Crystallization of poly(ethylene terephthalate) from oriented amorphous film

Abstract

Solution cast amorphous poly(ethylene terephthalate) (PET) films were hot drawn uni-axially at 80—130%min-1 to a draw ratio of 4—5 at 85—94°C to give amorphous films of high chain orientation in the global sense while the segmental orientation was entirely random. These films were isothermally crystallized at 110°C with film ends clamped tight. The kinetics of crystallization was followed by FTIR based on a computer resolution of the 1020 cm-1 band into trans-conformations in crystalline and in amorphous regions and gauche conformation. An induction period of 5—6 min was observed for the crystallization of the oriented film, while undrawn film did not show an induction period longer than 45 s. Comparison with stress relaxation data of these oriented amorphous films at 82—112°C indicates that the thermal relaxation of the global chain orientation by dis-entanglement and rubbery flow which precedes crystallization is responsible for the induction period. © 1987 The Society of Polymer Science, Japan. All rights reserved.