Electrical conductivity and electrostatic properties of radiationally modified polymer composites with carbon black

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Abstract
The electro-physical surface properties of polymer composites of ultrahigh-molecular-weight polyethylene containing 5, 10 and 15 vol% carbon black filler were investigated before and after irradiation by gamma-rays of a 60Co source. Measurements of the specific surface conductivity s, surface dissipation factor tans, volume dissipation factor tanv, and the maximum surface potential Umax after charging with positive or negative ions by dc corona discharge, were carried out at room temperature in air of 65% humidity. Umax was found to have a strong dependence on irradiation dose especially at doses ranging up to 1 Mrad. Also, s exhibits a substantial decrease of up to seven orders of magnitude at doses from 100 krad to 1 Mrad. These effects are supposedly linked with the radiationally stimulated destruction of carbon chains on the polymer composite surface. On the other hand, at doses higher than 1-2 Mrad there is an extraordinary high rise of the specific surface conductivity of the samples containing 5 vol% filler which reaches nine orders of magnitude and more. This is attributed to the formation of chains of carbon nanoclusters in the near-to-surface layer of the polymer composite.