Polymer matrix composites: Conductivity enhancement through polypyrrole coating of nickel flake
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The electrical resistance of polymeric materials loaded with conductive fillers can be divided into three major categories: the intrinsic resistance of the filler and matrix, the particle–particle contact resistance, and the tunnelling resistance. A method for decreasing both the particle–particle contact and the tunnelling resistance in nickel-filled low-density polyethylene composites which involves coating the nickel with polypyrrole (PPy) using admicellar polymerization has been developed. It is believed that these resistances are reduced by the formation of PPy "molecular wires" which occur 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 conductivity at concentrations well above the percolation threshold without significantly changing the thermal or mechanical properties of the composite. © 1998 Kluwer Academic Publishers
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