Effect of stretching on space charge behaviour of poly(vinyl chloride) as analysed by the thermal step method and the thermally stimulated depolarization currents technique

The space charge behaviour of poly(vinyl chloride) (PVC) films after stretching to various degrees has been studied by the thermal step (TS) and the thermally stimulated discharge current (TSDC) methods, the aim being to show the influence of the two likely conformations GTTG(-)TT and GTGTTT at the mmr local configuration terminal of any isotactic sequence on the space charge density and nature which appear when applying an electric field. It was demonstrated in previous work that stretching causes the conformational change GTTG(-)TT-->GTGTTT to occur irreversibly, so that the relative proportions of both configurations may be controlled by stretching. TS and TSDC results show that the polar orientation decreases as the degree of stretching increases. The results, when analysed in the light of previous findings, strongly suggest that GTTG(-)TT and GTGTTT conformations are sensitive to polarization changes and to injection charges from the electrode respectively. (C) 2000 Society of Chemical Industry.