Oyster-Inspired, Fast-Drying, Robust, and Multifunctional Waterborne UV-Curable Coating via Phosphate Chemistry Strategy

The development of waterborne ultraviolet light (UV)-curable coatings is crucial for reducing air pollution and mitigating human health hazards. However, conventional waterborne polyurethane acrylate (WPUA) UV-curable coatings suffer from a long initial drying time and inferior mechanical properties, limiting their applications. Herein, inspired by the rapid underwater curing and exceptional adhesion of oysters, we propose an innovative phosphate chemistry strategy to design a low-VOCs emission, fast drying, and robust WPUA UV-curable coating. Specifically, calcium dihydrogen phosphate (CDP) was integrated into the synthesized WPUA dispersions by using ultrasonic and homogenization techniques. CDP rapidly absorbed water through hydration and released moderate heat to improve the drying rate. The resulting phosphate hydrate crystals formed organic–inorganic hybrid networks and ionic chelation with the WPUA, enhancing the coating’s mechanical properties. At 1.2% CDP content, the WPUA@CDP coating achieved a 53% reduction in drying time, a 100% increase in hardness (reaching 2H), a 10% improvement in wear resistance, and a 167.86% increase in tensile strength. The coating exhibited low-VOCs emissions (27.3 g/L, well below 250 g/L regulatory limit) and enhanced flame retardancy, with a 53% increase in critical heat flux, reaching the B1–C level for building materials. This study demonstrates a simple, eco-friendly, and versatile approach to improving the production efficiency and performance of waterborne coatings.