High heat distortion temperature transparent polyurethanes

A transparent, highly crosslinked polyurethane having a high heat distortion temperature comprising:

• the highly crosslinked polyurethane having a heat distortion temperature of at least 280.degree. F. at 264 psi, said polyurethane made from at least one low equivalent weight hydroxy containing intermediate, said hydroxy containing intermediate having an overall hydroxyl equivalent weight of from about 40 to about 110, said low equivalent weight intermediate being a polyhydric alcohol having from 2 to 8 hydroxyl groups and a total of from 2 to 12 carbon atoms, a polyester polyol made from a lactone having from 4 to 9 carbon atoms and said polyhydric alcohol, or a polyester polyol made from a polycarboxylic acid having from 2 to 4 carboxylic acid groups containing from 2 to 12 carbon atoms and said polyhydric alcohol, or combinations thereof, said hydroxy containing intermediate reacted with a polyisocyanate to form a prepolymer, said polyisocyanate having the formula R(NCO).sub.n wherein R is an aliphatic or a cycloaliphatic having from 4 to 18 carbon atoms or an aromatic or alkyl substituted aromatic having from 6 to 15 carbon atoms and wherein n is from 2 to 4, wherein the equivalent ratio of said polyisocyanate to said hydroxy containing intermediate is from about 2 to about 12, said prepolymer being cured or partially cured with a polyol curing agent having an overall hydroxyl equivalent weight of from about 40 to about 110, said polyol curing agent being a polyhydric alcohol having from 2 to 8 hydroxyl groups and a total of from 2 to 12 carbon atoms, a polyester polyol made from a lactone having from 4 to 9 carbon atoms and said polyhydric alcohol, or a polyester polyol made from a polycarboxylic acid having from 2 to 4 carboxylic acid groups and containing from 2 to 12 carbon atoms and said polyhydric alcohol, or combinations thereof.