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CHAPTER 13, , EXPLOSIVES AND PROPELLANTS, wwwwwwww.wwww, , wwwww, , Chemical explosives perform their labour-saving tasks in every-day industry and militaryforces. They do their work, more cheaply, and with more effectiveness than is possible by any other means.", , aster,, 1, , wwwwwwwwmwwe, , wwwwwwwwww.wwwwwwwwwww****, , *, , EXPLOSIVES, , An explosive is "a substance or a mixture, which when subjected to thermal or mechanical shock,, sudden release, rapidly oxidised exothernnically into products of greatly increased volume, witha, , gets very, , of, ofpotential energy." The amount of power available from a given weight (or volume) explosive,, is called, , "power to weight (or volume), , ratio"., , Since the explosive reaction is exothermnic, so the products get heated to a high temperature, chemical change takes, and a high pressure is exerted on the surrounding. When this extremely rapid, which shatters the confining walls or, place in a confined space, an extremely high-pressure is developed,, , if developed at a relatively slower controlled rate, it may be used to propel projectiles., well, , One of the, , destructive, , purposes., explosives: They can be used for constructive as, reactions to do work., use the power produced in explosive, to, is, reactions, practical applications of explosive, down coal, mining, for blasting ores of iron and other metals, breaking, in industry, explosives are employedroad, mountains, (for the construction of, constructions), blasting holes in, Salts, quarrying limestone (for use in, a multitude, and, in, prospecting, dislodging rocks, but alsoperforming, tunnels), excavating earth (for dams), seismic, for, supporting purposes, in ammunition, not only for war,, SOrts of useful work. The other major use is aerial bombs, rockets, torpedoes, grenades, etc., and in all other, explosive ammunitions such as, should be fast to produce a large, Characteristics of an explosive : (1) Its rate of decomposition, increase in volume, due to heating, so that effective, vOlne of gaseous products exothermically,, effect, is very large., explosive is determined, stable under normal conditions: Stability of an, It, and, should, be, cheap, 2), by i decomposition point by DTA. In general, explosive must not be volatile, and hygroscopic and, S, container materials to form shock-sensitive salt., Uses of, , Ould, , be chemically stable, i.e., , should not react with the, , that, , bond, (5) It must have at least one chemical, cile should have low energy of dissociation., , Hhese, , -ON-CI,, cases is, , be, and O-Cl bonds. It may, , either, , zero or, , as, , pointed, , very small., vositive "oxygen-balance":, , can, , be, , easily, , broken, , Usually, explosive, that the ditference in, , The, , :, , In other, , words, its, , molecules, , contain, , electronegativities in, , oxygen-balance indicates the oxygen,, , 4) It should have a, to oxidize the C and H to CO and H,O respeccan be utilized, which, in, molecule., the, aned, or deficiency of oxygen by, as a percentage surplus, is, expressed, aly, oxygen-balance, weio, 8tConsider the oxidation a molecule C,H,0, C.HO, , xCO+{ H,O+|zx 16x 100, , Oxygen-balance z-(x+y/2)], =- Mol. wt. of C,H,O, , (499), , (x+y/2)J0

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500, Let us, , take, , ENGINEERING CHEMISTRY, specific cases, , Compound, , of actual, , x, , Mol. wt., , NH4NOg, , 80, , CoH (NO,)s (TNB), CHNO6 (TNT), CHN O6 (RDX), , CoHNOs (DDNP), , CsHgNO2 (PETN), , 1x16x 100, 80, , - 1.5x16x100, , 6-6-5-1.5, , 213, , = -, , 11.3, , Zero, , Zero, , 227, , 6-73-5, , -3.5 x166x100 =- 24.7, , 222, , 6-30, , Zero, , 196, , 5-6-3, , -3x16X, 100_- 24.5, 196, , 227, , 2-s, , 3x16 x100 =, 316, , nitrogen, explosive is, usually, liberated as N2, However, if nitrogen, computation of oxygen-balance. oxides are formed, formation of these must also, in, , this process., , 20, , 290, , 316, , Notes: (1) The bonded, , Oxygen-balance, , 3-0-1, , 213, , Pb(Na)2 (Lead azide), , calculation of oxygen-balance, , 15.2, , an, , and, , no, gas, is utilized in, be taken into oxygen, account, during the, , (2), , Nitrogen-containing, explosives, having low oxygen-balance, tend to, high oxygen-balance, form NO and, form CO; whereas, NO2, during, those with rather, (3) For successful, combustions, materialsexplosion., material(s), , with, must be admixed, oxygen-balance, oxygen-balance. For