Effect of hydrostatic pressure on the electrical properties of blend vulcanizates loaded with paraffin wax

Blend vulcanizates from styrene butadiene rubber and natural rubber with equal proportions incorporated with the percolation concentration (40 phr) of High Abrasion Furnace carbon black and loaded with different concentrations of paraffin wax were prepared using the conventional two roll mill technique. With the application of different values of hydrostatic pressure on samples loaded with wax, a third jump non-linear region, obtained from I–V characteristics, clearly appears and was shifted to lower fields as the applied pressure increased. Furthermore, the non-linear coefficient were increased at a pressure of 0.6 kg/cm2 and then decreased with further increase in pressure. On the other hand, the dc electrical conductivities were measured. At room temperature, it increased with increasing pressure for samples unloaded with wax while it has a minimum at a pressure of 0.4 kg/cm2 for other samples. The positive and negative pressure of conductivity were calculated and found to increase with increasing wax contents. Hydrostatic pressures was found to highly affect the behavior of the temperature dependence of the dc conductivity. The maximum temperature coefficient of conductivity recorded a maximum value at a pressure of 0.4 kg/cm2.