Polymer matrix composites: Conductivity enhancement through polypyrrole coating of nickel flake

The electrical resistance of polymeric materials loaded with conductive fil lers can be divided into three major categories: the intrinsic resistance o f the filler and matrix, the particle-particle contact resistance, and the tunnelling resistance. A method for decreasing both the particle-particle c ontact and the tunnelling resistance in nickel-filled low-density polyethyl ene composites which involves coating the nickel with polypyrrole (PPy) usi ng admicellar polymerization has been developed. It is believed that these resistances are reduced by the formation of PPy "molecular wires" which occ ur as a result of chain entanglements at high filler loadings. Coating the nickel particles with PPy leads to a three-order-of-magnitude increase in c onductivity at concentrations well above the percolation threshold without significantly changing the thermal or mechanical properties of the composit e. (C) 1998 Kluwer Academic Publishers.