Polysulfone/SiO2 Hybrid Shell Microcapsules Synthesized by the Combination of Pickering Emulsification and the Solvent Evaporation Technique and Their Application in Self-Lubricating Composites

Lubricant oil-filled polysulfone/SiO2 (PSF/SiO2) hybrid shell microcapsules are prepared by the combination of Pickering emulsification and the solvent evaporation technique. Silica particles are used as stabilizers. The structure and properties of the microcapsules are influenced by the silica particle concentration, agitation speed, and encapsulation temperature. The formation of PSF/SiO2 hybrid microcapsules is confirmed by a scanning electron microscope, Fourier transform infrared spectroscopy, and thermal gravimetric analysis. The resulting microcapsules prepared at the optimum synthetic parameters show a spherical, ideal structure with a rough outer surface, mean diameter of 5.0 +/- 0.6 mu m, shell thickness of 0.83 mu m, core content of 50.5 wt %, and excellent thermal stability with an initial evaporating temperature of 250 degrees C. The synthesized microcapsules are embedded into epoxy for application in self-lubricating composites. Investigated by friction and wear tests, the tribological properties of the self-lubricating microcapsule-incorporated epoxy composites attain a significant improvement.