Synthesis and properties of UV-curable waterborne urethane modified acrylic coatings with varying vinyl content

It has been an effective method to improve the metal protective performance of UV-curable waterborne coatings by increasing the crosslinking degree. Hence, a series of UV-curable waterborne urethane modified acrylic (UV-WUA) coatings with different vinyl content were prepared. Firstly, a functional prepolymer containing carboxyl and hydroxyl groups was synthesized by free radical copolymerization (FRCP) using acrylic acid (AA), 2-hydroxyethyl acrylate (HEA), methyl methacrylate (MMA) and butyl acrylate (BA). Next, it was grafted with different amounts of semi-adduct of isophorone diisocyanate (IPDI) and HEA (IPDI-HEA), and finally neutralized and hydrated, obtaining UV-WUA dispersions which were then cured by UV to acquire cured films and coatings. Meanwhile, molecular structures, molecular weights, particle sizes, and Zeta potentials were characterized. Then, the heat resistance, mechanical performance, adhesion and the pencil hardness of the coatings were also investigated. Moreover, their protective performance was tested by electrochemical methods, and the surface morphology was analyzed by atomic force microscopy. The results showed that the coating had desirable comprehensive performance when vinyl content reached 0.86 mmol·g⁻¹.