LOSS AND RECOVERY OF HYDROPHOBICITY ON RTV COATING SURFACES

Studies are reported on decay and recovery of hydrophobic properties o n clean and contaminated surfaces of silicone rubber based RTV coating . Treatment that led to hydrophobicity losses were water immersion and water condensation with and without a presence of dc electric field. Contact angles (receding angles) and surface leakage currents were mea sured on the treated surfaces. A suppression of the leakage current wa s observed and its link to the diffusion of the low molecular weight f raction from the polymer bulk and dry band arcing is discussed. Attemp ts aiming to restore the lost hydrophobic properties are also describe d. As a means of recovery, resting at ambient atmosphere, under UV irr adiation, and in vacuum at elevated temperature, was applied. The effi ciencies were verified through measurements of receding angles, surfac e leakage currents, and thermally stimulated depolarization currents.