Modeling concentration-dependent oligosiloxane diffusion for tangential hydrophobicity transfer

Hydrophobicity transfer is a key property of anti-pollution flashover coatings, making hydrophobicity transfer materials (HTM) essential in outdoor insulation for power systems. Uneven aging during operation, as well as structural designs aimed at balancing coating durability and anti-pollution flashover performance, can lead to the formation of HTM patterned surfaces. Tangential hydrophobicity transfer has been clearly observed on these surfaces. However, current studies and models do not provide a quantitative explanation for this phenomenon, which limits the understanding of their characteristics and optimization of their design. To address this gap, this study fabricated an HTM/glass patterned surface with a single hydrophilic/hydrophobic interface and performed tangential hydrophobicity transfer tests under artificial pollution condition. The results showed a logarithmic relationship between transfer distance and HTM interface width. Based on the experimental phenomena, a tangential diffusion model for oligosiloxane was proposed, and the concentration-dependent diffusion coefficient was calculated using Boltzmann-Matano method. Additionally, a finite element model was developed to simulate the hydrophobicity transfer process with high precision. Together, the HTM hydrophobicity transfer characteristics identified in this study, combined with the proposed oligosiloxane diffusion model and the finite element model of the patterned HTM surface, advance the theory of hydrophobicity transfer and establish a new foundation for the interpretation and design of patterned surfaces.