Electrical properties of composites of hard metal carbides in a polymer matrix

The electrical conductivity of composites containing hard metal carbide powder in a nonconducting polymer matrix has been studied. In composites with low and medium filler contents, the expansion of the nonconducting matrix with increasing temperature caused interruption of conducting paths and a rapid drop in conductivity (switching effect). In contrast, at high filler loadings (Φ P > 50 vol%), a continuous and slight decrease in conductivity with temperaute inducates a specific composite structure with a dense particle arrangement and a great number of conducting contants, which change only little during heating.