Nature of transient currents in polymers

Transient charging and discharging currents were measured in several polymers from room temperature to the glass transition temperature, and the effect of varying parameters such as field strength, electrode material, sample thickness, method of polymer preparation, and addition of impurities was investigated in some of them. Some limited comparative studies of the isochronal characteristics (i.e., current-temperature plots at fixed times) with the thermally stimulated depolarization and polarization currents were also carried out in order to test possible correlations between the phenomena observed by the different methods. All the results suggested that, at temperatures lower than the glass transition temperature and in low to moderate fields, the transient currents are essentially governed by dipolar mechanisms and are thus critically dependent on the position of the measuring temperature with respect to the temperature ranges of the various molecular relaxation processes characteristic of the material investigated.