Surface component of vacuum absorption and resorption currents in polymers. III. A source of dielectric loss

Abstract

For pt.II see ibid., vol.13, p.639 (1980). It is shown that, for a commercial co-polymer of hexafluoropropylene and tetrafluoroethylene, lateral charge transfer between the aluminium electrode edge and the immediately adjacent polymer surface dominates the dielectric loss currents in the frequency range 32 Hz-3.2 kHz. As a result the measured tan delta values vary with the electrode diameter. The variation decreases if the sample is allowed to age in air before dielectric loss measurements are made. This could be due to the formation of a thin oxide film on the aluminium electrode, and a decreasing probability of electron/hole tunnelling through the film as its thickness increases.