Polybutylene succinate, a kind of biodegradable polymer, shows thermally stimulated polarization current (TSPC) peaks at around -35 °C and 50 °C. The lower-temperature TSPC peak can be well explained by dipolar polarization. As for the higher-temperature TSPC peak, the permittivity increases more significantly with a decrease in frequency, and the increment in permittivity estimated from the TSPC area agrees with the difference in permittivity at a sufficiently low frequency and at a sufficiently high frequency. It is assumed that a hetero charge layer is formed in front of the two electrodes and that such space charge is responsible for both the higher-temperature TSPC peak and the permittivity increase. The dielectric loss factor also increases with a decrease in frequency, and the increment is in good agreement with the assumption that the dielectric loss is ascribed to conduction loss due to high conductivity at high temperatures. All the results indicate that mobile ions are dominant carrier species in polybutylene succinate.
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