Greener approach for fabricating transparent silica glass components through DLP using aqueous based photocurable suspensions
MA B. 1, TATAMI J. 2, IIJIMA M. 2
1 Graduate School of Engineering Science, Yokohama National University, Yokohama, Japan; 2 Faculty of Environment and Information Sciences, Yokohama National University, Yokohama, Japan
Fabrication of transparent silica glass components through additive manufacturing process using photo-curable suspensions have attracted large attention due to its wide possibility in structural design. Typical process for the design of photocurable suspensions involves the dispersion of reagent silica powders into a mixture of monomer and solvents with photo-radical initiators. However, these suspensions require the usage of organic solvents and extremely long post firing process in debinding and sintering to avoid structural collapse due the thermal decomposition of large monomer contents. In order to design more greener and safer process, here, we propose an aqueous based photocurable silica suspensions with low monomer (binder) content. The newly designed suspension involves the dispersion of SiO2 fine particles into aqueous media with the aid of hydrophilic polyethyleneimine (PEI) followed by the addition of a small amount of water-soluble monomers and photo-radical initiator. Through the flow curve measurement and continuous monitoring of the storage modulus of the designed suspension before and after photoirradiation, the high dispersion stability and an effective photocuring behavior was confirmed. The microstructural observation of the photocured bodies revealed that the diameters of the particles were slightly and uniformly increased and a necked structures were formed among the particles. Based on the FTIR and TGA analysis of silica powders collected from the suspensions before and after photoirradiation, we estimate that 4-HBA were first attached on PEI modified silica particles during suspension preparation, and then a polymerized shell of 4-HBA were formed on silica particles after photo-irradiation. A successful photocuring was achieved when the overlaps of the polymeric shells have occurred in highly concentrated suspensions having small interparticle distances. Finally, we demonstrate that the designed suspensions can be applied to digital light processing (DLP)-based 3D printing, followed by rapid drying/firing process to fabricate complex structured transparent SiO2 glass components.