Effect of temperature on the electrical properties of copolymer/carbon black mixtures

This work presents a study of the electrical conductivity of mixtures of carbon black particles in the ethylene butylacrylate copolymer matrix over the temperature range − 120 to 80 °C. The DC conductivity of these mixtures is examined and a positive temperature coefficient in resistivity effect is found for the carbon black concentration above the percolation threshold ϕC (ϕC ≈ 11%). AC electrical measurements in the frequency range 100 Hz to 0.2 MHz have allowed us to identify different mechanisms of the conduction in these composites. The temperature dependence of the dielectric response has been analyzed below the epoxy glass transition temperature, for various carbon concentrations. Jonscherʹs phenomenological model has been used for modelling the dielectric response of our composite materials. We find that the activation energy is insensitive to the presence of the carbon particles and we conclude that means that the carbon black particles do not interact or only weakly interact with the chain segments of the macromolecules in the copolymer.