The polymer-grafted carbon black (GC) was prepared by an anionic polymerization of methyl methacrylate in the presence of carbon black previously treated with n-butyl lithium. The electrical properties of the resistors obtained using the GC material were studied. For a comparison with the above resistors, resistors with a smaller grafting ratio or without grafting were also prepared. It was found that the resistivity increased with an increase of the grafting ratio and that, by comparing resistors with similar resistivities, resistivity variation with temperature was less for higher grafting ratios. The resistors with a resistivity in the range of ca. 103–106 Ω·cm showed a remarkably large positive anomaly, but, for a resistivity larger than 107 Ω·cm, the temperature coefficient was negative.
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Miyauchi et al. (1984) studied this question.