Effect of Oxygen Inhibition on the Kinetic Constants of the UV-Radical Photopolymerization of Diurethane Dimethacrylate/Photoinitiator Systems

The kinetic constants of propagation (k(p)) and termination (k(t)) for a diurethane dimethacrylate/l-hydroxycyclohexyl phenyl ketone (Irgacure 184) system were measured using a dark polymerization technique that employs real-time FT-IR spectroscopy to measure the conversion and reaction rate of the methacrylate group at different time points. The sample was placed between two optically polished KBr plates with a 10 mu m metal spacer. A series of measurements resulted in a gradual peak in the kinetic constants at a 0.15 conversion of the methacrylate group. The kinetic constants for the conversion, which ranged from 0.15 to 0.5, were used to obtain the parameters of the Anseth-Bowman model to generate a numerical simulation of the photopolymerization kinetics. The kinetic equations, the oxygen inhibition reaction-diffusion equation, and the macroradical mass balance model indicated that the gradual peak in the kinetic constant was caused by an oxygen inhibition reaction. The Anseth-Bowman model for k(p) and k(t) was effective even if oxygen inhibition occurred, when the oxygen inhibition reaction-diffusion equation was employed.