| Polyacrylate/nano-SiO2composite materials combine the advantages of polyacrylate including good film appearance, weather resistance, adhesion and those of inorganic nanometer powder including rigidity, abrasion resistant, UV-shielding property, and so on. So it is widely used in many fields such as coatings, adhesive, optical-electric materials, and so forth. In this paper, nano-SiO2is prepared and its surface is modified, and then polyacrylate/nano-SiO2composite emulsion is prepared through miniemulsion polymerization method. Preparation and surface modification of nano-silica and the influence of the addition of nanosilica on the properties of composite emulsion and films was studied. The main contents of this thesis are as follows:1. The properties, preparation method and modification method of nano-SiO2particles were reviewed. The properties, preparation method and applications of nano-SiO2/polyacrylate composite emulsion were introduced. It also provided a kind of design idea that studying the application properties of nano-SiO2/polyacrylate composite emulsion prepared through miniemulsion polymerization method as coating and other materials.2. With tetraethoxysilane as silicon source, monodisperse nano-SiO2microspheres were prepared by phase-inversion microemulsion method. To improve its dispersivity and compatibility of nano-SiO2microspheres in organic medium, silane coupling agent KH-570was used to modify the surface of nano-SiO2. The influence of the amount of modifier, reaction temperature and reaction time on modification effect were discussed. The result showed that the lipophilicity of modified nano-SiO2is enhanced and its dispersivity in organic medium is significantly improved. The optimum surface modifiction conditions:mass fraction of modifier is6%of the quantity of SiO2; reaction temperature is91o℃; reaction time is5h.3. The acrylate/nano-SiO2composite emulsion were prepared through miniemulsion polymerization of nano-silica powder with acrylic monomers. The structure, morphology, thermal and mechanical properties of composite emulsion and films were characterized. The influence of the amount of silica on the properties of composite emulsion and films was studied. The results showed that the composite emulsion particle shows core-shell structure. Thermal stability and mechanical property of films are greatly improved by adding nanosilica particles. The films has good transparency when nanosilica content is5%.4. With nano-SiO2modified by silane coupling agent KH-570as core, and then core-shell structure nano-SiO2/polyacrylate composite emulsion were prepared through miniemulsion polymerization method. The influence of the addition of modified nano-SiO2on the properties of composite emulsion and films was studied. The results showed that silane coupling agent is grafted onto the surface of nano-SiO2after modification. The composite emulsion particle shows core-shell structure, the diameter of composite emulsion particle is bigger than that of pure acrylate emulsion particle. Tensile strength of film of modified nano-SiO2polyacrylate composite emulsion is increased and its water absorption rate is decreased, water resistance of film is improved, compared with that of unmodified nano-SiO2polyacrylate composite emulsion. |
