Permittivity and electrical breakdown response of nylon 6 to chemical exposure

Environmental stress such as unintended exposure of aircraft wire insulation to aviation-related fluids is one cause of wire aging that increases the risk of electrical failure. In this paper, the dielectric properties of nylon 6, a common wire insulation material, were investigated under chemical exposure for up to 8 days in six fluids: distilled water, cleaning fluid, isopropyl alcohol, deicing fluid, jet fuel and hydraulic fluid. Real permittivity (ε') and dissipation factor (D) of aged samples were measured using an LCR meter over frequency range from 100 Hz to 1 MHz in an ambient environment (23 °C). It was found that ε' and D of aged nylon 6 exhibit distinct shifting behavior according to the polarity of the fluids in which it is immersed. Immersion in polar fluids gives rise to a strong effect of fluid absorption on the increase of polarizability of nylon 6, showing significant increase in ε' and D, along with moving of relaxations to higher frequencies. Electrical breakdown strength of nylon 6 was also observed to reduce dramatically following exposure to polar fluids. A two-parameter Weibull distribution was applied to analyze the distribution of electrical weak sites in chemically-aged nylon 6 and it is concluded that a different electrical breakdown mechanism could be responsible for the narrower distribution observed after polar chemical exposure than for the pristine material. Nylon 6 displayed resistance to aging in non-polar fluids, showing no significant change in complex permittivity and electrical breakdown strength.