Influence of Water and Silanol Contents on Some Electrical Properties of Silicone Oil

The precise measurement of water in silicone oils is difficult owing to the reaction of water with siloxane to give silanols. In this paper we report kinetic and equilibrium measurements of the water and silanol content in 50 cSt silicone oils from different manufacturers. Using various techniques, we show that the water content in silicone oil varies linearly with relative humidity. The silanol content was deduced and is never less than 80 to 150 ppm in dry oil; it increases nonlinearly with RH. The influence of water and silanols on several electrical properties of silicone oil is also discussed.