Preparation And Characterization Of Composite Coatings Of Silica Sol Modified By Organosilicone

In this paper, the modified silica sol which is alkali and low in the content of Na+ was prepared via ion exchange using water glass and methyl silinol-sodium as raw materials. And the factors such as pH,solid content and concentration temperature were also investigated. The particle size and solid content of the modified silica sol were increased by the means of condensation and ultrafiltration.The results show that when pH is in the neutral zone, the stable time is very short, and in the range of alkalinity the stable time increases with the increasing of pH. There is a metastable region in acidic zone.With the increase of methyl silanol, the stable time is shorter,and the particles are more orbicular.In the paper, an organic-inorganic composite sol was prepared firstly by using an alkaline silica sol modified by adding water-based organic silicon polymers. Then using sub-micron titanium dioxide, kaolin etc. as main skeleton materials, using nano-TiO2 and SiO2 etc. as functional fillers, a kind of environment friendly coatings with non-flammable and multi-functional properties were developed through appropriate process. And through the processes of spraying and baking, the organic-inorganic composite coatings on the treated aluminum alloy were obtained successfully. The preparation of coatings, coating process, the modification mechanism of silica sol as well as physicochemical properties, non-flammable properties of coatings etc.were studied.The research results show that silica sol particles are modified through the crosslinking of Si-OH originated from the hydrolysis of methyltrimethoxy silane (MTMS) and Si-OH in the surface of silica sol particles. The transparent coatings of silica sol modified by MTMS are composed of amorphous solid.The thermal stability is fine,and the corrosion resistance is enhanced with the lift of temperature for the coatings are more denser in the range of room temperature to 500℃. The results of flame resistance test show that the coatings hardly fire, flake off and produce toxic-gas and heavy smoke while meeting fire. The coatings firmly bond with aluminum alloy and form an inorganic glaze-like layer on the surface, which plays an important role in protection. The coatings have better stain resistance. Furthermore, the results of testing other properties (e.g. acid resistance, alkali resistance, boiling water resistance etc.) suggest that the coatings on aluminum alloy also have better physicochemical properties.