Dielectric Properties of PTFE Wiring Insulation as a Function of Thermal Exposure

The study of polymers used in electrical insulation of wiring is important to the aerospace industry due to potential loss of life and aircraft in the event of an electrical fire caused by breakdown of wiring insulation. In this work, the effect of thermal exposure on the permittivity of PTFE is studied in order to examine the feasibility of developing of a capacitive nondestructive testing method to indicate the presence of a significant defect in the wiring insulation, following thermal exposure, by measuring its permittivity. Measurements of permittivity, obtained using a Novocontrol dielectric spectrometer with a temperature-controlled sample cell, reveal a significant reduction in permittivity as a function of duration of heat exposure at 360degC. The capacity of PTFE samples was also measured over the frequency range 1 Hz to 1 MHz at various temperatures from -150 to 300degC.