Effect of hyperbranched acrylates on UV-curable soy-based biorenewable coatings

Utilization of biorenewable components in UV-curable coating formulations is both economically and environmentally beneficial, particularly when compared to their petrochemical-based counterparts. To produce UV-curable coatings of high biorenewable content with enhanced performance, acrylated epoxidized soybean oil (ASBO) was combined with biorenewable reactive diluent tetrahydrofufurylacrylate, adhesion promoters, photoinitiator and hyperbranched acrylates (HBAs) as synthetic tougheners. The HBAs were found to impart high functionality and low viscosity, thus increasing crosslinking in the coating network and improving mechanical and thermal properties such as film hardness, adhesion, solvent resistance, impact resistance, tensile modulus and toughness, glass transition temperature and thermal stability. Real-time Fourier transform infrared spectroscopy showed decreased acrylate conversion when compared with a reference formulation without HBAs, which was attributed to earlier coating network vitrification during UV irradiation. ASBO-based coatings were also thermally annealed to allow further reaction of unreacted components in the vitrified network. As a result, coating properties were further improved. Overall, the addition of HBAs as synthetic tougheners to UV-curable ASBO-based biorenewable coating systems was shown to greatly improve the corresponding coating properties. (C) 2010 Society of Chemical Industry