example, negative, TNB and, with some other, TNT, with, negative oxygen-balance, mixed, (4) Lead azide,, Pb(N)2, having, oxygen-balance does not get oxidized., (5) It should be sensitive to, in case, , with, , with ammonium positive, nitrate., , a, , are, , no, , impact, However, it is an, of detonators (or, time by the, period, of, or, initiating, by dropping a standard, application of, primary explosives),explosive., from a, since detonators, weight, heat/friction/mechanical, weight triggering the detonation, better 1s the, height on to the detonator., inmpact. Sensitivity is determined, The lesser the, sensitivity to friction and flame., sensitioity of the detonator., height from which the fall of the, Similar, standard, are, techniques, or, Secondary, high, to measure the, employed, explosives, tivity for military use is, are, usually,, to, enhanced by adding, insensitive, friction, mechanical, sensitizers, (or boosters), (6) It should possess brisance,, shock and, such as, i.e., high, tetryl and pentolite. fire. So their sens, shattering power., Some, should explode, , in, , a, , very short, , terms, , related to, , explosive detonates. Itsexplosives (1) Velocity of detonation, value, explosives. For example, VOD for, also, (VOD), depends upon, TNT, 75 km/s respectively., with, the, , given, , :, , density, density 1.0, 1.5,, , (or, , is the, , velocity with which, of, , compression), and 1.7 are, 46, , powdered, Explosive, is the, km/s,, and, km/s,, !, 68.5, strength, energy liberated per unit, hblasting gelatine (strongest commercal, mass of the, (iin Brisance refers to the, aynamite) on the basis, /g) or compared, of blastingexplosive (cal/g., shattering power of, (iv) Sensitivity of an explosive, gelatine is rated 100%., explosive., to, explosives may detonate by feath impact or friction or heat or, touch, some, given explosive, these, electric spark or, may not, ities, detonator Tvave. Some, detonate even, selection of explosives tor particularmay be quite, with, ha, blow. For, purpose. different., Sensitivity playshammer, a key role in the, (i), , a, , a, , a, , 92212: "10:

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EXPLOSIVES AND PROPELLANTSs, , 2, , 501, , CLASSIFICATION OF EXPLOSIVES, , Explosives are, usually, classified into following three broad groups, , (1) "Primary or initiating explosives" (or detonators) are highly sensitive explosives, which, , explode on receiving a slight-shock or by fire. Consequently, they should be handled with the utmost, care. They are mainly used in small quantities in shells and, cartridges to start or initiate the explosion, of the main explosive, which is comparatively less-sensitive., (2) "Low explosives" (or propellants) simply burn and they do not explode suddenly. Thee, chemical reactions taking place in such explosives are comparatively slow, and their burning, proceeds from the surface inwards in layers at an approximate rate of 20 cm per second. The gases, , evolved disperse readily, without building high pressures; and consequently, they can be controlled, , easily., (3) "High explosives" have higher energy content than the primary explosives. However, they, are quite stable and quite insensitive to fire and mechanical-shocks. Generally, a small amount of, , primary explosiveis placed in contact with a high explosive. Primary explosive staris the rapid, chemical reaction in the body of the high explosive, which then proceeds at a high rate of 1,500 to, 10,000 m/s. The volume of gases evolved, especially under the influence of high temperatures, developed, have a shattering effect., , 3, , PRIMARY EXPLOSIVES, , (1) Lead azide (PbN,) is very popular for military uses, due to its: () low cost, (i) excellent, initiating action, and (ii) stability in storage. However, it cannot initiate explosion in the compar-, , atively less-sensitive secondary explosives like cast TNT. Lead azide reacts with brass. Conse, quertly, the caps loaded with it are made of aluminium., (2) Mercury fulminate [Hg(CNO),1 is more sensitive as well as more expensive than lead, azide. However, it is slightly toxic and consequently, it is used to a lesser extent than lead azide., , (3) Tetracene [C,H,N,O] is low initiating primary explosive. It ignites easily, has high heat of, explosion and produces a large volume of gases. However, it is not used by the military. It is used, as a detonator., , (4) Diazodinitro