Conductivity and percolation in polymeric particulate composites of epoxy resin and conductive fillers

摘要

Composites of the polymer-filler type, when the filler is a conductive material, show electrical conductivity at a significant volume concentration of the conductive phase and their behaviour can be described in terms of percolation theory. In these heterogeneous systems the constituents have markedly different properties and the ratio of the conductivities of the two components is /spl sim/10/sup 10/-10/sup 20/. These systems obey the relation of the percolation theory /spl sigma//spl sim/(P-P/sub c/)/sup /spl alpha// where /spl sigma/ is the electrical conductivity of the composite material, P is the filler concentration by volume, P/sub c/ its threshold value and /spl alpha/ the critical exponent. In this work, composites of epoxy resin and metal powders (Cu, Ni, Fe) or carbon black, in various volume fractions were prepared and their DC conductivities were measured. Data obtained by DC measurements are treated using percolation theory and values of P/sub c/ and /spl gamma/ are estimated through a suitable algorithm.