Patent ID: 6939939

Claim:
A method for making an optical-quality, impact resistant polyurea/urethane material, comprising: reacting a first diisocyanate with a first polyol to form a urethane prepolymer having an equivalent ratio of at least about 3 isocyanate groups per hydroxyl group; reacting a second diisocyanate with a second polyol to form a hydroxyl-terminated extended chain polymer having an equivalent ratio of between about 3 and about 8 hydroxyl groups per isocyanate group; blending the hydroxyl-terminated extended chain polymer with a diamine to form a curing agent mixture; and reacting the urethane prepolymer with the curing agent mixture and a catalyst, wherein the catalyst is configured to promote the reaction of the hydroxyl groups of the curing agent mixture with the isocyanate groups of the urethane prepolymer, to form the polyurea/urethane material.