Strain rate-regulated sub-Rouse transition in polystyrene via dynamic mechanical spectroscopy

Abstract

The sub-Rouse mode in polystyrene after deformation was investigated via dynamic mechanical spectroscopy (DMA). Different tensile rates were adopted during the deformation, and the influence of tensile rate on chain relaxation behaviors and mechanical properties were analyzed thoroughly. The spectrum of internal friction is consisted by three relaxation peaks, local segmental relaxation (α transition), sub-Rouse mode (α′ transition), and Rouse mode (α″ transition), respectively. Significantly, the sub-Rouse relaxation intensity increases with the growing of the tensile rate at the same degree of deformation, and the tensile rate of 0.5 mm/min is regarded as the turning point to sub-Rouse relaxation. According to the strain-stress curves and the phenomenon of sliver crazes, it was inferred that some microcosmic orientation formed in the process of the deformation and the orientation structure is considered as the seed of the sliver crazes. What is more, the variation of sub-Rouse relaxation could also be attributed to the generation of the orientation.