Mechanism-Guided Spray Deposition of Rutile TiO₂/Epoxy/ODTMS Superhydrophobic Coatings for Weather-Resistant Bamboo...

Bamboo is a renewable and mechanically robust bio-based material with potential for sand-barrier construction; however, its long-term outdoor use is limited by ultraviolet-induced photoaging, moisture uptake, wind-sand abrasion, and biological colonization. In this study, a fluorine-free EP/TiO₂/ODTMS superhydrophobic coating was deposited on moso bamboo using a simple spraying process. Rutile TiO₂ was incorporated as a roughness-building and ultraviolet-shielding filler, waterborne epoxy resin served as a film-forming binder to improve particle anchoring and coating cohesion, and octadecyltrimethoxysilane was used to reduce the surface energy. The formulation containing 50-100 nm rutile TiO₂ and 2 wt.% epoxy resin provided the best overall balance between surface wettability and mechanical durability, with a water contact angle of 156.4° and a sliding angle of 6.9°. SEM observations revealed a hierarchical surface composed of TiO₂ particles and microscale agglomerates immobilized within the epoxy matrix. EDS and FTIR results supported the incorporation of TiO₂- and ODTMS-derived components, while UV-Vis-NIR diffuse-reflectance measurements showed an improved optical response in the ultraviolet region. The coating retained superhydrophobicity after sandpaper abrasion, gravel impact, and tape-peeling tests. After 672 h of xenon-lamp aging, the coated bamboo maintained a water contact angle above 150°, exhibited a total color difference of approximately 7.65, and retained 91.1% of its initial flexural strength. In addition, qualitatively reduced visible mildew colonization was observed during 45 days of high-humidity exposure. These results demonstrate that the spray-deposited coating provides a fluorine-free and potentially scalable approach for improving the water repellency, mechanical durability, and accelerated-weathering resistance of bamboo sand-barrier materials.