High-Performance Soybean-Oil-Based Epoxy Acrylate Resins: “Green” Synthesis and Application in UV-Curable Coatings

Novel soybean-oil-based (SBO-based) epoxy acrylate (EA) resins were developed via ring-opening reaction of epoxidized soybean oil (ESO) with hydroxyethyl methacrylated maleate (HEMAMA) precursor, a synthesized unsaturated carboxylic acid having two active C═C groups and a side methyl group. Experimental conditions for the synthesis of the precursor and the SBO-based EA (ESO-HEMAMA) product were studied, and their chemical structures were confirmed by FT-IR, 1H NMR, 13C NMR, and gel permeation chromatography. Subsequently, the volatility of HEMAMA was studied and compared with acrylic acid (AA). Furthermore, gel contents and ultimate properties of the UV-cured ESO-HEMAMA resins were investigated and compared with a commercial acrylated ESO (AESO) resin. At last, UV-curing behaviors of the SBO-based EA resins were determined by real-time IR. It was found that the HEMAMA precursor showed much lower volatility than AA, and the optimal pure ESO-HEMAMA resin possessed a C═C functionality up to 6.02 per ESO and biobased content of 65.4%. Meanwhile, the obtained ESO-HEMAMA biomaterials exhibited much superior properties as compared to the AESO resin. For instance, the obtained pure ESO-HEMAMA material possessed a storage modulus at 25 °C of 1.00 GPa, glass transition temperature (Tg) of 70.1 °C, and tensile strength and modulus of 13.4 and 592.1 MPa, which were 9.4, 3.6, 6.9, and 15.7 times the values of the pure AESO material, respectively. The resulting biomaterial with 30% of hydroxyethyl methacrylate diluent even reached a tensile strength of 28.4 MPa and Tg of 89.0 °C. Therefore, the developed SBO-based EA resins are very promising for applications in UV-curable coatings.