.

The invention also relates to a method of producing a propellant composition comprising:

a) providing a first hydroxyl-terminated polybutadiene having a number average molecular weight of from about 500 to about 10,000, and a hydroxyl functionality of from about 0.3 to about 1.5;

b) providing an isocyanate-terminated prepolymer having an isocyanate functionality of from about 2.0 to about 4.0;

c) mixing the first hydroxyl-terminated polybutadiene and the isocyanate-terminated prepolymer in a ratio of from about 0.1:1 to about 1:1; and

d) reacting the first hydroxyl-terminated polybutadiene and the isocyanate-terminated prepolymer at a temperature of from about 60° C. to about 150° C., for a time sufficient for substantially complete reaction between the first hydroxyl-terminated polybutadiene and the isocyanate-terminated prepolymer, thereby forming an urethane polymer.