Impact resistant polyurethane and method of manufacture thereof

A transparent non-elastomeric, high hardness, impact resistant polyurethane material comprising the reaction product of:

• (1) a polyurethane prepolymer prepared by reaction of a diisocyanate selected from the group consisting of 4,4′-methylenebis(cyclohexyl isocyanate), 3-isocyanato-methyl-3,5,5-trimethylcyclohexyl-isocyanate, meta-tetramethylxylene diisocyanate, and mixtures thereof with (a) at least one OH-containing intermediate having a weight average molecular weight of from about 400 to about 2000 selected from the group consisting of:
• (i) esterification products of adipic acid with one or more diols selected from the group consisting of 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, and 1,10-decanediol;
• (ii) reaction products of E-caprolactone with one or more diols selected from the group consisting of 1,4-butane diol, 1,6-hexane diol, neopentyl glycol, and 1,10-decanediol;
• (iii) polytetramethylene glycol;
• (iv) aliphatic polycarbonate glycols;
• and (v) mixtures of such OH-containing intermediates, and (b) a triol in an amount equal to 0.06 to 0.15 equivalents based upon a total of 1.0 equivalents of (a) and (b), and wherein the diisocyanate is reacted with the triol and OH-containing intermediate in an equivalent ratio of about 2.5 to 4.0 NCO/1.0 OH;
• and
• (2) at least one diamine curing agent selected from the group consisting of 2,4-diamino-3,5-diethyl-toluene, 2,6-diamino-3,5-diethyl-toluene, and mixtures thereof, in an equivalent ratio of about 0.95 to 1.02 NH2/1.0 NCO, wherein the polyurethane material has a heat distortion temperature of at least 300° F. at 264 psi.