Evaluation of electrical conductivity models for conductive polymer composites

The electrical conductivity of polymeric materials can be increased by the addition of carbon fillers, such as carbon fibers and graphite. The resulting composites could be used in applications such as interference shielding and electrostatic dissipation. Electrical conductivity models are often proposed to predict the conductivity behavior of these materials in order to achieve more efficient material design that could reduce costly experimental work. The electrical conductivity of carbon-filled polymers was studied by adding four single fillers to nylon 6,6 and polycarbonate in increasing concentrations. The fillers used in this project include chopped and milled forms of polyacrylonitrile (PAN) carbon fiber, Thermocarb(TM) Specialty Graphite, and Ni-coated PAN carbon fiber. Material was extruded and injection-molded into test specimens, and then the electrical conductivity was measured. Data analysis included a comparison of the results to existing conductivity models. The results show that the model proposed by Mamunya, which takes into account the filler aspect ratio and the surface energy of the filler and polymer, most closely matched the conductivity data. This information will then be used in the development of improved conductivity models. (C) 2002 John Wiley & Sons, Inc, J Appl Polym Sci 83: 1341-1356, 2002.