STRAIN-ENERGY FUNCTION OF STYRENE BUTADIENE RUBBER AND EFFECT OF TEMPERATURE

Biaxial and uniaxial tensile stress relaxation tests were made on square sheet specimens of styrene butadiene rubber (SBR), mounted in a universal biaxial tester within a temperature-controlled box, with the object of studying the effect of temperature on the strain energy function. The stress relaxation responses, usually for times up to 10 min, were obtained for various degrees of biaxiality, various extension ratios, and various temperatures within the limits of plus 25 to minus 45 degree C. The results indicated that if the Valanis-Landel representation of the strain energy function W equals SIGMA //i// equals //1**3 w( lambda //i) is adopted, then time and strain are factorizable over the indicated temperature range, with time and temperature being related in the usual fashion. The results verify the Valanis-Landel theory for various combinations of biaxiality.