Measured and simulated transient current in polyethylene terephthalate films below and above the glass transition temperature

Charging and discharging current were measured in polyethylene terephthalate films (25 /spl mu/m) with electrical field ranging from 24 to 72 MV/m and temperature between 40 and 140/spl deg/C. At temperatures far below the glass transition, the current behaviour was interpreted in term of dipolar mechanisms. While, in rubber state, the current deviate from the well-known Curie-Von Schweidler law. This behaviour was explained, assuming an additional current, due to charge injection at the metal-insulator interface. Numerical simulation, when taking into account these two components, can reproduce the change in the current-time shape. Comparison between measured and calculated current gave a good agreement.