Robust superhydrophobic coatings from modified siloxane resin

Abstract

Superhydrophobic coatings were produced from a modified siloxane resin that served as the low-surface energy (LSE) material needed to make superhydrophobic coatings. The authors used nanosilica to provide the desired surface texture needed for superhydrophobicity. They hypothesized that chemically bonding the LSE material to the surface of nanosilica will improve the durability of the coating. The mixture of nanoparticles and LSE material was applied on an aluminum surface, and it was heated to 150°C. A tin catalyst was employed to increase the reaction rate. The Fourier transform infrared spectra confirmed the chemical reaction between nanosilica and resin. The results showed that the coatings had contact angles higher than 150°C and a contact angle hysteresis (CAH) of less than 8°. The mechanical robustness of the coatings was investigated by an abrasion test. The CAH of the coatings with the catalyst after the abrasive test was 12°, while this angle was 22° without the catalyst. The coatings indicated good water/ultraviolet (UV) durability – for example, the CAH after UV treatment was 8°. Superhydrophobic coatings were applied using two different methods: spin-coating and spray-coating. For each application method, the weathering durability and mechanical properties of the coatings were compared. Considering the overall data, spray-coating is better than spin-coating in the terms of durability.