Percolation phenomena and electrical conduction mechanism of carbon black-polyethylene composites

In this paper, how finite or infinite carbon black (CB) clusters contribute to the ac conductivity /spl sigma//sub AC/ in CB-polyethylene composites below and above the percolation threshold p/sub c/ is discussed. It was found that the frequency dependence of /spl sigma//sub AC/ below p/sub c/ is due to ac loss current and a tunneling current between the finite carbon black clusters appears in addition to the ac loss current for the volume fraction of CB, p, very closely to p/sub c/. Above p/sub c/, a current independent of frequency governs /spl sigma//sub AC/ although the ac loss current still appears, which leads to a conclusion that a hopping conduction via finite clusters does not take place at least till 1 MHz.