Dual-Layered SiO₂ Nanoparticles and Epoxy Polymers for Self-Cleaning Coatings on Ceramic Glaze

Nonflushing urinals show promising potential in saving millions of gallons of water every year. The recalcitrant nature of ceramic surfaces poses a big challenge in creating an additional layer to repel urine. In this study, a greatly strengthened polymer self-cleaning coating was successfully covered on a smooth glaze surface via a dual-layered, micro/nanohybrid configuration. The first layer was built up as a base matrix that provides microsized roughness and connection with the second layer, which provided superhydrophobic groups. The hierarchical architecture of the microstructure on the first layer and nanostructure on the second layer displayed an interlocked interaction to protect the functional groups, thus leading to an enhanced mechanical stability. The spray-coated glaze displayed a high hydrophobicity with a water contact angle (CA) of about 150°. The coating still showed a CA of about 130° over 2300 cycles upon sandpaper abrasion and a CA of >139.6° after 500 finger rubbing cycles. Under a high water flux of 179 Gph flushing, a high CA of 134.6° after 168 h was maintained. When immersed in 1.8 wt % urea solution, the CA was as high as 146° after 50 days. In the strong acid/alkaline solution with a wide pH span ranging from 1.0 to 14.0, the coating still showed a high chemical stability with a CA of >145°. The surface also showed a CA of ∼129° after 760 detergent cleaning cycles. In addition, the antibacterial property reduced the use of disinfectants for sterilization. The dual-layered coating design using a scalable spray method opens pathways in creating a strong self-cleaning coating on commercially available ceramic surfaces.