Polybutadiene hydrogenated hydroxy-terminated

Another rubber which appears to be of interest for insulation of rocket motors is hydrogenated hydroxy-terminated polybutadiene (HHTPB). As this rubber is derived from HTPB, it is more compatible and would also have strong bond with the HTPB-based propellants. Further, as the quantum of unsaturahon is considerably reduced in HHTPB, the life of rocket motors insulated with HHTPB will also be more. In a nutshell, the use of HHTPB results in an increased stability to... 

Hydroxy-terminated liquid polybutadienes are prepared for reactions with diisocyanates to form elastomeric polyurethanes (see Chapter 6). Such materials can be prepared by anionic polymerizations as living polymers and then quenched at the appropriate molecular weight. These polybutadienes can also be formed by a free-radical mechanism. The microstructures of the two products differ, however, and this may affect the properties of the finished products. To form hydroxy terminated polymers by a free-radical mechanism, the polymerization reactions may be initiated by hydroxy radicals from hydrogen peroxide. 

Ethylene polymerized with diethyl peroxydicarbonate contains terminal ester groups (41). Using C-labeled cyclohexane peroxydicarbonate, the fate of the primary radicals during the polymerization of methyl methacrylate (MMA) and styrene has been studied (42). Although this reference includes no detailed analysis of the products, it indicates that ROOCO-terminated polystyrene telechelics may be obtained by this technique. A similar method has been used for the preparation of telechelic polybutadiene (43). The carbonate end groups are easily modified into terminal hydroxyl groups by hydrolysis. Hydrogenation of the carbonate functionahzed telechelic polybutadiene, followed by hydrolysis, srields hydroxy-terminated polyethylene telechelics. 

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