Abstract: Polyurethane elastomers having prolonged flex life are prepared by reacting a diisocyanate with polypropylene glycol (PPG) or triol and poly(tetramethylene ether) glycol (PTEG). The diisocyanate may be reacted with each glycol separately or they may be mixed before the reaction. A smaller amount of the prepolymer obtained from the polypropylene glycol or triol is mixed with a larger amount of the prepolymer obtained from the poly(tetramethylene ether) glycol and the mixture is reacted with a hindered aromatic diamine. Elastomers cured from the resulting mixed polyurethane were found to have an exceptionally high flex life and are particularly useful in the production of products which undergo dynamic flexing, as in the preparation of pneumatic tires, particularly the sidewalls thereof, because of their exceptionally long flex life.

Abstract: There is provided a modified polyurethane elastomer composition characterized by the presence therein of a substantial proportion in the range of from 5% to 35% by weight of the urethane of a nonfunctional hydrocarbon rubber, together with a curing agent for the urethane and a separate and distinct curing agent for the hydrocarbon rubber. Principal purposes of the present invention include the production of high strength castable elastomers which are nonmelting under conditions of high shear.