It is shown that such variables as filler, voltage, insulation wall and temperature exert significant influence on the electrical properties of silicone rubber-insulated wire when subjected to prolonged water-immersion tests. By proper filler selection, silicone rubber insulation can be obtained which will display improved stability under wet conditions. Voltage rating is dependent upon two variables--desired wall thickness and required immersion temperature. Long-term immersion demonstrated that silicone rubber has limited electrical stability in water as temperatures are increased. Compounds passed accelerated testing in water up to 70C. The stability of silicone rubber compared favorably with that of butyl rubber at that immersion temperature. It seems possible that silicone rubber could also withstand testing in 75C water. However, power cable insulation of silicone rubber, as presently compounded, cannot be recommended as resistant to accelerated testing in 90C water for more than short periods of time.
Annual Wire and Cable Symposium (Annual), Asbury Park, N. J., December 3, 1958. Prepared in cooperation with General Electric, Co.