Efficient reduction of photopolymerization shrinkage stress through microporous particles templated from Pickering emulsion droplets

Photopolymerization of acrylate based resin is a rapid, efficient and low-energy curing process that is achieving wide applications in many industrial fields. However, the volumetric shrinkage and the shrinkage stress of the cured resin have long been the major factor reduces adhesion strength of UV curable coatings onto the substrate. In this paper, the Pickering emulsion template method is employed to prepare elastic microporous particles with well-defined surface and internal structures and these microporous particles are thus added into the UV curable resin formulation to verify their capability to reduce polymerization stress through the microporous structure. The gel point time of UV-curable materials is delayed by 11 s with 1.5 wt% addition of the microporous particles and the double bond conversion at the gel point is subsequently increased. By real time MIR-photo-rheology and 3D line scanning laser confocal measurement, it is found that addition of microporous particles into the resin formulation can reduce the volume shrinkage of the resin by 61.2 % with only 1.5 wt% microporous particles, while the excellent mechanical and thermal properties of the cured resin is basically maintained.