Abstract
This article reports the results of dielectric, alternating current (AC) conductivity, differential scanning calorimetry (DSC) and dynamic mechanical analysis of graphite-filled polyester gradient composites. Dielectric, AC conductivity, DSC and dynamical mechanical measurements were performed on these gradient composites. Effects of temperature and frequency variation on dielectric constant (ε′), dielectric dissipation factor (tan δ) and on AC conductivity (σ AC) were determined. With the increase in graphite content, the dielectric constant increased gradually in the direction of centrifugal force, which confirms the development of a gradient structure. The Linchtenecker model fits well for the dielectric data obtained experimentally for these composites. Conduction occurring in the composites is due to electronic conduction. The activation energy, E a, varied with frequency and showed a semiconducting behavior of these composite. Cole–Cole plots for the gradient composites between ε′ and ε′ showed a dielectric relaxation for all the samples due to the motion of the dipolar groups of the polyester resin.
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