Fumed Silica alias ：combustion method ; Pelleted Hydrated Silica ; Hydrated Silica ; Silicondioxidehydrate ; Silica , hydrate ; SILICA ; Precipitated silica ;
CAS NO.: 10279-57-9
EINECS NO.：238-878-4
Molecular formula: SiO2.x(H2O)
Fumed silica is one of the most important nano inorganic raw materials. Because of its small particle size, it has large specific surface area, strong surface adsorption capacity, large surface energy, high chemical purity, good dispersion, thermal resistance, resistance and other aspects. With its superior stability, reinforcement, thickening and thixotropy, it has unique characteristics in many disciplines and fields Replaceable function.
It is widely used in various industries as additives, catalyst carrier, petrochemical industry, decolorizing agent, matting agent, rubber reinforcing agent, plastic filling agent, ink thickener, metal soft polishing agent, insulation filler, high-grade cosmetics filler and spraying materials, medicine, environmental protection and other fields. It also provides new material foundation and technical guarantee for the development of related industries. Compared with conventional materials, it has attracted great attention because of its special functions in magnetism, catalysis, light absorption, thermal resistance and melting point.
Fumed silica can be divided into hydrophilic and hydrophobic.
Hydrophilic fumed silica
Hydrophilic fumed silica was prepared by hydrolysis of volatile chlorosilane in oxyhydrogen flame. From a chemical point of view, these loose white powders are composed of high purity amorphous silica. Hydrophilic silica can be wetted and dispersed in water. In addition to the application in traditional industries, such as polyester, silicone, paint and coatings, hydrophilic fumed silica products are more and more successfully used in high-tech fields. The characteristics and high purity of fumed silica nanoparticles play a leading role in the application of electronic and optical fiber industry. The hydrophilic fumed silica has amorphous structure by X-ray analysis. According to different markets and application fields, we can provide products with different particle sizes and specific surface areas. Some fumed silica products can be compressed and supplied. Some products are pharmaceutical grade.
Functions of hydrophilic fumed silica: suitable for processing and adjusting to the best rheological property; reinforcement of silicone elastomer; thickening of non-polar liquid; flow aid for food and industrial powder; high chemical purity; excellent insulating property even at high temperature; liquid transformation into powder, such as medicine and cosmetics.
Hydrophobic fumed silica
Hydrophobic fumed silica is prepared by chemical reaction of hydrophilic fumed silica with active silane (such as chlorosilane or hexamethyldisilazane). It is hydrophobic (hydrophobic) and cannot be dispersed in water. In order to solve some special technical problems in industry, various types of hydrophobic fumed silica have been developed. For example, hydrophobic fumed silica can be produced by modifying hydrophilic fumed silica with silane or siloxane. In the final product, the chemical treatment agent is chemically bonded to the original hydrophilic oxide. In addition to the above advantages of hydrophilic products, hydrophobic fumed silica products are characterized by low hygroscopicity, good dispersion and rheological adjustment ability even for polar systems. Some products, after structural modification on the basis of hydrophobic treatment, can provide further help for customers to develop new products and improve the performance of products. For example, in the liquid system, hydrophobic fumed silica can reach a high content, but has little effect on the viscosity of the system.
Functions of hydrophobic fumed silica: the most suitable rheological property in processing and use; thickening of polar liquid, such as epoxy Resin; reinforcement of silicone elastomer; high addition, such as in molded products; good hydrophobicity, improving corrosion resistance; improving dielectric properties, such as in cable composites; powder flow aids, such as in powder coatings and fire extinguishing agents; in coatings and plastics Improve scratch resistance.
Famous brand of fumed silica ：
EVONIK ，WACKER，CABOT，SHENNA，TOKUYAMA
Fumed silica is mainly used as rheological additives in paints and coatings, which can effectively prevent sagging and thick edges in the construction process, and improve the construction efficiency.
In addition, fumed silica can also be used as anti sedimentation and dispersant in coatings, which can effectively prevent settlement and delamination of pigments and fillers, and improve the weatherability, scratch resistance and bonding strength between coating and substrate.
Anti settling agent:
Fumed silica is an ideal antifouling agent. Its hydrogen bond structure is very stable and uniform, and it is a three-dimensional network structure. It is very effective to prevent the precipitation of pigments in the coating system. Especially for the color paste system, the appropriate amount of additive will greatly improve the stability of the color paste, and can reduce the amount of wetting dispersant, so as to improve the applicability of the color paste and reduce the influence of the color paste on the coating system. At the same time, the anti settling effect of fumed silica is very beneficial to the storage of coatings, especially some pigments such as metal powder and flakes are easy to precipitate and can not be completely suspended. The use of fumed silica can ensure its dispersion and non precipitation.
Auxiliary dispersing agent:
In the powder system, due to the small particle size and high surface energy of fumed silica, they can be adsorbed on the surface of the coating powder and form a surface layer on the surface of the powder to improve the dispersion of the powder. In the same coating system, adding fumed silica can obviously shorten the dispersion time and improve the production efficiency.
Adding fumed silica to the wall coating can effectively prevent the coating from sagging, improve the smoothness of the construction surface, and greatly improve the washing resistance and aging time of the exterior wall coating. The bonding strength between the coating and the wall is also greatly improved, the film hardness is significantly increased, and the surface self-cleaning ability is also improved.
Adsorption of fumed silica on the surface of powder coating can form a movable layer, which can produce "ball" effect, prevent the powder coating from absorbing moisture and caking, and improve the fluidity of powder coating.
The main function of the floor paint is to control the rheology, improve the weatherability and scratch resistance of the floor paint, and improve the leveling performance of the coating.
