Enabling fast debinding of ceramic vat photopolymerization prints with supercritical carbon dioxide as a solvent

Abstract

Thermal debinding of 3D-printed ceramics that include a large fraction of polymeric binders, can take several days to perform, and often includes a long thermal pre-conditioning step. In addition, means to reduce the manufacturing time are limited. This applies for thermal debinding of dense ceramics, such as dental restorations, that have been printed using vat photopolymerization (VPP) based technologies. The thermal debinding of such ceramics can be made faster, more economical, and more ecological by extracting selected slurry components prior to thermal debinding. Thus, creating flow channels for pyrolysis gases originating from the remaining binder polymers to exit the material. Here, supercritical carbon dioxide (scCO2) extraction was used to create such gas flow channels and to study which slurry components can be dissolved from VPP printed polymeric and ceramic/polymeric parts without significant delamination, cracking, or part deformation. The scCO2 extraction resulted in the creation of significant 33 vol% of nanosized porosity in a pure polymeric as-built print, and 21 vol% of nanosized porosity in a ceramic/polymeric composite print, where the ceramic powder remains in the part. These gas flow channels may allow faster thermal debinding while avoiding the creation of other defects. In the process, 90 wt.-% of the dissolvable resin fraction was extracted from the ceramic/polymeric prints already in 2 h without significant delamination, while 70 wt.-% of the dissolvable resin fraction was extracted in 2 h from the pure polymeric prints as a reference. This presents a novel, successful demonstration of a chemistry that allows both VPP printing and scCO2 extraction.