Ambient temperature and UV-cured hybrid coatings from acetoacetylated non-isocyanate polyurethanes

Preparation of ambient and UV curing non-isocyanate polyurethane (NIPU) coatings has been reported using a series of acetoacetylated non-isocyanate polyurethane (AA-NI-PUPO) oligomers. Synthesized oligomers were characterized using various techniques such as Fourier transform infrared and nuclear magnetic resonance spectroscopy. AA-NI-PUPOs showed significantly lower viscosity compared to their non-acetoacetylated counterparts. Ambient temperature-cured systems were formulated by mixing AA-NI-PUPOs and different primary amine compounds in stoichiometric proportions. Michael addition reaction of acrylates and AA-NI-PUPOs was initiated by UV curing using a photobase generator as the catalyst. NIPU coatings were studied for various thermo-mechanical properties and corrosion resistance. The selected UV-cured and ambient-cured samples showed instant and 1-h tack-free time, respectively. Results revealed that with proper selection of acetoacetylated resin and crosslinker type, coatings with properties comparable to conventional PU coatings could be formulated. Moreover, UV-curable coatings with up to 90 wt% solid could be formulated using conventional monomeric acrylates as a reactive diluent. The study demonstrates the feasibility of formulating solvent-free rapid ambient curing non-isocyanate polyurethane coatings.