Ketocoumarin/triazine/thiol as new high speed photoinitiating system for free radical polymerization under visible light in aerated media

This paper describes the development of a new photoinitiating system for free radical photopolymerization of a multifunctional acrylate monomer under visible light in aerated condition. A ketocoumarin dye is combined with a 1,3,5-triazine derivative as co-initiator, to produce initiating radical species that trigger the polymerization reaction. Aliphatic thiols are combined with the dye-triazine system to overcome the oxygen inhibition, and the effect of thiol concentration and functionality is examined. Photopolymerization kinetic data, as obtained from RT-FTIR spectroscopy experiments, show that the relative photopolymerization rates are not affected by the presence of oxygen. Indeed, the photoinitiation process remains highly efficient in aerated as well as in laminated conditions. The photochemical mechanisms involved in this three components system is investigated by laser flash photolysis.