Electrical Conduction by Percolation Process in Insulating Polymer Containing Small Amount of Conducting Polymer

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Abstract
Electrical conductivity is studied in two component composites, one of which is insulating polymer (nylon6, nylon66) in fibers coated with conducting polypyrrole and the other, polyethylene in spheres without coating. Conductivity is enhanced by more than 15 orders of magnitude when the concentration of polypyrrole-coated insulating polymer exceeds 2–5 vol%, which corresponds to an effective polypyrrole concentration of 0.01–0.03 vol%. This insulator-metal transition-like characteristic can be explained by a percolation model. Thermoelectric power is proportional to absolute temperature and is independent of the concentration of polypyrrole-coated insulating fibers above the percolation threshold, which support the percolation model. The percolation threshold depends on the shape of the coated fibers of the insulating polymer but does not depend on the type of coated insulating polymer. The percolation threshold increases with decreasing length of polypyrrole-coated insulating fibers.