Photocuring behavior of interparticle photo-cross-linkable Pickering emulsions designed for shaping porous silica materials by DLP
TSUTAKI S. 1, YAMANOI Y. 1, TATAMI J. 1, IIJIMA M. 1
1 Yokohama National University, Yokohama, Kanagawa, Japan
Fabrication of porous ceramic components by stereolithography-based routes using photocurable emulsions will be a promising process due to the high flexibility in structural design. However, typical emulsion systems requires long and slow dewaxing/partial sintering of photocured bodies due to the large quantity of monomers/binders used to maintain the strength of photocured green bodies. Here, we propose two series of interparticle photo-cross-linkable Pickering emulsions, which are designed to be photocurable using reduced amounts of monomer to enable rapid post heating process. The effects of emulsion composition on their photocuring behaviors and printability using digital light processing (DLP) are discussed. The first emulsion was designed by mixing an aqueous dispersion of polyethyleneimine (PEI) modified silica particles treated with small amounts of water-soluble acrylate and photo radical initiator as continuous phase and isopropyl myristate (IPM) as dispersed phase. The second emulsion was designed by mixing an DMSO/water dispersion of functionalized PEI modified silica particles treated with small amounts of di-functional acrylate and photo radical initiator as continuous phase and IPM as dispersed phase. Although both interparticle photo-cross-linkable Pickering emulsions found to be photocurable in a complex structured silicone molds and further processable under rapid heating conditions for drying, dewaxing, and partial sintering without occurring structural collapse, the real-time monitoring of storage modulus of the emulsions under light irradiation revealed that the former emulsion possesses a time delay (c.a. 20 s) in photocuring after light irradiation which was not favorable for layer-by-layer DLP. We suspect this curing delay was due to the light capture in the dispersed phase occurred by higher refractive index of dispersed phase. By using the latter emulsion composition which did not occurred a curing delay, a complex structured porous silica bodies were successfully printable by DLP followed by rapid drying, debinding, and sintering.