Dielectric Breakdown of Polyethersulfone (PES) Film under DC Voltage Conditions

The dielectric breakdown characteristics of polyethersulfone (PES) film was investigated in a temperature range from 25 to 250°C, under dc voltage conditions. The temperature dependence of breakdown strength shows two distinct regions, referred to as I (25-150°C) and II (150-250°C). In region I, the breakdown appears to be electronic, as the breakdown strength is almost independent of the electric field rise time over times ranging from microseconds to seconds. In region II, impulse thermal breakdown due to ionic conduction appears to be a likely mechanism. The calculated ionic jumping distance 2¿i is found to be 1.5 nm at 200°C and 2 nm at 230°C, which are reasonable values for polymeric materials.