| The paper was intended to study a kind of waterborne acrylic resin exterior wall coatings with strong weatherability by the way of using inorganic nanoparticle as age-inhibiting addition.Based on the comprehensive summary of the research and application of the modern ultraviolet radiation stabilizing agent, we began with the property of the UV shielding and chose the nano-TiO2, SiO2, ZnO as the UV shielding agent. In this thesis, we made a summary of the preparation technology of the nano-materials, especially of the latest development of preparing nano-materials by the way of the wet chemical method. The preparation methods of the nanocomposite materials were summarized too.In order to solve the problem of conglomeration of the nanoparticle and make the nanoparticle disperse evenly in the coatings. In this way, we could succeed in improving the effect of modification .We originally put forward the in-situ sythesising nanoparticle method to modify coatings. Through this method, we made use of the technology of the wet chemical method and added the precursor of nanoparticle during the preparation of coatings. Meanwhile, the nanoparticle was formed on the face of the pigment. We also put forward the technique of in-situ dispersion to modify coatings .The key of the technique was to add the nanoparticle sol prepared by the wet chemical method into coatings instead of dropping the nanoparticle powder prepared by the technics of filtration and calcinations in the coatings. The preparation and the dispersion of the nanoparticle were finished in the same step by the first method. The second method could also solve the problem of dispersion in some way. Thus the efficiency of the modification could be assured.We succeeded in preparing the nano-TiO2 sol through the hydrolyzation of complex in the room temperature and preparing the nanoTiO2-modified coatings by the way of in-situ sythesising method. First, the UV absorbing and scattering characteristics of the nano-TO2 sol were studied. The sol of the nano-TiO2 had excellent shielding effect on UV radiation. UV transmittance below 320nm was nearly zero, and the absorbingof UV radiation was moved to short wavelength when the granularity of the nano-TiO2 was becoming finer. The influence of the technics of the hydrolyzation of complex on the UV shielding was studied. Then, we examined the weatherability of nano-TiO2-modified coatings prepared by the way of in-situ sythesising method. There were no aging phenomena such as chalking , bubbly , crackling , peeling-off after 1800h of the artificial aging process, which went far beyond the national standard for the super coating(the first level chalking after 600h of the artificial aging process). The common coatings reached first-degree chalking after 1600h of the artificial aging process.The stable nano-SiO2 sol was prepared by Sol-Gel method and the nano-SiO2-modified coatings were prepared by the way of in-situ dispersion method. The UV scattering characteristic of nanometer SiO2 sol was studied. The nano-SiO2 sol had excellent reflecting and absorbing effect on UV radiation. 90%UV below 400nm could be shielded by the nano-SiO2 sol. The time of the artificial aging of nano-SiO2-modified coatings prepared by the way of in-situ dispersion method was about twice as long as that of the nano-SiO2-modified coatings prepared by dispersing the nano-SiO2 powder in the coating directly. On the other hand, the fadeproof time (reaching the second level of color aberration) of the nano-SiO2-modified coatings was 1.83 times as long as that of the national standard for the super coatings. There was an increase in the fadeproof time of 25 percent over the common coatings.Both the nano-TiO2-modified coatings prepared by the way of in-situ sythesising method and the nano-SiO2-modified coatings prepared by the way of in-situ dispersion were strong weatherability coatings, which could resist 18 years' weathering if we calculated the result with the standard which argued that 100h of the artificial aging process was equal... |
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