硅橡胶绝缘介质的分子链运动与电极极化特性

Silicone rubber (SiR) possesses outstanding electrical characteristics, and its dielectric properties are easily affected by molecular chain motion and electrode polarization. We employed infrared spectroscopy and X-ray photoelectron spectroscopy to analyze the functional group and element in SiR specimen. Then, the glass-transition temperature was measured as a value of -123℃ owing to different scanning calorimetry (DSC). Frequency domain spectroscopy (FDS) was applied to detect the dielectric relaxation process in SiR at different temperatures. According to the FDS results the relaxation process α & δ caused by molecular chain motion could be observed on a high-frequency domain, while the DC conductivity induced by ion drift appeared on a low-frequency domain, particularly, an electrode polarization process appeared apparently on low frequency domain at high temperatures (140~200℃). The relaxation process α & δ caused by molecular chain motion followed the Cole-Davidson relaxation function, based on which the dielectric relaxation intensity and relaxation time distribution at different temperatures were calculated. Besides, the relaxation time constant of relaxation process α & δ as a function of reciprocal temperature obeyed the Arrhenius equation, with an activation energy of 0.10 eV and 0.14 eV respectively. Then, according to the Macdonald model, the polarization electrode process in SiR was analyzed, and corresponding parameters such as the free ion density, Debye length, free ion mobility, and diffusivity at different temperatures were obtained. The temperature dependency of free ion mobility obeyed the Arrhenius equation, with an activation energy of 0.39 eV. At last, the thermal stimulated depolarization current (TSDC) was applied to confirm the existence of relaxation process α & δ and electrode polarization.