Preparation and properties of UV curable rosin-based polyurethane coatings

Ultraviolet (UV)-curable coatings were prepared using rosin-based polyurethane as an oligomer with different active diluents and crosslinking monomers. The effects of different components level on the properties of the polyurethane coatings were investigated, and the effects of the mass ratio of the active diluents, crosslinking monomers, adhesion promoting monomers, photoinitiators, and curing times on the polyurethane coatings were discussed. The results showed that when hydroxypropyl acrylate was used as an end-capping agent, 40% of methyl methacrylateas a reactive diluent, 10% of dimethylol propane tetracrylate as a crosslinking monomer, 7% of hydroxyethyl diacrylate phosphate as an adhesion promoter, 4% of 1173 as a photo-initiator, and a curing time of 120 s. UV-curable resin exhibited the best coating properties: pendulum hardness of 0.63, 60 degrees gloss of 153.9, adhesion of grade 2, impact strength of 500 J m-2, and the water resistance exceeding 30 days.