Curing Kinetics of Methacrylate and Dual-Cure Interpenetrating Polymer Network (IPN) Resins for UV-Curable Additive Manufacturing via In-Situ Raman Spectroscopy

Curing kinetics of photopolymerizable resins are important for determining the printing parameters for resin-based additive manufacturing. Most traditional methods of analyzing the chemical and structural dynamics, such as photo-differential scanning calorimetry or infrared spectroscopy, can be difficult to perform in situ, but Raman spectroscopy is ideally suited for such studies. Here, we used non-contact Raman spectroscopy to better understand the curing kinetics of fully methacrylate resins, dual-cure interpenetrating epoxy-methacrylate polymer networks (IPNs), and chemically connected IPNs. We also investigated resins amendable for UV-assisted direct ink write printing to elucidate the effects of rheological modifiers. Peaks at 1640 cm^-1 and 915 cm^-1 were monitored to track methacrylate and epoxy conversion, respectively, and the disorder band around 15 cm^-1 and torsional band around 85 cm^-1 were monitored to determine the “structural kinetics” of the polymers, independent of chemical functionality. These results were fitted to a model to experimentally determine the kinetic rate constant, order, and ultimate conversion, all critical parameters for optimizing additive manufacturing processes.