Thermal properties of carbon-filled silicone rubbers for use in thermal expansion moulding

Abstract

The pressure produced by the thermal expansion of silicone rubber on heating when enclosed in a steel mould can be used to fabricate complex shaped reinforced plastic components. To improve the thermal conductivity of the rubber, the effects have been studied of adding between 25% and 30% by volume of carbon, both as chopped carbon fibre and carbon black. Measurements have been made of the thermal conductivity between 30° and 170° C, and of the thermal expansion between 23° and 140° C. It was found that the chopped fibres were more efficient than the carbon black in increasing the thermal conductivity, giving approximately 100% increase in conductivity over that of the pure rubber for a 30% loading. The addition of carbon led to a decrease in the thermal expansion of the rubber by an order of 30%. The bulk modulus of the rubber was found to increase slightly, by less than 10%, when the carbon was added.