Inhibiting liquid permeation into silicone rubber by superhydrophobic coating for prolonged service life

Liquid permeation into silicone rubber (SR) may lead to the degradation or complete failure of the composite insulators. Aiming to inhibit liquid permeation, two kinds of superhydrophobic coatings are applied to the SR surface. The liquid permeation properties of SR with different types of liquids are investigated, and the Langmuir diffusion model is applied to analyse the experimental data. The results show that the composite superhydrophobic coating can effectively inhibit liquid permeation by reducing the contact area between the surface and liquid, and the stable structure of the composite coating can maintain the performance after the liquid permeation and effusion. However, the nano-particle coating without the polymer binder experiences severe performance degradation during the immersion test, and it cannot restrain the liquid permeation anymore after it loses the superhydrophobicity. As a validation of the effective protection, the insulation resistivity change was measured. The resistivity decreases sharply for the pristine SR after water permeation; however, the decrease is much smaller for the coated SR. The current study not only provides new insight into the liquid permeation properties of SR with different surface wettability but also suggests an effective measure to prevent liquid permeation into SR.