Aging In Quenched Polymers Under The Condition Of Tensile Strain

This paper studies the phenomenon of that structures and properties of some glassy polymer materials under finite strains change with time, and three kinds of common plastics, general-purpose PVC, engineering ABS and PC, are chosen as study objects. In order to understand the nature and mechanism of strain-induced aging, samples of these polymeric materials are quenched separately to make them reach non-equilibrium states, and then left under finite strain for different times to observe changes of chain and condensed structures of these materials with time.Our mechanical test results show that, after aging under strain, although the yield stress and elastic modulus of samples of not only PVC and ABS, semi-crystalline materials, but also PC, a non-crystalline material, increase with aging time, the yield stress and elastic modulus of samples aged under tensile strains are larger than those of physical aging samples in the same aging time.And the dynamic mechanical property test results indicate that the storage modulus of samples of physical aging and strain-induced is trending up with aging time goes, and in the same aging time, the storage modulus of the strain-induced samples is larger than that of the physical aging samples, suggesting that part of the energy is stored in the strain-induced samples.According to these test results of mechanical properties, it is suggested that the behavior of strain-induced samples was changed from ductility to brittleness and to exert strain accelerated the physical aging process. In order to verify this suggestion, we measured samples of ABS, PVC and PC materials with the differential scanning calorimeter (DSC).The DSC measurement results indicate that, for not only strain samples but also physical samples of ABS, PVC and PC sensible materials, endothermic peaks appeared around the temperature of Tg, and areas of those endothermic peaks increase gradually as the aging time goes. Moreover, in the same aging time, enthalpy absorption peak areas of the strain-induced samples are larger than those of the physical aging samples. It suggests that the strain-induced samples formed structures more stable than those of the physical aging samples.