Preparation and performance of UV curable polyurethane coating for metal surfaces

During the last 20 years, UV curable coating has achieved fast growth in the coating market. Growth of UV coatings have grown from their first application in furniture coatings to embrace many industries viz. electronics, printing and automotives due to its fast production rates, low temperature cure and reduction in volatile organic compounds (VOC). However, it faces problem regarding viscosity, in the conventional UV – cured coating system, the reactive diluents are used to reduce the viscosity. Here, we have used renewable resources in the preparation of polyurethane acrylate (PU) coatings to reduce VOC. A series of UV – curable Polyurethane acrylate prepolymers were synthesized by reacting Polyols from sesame oil (edible) using different ratio of Polyols, aromatic isocynate, and aliphatic isocynate, 2-Hydroxy ethyl methacrylate, (2-HEMA) and dibutyl tin dilaurate as a catalyst. UV curable polyurethane acrylate was formulated using reactive monomer as a diluent and Benzophenone as a photointiator. These coatings are cured by Ultra Violet radiation (Medium Pressure Mercury Lamp (200 Watt/inch) (280-360nm).The study of mechanical and chemical properties of cured resin films showed that hardness, and impact resistance increases with increase in cross link density (XLD). This could be due to increase in interaction of reactive monomers to the resin which increases number of double bonds and hence the XLD.