CORONA CHARGING OF ELECTRETS - MODELS AND RESULTS

We summarize experimental results obtained with the corona charging technique for polymers, mainly Teflon FEP and PVDF. Emphasis is put on the hypothesis underlying the models employed to explain the experimental results. The following subjects are discussed: the cross-over effect in polyethylene; the voltage buildup and decay at room temperature and the thermally stimulated discharging in Teflon FEP, stressing in this last case the participation of the electrode charges; the voltage buildup and decay for PVDF in the alpha and beta-phases. On the theoretical side, solutions for the constant current mode are presented, which are based on models of drift, polarization, and both drift and polarization with formation of a depletion layer; dispersive transport and surface conduction are also touched upon.