| Acrylic latex with various classes, low price and excellent performance is one of representative emulsion polymers, which is widely applied in chemical materials, spin, leather, etc. However, acrylic latex has some disadvantages, for exemple difficultly forming film in low temperature, easily returning viscidity in high temperature and low hardness. Therefore, the performance of acrylic latex need to be impoved urgently.In the paper, the nano-SiO2/(acrylic resin) composite latex was synthesized by in- situ emulsion polymerization of methyl methacrylate(MMA) and butyl acrylate(BA) in the presence of silica nanoparticles, which were modified by silane coupling agent (SCA). The effect of processing parameter on the modification of silica nanoparticles, the technology parameter of composite latex prepared, the structure and performance of composite latex, the thermal stability of the hybrid film formed by the composite latex and the performance of coatings prepared by the composite were studied.Firstly, after modification with silane coupling agent, the silane is grafted onto the surface of silica nanoparticles to form the organic layers, which can efficiently prevent the silica nanoparticles from aggregating and lead to individually homogeneous dispersion in the in-situ emulsion polymerization. Additionally, at polymerization conditions, the silane layers further improve the compatibility of silica nanoparticles with the acrylate monomers. The proper processing was that pH is 3～4; reaction temperature was 80℃; reaction time was 120 min and the addition of silane coupling agent was 10wt%.Secondly, according to the theory of designing materials, the structure of nano-SiO2/(acrylic resin) composite latex was designed and the recipe and processing of composite latex was reserached. Then the composite latex was prepared and the polymerization mechanics was discussed.Thirdly, the chemical structure of nano-SiO2/(acrylic resin) composite latex was measured by FT-IR spectroscopy. It can be seen that the FT-IR spectrum of composite latex has all the characteristic bands of nano-silica and pure polyacrylate latex but was not simply a combination of both the FT-IR spectra. Theζpotential of composite latex is negative, which is as the same as theζpotential of pure polyacrylate latex. Meanwhile, the value ofζpotential of composite latex approximates the value of pure polyacrylate latex. Possibly the reason is that silica nanoparticles are not isolated but encapsulated in the center of composite latex. In addition, comparison with the particle size distribution of silica nanoparticles and nano-SiO2/(acrylic resin) composite latex is in good agreement with the result. The viscosity of the composite latex is not changed and then is rising rapidly as the content of silica particles increase, but the viscosity is fixed as the graft ratio of silica nanoparticles increase. At last, the performance of the composite latex is as same as the acrylic latex. Fourthly, the thermal stability of the hybrid film formed by the nano-SiO2/(acrylic resin) composite latex was investigated by fourier transform infrared spectrometer (FT-IR), atomic force microscopy (AFM) and thermogravimetric analysis (TGA). Then the theory of thermal stability was analysed and the active energy was obtained by the theory of kinetics. Lastly, according to the recipe and process of traditional coatings, the coatings were prepared with the nano-SiO2/(acrylic resin) composite latex. Consistence of coatings flim is enlarged by the raise of degree of cross linking, which improves the weather resisting property and pollution resistance of the coatings. The stability in low temperature, contrast ratio, water resistance, alkali resistance, pollution resistance, wash resistance and weather resistance reach or exceed the premium grade in Chinese Standard.
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