Depth-Of-Cure Study and Printing Resolution Analysis of Stereolithography 3D Printing Resins*

Stereolithography (SLA) is a 3D printing method of polymer resins using photoinitiated polymerization. We have studied how the photopolymerization characteristics of SLA photocurable resins affect the 3D printing resolution and mechanical properties. The characteristics include the depth-dependent UV polymerization kinetics. In particular, real time FTIR (RT-FTIR) with attenuated total reflectance (ATR) sample stage was used to study the UV penetration depth effects on the photopolymerization kinetics in terms of the rate of polymerization and monomer conversion at different UV irradiation times and intensities. Three types of commercially available FormLab SLA resins are compared for the study of printing resolution and depth-of-cure characteristics. Additional tuning of depth-of-cure characteristics has been performed by mixing additional photoinitiators or inhibitors. Post UV-curing on the 3D printed samples is performed to further manipulate their mechanical properties with an aim to elucidate how the network structure in SLA samples affect the stress-strain behavior of thermosets under tensile elongation. The layer curing process and morphology has been also investigated by DSC and microscopy.