Development, Dielectric, and Thermal Studies on HAF Carbon-filled Polyester Gradient Composites.

In this study, high abrasion furnace carbon having particle size 28–36 nm has been incorporated in unsaturated polyester resin to develop gradient composites. Dielectric measurements have been conducted on the graded composites by using a LCR meter. Effect of temperature and frequency variation on dielectric constant (ε′), dielectric dissipation factor (tan δ ) and on a. c. conductivity (σ a.c.) of the samples have been determined. Dielectric measurements have been performed in the temperature range from 30°C to 150°C and in the frequency range 1–10 kHz. Dielectric constant increases gradually with the increase of filler content in the direction of centrifugal force, which shows the existence of gradient structure in the composite. This is confirmed based on the microstructures observed at different positions in the graded composites. On increase of frequency, reduction in dielectric constant in carbon-filled polyester composites has been formed. Dielectric constant and a.c. conductivity increased with increase in temperature. ε′ variation with temperature shows a plateau which shifts from 145°C to 125°C on increase of carbon content. Linear dependence of ln σ 0 on Ea follows the compensation law for HAF carbon-filled polyester gradient composite, which is similar to semi conducting composite behavior. Tg obtained by DSC plots for samples 1–4 are higher as compared to polyester resin