Superhydrophobic nanocomposite coatings for electrical insulators

The polysiloxanes in question were a trimethoxy (2,2,4-trimethyl pentyl)-based silane; a mixture of methyl methoxy siloxane with methylsilsesquioxane; a mixture of dimethyl siloxane, methylsilsesquioxanes and n-octyl silsesquioxanes.

The polysiloxane properties were investigated by thermogravimetric (TGA) and hydrophobic (contact and sliding angles) analysis, indicating great differences on thermal properties and surface free energy. The polysiloxane binders were loaded with different sizes of microsised alumina trihydrate (ATH) and organophilic nanosilica functionalised with octyl-silane and polydimethylsiloxane (PDMS). Afterwards, the effectiveness of these materials as coatings for glass electrical insulator was evaluated.

Reducing the formation of conductive surface paths

Test results showed that the polysiloxane based on a mixture of methyl methoxy siloxane with methylsilsesquioxanee loaded with ATH and PDMS-treated silica exhibited the most promising characteristics as high contact angle, self-cleaning ability, good adhesion to the substrate and low number of leakage current peaks during the tracking and erosion resistance test. As the researchers point out, such characteristics can bring benefits on electrical insulators like reducing the formation of conductive surface paths and the consequent degradation of the coating by dry band arcs, increasing its resistance when exposed to the electric field.

The study has been published in Progress in Organic Coatings, Volume 168, July 2022.