DC and AC electrical conductivity of electro-deposited carbon-black-epoxy composite films

Carbon-black-epoxy composite films were prepared by cathodic electro-deposition of a dispersion containing carbon black and epoxy resins. The films, after baking at elevated temperature, show a semi-conducting behavior. Using DC conductivity measurements it was possible to determine the glass transition temperature of the samples, the conductivities of which lie in the sensitivity range of the instrument. Conductive samples show a positive temperature coefficient both below and above T,. Based on the electrical impedance data extracted from the electrochemical impedance spectra, the exponents x and y were determined for the frequency dependence of the complex conductivity and complex dielectric constant as 0.8 and 0.2, respectively. These values are in good agreement with the classical values of x = 0.72 and y = 0.28. It was also found that these exponents are the same for all the CCB contents studied. (C) 2008 Elsevier B.V. All rights reserved.