, Nylon 616, 77, 382-385, 418, 444, Nylon 6/10, 77, 382-385, Nylon DAM, 53, 54, 57, 314, Nylon 50% RH, 53, 54, 57, 314, oriented, 92, twisted, 109, polyanhydride, 33-34, polyarylate, 428, polyaryletherketone (PAEK), 579, polybutylene, 428, polybutylene terephthalate (PBT), 77, 428, 444, polycarbonate (PC), 11,46,53,54,57,73,75, 161, 182,, 198,236,314,343,382-385,392,428,444, polyelectrolytes, 260, 266, 268-269, polyester, 11, 33, 77, TP, 11,226,228,237,428, TS, 228, 257, 266, 325, 356,430, 496, polyetheretherketone (PEEK), 428, 444, polyetherimide (PEl), 428, 444, polyethersulfone (PES), 444, polyethylene naphthalate (PEN), 175, 239, polyethylene (PE), 54, 57, 95, 104, 111, 162, 198, 239,, 306,314,332,382-385,390,428-429,450,451,478,, 591. See also high density polyethylene (HDPE);, low density polyethylene (LDPE), chlorinated, 427, cross-linked, 428, LLPDE, 11, 237, 428, MDPE, 382-385, 428, UHMWPE, 95, 428, , 677, , polyethylene terephthalate (PET), 11, 174-175, 237,, 239,408,428, chlorinated, 496, polyimides (PIs), 390, 429, 496, Polymat database, 414, 415, 596-597, Polymer Search on the Internet (PSI), 31, 416, polymethyl methacrylate (PMMA), 85, 261, 375,426, polyolefins (PC>s), 95, 268, 390, 419, polyoxymethylene (PC>M). See polyacetal (PC>M), polyphenylene oxide (PPC», 343, 382-385, 431, 444, polyphenylene sulfide (PPS), 418, 429, 444, polypropylene (PP), 11, 54, 57, 76, 77,109,117,135,, 153,154,162,166,174,182,195,237,239,252,314,, 375,382-385,390,429,440,444,455,456,478, polystyrene (PS), 11, 54, 57, 162, 239, 314, 382-385,, 429,444,469,478,577, crystal, 279, expandable, 427, 500, high impact (HIPS), 377, 382-385, polysulfone, 53, 54, 57, 314, 382-385, 429, polytetrafluoroethylene (TFE), 95, 202, 221, 240-241,, 375,382-385,407,427, polyurethane (PUR), 96, 111, 124, 221, elastomers, 96, 270, 365, formation and curing of foam, 499-500, properties of, 382-385, TP (TPU), 429, TS (TSU), 430-431, polyvinyl chloride (PVC), 11, 74, 92,109,111,149,167,, 195,239,347,390,429,525, flexible, 198,382-385,478, rigid, 382-385, 478, PC>M. See polyacetal (PC>M), pooling of patents, 289, pouch heat-sealed containers, 239, powder coating, 530, PP. See polypropylene (PP), preimpregnation, 510, press fit, 188-189, pressure bag molding, 517, principle of reduced variables, 41, 42, printing, 546, process, 435-566. See also specific processes, control over, 530-533, equipment for, 533-537, finishing and decorating, 537-546, joining and assembly, 546, material behavior in, 447-454, materials interaction with, 74-75, 277-285, product performance and, 435-447, property and, 454-457, reinforced plastic, 503-523, safety with, 547-551, selection of, 552-566, tooling for, 457-463, troubleshooting, 546, variables in, 551-552, processing variables, 20, 551-552, Processor Collaborative Venture (PCV), 289-290, processor contract, 290, product cost, 575

Page 695 : 678, product liability law, 290, propagating neck, 89, proportional limit, 47, 52, 310, propulsion exhaust, 122-123, Prospector, 31, 593, protection of design, 290, prototypes,S, 177-179,206,261, building, 447, 535, chair, 253, testing, 37, 178, 206-207, PS. See polystyrene (PS), pseudo-elastic design method, 40, 132-133, PTFE. See polytetrafluoroethylene (TFE), pultrusion, 517, punch shear test, 60, 312, puncture loading, 93-94, PUR. See polyurethane (PUR), PVc. See polyvinyl chloride (PVC), PV factor, 218-219, 410, , Q, quality control (QC), 206, 296, statistical process control and, 333-334, testing and, 299-300, 333, quality system regulation (QSR), 174, 285, quasi-isostatic method, 241, quasi-isotropic construction, 507, quotations, 290, 569, 579, , R, radiation, 106-107,404,405-406,432, rain erosion, 98, rapid prototyping (RP), 178-179, rapid tooling, 178-179, RAPRA search engine, 31, 416, rate theory, 114-115, reaction injection molding (RIM), 528, reactive extrusion recycling (REX), 372-373, reactive polymers (RPs), 348, reaming, 535-537, recovery, 73, recreational products, 33, recycling