Water-based Polyurethane / Modified Nano-silica Composite Coatings

In this paper, according to the high surface activity of nano-particles, nano- SiO₂ wasmodified by TDI activation method and coupling agent grafting method respectively.Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA)results demonstrated that the nano-SiO₂ was combined with the grafted organic viachemical bonds. And a larger grafting ratio was obtained via TDI activation method. Fromtransmission electron microscopy (TEM) images, it can be observed that stable sterichindrance layer was established on the surface of nano-particles after the graftingmodification. The dispersibility of the modified nano-particles was increased, and thecompatibility between the nano-particles and the polyurethane matrix was also improved.Waterborne polyurethane emulsion was prepared by prepolymer mixing process andaceyone process. The effects of change of dimethylolpropionic acid (DMPA) content andR (NCO/OH) value on the properties of emulsion and adhesive were researched. Nanocompound coating was prepared by adding non-modified and modified nano-SiO₂ intowaterborne polyurethane coating. The cohesion, hardness, wear property and resistance towater, acid and alkali of the waterbome polyurethane coating were estimated in order tocontrast the coating performances modified by different grafting methods. The resultsshowed all of these properties were improved to some extent, and the properties of nanocompound coating changed with the variation of filling ratio. The preferred modificationmethods and the preferred filling ratio of each kind particles were educed by comparingdifferent kinds of properties.