ANALYSIS OF CHARGING AND DISCHARGING CURRENTS IN POLYETHYLENETEREPHTHALATE

Charging and discharging currents in polyethyleneterephthalate samples for different polarization times, temperatures, and fields and for di fferent 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 th e polarization time is long or the polarization field is high, dependi ng on the product time x field. The discharging current is strongly de pendent on the external resistance used in measuring circuit. Three ch aracteristic 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 t hird part, reported for the first time in this paper, represents the c urrent that is released from the sample for a long time and sometimes is considered as a parasitic current. If the external resistance is bi g enough, this current can lead to increases of the voltage on the sam ple. The slope of the discharge current is dependent on the charge con tained in the sample.