Soy-based UV-curable thiol-ene coatings

Novel soy-based thiols and enes were synthesized and characterized. Then, soy-based thiol-ene UV-curable coatings were formulated and their coating physiochemical properties were investigated in detail. The use of biorenewable resources, combined with environmentally friendly UV-curable technology, provides a green + green solution to the stricter regulations in the coatings industry. Novel soy-based thiols and enes were synthesized through the Lewis acid-catalyzed ring opening reaction of epoxidized soybean oil with multifunctional thiols or hydroxyl functional allyl compounds. FTIR and NMR confirmed the formation of the target compounds. The soy-based thiols and enes were formulated with petrochemical-based enes and thiols, respectively, to make thiol-ene UV-curable coatings. Typical coating film properties, thermal properties, and photopolymerization kinetics of these coatings were studied. Soy-based thiol-ene coatings having lower functionality thiols and enes have poor UV curability and coating properties, which was attributed to the lower crosslink density. Soy-based thiols and enes with higher functionality can be UV-cured in combination with petrochemical-based enes or thiols even without the presence of free radical photoinitiators. Better coating film properties were obtained from these higher functionality thiol-ene systems that were toughened by commercial hyperbranched acrylates.