Characterizing photopolymer resins for high-temperature vat photopolymerization

The availability of engineering polymers for vat photopolymerization (VP) additive manufacturing is limited. This limitation primarily stems from the inability of standard VP systems to recoat high-viscosity resins (> 3 Pa s). High-temperature vat photopolymerization is a new process-based VP platform that enables processing of viscous photopolymer resins (viscosity > 3 Pa s). Research in this area has been focused on demonstrating expanded access to new polymer families, and studying the effect of printing temperature on mechanical and esthetic performance of printed parts. However, methods to determine the printing temperature that prevents the occurrence of thermally induced polymerization (i.e., thermal stability) in the resin have not been established. In this work, the authors have applied characterization techniques such as thermogravimetric analysis, Rheology and differential scanning calorimetry to determine the printing temperature for processing viscous photopolymer resins. As a case study, the developed characterization techniques are applied to: (1) photopolymer that is solid at room temperature, (2) polymer with viscosity of 21 Pa s at room temperature, and the temperature at which the resins can be printed without triggering thermally induced polymerization is successfully determined. The results of this work will act as a materials’ characterization and process parameter development guide for high-temperature VP systems, thus enabling expansion of VP materials catalogue to engineering materials that were previously unprocessable.