Electrical conduction in aromatic polyamides

Electrical conduction in the aromatic polyamides commercially known as Nomex or HT-1 film is studied over a temperature range of 50-200°C and electric-field strengths up to 400 kV-cm^-1 over a time range of 1-60 min. This material has excellent thermal and mechanical properties, making it suitable for high-temperature application. Conduction currents were measured as a function of electric-field strength and time of application of voltage in as-received films 75-125 μm thick. Measurements were also carried out on specimens which were heat-treated for 6 h at 260°C. Thermally treated samples yielded lower but more reproducible currents. At low electric fields the conductivity is independent of the applied-electric-field strength or its polarity, suggesting that it is ohmic. At higher field strengths (10-300 kV-cm^-1) the current is a function of both the time of application and the magnitude of the field strength. The conduction currents measured at various constant electric-field strengths are examined in the light of Schottky, Poole-Frenkel, and ionic conduction mechanisms. The latter is shown to yield reasonable results if suitable assumptions are made for some of the parameters