Photo-Curing Kinetics of 3D-Printing Photo-Inks Based on Urethane-Acrylates

In this study, photo-curing kinetics for urethane-acrylate-based photo-inks for 3D printing were evaluated using a photo-differential scanning calorimetry analysis. Initially, the photopolymerization kinetics of di- and monofunctional monomers were separately studied at different temperatures (5-85 degrees C). Later, the photo-curing kinetics and mechanical properties of photo-inks based on different monomer mixtures (40/60-20/80) were evaluated. The results showed that urethane-dimethacrylate (UrDMA) and urethane-acrylate (UrA) had no light absorption in the region of 280-700 nm, making them a proper crosslinker and a reactive diluent, respectively, for the formulation of 3D-printing photo-inks. The kinetics investigations showed a temperature dependency for the photo-curing of UrDMA, where a higher photopolymerization rate (R-p,R-max: from 5.25 x 10(-2) to 8.42 x 10(-2) 1/s) and double-bound conversion (DBCtotal: from 63.8% to 92.2%) were observed at elevated temperatures (5-85 degrees C), while the photo-curing of UrA was independent of the temperature (25-85 degrees C). Enhancing the UrA content from 60% to 80% in the UrDMA/UrA mixtures initially increased and later decreased the photopolymerization rate and conversion, where the mixtures of 30/70 and 25/75 presented the highest values. Meanwhile, increasing the UrA content led to lower glass transition temperatures (T-g) and mechanical strength for the photo-cured samples, where the mixture of 30/70 presented the highest maximum elongation (epsilon(max): 73%).

Automated summary

The photo-curing kinetics and mechanical properties of urethane-acrylate-based photo-inks were evaluated in this study. It was found that the photopolymerization of urethane-dimethacrylate was temperature dependent, while the photopolymerization of urethane-acrylate was independent of temperature. The composition of the monomer mixture also influenced the photopolymerization rate and conversion, as well as the glass transition temperature and mechanical strength of the cured samples.