phenol (DDNP) is quite sensitive and has high brisance and, consequently, can, initiate explosion even in less-sensitive high explosives. It is widely used in commercial blasting caps., 4, , LOW EXPLOSIVES, , (1) Black powder (or gun-powder) is a mixtureof 75percent potassium nitrate, 15 percent charcoal, and 10 percent sulphur. It contains sufficient oxygen to combine with the other elements present,, when itis ignited. The decomposition reaction is:, , 10 KNO+3S+8 C, , 3 3K,SO,+2 K,CO,+6 CO,1+5 N,T, , The excess of carborn and sulphur take part in the slower reduction processes, leading to the, , evolution of more gases, , 4 KCO+7S, 4 KSO+7C, , KSO+3 KS +4 CO,T, 2 2K,co,+2 KS2 + 5 CO,T, , effect. It is an excellent and cheap, Large volume of gaseous products account for its explosive, gives it a slow heaving, plosive for blasting down of coal, as its low velocity (about 400 metres/sec), uses are time in delay-fuses, for, on that does not shatter the coal unduly. Its other important, bombs, and saluting, 4sting and in shells, igniters and primer assemblies for propellants, practice, , charges., , 2022:2:1 15:43

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502, , ENGINEERING CHEMISTRY, Smokeless powder (or nitrocellulose) is prepared by treating cellulose with nitric and sulphuri., , Aric, , e, , nitrocellulose so-formed is dissolved in a mixture of ether and alcohol and then, solvent is, , orate,when a jelly-1ike solid is lef behind. Since the product is likely to react with traces of acid, lDerated during storage, so "stabilizer" like diphenylamine is added to it and the product then pressed into, cylindrical rods. It is called smokeless powvder, because it, produces carbon dioxide, carbon nmonoxide., nitrogen, water, 5, , vapour and almost, HIGH EXPLOSIVES, These fall into, four, , 9 Single, this group are:, , no, , smoke., , groups:, , compound explosives contain only one chemical compound. Important members of, , () Amnnonium nitrate' is, very stable, non-toxic,, as, , about half, nitrate is, , powerful, , as, , TNT and, , cheap, , and has low brisance-value. It is, , mostly, in making binary, explosives. Ammonium, dangerous to store near any inflammableemployed, material. Moreover, it cannot be used in, , alloys of copper (like brass), since, , it, , contact with, , forms terammino, , cupric nitrate, which detonates easily., (in) 2:4:6trinitrotoluene, (TNT) is a high explosive made by nitrating toluene. It is most, used in, and under -water, shell-firing, widely, explosions and is well-suited for loading in containers,, because of its low, melting point (81°C). Its importance for, excellence in the, military use comes from its comparative, : (a) It is, following, respects, safe, storage. (b) It is non-hydroscopic. (c) It is a violent explosive in manufacture, transportation, and, to form unstable, disruptive explosive. (d) It does not react with metals, compounds., (iii), , Pentaerythritol, , tetranitrate, , (PETN) is an extremely, military explosive., powerful, sensitive and standard, (iv) Cylonite (or RDX or, cyclotrimethylene, is, sensitive, but less toxic than TNT., RDX came intotrinitroamine) a powerful high explosive. It is more, explosive, during World War II., prominence as military as well as an, (o) Picric acid (or, , trinitrophenol), , metals to form shock-senstive, picrates., , industrial, , is, , a, , high explosive, largely, , replaced by TNT, because it, , attacks, Tetryl, (or nitroaryl nitroamine) is used, as booster, a, single base high explosive has been, and in, binary explosives and its use as, abandoned., (2) Binary explosives consist, of mixture of "TNT with, to make and, to, other explosives., superior, single, compound explosives in certain, They are more convenient, ingredient of these binary explosives,, because, it, applications. TNT is an important, sive mixtures are heated to, has a low, melting, liquid state and poured into, point., Important binary explosives are, the containers Generally, binary expl, and allowed to, () Amatol is an, solidity, explosive mixture of TNT with, smoke-giving, explosive with strengtn, nitrate (50 to 80%). It is, is used as, equal to INT. It hasammonium, blasting charges in large caliber, the, w, shells., of being, disadvantage, (in) Pentolite (a mixture of, hydroscopic., TNT and, PETN, 50% each)., (ii) Tetrytol (a mixture of 70%%, tetryl, and 30% TNT)., (iv) Tropex (a mixture of, 40% RDX, 40%, (o) Titronal (a mixture of, and 20% Al, 80TNT, and TNT,, powder)., 20%, (vi), , Al, flakes)., special, they can be melted and poured easily., effects like higher, energy, Each, , since, , of these combination has some, , output and lower cost, cost of, niin", of nnaking, er, , 20972:41E 16

