Polyurethane-urea elastomers based on propylene oxide-tetrahydrofuran copolymers

A polyurethane-urea elastomer, comprising,

• the reaction product of propylene oxide-tetrahydrofuran copolymers, polyisocyanates and aromatic diamine chain extenders, said copolymers having a molecular weight of from about 300 to about 10,000 and containing from about 5 percent to about 75 percent of propylene oxide based upon the total weight of said copolymer,
• said copolymers containing hydroxyl end groups,
• said polyisocyanates reacted with said hydroxyl terminated copolymers to form prepolymers having isocyanate end groups, the equivalent ratio of said isocyanate groups of said polyisocyanates to said hydroxyl end groups ranging from about 1.25 to about 3.0,
• said aromatic diamines having from 6 to about 20 carbon atoms and selected from the class consisting of shielded aromatic diamines and non-shielded aromatic diamines,
• said prepolymer containing said isocyanate end groups chain extended through either bulk polymerization by reaction with said shielded aromatic diamines or through a solution polymerization by reaction with said non-shielded diamines to produce said polyurethane-urea elastomers, the equivalent ratio of amine groups of said aromatic diamines to said isocyanate end groups ranging from about 0.8 to about 1.2,
• said copolymer containing hydroxyl end groups having a low viscosity,
• said polyurethane-urea elastomers having good tensile strength at ambient temperatures and at 100.degree. C, and good flex properties.