Silicone rubber with improved hydrophobicity

In outdoor insulation, a hydrophobic surface is crucial for minimizing leakage currents during severe weather conditions and in polluted environments. Silicone rubber is a commonly used insulation material with good hydrophobicity. However, the hydrophobicity may be temporarily reduced or even lost when silicone rubber worked under extreme pollution events, but will gradually recover with time. The current work is aiming at developing a silicone rubber formulation with improved hydrophobicity, such as increased hydrophobic recovery rate. This was achieved by adding silicone-based additives. The loss and recovery of hydrophobicity of the materials after exposure to corona discharges, as well as the hydrophobic transfer ability, were assessed by contact angle measurements. In addition, an inclined plane tracking test was carried out according to IEC 60587. The modified silicone rubber exhibited a more durable hydrophobicity during corona treatment and a faster recovery after end of exposure. The resistance to tracking and erosion behavior was maintained, compared to the reference materials. Unexpectedly, no improvement on the hydrophobicity transfer performance was noted.