Electrical conductivity of poly(vinyl chloride) filled with PAN-based and pitch-based carbon short-fibers 1

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Abstract
Poly(vinyl chloride) (PVC) was filled with PAN-based and pitch-based carbon and graphite short-fibers with up to 100 phr (volume fraction Φf = 0.39-0.45) by roll mixing. Carbon short-fibers were aligned in the roll direction although some fibers were broken during roll mixture. Volumetric electrical conductivities (σ) were measured for these sheets by the square four-point probe method and the two terminal method. The conductivities increased as Φf and the fiber length increased. The conductivities of specimens filled with graphite fiber were larger than those filled with carbon fibers. The larger Φf, the smaller the influence of the specimen length on σ. In order to improve mechanical properties of the materials, the influence of the coupling agent for carbon short-fibers on electrical conductivities was investigated. Since the short-fibers were covered by the coupling agent, the electrical conductivity of the filled material was lowered. The influence of orientation of short-fibers on σ was clearly detected by the two terminal method, but anisotropy was not detected by the square four-point probe method.