Increase of spatiotemporal resolution and reproducible layer thicknesses in cationic vat photopolymerization

Abstract

In this paper, the 3D DLP printing of an epoxy-based material controlled by pyridine derivatives was investigated. The impact of the pyridine structure and concentration on the cationic polymerization kinetics was explored. An increase of the inhibition time and a decrease of the heat flow were observed and attributed to the trapping of the initiating species and the stabilization of the growing chains. This allows for the confinement of the polymerization process and limits the presence of lateral defects around the printed objects. Furthermore, the validity of the Jacobs law was discussed. Due to the photoinitiator photolysis, an increase in the penetration depth was observed in relation to the solidification delay. A model was developed to relate the change of the printed layer thickness to the applied light dose, taking this phenomenon into account. This led to a more precise determination of the critical energy.