plastics, 369-373, reinforced plastics (RPs), 109, 112, 177, 304, 348-359,, 409,437,503-523, advantages 'Of, 137-138, characterization of, 504, cost ,of, 511-512, design tboory for, 357-359, directi(}nal property of, 152-153, 504-509, fatigue for, 86-'81, future uses of, 523, materials in, 509-512, micromechanic behavior of, 509, pipes, 208-217, processes for, 512-523, property range for, 359, reinforced RIM (RRIM), 528, reinforced thermoplastics (RTPs), 66,152,503, , Index, reinforced thermosets (RTSs), 46, 59, 66,152,159,, 208,503, relative thermal index (RTI), 323, relaxation modulus, 42, research and development of plastics, 589, residence time, 453, residual stress, 179-180, 279-280, resin transfer molding (RTM), 517-520, retortable pouches (containers), 240, reusable containers, 239, rheolog~38-39,41-42,448, , rib construction, 142-144, 192, right-to-know laws, 290, rigidity, modulus of, 61, 62, risks, 276-277, Rockwell hardness, 315-316,411, roofs, 248-250, room temperature vulcanization (RTV), 178, 431, rotational molding (RM), 200-202, 440, 528-529, routing, 537, RP. See reinforced plastics (RPs), RTP. See reinforced thermoplastics (RTPs), RTS. See reinforced thermosets (RTSs), rupture, creep, 68-69, 70,81,86, rupture, modulus of, 55-56, 311, , s, safety, design and, 275-276, processing and, 547-551, safety factors (SF), 129-130, sandwich construction, 150-151, sawing, 537, Scleroscope hardness, 316, screw threads, 189, 191-192, SCRIMP (Seeman Composites Resin Infusion, Process), 522, secant modulus, 49, 50, 310, selection of plastic, 412-434, databases, 412-416, preliminary considerations, 417-425, property categories, 431-434, worksheet, 416-417, shape of design, 141-142, 155-158, 553-555, sharkskin, 453, shear modulus (G), 60, 61, 62, shear rate, 447, shear strength, 61, 312, shear stress-strain, 60-62, sheet molding compounds (SMC), 430, 509, 510-511, shop-rights, 290, Shore hardness, 316, 411, short-term load behavior, 45-63, shrinkage, 125-126, 165-170,308-309,442-443,453, definition of, 125, processing and, 170-174, shrink wrap, 240, silicones, 124,365,386-388,391,431, simply supported structures, 138, size of product, 155-158,204-205,555

Page 696 : Index, skin packaging, 238, smoke, 124, snap fits, 270-272, snap joints, 155, S-N curve, 82, 84, 86, Society of the Plastics Industry (SPI), 163, 558, software programs, 30-31, 291, 602-610, solid waste, 577, soluble core molding, 472-473, 517, sonic testing, 303, space, plastics in, 34,108-109,119-122, specific density, 305, specific gravity, 305, spray-up, 522, springs, 145-147, sputter plating, 545, stability of design, 125-127, 397, 433-434, 442-446, stampable reinforced thermoplastics (SRTPs), 152, stamping, 522, 545, static analysis, 129, static fatigue, 86, static torsion test, 60, statistical process control (SPC), 333-334, statistical quality control (SOC), 334, stereolithography, 178, sterilization, 106-107, 403, stiffness, 151,318,380, chairs, 251-252, pipe, 211, 212-213, strain, definition of, 46, strain-induced loads, 138, strength, 318, 380, of design, 211, flexural, 55-56,311, tensile, 46, yield, 47, 310, 311, stress cracking, 104-106, 332, stresses, analysis of, 302-303, applied, 432, concentration of, 180-181, definition of, 46, hoop, 94, m ul tiaxial, 140, residual, 179-180, 279-280, thermal, 174, 399, in thermoforming, 283, stress relaxation, 42, 64-65, 72-73, 114, 316-318, 423, stress-strain, 213-214, compressive, 59, data application, 62-63, flexural, 55-58, shear, 60-62, tensile, 45-55, time and, 42, stress whitening, 70, 105, structural foam (SF), 363-367, structure of plastics, 340-345, styrene-acrylonitrile (SAN), 382-385, 429-430, styrene-maleic anhydride (SMA), 430, styrenes. See polystyrene (PS), sublimation printing, 545, , 679, , surface resistivity, 327, surfaces of plastics, 177, 546, 558-560, surfacing reinforced mat, 511, surgical products, 260-261, syntatic foam, 500-502, , T, Taber abrasion test, 297, tape test, 297-298, tariffs, 