Modifications of dielectric properties of polyamides induced by long-term exposure to corona

Long-time exposure of polyamides to energetic discharges and oxidizing gases can cause modifications of their dielectric properties. To quantify the effect, samples of pure and filled polyamides were aged in a corona treatment system. The corona induced changes in complex permittivity of both materials were investigated utilizing frequency domain dielectric spectroscopy. It was found that both the real and imaginary parts of the complex permittivity increased after the treatment, especially at low frequencies. This was associated with increased dc volume conductivities measured for both materials. The experimental data were analyzed by using a model incorporating Havriliak-Negami dipolar relaxation, dc conduction and low frequency dispersion for identifying the most affected by corona treatment processes.