The Effect of Temperature on the Kinetics of UV Curing Studies by Real-Time FTIR-ATR Spectroscopy

Real-Time FTIR spectroscopy was used to study the effect of temperature on the kinetics of UV curing from room temperature up to 160°C. Irradiation was performed at 313 rim to simulate the emission of a XeCI excimer lamp. Various acrylates and photoinitiators were used to study the influence of the viscosity and the effect of the initiator on the polymerization rate, the induction period, and the ultimate conversion. In highly viscous formulations, the polymerization rate distinctly increases with temperature due to the drop of viscosity, whereas in systems with low viscosity, the polymerization rate only little increases or is even independent of temperature.
Depending on the type of photoinitiator used, termination processes can lead to a decrease of the polymerization rate at higher temperatures. The induction period decreases due to the decreasing solubility of oxygen in the reactive formulation. However, in systems showing a decay of the polymerization rate, it re-increases at higher temperatures.