Electrically conductive resins are needed for bipolar plates used in fuel cells. Currently, the materials for these bipolar plates often contain a single type of graphite powder in a thermosetting resin. In this study, various amounts of two different types of carbon, carbon black and synthetic graphite, were added to a thermoplastic matrix. The resulting single-filler composites were tested for electrical conductivity, and electrical conductivity models were developed. Two different models, the Mamunya and additive electrical conductivity models, were used for both material systems. It was determined how to modify these models to reduce the number of adjustable parameters. The models agreed very well with experimental data covering a large range of filler volume fractions (from 0 to 12 vol% for the carbon black filled composites and from 0 to 65 vol% for the synthetic graphite filled composites) and electrical conductivities (from 4.6 x 10(-17) S/cm for the pure polymer to 0.5 S/cm for the carbon black filled composites and to 12 S/cm for the synthetic graphite filled composites). (c) 2006 Wiley Periodicals, Inc.