291, taste of plastic, 431, technical cost molding (TCM), 571-573, temperature. See thermal property, temperature differential test, 304, temperature index, 400, tensile creep failure, 63, tensile impact test, 312-313, tensile property, 45-55, 309-311, tensile strength, 46, tensile stress, 94, terminology, 36, 291, 630-647, testing, 296-334, classification and, 299, complexity of tests, 300, destructive, 297-302, flaw detection, 303-304, limitations of, 304-305, nondestructive, 32, 274, 297-304, personnel for, 300, quality control and, 299-300, 333, specifications and standards for, 300-302, stress analysis, 302-303, test rate, 53-55, TFE. See polytetrafluoroethylene (TFE), thermalpropert~ 102-104,319-326,380,391-400,431, aging,323-324,399-400, expansion and contraction, 98-101,168, thermodynamics, 453, thermoforming (TF), 198-200,283-284,435,493-496, thermoplastic elastomer (TPE), 263, 359-361, thermoplastics (TPs), 10,45,74,367,454, applications for, 390, definition of, 338-339, fatigue strength of, 83, 84, properties for, 382-385, reinforced, 66, 152, 503, temperature effect on, 102, 104, thermal property, 394, tolerances for, 159,308-309, types of, 425-430, thermoset elastomer (TSE), 359, thermoset plastics (TSs), 10, 65, 439, applications for, 390-391, definition of, 339-340, properties for, 386-388, reinforced,46,59,66,152,159,208,503, temperature effect on, 102, 104, thermoforming, 496, tolerances for, 159,309, types of, 430-431

Page 697 : 680, , Index, , threads, 183,191-192, external, 176, internal, 189-190, thread tapping, 537, three-point loading, 55, time dependence theory, 113, tip relief, 220, tolerances, 125-126, 158-164,308-309, dimensional control and, 442-446, extrusion, 193-195, inspection and, 443-446, processing and, 170-174, thermoforming, 199-200, thickness, 555, tight, cost advantages of, 173-174, torsional beam springs, 147, torsional pendulum tests, 60, 62, torsion modulus, 61, torsion property, 62, tort law, 291, toughness, 47, 318-319, 376-380, toys, plastics in, 229, TP. See thermoplastics (TPs), trademarks (TM), 291, trade names (IN), 291, transfer molding (TM), 527-528, transparenc~330,432, , transparent products, 229-237, troubleshooting, 292-295, 546, TS. See thermoset plastics (TSs), turning, 537, , u, ultimate elongation, 52, ultra high molecular weight polyethylene (UHMWPE),, 95,428, ultrasonic tests, 304, ultrasonic welding, 273-274, 550, uncertainty, 130, undercuts, 187, 198, Underwriters Laboratories (UL), 103,285-286,324,, 382,388,400, UL 94, 124, 332, unidirectional construction, 507, urea, 386-388, 430, urethane, 11,325,391. See also polyurethane (PUR), U.S. Patent and Trademark Office (PTO), 291, U.S. Patent Classification System, 289, uses of plastics, 3, 33-35, UV degradation, 106, , v, vacuum bag molding, 523, vacuum forming, 283, 440, vacuum metallizing, 545, value added (VA) analysis, 587-588, vessels, process for, 514-515, , Vicat hardness, 316, vinyl dispersion, 530, Vinyl Institute, 373, vinyls, 96, 162, 390, viscoelastic and rate theory, 113, viscoelastic creep. See creep property, viscoelastic creep modulus, 64, 65, 71-72,, 77,317, viscoelasticity, 39-41, 55, 446-447, linear, 113-114, rheology and, 38-39, viscous flow, 45, volatiles, 453, volume resistivity, 327, , w, wall thickness, 142, bearings, 218, injection molding, 183, 184-185,278-279,, 468-469, rotational molding, 201, warranties, 291, water. See moisture, water filters, 264-266, wear of plastic, 410-412, 433, weathering, 101-108, 331-332, 434, assessing effect of, 107-108, resistance to, 106, wedge compensator, 303, weep point, 214, weight displacement (WID) ratio, 111, welding, 273-274, 549, 550, weld lines, 175-176, 185-186,281,553, weld overlays, 217, witnesses, expert, 287-288, wrap containers, 239, , x, x-ray testing, 304, , y, yield point, flexural, 56, shear, 60, tensile, 213, 310, yield strength, flexural, 311, tensile, 47, 310, Young's modulus. See elasticity,, modulus of, , z, z-axis construction, 507