Influence of pressure on the electrical conductivity of metal powders used as fillers in polymer composites

Abstract

In this work, the influence of pressure on the electrical conductivity of metal powders (copper, nickel, and iron), used as fillers in conductive polymer composites, was investigated. It was found that the conductivity of the powders as a function of the applied pressure, P, is described by the equation: σ= k( P- P 0) n . In this equation, P 0 is the minimal pressure necessary for the appearance of conductivity and it is affected by the presence of oxidized layers on the surface of the metal particles. Exponent n depends on the kind of the powder and the particle size. It is also affected by the properties of the oxidized layers on the surface of the particles. Coefficient k depends only on the kind of the powder. It was shown that the conductivity of copper powder increases exponentially with increasing particle size. The value of the packing factor, F, increases with the applied pressure, due to the deformation of the particles. It is affected by the hardness of the powder particles. The conductivity of powders with small and big copper particles was compared with the conductivity of polymer composites, based on epoxy resin with the same powders as fillers.