Temperature Effect on the Dielectric Response of Carbon Nanotubes Particles Filled Polyester Polymer Composites

Polyester/carbon nanotubes composites were prepared, and the frequency and temperature dependence of the electrical properties were studied at concentrations below and above the percolation threshold. The analysis of the complex permittivity using the derivative formalism allows us to overcome difficulties caused by the high electrical conductivity, which can mask the dielectric relaxation processes. The dielectric permittivity was analyzed using the Havriliak-Negami model taking into account the effect of electrode polarization. This analysis enabled us to describe quantitatively the experimental data, to calculate the ohmic conductivity and the parameter characterizing the contribution of the ohmic conduction to the complex dielectric permittivity. Above the percolation threshold, using the complex permittivity the dielectric data were analyzed at several temperatures. Both below and above the percolation threshold, the activation energy decreases with an increase in the concentration of carbon nanotube in the composite, which may be due to an increase of charge carrier density leading to a decrease of the domain boundary potential of carbon nanotube aggregates in the polyester matrix.