Enhancing UV Photopolymerization by a Red‐light Preirradiation: Kinetics and Modeling Strategies for Reduced Oxygen Inhibition

Abstract

ABSTRACTA novel strategy for red‐light‐controlled oxygen inhibition for improved UV‐light‐initiated monomer conversion is theoretically presented for the first time. The dual‐wavelength kinetic equations are derived, numerically and analytically solved for the oxygen and photoinitiator concentration profiles. The UV‐light‐initiated Type I conversion efficacy is an increasing function of its concentration (C20) and the light dose at transient state, but it is a decreasing function of the light intensity, scaled by [C20/I20]0.5, at steady state. In contrast, the red‐light‐initiated Type II efficacy is mainly dose dependent. Longer red‐light preirradiation time (TP) leads to a shorter UV‐light TID of UV‐light conversion, which is strongly red‐light dose dependent, rather than intensity dependent. The numerical new finding is also predicted by the analytic formulas showing that oxygen and monomer conversion are strongly red‐light dose dependent in a Type II mechanism. Finally, strategies for controlled initiation–inhibition switch based on two mechanisms, (a) oxygen inhibition for improved conversion and (b) radical inhibition for spatial confirmation in 3D printing, are presented. To conclude, UV‐light conversion could be improved by a red‐light preirradiation and more importantly and could be customizely tailored by the controlled induction time. UV‐light photopolymerization conversion could be improved by a red‐light preirradiation and could be customizely tailored by the controlled induction time. The UV‐light‐initiated Type I conversion efficacy is an increasing function of its concentration and the light dose at transient state, but it is a decreasing function of the light intensity at steady state. In contrast, the red‐light‐initiated Type II efficacy is mainly dose dependent. Longer red‐light preirradiation time leads to a shorter UV light. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 683–691