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Synthesis of Thiokol Rubber, , Thiokol owes its origins to two chemists, Joseph C. Patrick and, Nathan Mnookin, who were trying to invent an inexpensive, antifreeze. In 1926, in the course of an experiment involving, ethylene dichloride and sodium polysulfide, they created a gum, whose outstanding characteristic was a terrible odor. The substance, clogged a sink in the laboratory, and none of the solvents used to, remove it were successful. Then the frustrated chemists realized, that the resistance of the material to any kind of solvent was a, useful property. They had invented synthetic rubber, which they, christened "Thiokol," from the Greek words for sulfur (theion) and, glue (kolla). Thiokol Chemical Corporation was subsequently, founded on December 5, 1929., , - Thiokol is a trademark used for any of various polysulfide, polymers in the form of liquids, water dispersions, and rubbers, used in seals and sealants., , s $ $s $s, @ || lle Heat I ;, n CICH,CH,Cl+ n Nag— § Naa H,CH,C—S— +nNad, 1,2-Dichloro ethane, Sodium poly sulfide, , Thiokol rubber, , Procedures:, , In a beaker containing 100 ml. of dist. water, dissolve 5 g. of, sodium hydroxide and heat to boiling., , Add 10 g. of sulfur in small lots with constant stirring until a deep, red solution is obtained due to the formation of sodium, polysulphide., , Allow the solution to cool to below 83°C, the boiling point of 1, 2dichloroethane, and add 20 ml. of 1, 2-dichloroethane with stirring., Continue to stir for a 20 min. while a rubber polymer separates out, as a lump., , Decant the supernatant liquid and wash the product several times, with water and leave in the fume cupboard for a few minutes to, allow excess |, 2-dichloroethane to evaporate.
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Uses:, , 1. It is used for making gaskets, seals and hard rubber products to be, exposed to oil and pressure., , 2. Thiokol rubber mixed with oxygen releasing chemicals is used as a, solid fuel in rocket engines., , 3. It is used for making hoses and linings of vessels used in the, manufacture of chemicals.
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Aim: To prepare Urea formaldehyde (U-F) resin., , Experiment No. 4, , Chemical required: Urea (2g), 40% aq formaldehyde solution or formalin (5 mL), conc. H,SO,, , (3-4 drops)., , Theory, , Urea formaldehyde resins are formed by condensation of urea and formaldehyde in acidic, , medium in following steps:, , Step 1. Formation of methylol urea derivative, , Initially urea and formaldehyde react to form methylol urea derivatives depending upon, , forsmaldehyde (U/F ratio)., , H—— N ——H, c=, H—— N—-H, , Step 2: Polymerization of methylol urea, , U/F=1:1, , , , U/F=1:2, , H—— N —— CH,OH, , c=—=O0, , H—— N——-H, , Monomethylol urea, , H—— N —— CH20H, , C=O, , H—— N——CH,OH, , N,N-Dimethylol urea, , Several molecules of methylol urea derivatives condense with loss of water molecules to, , form a highly cross linked urea formaldehyde resin.
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-nH,0, . N “CH, N CH2 *, * N ‘CH2 N CH2 as +n, , Procedure, , Take a 5 mL of 40% aqueous formaldehyde solution in a 100 mL beaker. To this add 2 g, urea powder. Stir with a glass rod to make a saturated solution. Add a few drops of conc. H2SO4, and stir vigorously till a white solid mass is formed. Filter the residue and wash it several times, with distilled water to remoye any‘acid. Dry the residue in folds of filter paper or in an oven and, weigh. Report the yield of urea formaldehyde polymer formed., , Observation, Weight of,empty watch glass = W: g, Weight,of watch glass + poymer formed = W2 g, , Weight of polymer formed = W2- Wi g, , Result, , Weight of urea formaldehyde resin = W g
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EXPERIMENT No., , AIM: To preparation of glyptal resin., APPARATUS: R.B. flask, water condenser, conical flask, test tube., , REQUIREMENTS: Phthalic anhydride, glycerol, R.B. flask, beaker,, water condenser., , PROCESS:, , 1. In 250 mI R.B. flask, take 15 gm of phthalic anhydride and 11, , ml glycerol., , Attach a water condenser to the neck of flask; reflux the, , content of flask on stand bath at 130°-170°c for 15 min., , 3. After this period transfer the brown yellow resin in to a, previously weighted test tube., , 4. Note down the weighty of glyptal resin formed glyptal is resin, soluble in acetone., , N, , OBSERVATION:, , Weight of the glass capsule =, Weight of polymer + glass capsule =, Weight of polymer =, , CHEMICALS:, 1, Burette :, 2. Conical flask :, 3, Indicator :, 4. Co lour change :, , CALCULATIONS:, Acid value of polymer = molecular weight of KOH * normality of KOH *, , br, Weight of the sample, , RESULT:, , Weight of glyptal resin formed =
