The Study on Surface Properties of Nanoparticle-Modified Microcapsules

The cracking of electrical insulation materials seriously influences the modern life due to the wide application of electricity. It would consume large amounts of manpower resources, material resources and financial resources when the broken electrical insulation materials were replaced. The poly (urea-formaldehyde) microcapsules containing dicyclopentadiene were doped into electrical insulation materials for cracks self-healing. But the microcapsules was easily broken due to the insufficient thickness of shell wall. Therefore the wall materials needed to be modified so that the microcapsules could meet certain properties requirements. In this paper, nanoalumina and nanosilica were added respectively to modify the shell wall in the process of preparing microcapsules. The surface properties of microcapsules were studied. The surface morphology, roughness and wall thickness of microcapsules were observed with scanning electron microscopy and optical microscope. The particle size distribution was measured with laser particle size analyzer. The results demonstrated that the average particle size of microcapsules doped with nanoalumina was biggest. The average particle size of microcapsules modified by nanosilica was slightly smaller than pure microcapsules without doping nanoparticles. In addition, microcapsules with a nanocomposite shell wall were more rough and had bigger thickness comparing with unmodified microcapsules in the shell wall. However, the outer surface of microcapsules doped with nanoalumina was more rough than the microcapsules doped with nanosilica while the result of the inner surface was opposite. The thickness of microcapsules doped with nanoalumina was biggest, and the thickness of microcapsules doped nanosilica was bigger than the pure microcapsules. According to the further analysis of the mechanism, it was deduced that there were crosslinking reactions between nanoparticles and the active groups of poly (urea-formaldehyde), and it promoted more poly (urea-formaldehyde) debris to crosslink into the shell wall. The results have a great role in promoting the improvement of the microcapsules in the shell wall, and provide a new idea for further research.