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EXPLOSIVES AND PROPELLANTS, , 503, , (3) Plastic explosives are combination of explosives, which are in plastic state and can be hand, u10ulded/press-loaded and ,made into various shapes, without any serious risk. They are mainly used for, , industrial applications, , and, , military uses. A simple combination to get plastic, is a high, explosive (which gives the destructive powder) mixed with wax or oil (which makes it less sensitive, , explosive, , as well as more plastic). Sucha material may be moulded into a sheet or a putty-like mass. Due to, , their engineering applications, they are available as flexible-sheet explosives. Generally, they contain, a high explosive (like PETN). These sheets can be cut into the, desired shapes and thus, can easily, be fixed to a metal part by an adhesive. Special caps are used to start, explosion., , (4) Dynamites are explosives containing nitroglycerine (NG) as the principal ingredient. Nitro, , glycerine is an oily-liquid, which detonates by pressure, shock or spontaneously above 50C., 4, , CaHs(NO3,, , 1, , 1 volume, , 10, , H,OT +6N, 1+12 CO 1+O1, , 10,000 volumes at temperature of explosion, , The explosion is so sudien that nitroglycerine would shatter the breech of rifle, before the bullet had, time to move. It also pulverizes rock, instead of breaking it into fragments of usable size. For these, reasons as well as on account of the danger in handling and the impossibility of safely transporting, , the substance, it is usually mixed with an inert absorbent (such as wood pulp, starch meals, sawdust, etc.). The amount of absorbent that is added to the dynamite varies with its relative strength., , 9 Straight-dynamites contain from 15 to 60% nitroglycerine in wood meal with sodium nitrate., Sodium nitrate is used as an oxidising agent for providing oxygen, so that good fume properties, and good execution can be obtained. Their important uses are blasting of hard rocks, coal and other, , minerals, and demolitions, etc., (i) Blastinggelatin-dynamites are those in which the NG has been partly gelatinized by nitro-cotton (or collodion cotton). Usual approximate composition of blasting gelatin is 91.5% NG ; 8%, , nitro-cotton, 0.5% CaCO3. They are jelly-like substances, very powerful, water-proof, excel from, the point-of-view of fumes and do not flow, but stick well in holes into which they have been, loaded. They can be used under wvet-conditions, where high loading density is desired. Their chief uses, are submarine blasting, tunnel driving, deep-well shooting, and at places where maximum shattering, , effects are desired., (i) Gun-cotton (or cellulose nitrate) is obtained when cotton is steped for half-an-hour in a cooled, mixture of conc. nitric and conc. sulphuric acids., , CH,O(NO)J +3 H,o, , CHO,(OH)3+3 HNO, , Dry gun-cotton explodes very rapidly (in a few ten thousandth of a second) when set on fire,, but when wet, it is set-off by a small mount of another explosive. Fulminate of mercury, Hg(CNO), , is commonly employed. Dry gun-cottn is also ignited by shock. Dry gun-cotton in fibre-form is, used in torpedoes and submarine mines. It is used as a propellant in rifles or artillery shells. Its rate of, explosion, being reduced in such cases, by mixing it with other substances, and by forming it into, granules of particular shape and size., , (iv) Cordite (a form of smokeless powder made by aissofving gun-cotton (65 parts), nitroglucerine, (30 parts), and petroleum jety or "oaseline" (5 parts) in acetone. The resulting paste is rolled and cut, is, , into pieces of different imensions, according to the rate ofexplosion desired. When the acetone, The vuseiine acts, as stabilizer and cooling-agent on the, evaporates, the horny cordite remains., powder, as it has a tendency to lower the temperature ot explosion. The gun-cotton slows down, the explosive reaction of NG and makes cordite an excelent propellant for large caliber naval quns., , ( (v) Gelignite consists of 65% blasting gelatine and 35% of absorbing powder. It is a powerful, , plosive, which, , can, , be used under water.

