Biobased reactive diluent for UV-curable urethane acrylate oligomers for wood coating

Castor oil (CO)-based reactive diluent for UV-curable urethane acrylate oligomers was synthesized by the reaction of a CO with diethanolamine and the resultant product was subsequently reacted with allyl chloroformate. The reactive diluent was characterized by FTIR and 1H NMR techniques. This reactive diluent was incorporated in a urethane acrylate oligomer and photoinitiator at different weight fractions varying from 5 to 25 wt% for UV curing. The effects of reactive diluent concentrations on the viscosity of the formulations along with mechanical, chemical, and optical properties of UV-curable coatings were studied. Furthermore, the cured films were evaluated for glass transition temperature (Tg) determined by differential scanning calorimetry and thermal stability by thermogravimetric analysis. Gel content and water absorption of UV-cured films were evaluated.