Potential decay on silicone rubber surfaces affected by bulk and surface conductivities

A decay of electric surface potential on a pre-charged gas-solid interface involves several charge transport processes and each of them may become dominant under certain environmental conditions (temperature, pressure, humidity). In the present paper, surface potential decay on flat samples of different kinds of silicone rubber used in HVDC applications is analyzed at reduced pressures of ambient air that allows for minimizing the involvement of the gas phase, i.e. surface charge neutralization by gas ions. Effects imposed solely by bulk and surface conduction in the solid material are studied experimentally and by means of computer simulations. The results allow for evaluating threshold values of volume and surface electric conductivities at which these mechanisms become most essential. Field dependent bulk conductivities are deduced from the surface potential decay characteristics obtained for the studied materials.