AbstractElectrical properties, such as dissipation factor and electric conductivity, were studied for silicone rubber sheets. The specimens were prepared by the reaction of α,ω‐dihydroxypolysiloxane with ethoxysilane, using dibutyltin dilaurate as a catalyst, at a relative humidity of about 100 at various temperatures and for various reaction times. It was found that the electrical properties were a function of the vulcanizing conditions; i.e., the further the vulcanization proceeded, the higher the dissipation factor and the electric conductivity. A reaction describing deterioration in electrical properties was then considered. Infrared spectroscopic studies on dibutyltin dilaurate showed that the dibutyltin dilaurates were partly hydrolyzed to lauric acid and dibutyltin dihydroxide. It was concluded that electrical property deteriorations, which were caused by changes in the vulcanizing conditions, were due to dibutyltin dilaurate hydrolysis. However, since the decomposed products were finally oxidized at elevated temperatures in an oxygen atmosphere, with a subsequent change to electrically inactive compounds, the initial electrical properties were recove
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