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ENGINEERING CHEMISTRY, , 504, Table 1:Gun powder versus dynamite., , Property, 1., , Cost., , 2., , Blasting action,, , Dynamite, , Gun powder, , About 5 imes costiier than gun powder., , Very cheap, shattering Ppower and, High lifting power and produces large | High, small blocks on quarrying., , produces, , blocks on quarrying, , 3., , Tamping., , Does not require hard temping., , Very hard temping is, , required for efficient use., , About 6 times that of gun powder., , 4., , Destructive power., , Weak., , 5., , Efficinecy., , Compartively low., , 6., , Uses., , In quarrying stones., , Comparatively much larger., For, , mining, tunneling, , and, , under water., , quarrying, , -, , 6, , PRECAUTIONS DURING STORAGE OF EXPLOSIVES, Following precautions should be taken while storing the explosives., (1) Different explosives should be stored in separate, boxes, (2) Detonators and explosives should be stored totally, separate, , (3) Flame lantern should be not used in any case. When, power failure takes place, use of only torches, should be made for lighting, purposes., (4) All the electric fittings and wirings should be, properly insulated and frequently clhecked., (5) Only authorized persons should be allowed to the, explosive store. The authorized person must wear, magazine shoes having not be allowed., , (6) Jerks or drops of explosive should not be allowed., (7) Smoking/fire should be strictly prohibited within a, radius, (8) The magazine should not be constructed within 500 m of 50, (9) The, , boundary, , of the, , m, , from the explosive store, , from any, , (nagazine)., , working kiln or furnace., , should be, explosive, protected by high barbed-wire, Caution Boards" should be installed, around it. Watchman, fencing and proper, should guard the, (10) Lightning conductors should be provided to, magazine round the clock., safeguard the magazine., (11) Magazine should not be, during, opened, the, should be allowed to remain the, of the, approaching, store, , a, , or on, , magazine during such storm. thunder, , vicinity, , 1, , storm and, , no, , BLASTING FUSESs, A fuse is "a thin, water-proof canvas, of tube, burn at a given, speed for setting Of Charges oglength, explosrve. Fuses, (al, , containing, gun-powder (or TNT) arrangea, are of, two types:, where, , Safety, employed in initiating, cansists of a small diameter, caps,, O, electrical, core, Dlc, It, is, fabrics., made to have an, proofed, powaer, enclosed in a firing, fuse is, , approximate, , Detonating, , fuse has, , a, , a, , shot in, , velocity of over 6,000 metres, , velocity explosive, such as TNT, conte, , in, , to, , is not, , used. A safety fuse, of wrapper of water, of 30 to 40, seconds per foot (or, , covering, , burning speed, blasting, sufficient, point of safetu,, length, , about 1 cm s *). When a fuse is used to, time is allowed for the shot-firer to reach afire, , (b), , person, , a, , is, , p, , so that, usedso, that ample, u, , per second and, small-diameter, bent, consists of charge, , high, charge of, nrougnoutof its length and this oa, tube., nation of the, ole charge, regardless, The, line, of fuse (called cordean, its, causes, charges of explosive in deep-holes, velocity. Such fuses, are practically, instantntaneous deto, used, used, is in, , contact with the char8e, , a, , a, , principally for, for exploding, e, , 2022/:S 10.

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ENGINEERING CHEMISTAY, , 506, , while, , top ;, tank, when lNG, After nitration, the mixture is run into a, then with dilute, water,, with, lower layer. The NG layer is separated, washed first, completely. It is then converted into, rISeS to, , 4 CH,(NO2, , torm, , sodium, , carbonate, erent desired, , (2%) to remove traces of acids, solution, of dynanmites by absorbing in specific inert materials., , Decomposition reaction:, , excece.., , 12CO+ 6, , types, , 10 H2O+O,, , (6) Pentaerythrital tetranitrate (PETN) is prepared by usIng Canni20r0 reaction between ormal-, , dehyde and acetaldehyde in the molar ratio 4:1. Thus:, , Ca(OH), , CH,CHO+4 HCHO -, , CHONOD, , CH,OH, 3 HNO (conc.), , HOHC-C-CH.OH, HSO (conc.), , ONOH,C-C-CH,ONO,, , CH,ONOD, , CHOH, Pentaerythritol, , PETN, , Decomposition reaction:, , C(CHONO,)4, 3 CO+2 CO+4 H,O+2 N,+180 kcal, cyclonite (cyclomethylene trinitroamine) is prepared by treating, tetraamine with nitric acid. Thus, hexamethylene, (7) RDX, , or, , (CHN, +4 HNO, 9, , Hexamethylene tetraamine, ROCKET PROPELLANTS, Rocket