Electrical conduction in polyimide-FEP fluoropolymer films

The aromatic polyimide has excellent mechanical, electrical and chemical properties. Absorption and conduction currents are studied over a temperature range of 50 to 200°C in Teflon coated film (25.4 μm Kapton® base with 12.7 μm coating of Teflon® FEP fluoropolymer resin on one side) and the influence of parameters such as field strengths and electrode materials are investigated. The charging current decays with time according to t^-n (decay constant) with the value of index n in the range of 0.66 to 1.25. The discharging current decreases with the value of n in the range of 1.47 to 1.59 for the temperature range investigated. The dielectric loss factors at low frequency were evaluated from the absorption currents. For temperature up to 90°C one broad peak is observed at frequencies around 3×10^-4 Hz. For temperatures (>120°C) the magnitude of the loss factor increases by an order of magnitude and no peaks are observed. Results on conduction currents are also reported for temperatures 90-200 °C and fields up to 100 kV/cm. The activation energy of 0.70 eV and the ionic jump distance in the range 19-28 nm have been evaluated.