CRYSTALLIZATION DURING HOT-DRAWING OF POLY(ETHYLENE-TEREPHTHALATE) FILM - INFLUENCE OF THE DEFORMATION MODE

We have examined the influence of the strain-rate mode-constant extens ion rate (CER) and constant strain rate (CSR)-on crystallization kinet ics during hot-drawing of poly(ethylene terephthalate) film. It was fo und that strain rate/draw time superposition, previously observed in C ER drawing, is also applicable to CSR drawing, and that the temperatur e dependence of the shift factor is essentially the same in both modes of deformation. In CSR drawing, crystallization onset occurs at short er times and the rate of crystallization is higher. Further analysis o f the CSR data confirms previous CER data showing that at high strain rates the crystallization rate during drawing increases with temperatu re, and that this trend gradually reverses as strain rate decreases.