propellant, , combustion taken place,, , is, , (CH,NNO,)3 +NH,NO, +3 HCHO, RDX, , Formaldehyde, , either a high oxygen-containing fuel or a, , difinite and controlled manner with the mixture of fuel plus oxidant, wnose, evolution ofa huge volume of gas., quickly, producinga very large volume, A, 3,000°C and a pressure of 300, hot gases, of, at a, (usually, which, kg/cm*),, exit througha, at, supersonic velocity. This act of, small opening (calledtemperarure, 'jet or "nozzle, reaction (cf., Newton's third law ofpushing the gas backwards, te, an, of exhaust, motion), which moves the produces, equal and, velocity, the rocket performance, rocket forward. With the opp, inc, signalling, carrying a life, hurling explosives atincreases. Rockets are used for, an, pyrotechnic, Characteristics of a, enemy, putting space, thrust delivered divided good propellant : (1) It should, into orOit, c, capsule, have high, by the rate of propellant (fuel, weight products (like, specific, ecific impulse the, H CO, CO» and Na), plus oxidant) burnt. impulse, (specific, impu, should possess low ignition, oduce louw mo, delay ignition duringis combustion. (3) It should (2) It should prod, of an, oxidising agent. It is expressed delay the time taken by, burn at a slow and. steady rate (4) It, over a wider, the, in mili seconds). (5) It, range of temperatu, propellant to catch fire in tnldpres, does not detonate, (7) It should be, should possess, be stable, under, to, (9) It should be, density. (6) It sho. ie, t, shock, heat or impact. (8) Itsafe handle and storehigh, uu, under, 1ot vroduce toxicnon-corrosive and, should be readily, ordinary condittion,, non-hydroscopic., (12) 1t should, products., (10) It should leave no ignitable at predictable, burning ratc, Note:, predict, produce, 11) Itshould, solid, Specific, high, is, impulse, the, residue, after, force) due to momentum of, thrust in, temperature on, , propellant, , in, , a, , reacts, , olecular, , the, , where F= thrust, P= exit, , (kg/m/kg, , pressure (kg/mf); P.=, , ignition:, kg per second, xiting gases and, per kg of the combustion., is, fuel burnt. The value of thrust (or, given by:, va, F, +(P.Pa) Açe, mass flow, , ropulsive, , ambient gas (kg):8=, due to, gra, pressureacceleration, (9.81 mf/s) ; v = exhaust velocity(1m/, (kg/m); and A,= gravity, nozzle exit, 6, are2rd):2? L

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EXPLOSIVES AND PROPELLANTS, , 507, , CLASSIFICATIONS OF PROPELLANTS, , 10, , The chemical propellants are classified into solid and liquid categories, (1) Solid propellants may be "homogeneous'" or "composite". When solid propellant or a, mixture of propellants is thoroughly mixed in a colloidal state, it is called homogeneous solid propellant., , When a single propellant is employed, it is called a single-base propellant. For example, nitro-cellu-, , lose, also known as gun-cotton or smokeless powder. On the other hand, a solid propellant which, , contains two materials, is called double-base propellant. For example, ballistite, containing, nitrocellulose and nitroglycerine mixture, is a powerful double-base solid propellant. Cordite,, composed of 65% nitrocellulose, 30% nitroglycerine, and 5% of petroleum-jelly, is another double, basepropellant. In this, petroleum-jelly functions as a plasticizer. General composition of a double-, , base propellant is 50 to 55% nitrocellulose and 40 to 45% nitroglycerine. Diethylphthalate, upto 5%,, is also added and this acts as solvent cum plasticizer, thereby giving a homogeneous plastic mass, which, can be woxked smoothly. In addition to it, upto 1% of diphenylamine is added, which acts a, , stabilizer. Such propellant gives a flame temperature of about 2,700°C and the volume of the gases, is about 1,500 time_ the original volume., When an óxidising agent is dispersed in a fuel mass, the solid propellant is called heterogeneous, or composite. Gun-powder is. the oldest composite propellant. It gives a flame temperature of, 800-1,500°C and the volume of the gases is about 400 times the volume of the charge. Other, oil ; 80%% ammonium, composite solid propellants are 75% potassium perchlorate plus 25% asphalt, , perchlorate plus 20% resin binder ; 46% ammonium picrate, 48% sodium nitrate, and 8% plastic, , resin binder. In selecting the oxidiser, it should be seen that it is non-hygroscopic, stable in contact, , with fuel and does not form any corrosive products. Oxidant potassium perchlorate leaves behind a, , white residue of potassium chloride particles ; while ammonium