Multi-physics simulation and experimental study of the reaction kinetics process of oxygen inhibition zone formation in constrained-surface stereolithography process

Abstract

In this paper, based on the mechanism of oxygen inhibiting the curing of acrylate-based monomers, the reaction kinetics model for the formation of the oxygen inhibition zone is established. This model is applied to study the variation of the thickness of the oxygen inhibition zone with the process parameters and the microscopic characteristics of the constrained substrate with the PDMS film as the oxygen permeation window. Experiments are performed on substrates with different micropore area ratios, and the experimental results are in good agreement with the simulation. The research results show that the thickness of the oxygen inhibition zone can be up to 28 µm while the thickness of cured layer can be over 140 µm. The thickness of the oxygen inhibition zone increases with the increasing PDMS film diffusion coefficient, oxygen concentration, constrained substrate area ratio, and micropore size, but decreases with the increasing light intensity, photoinitiator concentration, and PDMS film thickness. When the micropore area ratio are too small, or the micropore diameter is too large under the same area ratio, an obvious periodic microstructure will appear on the surface of the cured layer, affecting the quality of the cured layer surface. The reaction kinetics multi-physics model for the formation of inhibition zone in constrained-surface stereolithography process has been established, considering the photopolymerization reaction kinetics and the effect of oxygen polymerization inhibition, as well as the influence of the substrate’s micropore array and PDMS film’s characteristics on oxygen mass transfer during polymerization. The effects of factors such as the microscopic characteristics of the substrate and the oxygen diffusion coefficient of the PDMS film on the inhibition zone have been investigated. Photopolymerization experiments are performed on substrates with different micropore area ratios, and the experimental results are in good agreement with the simulation. The research results show that the thickness of the oxygen inhibition zone can be maintained at 28 µm under reasonable control parameters, while the thickness of cured layer can be over 140 µm, meeting the requirement of achieving the minimum oxygen inhibition zone for continuous printing. • The reaction kinetics multi-physics model for the formation of inhibition zone has been established. • The effects of factors on the inhibition zone have been investigated. • Photopolymerization experiments are performed and the experimental results are in agreement with the simulation. • The optimized parameters meet the requirement of achieving the minimum oxygen inhibition zone for continuous printing.