Improved thermally stimulated current techniques and quenching polarization of polypropylene

Step heating TSC as well as bound charge and residual charge measurements were performed in polypropylene (PP) to give static TCS spectra. All the results demonstrated good agreement of a –15°C temperature shift relative to the spectrum of normal TSC at a rate of 2°C/min. By carefully examining the discharge sources, a charging method was proposed to study the variation of stored polarized charges on the quenching process. The quenching polarization current showed a charging peak. The reason for this was that the structure or configuration of the polymer at a high temperature is kept at a lower temperature and this structure can hold more bound charges in the lower temperature than in the higher temperature. Thermal-cycle polarized TSC measurements further show that some bound charges enter into deeper energy levels in the quenching polarization process. This result provides a better means of polymer preparation and shows the danger of using the polymer in a high DC field or radiation conditions.