perchlorate leaves no solid residue,, , but its combustion products contain hydrogen chloride and water, which form a toxic and corrosive fog., , (2) Liquid propellants possess many advantages, propellants are more versatile and the engine using them can, , the solid propellants. Thus, liquid, be checked and calibrated more easily., propellant is quite delicate and cannot, , over, , However, unlike, , solid propellants,, , the, , engine using liquid, , withstand any rough handling. Liquid propellants may be monopropellants or bipropellants., , Monopropellant: A monopropellant hasfuel as well as oxidiser in the same molecule or in a, , solution, , containing both these. For example, hydrogen peroxide, nitromethane, ethylene oxide, hydrazine,, methanol and 78.6% hydrogen peroxide are some of the, propyl nitrate and a mixture of 21.4%, common monopropellants. A monopropellant must be safe to store and at the same time, it should, burn smoothly. Hydrogen peroxide is not easy to store and handle, due to its reactively. Moreover,, metal oxides catalyse its decomposition. So, storage tanks for it are made of special materials., Table 2: Solid propellant versus liquid propellant., , Liquid propellant, , Solid propellants, , They have high specific impulse., , 1. They have low specific impulse., 2., , They can easily and safely stored, handled and | They have storing, handling and transporting, , problems., , transported., , 3. The engines used for them are of sin1ple design., , The engines used for them are more delicate and, cannot withstand any, , 4, 5., , 6., , They are more economical in, Manipulations with solid propellants, use., , is, , dificult., , It is difficult to check and calibrate the engines, using these., , rough handling., , They are comparatively less economical in use., They are more versatile., Engines using them can be checked and calibrated, more easily.

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508, , ENGINEERING CHEMISTRY, , Injection, , C12Has+18.5 O2, , chamber, , TTTTT, , 12 CO2+13 H20, , Combustion, chamber, , Fig. 1. Use of bipropellant in a rocket., Combustion reaction between, liquid oxygen produces a huge, kerosene, volume of, , and, , Bipropellants, , which forces the rocket, , gaseous CO2 and Hz0,, upwards with a high-speed., , the thrust of, , widely, these, liquid fuel plus, combustion chamber separately., oxidiser, kept separately, are injected, used fuels are liquid, alcohol, aniline, and kerosene oil. Commonly, hydrogen, hydrazine, ethyl, Ethyl alcohol admixed with 25%, of water, although reduces, water is a, fuel. Addition, flame, temperature, yet it reduces the molecular-massgood, which compensates for, of, reduction in performance. The common, combustion, oxvgen, ozone, hydrogen, oxidisers emploved are gases,, peroxide, fuming nitric acid and, toxic. safe and good oxidising, liquid fluorine. Liquid oxygen isliquid, agent, but it has to be stored under, nonOzone is very powerful oxidising, in insulated, but it is, pressure, agent,, containers., Liauid fluorine is volatile, toxic, corrOSIve,, quite toxic and can explode at, very, high, reactive,, but, concentrations., difficult to store and handle., very good oxidising, agent. Also it is, in the, , are more, , used. In, , Short Answer Ques tions, 1., , Detonator is, , 2., , Detonators, , required to explode TNT. Give reason., Ans. TNT (a high, stable, (Bangalore, Feb. 96), explosive) itself, and less-sensitive to fire and mechanical, Conseauently, a small amount of detonatoris(aquite, shocks., pimaryonexplosive) is placed in contact with, Detonator, being highly-sensitive exXplosive, exploae, TNT before use., a, receiving, initiation of explosion in TNT., slight shock or fire, thereby, a, , are, , used in, , conjunction with high explosives. Give, , causing, , reason., , (Bangalore, March 94, Aug. 95), High explosive is quite stable ana, fire and, mechanical shock. So in order to, small amount of a detonator (or primaryneariy isensitive to contact, with it. Detonator on, in, the explosion of, slight shock or fire explodes, thereby initiating pvsplaced, receiving, high explosive., Ans., , fire it., a, , a, , 2022/213 00.4

