Anomalous Charging Current in PEN Films: Temperature effect

Electrical charging current in Poly(ethylene naphthalene-2,6-dicarboxylate) was investigated in a wide temperature range around the glass transition temperature Tg. A 25 μm thick films were submitted to direct electrical field between 24 and 72 MV/m at a constant temperature in the range 80-180°C. The current-time J(t) characteristics showed that the current increases, after a few minutes of polarisation, then decreases, which reveals a peak. This last appears at a temperature localised between 80 and 100°C then disappears at the temperatures higher than 150°C. These characteristic temperatures are connected respectively to the transition beta* and the pre-melting of cristallites confirmed by the differential scanning calorimetry. The exploitation of the steady-state current showed a break in the curve of current according to the reverse of the temperature J(1/T) at a temperature bordering Tg. This behavior was associated to an ionic conduction in the material volume.