Underwater UV-Curable Resin from Lac Terpenic Acid: Transforming Shellac Waste into Multifunctional Coating

Lac terpenic acid (LTA), obtained from shellac processing waste, is a sustainable biomass for high-performance materials. We converted LTA into an underwater UV-curable resin via acrylation and copolymerization with glycidyl methacrylate (GMA). UV curing underwater accelerated polymerization six-fold compared to that in air, producing coatings with smoother surfaces. At 40 wt% GMA, the coating (LGM0.4) achieved lap-shear strength of 6.66 MPa, bending strength of 14.64 MPa, and tensile strength of 9.22 MPa. It also resisted corrosion from acids, alkalis, high temperatures, etc., and adhered strongly to steel, aluminum, PVC, and glass. Furthermore, it integrated multiple functionalities including hydrophobicity with a water contact angle of 107°, self-cleaning and stable orange fluorescence under 365 nm UV irradiation. This work offers a practical and scalable approach to convert shellac waste into high-performance coatings.