The present invention teaches a new process to produce novel, hard, optically clear, 
impact-resistant 
polyurethane polymers that are characterized by excellent 
thermo mechanical properties and 
chemical resistance, and the polymers made as a result of such a process. The polyurethanes are made by reacting a) a 
prepolymer made by reacting a polyisocyanate with a primary amine-terminated polyether with an amine functionality of about 2 and a molecular weight of >1000, and in which the free —NCO content of the resulting 
prepolymer is >18% by weight; with b) (i) a 
polyol having an average hydroxyl functionality greater than or equal to 2 and an average hydroxyl 
equivalent weight of from about 300 to about 1,000, and (ii) a curing agent that has 
isocyanate reactive groups, a functionality of 2 to 3 and a molecular weight of <400. More preferably the 
prepolymer is made by reacting a cycloaliphatic polyisocyanate with a primary amine-terminated polyether 
diamine of 2000 to about 2500 molecular weight, the 
polyol is either a 
polyester polyol triol with a molecular weight of between about 540 and 900, or a polyether glycol with a molecular weight of between about 650 and 2000, or a 
polyester polyol 
diol with a molecular weight of up to 2,000, and the curing agent is either 
dianhydrohexitol, an 
aromatic diamine, an aromatic ring containing 
diol or a 
cyclohexanedimethanol.