Dielectric polarization and relaxation behaviour of AC aged polyethylene with liquid electrodes

Thermally stimulated discharge current (TSDC) measurement and dielectric spectroscopy of low-density polyethylene (LDPE) aged with an AC field and liquid electrodes are reported. The dielectric response of aged sample after DC poling at 70/spl deg/C shows two parallel relaxation processes. At low frequencies an LFD (low-frequency dispersion) process with a constant /spl epsi/"//spl epsi/' ratio is dominant, possibly due to the presence of ionic species in LDPE. At higher frequencies an additional dipolelike relaxation occurs as a result of charge injection and trapping enhanced by electrical ageing. Without DC poling at high temperature only the LFD is evident. The unaged sample does not show any fundamental changes in the dielectric response after additional DC poling, thus indicating the absence of a significant trap density.<
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