Synthesis And Characterization Of Nano-ZnO/Polyacrylate Composite Latex

In the first part of this thesis, inorganic-organic composite latex, nano-ZnO/P(MMA/EA) was obtained via in-situ emulsion polymerization, by using siloxane modified nano zinc oxide, methyl methacrylate and ethyl acrylate as raw materials. The results of five emulsion polymerization processes were compared with each other. Adopted the potassium persulphate-sodium bisulfite redox initiator system and sub-temperature control polymerization. The following technical parameters, the ratio and amount of the emulsifiers, the temperature and reaction time of the emulsion polymerization, the dosage of the initiator, the dispersion time of nano-ZnO and the pre-emulsion time, the stirring speed during polymerization, were all optimized. The optimum technical parameters were concluded in this paper. The core-shell composite particles were prepared, contending modified nano-ZnO particles.Based on these works, the effects of nano-ZnO and the amount of PEG on monomer conversion, coagulum percentage, emulsion viscosity and mean particle size were studied. The initiator was added into the reaction system by semi-continuous dropwise. The monomer conversion, zeta potential and average particle size of polymerizing system with nano-ZnO was compared to that of another polymerizing system without nano-ZnO. It was found that the former, with relative short induction period, was easier to form core structures. At the same time, for the particle size of latex, it also took relative short time to reach the maximum. TEM images indicate that morphologyof the nano-ZnO/P(MMA/EA) composite particle is a multi-core coated with the copolymer. The composite particles have a higher and wider range of glass transition temperature than the normal pure copolymer.In the second part of the paper, the PMMA was produced by emulsion polymerization with methyl methacrylate (MMA) as the monomer; sodium dodecyl sulfate (SDS), nonylphenol polyoxyethylene vinyl ether (OP-10) and hexadecyl trimethyl ammonium bromide (CTAB) as the emulsifier; 2,2-Azobis(2-methyl propion amide)dihydrochloride(V50) as the initiator. The amount of the monomer werediscussed, the type and amount of emulsifier, the amount of the initiator, reaction temperature and time, the type and dosage of dispersant agent in ultrasonic irradiation on the impact of the polymerization.In addition, the effects of nano-ZnO (with or without ) and the type of the nano-ZnO (modified nano-ZnO or pristine nano-ZnO particles) on the emulsion polymerization aided with ultrasonic wave irradiation were discussed. The mean particle size and zeta potential of the system during the polymerization were studied. It is found that nano-ZnO had an impact on nucleation process in emulsion polymerizing system. The main nucleation ways of the reaction system involving pristine nano-ZnO were micelle-nucleation and homogeneous nucleation. For modified nano-ZnO, monomer adsorption occurred on its surface, which was unfavorable for polymerization. The stability and zeta potential both decreased when the amount of modified nano-ZnO beyond a certain extent. The SEM/TEM images indicate that morphology of the latex particles produced by ultrasonic irradiation emulsion polymerization and the composite particles are spheroidal and blocky respectively.