Dispersion Of Amorphous Silica In Water Medium And Preparation Of Amorphous Silica/TiO₂ Composite Particles

Carbon-white were widely used in rubber and plastic industries because of its excellent physical and chemical properties.Compounding carbon-white with TiO2 particles can give play to the coordination effect of carbon-white,and realize the economization and replacement of TiO2.The carbon-white/TiO2 composites were prepared by mechanochemical method.The processes of preparation and influencing factors were optimized,and the pigment properties,ultraviolet shielding properties and composites structures of production were characterized.The composite mechanisms of carbon-white and TiO2 particles were also studied.(1)The depolymerization and dispersion of carbon-white and Ti02 in water medium were discussed.Results showed that the effects of adding dispersant and mechanical grinding were the best,and the orders of influencing factors were as follows:milling time>ratio of grinding media to material>slurry concentration>dispersant dosage.The dispersion of carbon-white and TiO2 were significantly improved under the optimal conditions,and the particle sizes of carbon-white decreased from 25.5 ?m to 10.97 ?m,the median diameters and D90 of TiO2 decreased from 0.52 ?m to 0.30 and 3.21 ?m to 0.54 ?m,respectively.(2)The technology and characterization of carbon-white/TiO2 composites prepared by mechanochemical method were researched in the laboratory condition.At the optimal conditions,the hiding power compared to the pure TiO2 of carbon-white/anatase composites,carbon-white/coated rutile composites and carbon-white/uncoated rutile composites were 74.82%,85.43%and 86.29%,respectively.The pigment performances of carbon-white/TiO2 composites were similar to that of titanium dioxide.(3)Pilot tests were conducted in industry following designed process requirements and parameters.Results showed that carbon-white/rutile composites were successfully prepared in industrial production.When the contents of TiO2 were 50%and 67%,the hiding power compared to the pure TiO2 of composites were 71.70%and 126.79%.The pigment properties were superior to the laboratory product.Adding the composites to prepared the architectural coatings,and the coating contrast ratio were similar to the rutile pigment and greatly superior to the anatase.(4)The ultraviolet shielding properties of composites were also researched.The composite powders had a strong absorption in 200-400 nm of ultraviolet rays,and the absorption behavior was similar to rutile,inferred that the composites had a excellent ultraviolet shielding performance.(5)The composite mechanisms of carbon-white/TiO2 composites were also studied.TiO2 were coating on carbon-white because of the formed of Ti-O-Si bond by hydroxyl condensation,and the new chemical bonds caused to the binding energies of Si,O,and Ti changing.At the same time,some free TiO2 particles inserted into the holes and clearances of carbon-white by weak Van der Waals force and hydrogen bond interaction,and eventually formed carbon-white/TiO2 composites which were stable and had excellent performance.