Electrical Conductivity and Dielectric Dispersion of Polyvinylchloride – Graphite Composites

CZU 537.31+546.05

DOI  https://doi.org/10.5281/zenodo.1053753

The paper deals with the dielectric properties of polyvinylchloride (PVC)-graphite (Gr) composites in a wide range of temperatures (20–150°С) and frequencies (25–10⁶ Hz). The PVC-Gr composites have been prepared using powder technology by a thermal pressing method in a hydraulic press followed by a rapid cooling in the mixture of water-ice (quenching mode). The dielectric permittivity and electrical conductivity of the PVC-Gr composite system obeys the power law of the percolation theory. The percolation threshold of these composites is 6%vol. of Gr. At certain graphite concentrations, the PVC-Gr composites exhibit a high dielectric permittivity, high loss and high DC- and AC-conductivity. When increasing the applied field frequency, the dielectric constant decreases, while the electrical conductivity, on the contrary, increases. It is shown that the main mechanism of the AC-conduction in the PVC-Gr insulating dielectrics is the barrier-hopping, according to which electron jumps occur over the states localized near the Fermi level. In addition, the temperature-frequency dispersion e¢ and tgd was considered and the peculiarities of dispersion curves were revealed.

Keywords: composite, electrical conductivity, dispersion, percolation, polyvinylchloride, graphite, dielectric permittivity, dielectric loss.