Study of space charge relaxation in PMMA at high temperatures by dynamic electrical analysis

Dynamic electrical analysis shows that at high temperatures (above the glas s transition temperature), the electrical properties of polymethyl methacry late are strongly influenced by space charge. In this paper we present an s tudy of space charge in this material and its conductive properties by dyna mic electrical analysis, using the electric modulus formalism. The complex part of the electric modulus was fitted to Coelho's model, which considers ohmic conductivity and diffusion as the prevailing mechanisms of charge tra nsport. The complex part of the electric modulus exhibits a peak in the low frequen cy range that can be associated with space charge and a good agreement betw een experimental and calculated data is observed after the fitting process to the Coelho's model. The data obtained indicate that the electrode is par tially blocked. The conductivity determined is thermally activated and it i ncreases with the temperature due to an increasing mobility, that is also t hermally activated. (C) 2000 Elsevier Science Ltd. All rights reserved.