Evaluation of a.c. conductivity behaviour of graphite filled polysulphide modified epoxy composites

Composites of epoxy resin having different amounts of graphite particles have been prepared by solution casting method. Temperature dependence of dielectric constant, tan delta and a.c. conductivity was measured in the frequency range, 1-20 kHz, temperature range, 40-180degreesC for 0.99, 1.96 and 2.91 wt% graphite filled and unfilled epoxy composites. It was observed that the dielectric constant, tan delta and a.c. conductivity increase with increasing temperature. Near the transition temperature the materials show anomalous behaviour for the observed properties. Peaks of dielectric constant, tan delta and a.c. conductivity were observed to shift towards lower temperature with increasing frequency. Clear relaxation (tan delta) peaks around 169degreesC were observed in epoxy resin, which shifted to lower temperature side on increasing the frequency. Addition of 2.91 wt% graphite shifted the tan delta peaks towards higher temperature side by creating hindrances to the rotation of polymer dipoles. Addition of 2.91 wt% graphite leads to an increased relaxation time tau of dipoles in poly-sulphide epoxy from 1.44 x 10(-5) - 3.92 x 10(-5) (s) at 90degreesC by creating the hindrance to the rotation of dipoles.