The mechanical properties of a salt‐filled polyurethane elastomer have been investigated at high rates of strain and at several temperatures. Constant strain‐rate tests up to 27 in./in./sec at temperatures from 40 to 160°F have been performed to determine the relaxation modulus in tension and the effects of strain and temperature on this modulus. The effects of time, strain, and temperature have been found to be separable for this highly filled material even after de‐wetting has occurred and the stress‐strain curve becomes highly nonlinear. The relaxation modulus has been evaluated over a time range from10−4to102sec at 70°F.