ANALYSIS OF CHARGING AND DISCHARGING CURRENTS IN POLYETHYLENETEREPHTHALATE

Charging and discharging currents in polyethyleneterephthalate samples for different polarization times, temperatures, and fields and for different measuring intervals are measured. Special attention is paid to external measuring circuit. The current obeys a Curie-von Schweidler law only for short times. The charging current changes its shape if the polarization time is long or the polarization field is high, depending on the product time x field. The discharging current is strongly dependent on the external resistance used in measuring circuit. Three characteristic parts are observed. The first part fits well with a Debye relaxation function. The second part seems to be a straight line and the slope is dependent on measuring resistance and the charge existing in the sample. As the resistance is higher the slope is higher. The third part, reported for the first time in this paper, represents the current that is released from the sample for a long time and sometimes is considered as a parasitic current. If the external resistance is big enough, this current can lead to increases of the voltage on the sample. The slope of the discharge current is dependent on the charge contained in the sample.