The resistivity of conductive composites ofNBR(Butadiene nitrile rubber)filled with conductive car-bon black and two kinds of special organic fillers was mea-sured from room temperature to 90℃.In such semiconduc-tive systems.A possitive,temperature coefficient(PTC)phenomenon is observed,whose intensity depends on thetype concentration and other physical and chemical proper-ties of carbon black.Two empirical formulae are obtainedby a the-oretical fitting method from the experimental da-ta.One is for the resistivity of NBR/CB composites at roomtem perature and the other is for the resistivity of NBR/N550 composites with relatively high concentrations N550carbon bl(?)ck in the temperature range of 30～90℃.Thestability of resistivity is also discussed.
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