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Proceedings Paper

Formation and relaxation of space charge in corona-poled polystyrene
Author(s): S. N. Fedosov; G.F. Leal Ferreira; Jose A. Giacometti; Mauro M. Costa
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Paper Abstract

The 20 micrometers -thick samples of amorphous atactic nonpolar polystyrene (PS) have been poled in a corona triode at a constant current of 2 nA up to 2 kV at different constant temperatures Tp, while the kinetics of the surface potential was continuously recorded. Then the sample were subjected to the thermally stimulate depolarization (TSD) in one of three modes; with short circuited electrodes, with the 3 mm-thick air gap, or with a PTFE 9 micrometers -thick spacer. It has been shown that the constant current corona method can be applied to measure the dielectric constant at infra- low frequencies. At Tp > 80 degrees C the curves became sub-linear due to injection of the charge carriers in the bulk. The best fitting was obtained with Arkipov- Rudenko-Sessler-Ferreira's model assuming charge transport modulated by deep trapping and detrapping. The product of the carrier mobility and the trapping time has been found as 4.4 X 10-13 m2V-1 at 80 degrees C. The TSD-SC current shows a very sharp positive peak at 110 degrees C, and TSD-AG gives two negative peaks at 114 and 129 degrees C, and TSD-DS current contains a broad positive peak at 117 degrees C and a negative one at 132 degrees C. The peak temperature were higher than glass transition temperature Tg equals 95 degrees C proving that all peaks have been caused by charge redistribution and not related to the a relaxation. It has been proved that there are two components of the charge, presumably the surface and the volume ones, with the surface charge being more thermally stable than the volume charge. It appeared that the positive charge from corona penetrates deeper in PS than the negative ones.

Paper Details

Date Published: 14 December 1999
PDF: 8 pages
Proc. SPIE 4017, Polymers and Liquid Crystals, (14 December 1999); doi: 10.1117/12.373718
Show Author Affiliations
S. N. Fedosov, Odessa Technological Institute (Ukraine)
G.F. Leal Ferreira, Univ. of Sao Paulo (Brazil)
Jose A. Giacometti, Univ. of Sao Paulo (Brazil)
Mauro M. Costa, Federal Univ. of Mato Grosso (Brazil)

Published in SPIE Proceedings Vol. 4017:
Polymers and Liquid Crystals
Andrzej Wlochowicz, Editor(s)

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