Role of Stress Relaxation in Stress-Induced Polymer Crystallization

Stress relaxation is a common process that reduces the deformation of polymer coils against the strain-induced crystallization during the processing of polymeric materials for fibers, thinfilms and molding plastics. By introducing Maxwell model of stress relaxation into each polymer in dynamic Monte Carlo simulations, we compared stress-induced to strain-induced polymer crystallization under parallel conditions of various strain rates and temperatures. The results demonstrated the scenario of competitions among the factors of stress relaxation, strain rates and temperatures in the crystallization process. We found that, owing to fast stretching, the limited extent of stress relaxation plays the dominantly kinetic role rather than the expected thermodynamic role in the retardation of crystallization, similar to the factor of high strain rate. In addition, we observed the enhanced stress relaxation during the post-growth process of polymer crystallization, which influences the finally achieved crystallinity and crystal morphology. Our results facilitate a better understanding of polymer crystallization during the fast stretching processing.