The present invention relates to molded
polyurethane /
urea elastomers, and specifically to improved
polyurethane /
urea elastomers having high temperature stability to about 140–150° C. and low temperature flexibility at about −35–(−40)° C., for use in dynamic applications. These elastomers are particularly useful for application in belts, specifically in automotive timing or synchronous belts, V-belts, multi V-ribbed or micro-ribbed belts, flat belting and the like. The
polyurethane /
urea elastomers of the present invention are prepared by reacting polyisocyanate prepolymers with symmetric primary
diamine chain extenders, mixtures of symmetric primary
diamine chain extenders and secondary
diamine chain extenders, or mixtures of symmetric primary diamine chain extenders and non-oxidative polyols, which are all chosen to eliminate the need for catalysts via standard molding processes, and to improve phase separation. The polyisocyanate prepolymers are reaction products of polyols which are nonoxidative at high temperatures, such as
polycarbonate polyols,
polyester polyols, or mixtures thereof, with organic polyisocyanates which are either compact, symmetric and aromatic, such as para-
phenylene diisocyanate, 1,5-
naphthalene diisocyanate, and 2,6-
toluene diisocyanate, or are aliphatic and possess trans or trans,trans geometric structure, such as trans-1,4-
cyclohexane diisocyanate and trans,trans-4,4′-dicyclohexylmethyl diisocyanate.