DIELECTRIC-RELAXATION AND ELECTRICAL-CONDUCTION AT LOW-FIELD OF MINERAL-FILLED EPOXY

Authors
Citation
Sl. Wu et Ic. Tung, DIELECTRIC-RELAXATION AND ELECTRICAL-CONDUCTION AT LOW-FIELD OF MINERAL-FILLED EPOXY, Journal of Materials Science, 31(8), 1996, pp. 2177-2186
Citations number
16
Categorie Soggetti
Material Science
ISSN journal
00222461
Volume
31
Issue
8
Year of publication
1996
Pages
2177 - 2186
Database
ISI
SICI code
0022-2461(1996)31:8<2177:DAEALO>2.0.ZU;2-1
Abstract
Dielectric properties and conduction of the epoxy and its composites w ere measured over the temperature range -20 to 70 degrees C and the fr equency range 10(-4)-10(-1) Hz. Dielectric properties were obtained by performing Fourier transforms on the charging and discharging curves. The resulting isothermal frequency spectra of dielectric constants an d dielectric loss factors were analysed using the Cole-Cole law to obt ain the activation energy for each material. The activation energies w ere also obtained for isothermal d.c. current. Current density-electri c field-temperature characteristics are obtained for field levels up t o 60 kV cm(-1), with step excitation of the applied field and currents recorded after a delay time of 10 min. Current density and electric f ield were computed and plotted for constant temperature. The linear (o hmic) curves were obtained for fields up to about 60 kV cm(-1) for tem peratures up to about 20 degrees C. The non-linearity at the higher fi elds and temperatures did not imply the occurrence of non-ionic conduc tion. It has been demonstrated that both electric conduction and relax ation behaviour were ionic and could be fit by the Nakajima model for the unfilled epoxy and the Taylor model for the composites.