Controllable preparation of isophorone diisocyanate microcapsules with silica/polyurea hybrid shells and application in self-healing epoxy coatings

Isophorone diisocyanate (IPDI) microcapsules with silica/polyurea hybrid shells were successfully synthesized via interfacial polymerization and in situ polymerization in an oil/water emulsification system. The micromorphology and surface silicon species-modified microcapsules were studied by scanning electron microscopy and X-ray photoelectron spectroscopy. The components of the microcapsules were analysed by Fourier transform infrared spectroscopy. The resultant microcapsules have diameters of 76.5 ± 16.5 μm, shell thicknesses of approximately 2.3 μm, and core fractions of 76.5 wt%. Meanwhile, the thermal stability, storage stability and solvent resistance of the microcapsules were evaluated. The results showed that silica/polyurea microcapsules had excellent thermal stability with the initial decomposition temperature, increasing by approximately 92 °C compared with that of polyurea microcapsules. More than 65.0 wt% active core fraction of silica-modified microcapsules was reserved after six months in air or 40 days in water. The microcapsules were incorporated into epoxy resin coatings. The scratch and self-healing test of the coatings proved that the silica-modified microcapsules healed the scratch successfully.