Real-Time Cure Monitoring of UV-curable Systems by Using Dielectric Analysis and Infrared Spectroscopy

In the present work, the photopolymerization kinetics has been studied by real-time infrared spectroscopy (RT-FTIR) and in situ dielectric analysis (DEA) . We were able directly correlate the dielectric properties of resins studied and the monomer conversion during the irradiation time. By monitoring changes in the electrical properties of the UV curable formulation, the polymerization rate and cure extent can thaus be determined in real-time. Dielectric analysis has become an effective instrumental method for monitoring a variety of polymer resin processing properties. This is because the dielectric properties are sensitive to the changes of resins properties linked to the mobility of the polymer molecules. A linear correlation was found between the dielectric loss factor and acrylate or epoxy monomer conversion for radical or cationic photopolymerization reactions. By this technique, for the same sample, others properties can also be monitored in on-line processing, such as the diffusion properties in coating films and the effect of moisture, the temperature, the viscosity, the Tg and the shrinkage. DEA measurements are especially attractive because information they have the potential of providing fundamental information on the curing processes and can be performed on-line in UV-curing industrial applications.