| In recent years, the development of high-performance water-based coatings with low cost becomes the mainstream of coatings industry. The process to make the polymer nanometer-hybrid materials is the one of most important methods in the preparation of the high performance polymer material. Conventional polyacrylate emulsion has many deficiencies, such as "hot sticky and cold brittle" and poor water resistance, etc. Organic silicon/nano-SiO2modified acrylic composite emulsions, which exhibit an ensemble of properties of good water resistance, excellent thermal stability and weather resistance, have a wide range of potential applications such as coating, adhesives, paints and leather finishing agent, etc. The research of using inorganic nanoparticles and silicone modified acrylic emulsion has become increasingly active in recent years, and there will be good prospects of development because its excellent comprehensive performance.Firstly, in this paper, polyacrylate emulsion with hard core and soft shell structure was synthesized by soap-free emulsion polymerization and core-shell emulsion polymerization with MMA and BA as the main raw material. The influence of core-shell ratio, reaction temperature, varieties and dosage of emulsifier on emulsion properties was investigated. Choosing two kinds of polymerizable anionic and nonionic emulsifiers (SW-102/DNS-86) as composite emulsifiers, and their consumption was4%, the mass ratio of them (SW-102/DNS-86) was2:1, the ratio of core-shell was40:60, the reaction temperature was75～78℃, the total reaction time was6h, the mass of redox initiator (KPS/SHS) was0.5%and the ratio of KPS/SHS was3/2, the core-shell polyacrylate emulsion with good properties was made.Secondly, on the basis of optimal conditions of the study on pure core-shell polyacrylate emulsion, choosing the appropriate organic silicon monomer and different form nano-SiO2modified polyacrylate emulsion in the process of polymerization. Silicone/nano-SiO2modified polyacrylate composite emulsion with good polymerization stability could be obtained according to following conditions:2%A-174organic silicon was dropped into the system with30%shell monomer after pre-emulsion, SiO2 nanoparticles were obtained from1%TEOS via sol-gel process, the reaction temperature was75～78℃and the stirring speed was200r/min. We obtained the stable silicone/nano-SiO2modified polyacrylate composite emulsion with high solid contend of53%, high conversion rate of96.2%and the average particle size of160.4nm.Thirdly, Those polymers structure were characterized by Differential Scanning Calorimeter (DSC), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectoscopy (FT-IR) and Thermogravimetric Analysis(TGA). The DSC curves showed that both core-shell polyacrylate emulsion and composite emulsion were two glass transition temperatures (Tg), while the conventional polyacrylate emulsion only one glass transition temperature; the TEM showed that both core-shell polyacrylate emulsion and composite emulsion particles exhibited an apparent core-shell structure; FT-IR confirmed the organic silicon and nano-SiO2were effectively grafted to the polyacrylate molecular chain; TGA confirmed the composite emulsion film had better thermal stability compared with those of conventional polyacrylate emulsion.Finally, conventional polyacrylate emulsion and core-shell polyacrylate emulsion were compared in the viscosity, solid content and other aspects of performance. Moreover, composite emulsion and a commercially available BASF emulsion were compared in the solid content and other aspects of performance. The results showed that the core-shell polyacrylate emulsion possess better water resistance, lower viscosity and good film-forming performances than conventional polyacrylate emulsion; Composite emulsion owns higher solid content, smaller particle size and better water resistance than BASF emulsion. |
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