UV radiation curing of epoxidized palm oil–cycloaliphatic diepoxide system induced by cationic photoinitiators for surface coatings

Epoxidized palm oil (EPO) can be cured with ultraviolet (UV) radiation using either radical, cationic or hybrid initiation. Cationic curing system has been chosen in this study due to the fact that epoxy groups present in EPO can be utilized directly to form cross links. Curing was carried out in a 20 cm wide UV IST machine. Triaryl sulphonium salts and ferrocenium salt were used as cationic photo initiators. Formulations were developed based on selected grades of EPO. Other materials employed included different types and concentrations of photo initiators, monomers and photo-sensitizer. The effect of post-cure conditions was also studied. The properties of the cured film, namely, pendulum hardness, percentage of gel content and tensile strength were determined. It was found that triarylsulphonium hexafluorophosphate exhibited low solubility in EPO. Addition of a vinyl ether monomer to the formulation did not enhance pendulum hardness and gel content of the cured films. Post-cure temperature had no significant effect on the properties of the cured film. The FTIR studies showed evidence of the ring opening of the epoxide groups present in the formulation.