Polyurea/urethane optical material and method for making it

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 and a catalyst to form a curing agent mixture, 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;
• and
• reacting the urethane prepolymer with the curing agent mixture to form the polyurea/urethane material.

Optical-quality, highly impact resistant non-elastomeric polyurea/urethane comprising the reaction product of:

• a urethane prepolymer formed by reaction of a first diisocyanate with a first polyol;
• a curing agent mixture comprising a hydroxyl-terminated extended chain polymer and a diamine, the hydroxyl-terminated extended chain polymer formed by reaction of a second diisocyanate with a second polyol;
• and
• a catalyst configured to promote the reaction of the hydroxyl groups of the curing agent mixture with the urethane prepolymer.