RELAXATIONS IN SEMICRYSTALLINE POLYETHYLENETEREPHTHALATE USING THERMALLY STIMULATED CURRENTS

Relaxation processes at temperatures above 20 degrees C in semicrystal line polyethylene-terephthalate have been studied using thermally stim ulated depolarization currents (TSDC). The discharge curve shows three relaxation peaks (alpha(c), rho(c) and rho) whose positions and inte nsities depend on the polarization conditions and the crystallinity. R elaxations alpha(c) and rho(c) are heteropolar, while rho may be homo polar or heteropolar according to the polarization temperature used. T he effect of the crystallinity on these relaxations has been analysed by the thermal steps stimulation (TSS) method applied to an amorphous sample. Results show that alpha(c) is fundamentally a dipolar relaxati on associated with the amorphous interlamellar zone. The relaxation rh o(c) is associated with the release of a free charge trapped in the am orphous regions, and rho is a Maxwell-Wagner-Sillars relaxation assoc iated with crystalline amorphous interphases. For polarization tempera tures above 150 degrees C, two relaxations are observed only as a cons equence of overlapping rho(c) and relaxations. rho relaxations. (C) 1 998 Chapman & Hall.