ELECTRICAL CONDUCTION IN CARBON-POLYMER COMPOSITES.

THE ELECTRICAL PROPERTIES OF TWO CARBON-POLYMER COMPOSITES ARE DISCUSSED: CARBON BLACK IN A POLYVINYLCHLORIDE-BASED RESIN AND A PYROLYZED POLYIMIDE WHICH, IT IS SUGGESTED, CONTAINS CARBONIZED MICROSCOPIC ISLANDS. FROM STUDIES OF THE OPTICAL PROPERTIES AND THE TEMPERATURE DEPENDENCE OF THE RESISTIVITY IT IS CONCLUDED THAT FLUCTUATION-INDUCED TUNNELING OCCURSIN THE CARBON-POLYVINYLCHLORIDE COMPOSITE AND THAT CHARGINGENERGY-LIMITED HOPPING OCCURS IN THE PYROLYZED POLYIMIDE. THE DIFFERENT CONDUCTION MECHANISMS ARE SHOWN TO BE A CONSEQUENCE OF THE SIZE, SHAPE, AND GEOMETRICAL ARRANGEMENT OF THE MICROSCOPIC CONDUCTING REGIONS IN THE COMPOSITES.