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PELLANTS, AND PROPE, , 509, , E X P L O S I V E, , 3. What are fuses ? Give examples., , (Bharathiar, Nov. 97), , Ans. Fuse is a thin water-proot canvas length of tube form containing gun-powder arranged to burn, ven speed for setting ott the charges of explosive at a proper time. Examples of fuses are: () safety fuse,, , and (i) detonating, , fuse., , (Madras, Oct 97), , . Name two high explosives., , Ans. TNT, dynamite and gun-cotton., , 5.What is cordite?, , Ans. It is made by dissolving 65 parts of gun-cotton, 30 parts of nitroglycerine and 5 parts of petro, , leum-jelly in acetone., , 6.What is a, , rocket, , Ans. It is either, , a, , propellant?, high-oxygen-containing fuel or a, , mixture of, , a, , fuel plus oxidant, whose combustion, , takes place in a definite and controlled manner with the evolution of a huge volume of gas., 7. What is a monopropellant ? Give an example, , Ans. It is a chemical substance, which can act both as a fuel and oxidizer. For example, hydrazine., 8. Give the example of a binary high explosive., Ans. Amatol (a mixture of 50% TNT and 50% ammonium nitrate)., 9. What is meant by oxygen-balance of an explosive?, molecule of the, Ans. It is difference between the oxygen contained in the, required to oxidise the C and H contained in it., , explosive and, , the oxygen, , 10. Name two primary explosives., Ans. Lead azide and mercury fulminate., , 11. Name two low, , explosiver, , ., , Gun-powder and smokeless powder (nitrocellulose)., 12. What is RDX?, explosive)., Ans. Cyclotrimethylene trinitroamine (a powerful high, Ans., , 13. What are dynamites ? Give an example., as the principal, Ans. Explosives containing nitroglycerine, nitrate., sodium, with, contains 15 to 60% NG in wood meal, , 14. What is gun-cotton?, Ans. It is a, , high explosive, obtained by steeping, , cotton for, , ingredient. For example, straight-dynamite, , 1/2 hour in a cooled mixture of conc. HNOa, , and conc. HSO4, , as a, , 15. What is TNT?, obtained by nitrating toluene., Ans. It is a high explosive,, form a self-igniting mixture that has been used, 16. Hydrazine (N,H4) and nitrogen tetraoxide (N204) Write a balanced, and, equation for this reaction., are N2, H20., rocket propellant. The reaction products, 3, N2 (8) +4 H2O (g), Ans. 2 NH4 (g) +N2O4 (8), , Test our Understandirg, 1., 2., , 3., , classification of explosives (with, , Write short notes on : (i), explosives., dynamites, (iv) plastic, and explain, are, , the characteristics, , examples), (i) requisites, , (it), (Raj, May 01), , of explosive,, , of a good propellants?, , propellants, (a) What, of solid and liquid propellants., (b) Compare the properties, essential requirements ofan explosive?, (a) What are the, of : () rocket fuels, (i) propellants., (b) Write a brief account, , (Andhra, June 01), , (MK, April 01)

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ENGINEERING CHEMISTRY, Explain, ives ? Explain, the, , explosives, , of, , 510, What, , What, , (a), , 4., , manufacture, , 6) Distinguish, , between, , note, ()Write short, , a), , the basic, , explosives ?, of dynamite., and applications, , are, , Describe, , are, , the, , on, , primary, , and secondary, , explosives., , of dynamite., , Mention, , different, , types of, , dynamites., , (Karnataka, May 97), (Anna, Dec. 97), , What is detonation ?, , 5. (a), , (b), (c), , explosives classified?, classified ? What, are explosives, Define an explosive. How, , How, , are, , sive?, , 6., , requirements, , TNT., , manufacture, , chemical, , (a), , What are rocketpropellant?, , How are they, , are, , good explo(Madras, April 97), , of, the requirements, , classified? What are the, , a, , selection, requirements for the, , (Madras, Oct. 97), , of a propellant?, , (b) Name any two high explosives., , (Bangalore, Aug. 97), , requirements of a good propellant., (c), 7. (a) What are the requirements of an explosive? Explain., Give the, , (Bharathidasan, Nov. 97), , ?, , (b) What are the requirements of a good explosive, (c)What are propellants? Explain the classification of propellants with suitable example., (M.K, Nov. 97), , (Bharathidasan, Nov. 97), (Utkal, 97), , 8. (a) Write two factors for the selection of a propellant., (b) Write short note on explosives., 9. (a) What are explosives ? How are they classified ?, 10., , (b) Write short notes on: () dynamites, (i) requirements of, (a) Give two examples each of monopropellants and, , (Kerala, Aug. 96), , good propellant., , bipropellants, , (Bangalore, April 97), , used in rocket., , (b) What are the uses of explosives?, Amravati, 98 Summer, 11. (a) Explain the term, and discuss the nature, "detonation, of the, process. Give examples of a few, detonators and high explosives., (b) What kinds of compounds are desirable as, , rocket fuels and, , why, , ?, , (Amravati, 97 Winter), , 2022/213 1614-