Curing kinetics of UV-initiated cationic photopolymerization of divinyl ether photosensitized by thioxanthone

摘要

Photodifferential scanning calorimetry was used to investigate the photocuring kinetics of UV-initiated cationic photopolymerizations of 1,4-cyclohexane dimethanol divinyl ether (CHVE) monomer with and without a photosensitizer, 2,4-diethylthioxanthone (DETX), in the presence of a diaryliodonium-salt photoinitiator. Two kinetics parameters, the rate constant (k) and the order of the initiation reaction (m), were determined for the CHVE system with different amounts of added DETX photosensitizer (0-1 wt %) and at different isothermal temperatures (25-55 degrees C) using an autocatalytic kinetics model. The photosensitized CHVE system exhibited much higher k and m values than did the nonphotosensitized system, which was attributable to the effects of photosensitization. Furthermore, the values of k and m for both CHVE systems increased significantly with increasing isothermal temperature because of a thermal contribution toward increasing the mobility of active species. The addition of DETX lowered the activation energy for the UV-curable vinyl ether system. The collision factor for the system with DETX was higher than that obtained for the system without DETX, indicating that the reactivity of the former was greater than that of the latter because of the photosensitization effect. (c) 2005 Wiley Periodicals, Inc.