Siloxane-Modified UV-Curable Castor-Oil-Based Waterborne Polyurethane Superhydrophobic Coatings

In recent years, superhydrophobic coatings with self-cleaning abilities have attracted considerable attention. In this study, we introduced hydroxyl-terminated polydimethylsiloxane (OH-PDMS) into castor-oil-based waterborne polyurethanes and synthesized silicone-modified castor-oil-based UV-curable waterborne polyurethanes (SCWPU). Further, we identified the optimal amount of OH-PDMS to be added and introduced different amounts of micro- and nanoscale heptadecafluorodecyltrimethoxysilane-modified SiO₂ particles (FAS-SiO₂) to prepare rough-surface SCWPU coatings with dense micro- and nanostructures, thus realizing waterborne superhydrophobic coatings. The results show that when the OH-PDMS content was 11 wt% and the total addition of FAS-SiO₂ particles was 50% (with a 1:1:1 ratio of 100 nm, 1 µm, and 10 nm particles), the coatings exhibited a self-cleaning ability and superhydrophobicity with a contact angle of (152.36 ± 2.29)° and a roll-off angle of (4.9 ± 1.0)°. This castor-oil-based waterborne superhydrophobic coating has great potential for waterproofing, anti-fouling, anti-corrosion, and other applications.