Synthesis of HTPB and CTPB Prepolymers by Anionic and Free-Radical Polymerization

This report describes the synthesis and characterization of polybutadienes and polyisoprenes possessing hydroxyl and/or carboxyl functionality. Polymer formation was accomplished through anionic or free radical initiated reactions. Characterization of the materials involved analyses for molecular weight, molecular weight distribution, microstructure, end-group content, and solution viscosity. The objectives of the program were to scale up the anionic polymerization of butadiene to produce a superior HTPB prepolymer, and to prepare by free radical techniques superior HTPB as well as hydroxyl- and carboxyl-terminated polymers for solid propellant binders. Large- scale (100 gm) anionic polymerization of butadiene was carried out with two different dilithio initiators. A prepolymer (HTPB) exhibiting greater uniformity in properties was obtained with a commercial initiator than with an initiator prepared in-house. Free radical polymerizations of butadiene and isoprene were carried out to give sufficient quantities of prepolymers for propellant development studies.