자외선경화형 자가광개시 아크릴레이트의 경화특성 연구

Abstract

Self-photoinitiating acrylate(SPIA) which can undergo self-initiation under UV irradiation was synthesized by a Michael donor (e.g. ethyl acetoacetate) with a Michael acceptor (e.g. hexanediol diacrylate) in the presence of a base catalyst. The SPIA polymerizations were investigated by photo-differential scanning calorimeter (photo-DSC) and surface physical properties such as pendulum hardness and pencil hardness. The results showed that the SPIA can cure upon UV irradiation by itself without a photoinitiator. But we found out that both the curing rate and the conversion were too low for the self-curing reaction of SPIA. In order to have the SPIA curing properties improved, we introduced the SPIA/cationic hybrid system and observed the effects of the addition of commercial free radical type monomer, photoinitiator and sensitizer on the curing behaviors. The experimental data revealed that the polymerization reactivity and the ultimate conversion were enhanced by the addition of monomer, sensitizer and Norrish I type photoinitiator. SPIA/cationic hybrid system was the best suitable to improve the SPIA curing properties. The kinetic analysis indicated that the cationic monomer and photoinitiator apparently accelerated the cure reaction and rate of the hybrid SPIA system, mostly due to the synergistic effect of cationic monomer and photoinitiator increasing the mobility of active species and the generation of reactive species (free radical, cation) during the photopolymerization process. The physical properties showed that, unlike typical free radical system, the hybrid systems did not show oxygen inhibition effect because of cationic reaction on the coating surface.