Thermally stimulated and isothermal discharge of corona-charged polypropylene

Details are reported of short- and open-circuit thermally stimulated current (TSC), isothermal charge decay, and absorption current measurements. These measurements were conducted on corona-charged 50-μm-thick commercial-grade isotactic polypropylene (PP). The appearance of a peak centered at 140°C in open-circuit TSCs that is absent in short-circuit TSCs shows that this peak is due to the charge trapped in trapping sites located at the surface or in the near-surface region. However, the traps giving rise to three other peaks common to both type of TSCs are clearly bulk traps. Anomalous short-circuit TSCs (flowing in the same direction as the charging current), observed for high-temperature-charged samples, can be understood in terms of space-charge-limited drift of charge carriers toward the collecting electrode