Influence of accelerated aging on dielectric properties of extruded Nylon 6 film

Thermal degradation is one major cause of wire aging, increasing the risk of electrical failure. Further, exposure of wire insulation to fluids commonly used on aircraft may also compromise the dielectric performance of wire insulation. In this paper, the dielectric properties of Nylon 6, a common wire insulation material, are investigated under various conditions of accelerated aging. Thermal exposure below the melting point (220°C) for up to 20 hours was performed on extruded Nylon 6 films, and chemical exposure was conducted for up to 8 days in six fluids: jet fuel, deicing fluid, hydraulic fluid, cleaning fluid, isopropyl alcohol and distilled water. Real permittivity (ε') and dissipation factor (D) of aged samples were measured using parallel plate electrodes and an Agilent E4980A LCR meter over frequency range from 100 Hz to 1 MHz in an ambient environment (23°C). The results show that both ε' and D decrease significantly in a short thermal exposure time (1 hour) but do not exhibit significant time dependence in the longer term. The dielectric relaxation of Nylon 6 changes according to the type of fluid in which it is immersed, falling approximately into two classes according to whether or not the fluid is polar in nature. Following immersion in non-polar fluids (hydraulic fluid and jet fuel) the observed change in ε' and D is small, whereas large increases in these parameters are observed following exposure to polar fluids: water, isopropanol, cleaning fluid and deicing fluid. Dielectric breakdown strength was observed to reduce dramatically following exposure to polar fluids.