Waterborne bio-based UV-thermal dual-curable coatings with excellent mechanical properties and thermal resistance based on citric acid modified epoxidised soybean oil

Abstract

Waterborne bio-based UV-curable coatings have attracted enormous attentions due to their environment friendliness and safety. However, residual neutralizing agents, long-chain aliphatic hydrocarbons derived from epoxidised soybean oil, and the oxygen inhibition inherent in the UV curing process often cause poor thermal resistance and mechanical properties of the epoxidised soybean oil-based waterborne bio-based UV-curable coatings. Herein, the epoxidised soybean oil was hydrophilized by citric acid and poly (ethylene glycol) diglycidyl ether without the use of neutralizing agents. The hydrophilized epoxidised soybean oil was subsequently compounded with bisphenol A epoxy resin to prepare high-performance waterborne bio-based epoxy methacrylates. Finally, a high-performance waterborne bio-based UV-thermal dual-curable coating was obtained by blending waterborne bio-based epoxy methacrylates with waterborne isocyanate curing agent. The results demonstrated that waterborne bio-based epoxy methacrylates possess high bio-based content, low viscosity, and remarkable storage stability. Furthermore, waterborne bio-based UV-thermal dual-curable coatings with high cross-linking density exhibited outstanding mechanical properties and thermal resistance. For example, the waterborne bio-based UV-thermal dual-curable coatings P0805I4 exhibits a breaking elongation of 30.75%, maximum tensile strength of 16.68 MPa, T10% at 285.33 °C, and adhesion class level of 0. Our research not only introduces high-performance waterborne bio-based UV-thermal dual-curable coatings, thereby extending the application domains of soybean oil-derived waterborne bio-based coatings, but also presents a valuable strategy for advancing high-performance, sustainable, waterborne, and environmentally friendly materials.