Exploration of the space charge behaviour of polyethylene using measurements of thermally stimulated discharge currents coupled with the determination of space charge distributions by the thermal step method in hydrogenated poly(vinyl chloride)

By using the thermally stimulated discharge currents (TSDC) technique and c oupling it with the thermal step (TS) method, which allows accurate measure ment of the space charge distribution tan outstanding electrical property), both the relaxation and the relative contribution of the intrinsic polariz ation charges and the extrinsic trapped charges have been analysed for a se ries of poly(vinyl chloride) (PVC) materials after partial hydrogenation as a precursor structure of polyethylene (PE). The alpha relaxation related t o the release of frozen-in dipole orientation, and the rho relaxation which is due to the trapping of extrinsic charges have been found to vary, both in intensity and in temperature, with the percentage of ethylene units. On the other hand, the TS measurement of the space charge distribution prior t o and after destroying the polarization charges according to the TSDC behav iour, allows one to correlate, as a first approximation, those types of spa ce charge with the molecular microstructure, of either PVC or PE parts. Eve n if further work remains to be done, the results, as discussed in the ligh t of earlier work on tacticity-driven microstructure-PVC property relations hips and on space charge distribution of PVC after hydrogenation, studied b y the TS method, provide an original although still tentative interpretatio n of the space charge behaviour of PE. (C) 1999 Elsevier Science Ltd. All r ights reserved.