The Surface Modification Of Nano-particles And Application In Coatings

It has become the focus of research to apply nano-particals in the traditional coating preliminary to form new functional composite coatings. But for the strong activity of nano- TiO2, the conglobation will happen easily, and it will greatly reduce the application effect in coating.And for the hydrophilicity, it's hard to break up uniform in resins, so air gaps appear in the interface, then the high polymer in the interface will happen degradation reaction or embrittlement reaction, and coatings performance will fall down. So it is the premise of application in coatings to modify the surface of nano-particals in order to reduce or eliminate conglobation and increase the dispersity of the Nano-particals in coatings.At first the methods of modifying nano- TiO2 had been explored, we used oleic acid, sodium laurate, triethoxyoctylsilane(A-137),γ-methyl acryloyoxypropyl trimethoxy silane (KH-570)to modify the surface of nano-particals. The results showed that it was unsatisfactory of using oleic acid and sodium laurate to modify the surface of nano-TiO2 particle and the modified products were unstable; Silane coupling agent can improve the surface properties of nanoparticles effectively, nano-particals can be evenly dispersed in organic solvents, but the KH-570 was slightly better than A-137, therefore, KH-570 was selected to modify the surface of nano-particals in this paper. The best modification process is obtained through performance test: mix isopropyl alcohol and water proportionally, add KH-570 to the mixture, with one hour mechanical agitation, next, add nano-particals, drying it 12h at 80℃, then drying it 2h at 120℃. Settlement experiments result shows that the modified TiO2 can steady suspend more than 7d in organic solvent; the TEM shows the modified TiO2 particles are nanometer and whose average size is almost less than 100nm. Wetting test and the FT IR show TiO2 particles have been changed from hydrophilic to hydrophobic, nano-particals can be uniformly dispersed in the organic solvent.Add the modified nano-particals into fluorocarbon coatings, the adhesion, the dirt-pick, the anti-ultraviolet, hardness, acid resistant, alkaline resistant of the coating were tested and these performance are far above the national standard and comply with the metal surface of external paint industry standard. Artificial aging resistance experiment is accelerated aging test, the light intensity is far above the ordinary natural light, testing time for 360 hours, during this period the coating keeps non- luster lost, non-discoloration, non-pulverization. Besides, surface hydrophobicity of the self-cleaning properties were characterized, the contact angle of the nano-modified coating significantly increased to 90°as compared to the unmodified coating. Lastly, the surface hydrophobicity of self-cleaning effect is better.Add the modified nano-particals into the penetrative organic silicon waterproof protective agent, the bibulous rate, water depth and water effect of the coating were tested. The results show that the bibulous rate is dramatically reduced, water absorption reduction reaches 85%. The water depth and water effect of the coating both improved.