Charging and discharging of Lexan in vacuum

Lexan (polycarbonate) samples cut from commercially available sheets were equipped with vacuum-evaporated aluminum electrodes, and subjected to voltages of 1000 V and either 3000 or 5000 V. The charging and discharging currents were measured from a starting time of 15 s after voltage application to 1000 s. The electrode configuration allowed both surface and bulk currents. By changing the size of the electrodes, the total current was separated into perimeter-dependent and area-dependent terms. The experiments were carried out in vacuum and samples were kept in vacuum for various lengths of time to observe the effects of loss of volatiles on the measured currents. The effect of the vacuum aging on the currents 60 s after the step voltage was applied for a soap-cleaned sample was evaluated. The results indicate that sample-to-sample differences are more important than vacuum aging