Vinyl-terminated photoactive citric acid derivatives for fabricating hard yet flexible soybean oil-based UV-curable coatings

Soybean oil-based UV-curable coatings are important for green and sustainable materials. However, achieving simultaneous high hardness and flexibility in the soybean oil-based UV-curable coatings is challenging, and the preparation of these coatings often requires petroleum-based reactive diluents that are harmful to the environment and human health. In this study, vinyl-terminated photoactive citric acid derivatives are synthesized to replace the petroleum-based reactive diluents for fabricating soybean oil-based UV-curable coatings. The vinyl-terminated photoactive citric acid derivatives contain numerous hydroxyl groups, which enhance the polarity and cohesion strength of the polymer molecule. Therefore, the hardness, elastic modulus, flexibility, and impact resistance of the soybean oil-based UV-curable coatings prepared by replacing 50 % trimethylpropane triacrylate with the trifunctional vinyl photoactive citric acid derivatives reach 3 H, 2197.10 MPa, 5 mm, and 45 cm, respectively, which are better than the soybean oil-based UV-curable coatings using the trimethylpropane triacrylate as reactive diluents. The prepared vinyl-terminated photoactive citric acid derivatives can not only reduce the use of petroleum-based reactive diluents but also improve the performance of soybean oil-based UV-curable coatings. This study also provides a novel approach for fabricating bio-based UV-curable coatings integrated with high hardness and flexibility. • Vinyl-terminated photoactive citric acid derivatives are prepared. • Citric acid derivatives reduce the usage of petroleum-based reactive diluents. • Citric acid derivatives are utilized in soybean oil-based UV-curable coatings. • The coatings are integrated with high hardness and flexibility. • The reactivity of citric acid's three carboxyl groups with epoxy groups varies.