Aging of silicone rubber materials in marine environment

Silicone rubber samples of 4 material compositions have been energized with AC and DC voltages in a coastal outdoor environment. During the test, leakage current measurements together with visual inspections were used to monitor their performance. The samples were selected according to a 2/sup 3/ factorial test plan, where electrical stress, content of ATH-filler and content of silicone oil were the factors. Chemical analyses were performed on the samples after 18 months of electrical aging. Surface consumption of ATH was studied by reflection infrared spectroscopy. Changes in surface roughness were characterized by scanning electron microscopy. Different behavior between the AC and DC energized samples were found, in the electrical performance during the test and in the chemical analyses afterwards. Addition of silicone oil improved the long-term electrical performance. High level of ATB filler increased, initially, the leakage current activities. However, it was the samples with the highest level of filler which best preserved their hydrophobicity.