Investigation of termination reactions in photoinitiated radical polymerisation of UV powder coatings

The termination mechanisms occurring in a UV-powder coating system during photopolymerization process are investigated and compared to a conventional acrylate monomer system. First, the photoinitiator concentration, viscosity and conversion of the monomer effects on the termination reaction occurring in photopolymerization of a bifunctionnal acrylate are assessed leading to the study of curing kinetics of an UV-powder urethane diacrylate based system. It will be shown that termination could occur mainly by Primary Radical Termination. This mechanism could be related to low reactive double bonds concentration and high photoinitiator concentration in the UV-powder resin. Moreover, environmental effect, will point out the role of oxygen effect on polymerization mechanisms.