Dispersion Technology Of Nanopowders Applied In Emulsion Polymerization And Electroless Deposition

This thesis is mainly dealt with the aggregation of SiO2, PTFE and SiC powders in applications. According to their respective features, the different disperse methods are used to explore the dispersing conditions and extend their applications, so that their nano-effects are used.Nano SiO2/acrylates composite latex was prepared by in-situ polymerization. The membrane resistance and euphotic rate of nano SiO2/acrylates hybrid emulsion have been improved because of the high hardness, light quality properties of the nano SiO2. Nano SiO2 powders are hydrophilic with bad organic phase compatibility due to a lot of silicon hydroxyl on their surface. To solve the compatibility of nano SiO2 and polymer emulsion, SiO2 nano powder is dispersed in the mixture of methyl metharcrylate, butyl acrylate and acrylic acid with high pressure shearing homogenizer (HPSH), and then, nano SiO2/acrylic ester emulsion is synthesized via in-situ polymerization. The best experimental formula has been explored. The influence of the ratio of OP-10 to sodium dodecyl benzene sulfonate (SDBS) for the stability of the emulsion is discussed, and the conversion rate of the monomer and the water resistance related to the additive amount of nano SiO2 are dealt with. Nano SiO2/acrylic ester emulsion is characterized using TGA,UV-VIS and TEM, respectively. The results indicate that the HPSH is effective in improving the agglomeration of SiO2 nano powder and the SiO2 nano powder can be uniformly dispersed in the process of polymerization. When the additive amount of SiO2 is 5% (ratio of mass) and the ratio of OP-10 to SDBS is 2:1 (ratio of mass), the monomer conversion, the stability of nano SiO2/acrylic ester emulsion and the thermal stability for the film of nano SiO2/acrylic ester emulsion are all perfect.Polytetrafluoroethylene (PTFE) possesses thermal stability and good self-lubricity, while nano SiC possesses high hardness, excellent wear and corrosion properties. In the chemical nickel plating technology, PTFE microns powders and nano SiC powders are added to obtain antifriction and decay resistance composite coating for industrial mold. The effects of different surfactant and different scattered ways on PTFE and SiC scattered in the plating are studied, and the compositions, structures and properties of Ni-P-PTFE, Ni-P-SiC composites coating were also investigated. The results show that the increase of temperature and pH value all can improve chemical nickel deposition rate at the certain concentration of main salt, but solution stability decline at higher temperatures than 90℃, pH value more than 5.0. The structure of Ni-P-PTFE, Ni-P-SiC composite coatings are amorphous. The PTFE microns powders and nano SiC powders can be dispersed homogeneously in the plating by using ultrasonic dispersing and surfactant, and the stable time can reach 3 hours. Salt spray test shows that the corrosion resistance Ni-P-SiC composite coating much better than that of the same thickness Ni-P coating. The corrosion resistance of Ni-P-PTFE composite coating is slightly less than that of the same thickness Ni-P coating, but Ni-P-PTFE composite coating possesses excellent self-lubricity, which can be applied to various rubber mold coating.