Measurements of space charge on HDPE specimens during long-time depolarisation

Space charge measurements having the purpose to infer long-term depolarisation characteristics of high-density polyethylene (HDPE) specimens are presented and discussed in this paper. Two techniques are used for space charge observation, that is, pulsed electroacoustic (PEA) method and laser intensity modulation method (LIMM). The qualitative and quantitative information coming from the two techniques are fairly close, considering the inherent differences, and show a very slow charge release with time. This is explained by quite deep traps involved in charge transport, as shown by the results of trap-controlled apparent mobility and trap depth distribution obtained from space charge measurements under depolarisation.