Nonequilibrium tensile deformation of amorphous polymers in the rubbery state: Temperature, strain rate, and strain effects. I

Abstract

Abstract We analyze nonequilibrium tensile deformational behavior of an amorphous uncrosslinked random copolymer of styrene and acrylonitrile stretched above its Tg at various temperatures and constant strain rates. The variable investigated is the force required to pull the specimen to a certain strain level. Our results suggest the deformational behavior in the rubbery state can be incorporated in a universal scheme where strain, strain rate, and temperature effects are all superposed, e.g., the effect of strain is identical to the effect of temperature and strain rate. This unexpected result is true within two contiguous but distinct regimes of strain, on both sides of ca. 40% strain, suggesting that non-equilibrium extension at constant pulling speed in the rubbery state occurs by at least two successive mechanisms. Our results also reveal that the physical parameter which should be used to achieve a true superposition of strain rate and temperature data is not as simple as has long been commonly prop...