Non-Destructive Assessment of Thermally Aged Polyimide Films Using Electrical Properties

This paper investigates the evolution of the electrical properties of polyimide (PI) films subjected to thermal aging in air at 280° C for up to 60 days. Two non-destructive electrical techniques-dielectric spectroscopy and DC conductivity measurements-were employed to characterize degradation behavior at different aging stages. The dielectric spectroscopy results reveal progressive changes in permittivity and dielectric losses with aging, associated with the evolution of interfacial polarization and dipolar relaxation. In parallel, DC conductivity measurements indicate a monotonic increase in charge transport, suggesting the accumulation of mobile carriers during thermal degradation. These findings provide experimental evidence and physical insight into the electrical aging behavior of PI films under high-temperature conditions relevant to aerospace applications.