Quantitative analysis of hydrophobicity loss due to electric field strength

Hydrophobicity and the ability to recover hydrophobicity after loss are the base of an outstanding operation behaviour of silicone as insulating material. The imperfect understanding of the fundamentals of hydrophobicity loss and recovery stems from the difficulty of separating the various direct and indirect mechanisms. Measurements of the static contact angle of surfaces stressed with vertical electric field prove the influence of the electric field on hydrophobicity loss. On the other hand no significant influence on hydrophobicity can be observed after ageing the surface using electric field stress parallel to the silicone surface. These results will form the basis for a physically based model for interpretation of hydrophobicity loss and recovery. The results provide the opportunity for systematic investigations concerning hydrophobicity loss and recovery comparison of different surfaces, because of the high reproducibility of the electric field compared to the more stochastic behaviour of partial discharges. With this knowledge suitable testing methods can be developed to evaluate long term hydrophobicity behaviour.