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

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 Co-60 source. Measurements of the specific surface conductivity sigma(s), surface dissipation factor tan delta(s), volume dissipation factor tan delta(v), and the maximum surface potential U-max after charging with positive or negative ions by de corona discharge, were carried out at room temperature in air of 65% humidity. U-max was found to have a strong dependence on irradiation dose especially at doses ranging up to 1 Mrad. Also, sigma(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.