シリコーン油 : ポリプロビレン複合絶縁系の界面現象

Abstract

In this paper, thermally stimulated currents (TSC) in silicone oil, biaxially stretched polypropylene (PP) films and their composed insulating systems have been investigated. The influence of the oil/PP interaction (such as swelling) on TSC has been discussed. Four and three TSC peaks were found in silicone oil and PP film, respectively, and their origins were discussed. The oil-immersed PP film having thin oil layer between a PP film and an electrode showed remarkable TSC peaks at 50 and 80℃, suggesting that they were due to interfacial polarizations. From the comparison of the peak temperatures of TSC with those mechanical losses, the TSC at 50 and 80℃ are considered to be related to the upper glass transition and the α relaxation of PP, respectively. This suggests that these two peaks are due to carrier traps in the amorphous parts restrected by crystallities and in the crystalline parts in the PP surface regions adjacent to oil, respectively. The dependences of TSC spectra upon impregnating temperature and viscosity of silicone oil showed a close correlation with the swelling of polypropylene obtained from the thoretical equilibrium equation for swelling.