Physical and chemical properties of precipitated silica Scientific name Precipitated hydrated silica
Molecular formula SiO2 * nH2O
Main ingredient SiO2
The original particle size is less than 0.3μm
Relative density 2.319～2.653
Melting point 1750℃
Appearance White amorphous powder
Solubility insoluble in water and acid; soluble in caustic soda and hydrofluoric acid
1.3 Main application fields of precipitated silica
Silica is a highly dispersed amorphous powder or flocculent powder with light weight, high electrical insulation, porosity and water absorption. Its original particle size is less than 3um, so the surface area is large, and it has good reinforcement and viscosity enhancement, as well as good dispersion, suspension and vibration liquefaction characteristics. It has been widely used in plastics, rubber, paper, coatings, dyes and inks. In several fields, especially in the rubber industry, silica ranks first for its superior reinforcement and transparency.
Depending on the quality, it has different applications. Precipitated silica is mainly used in automotive rubber tires, pesticide feed, paint, toothpaste and other additives.
Precipitated silica is widely used as filling and reinforcing agent for rubber and plastics, ink thickener, paint and coating additive, synthetic lubricating grease and silicone grease thickener, tanning industry flat agent, pesticide dispersant, papermaking filler, synthetic Resin (polyester resin, elastic polyurethane) additives, electrical and electronic industry insulation fillers and daily chemical raw materials and other industries. At the same time, it is used as an opening agent for polypropylene and non-toxic PVC plastic films and an anti-caking agent and carrier for food, pesticides and medicines.
In the resin matrix composite material, the silica particles can be fully and uniformly dispersed in the resin material, so that the strength, toughness and ductility of the epoxy resin material are greatly improved, the wear resistance and the surface finish of the material are improved, and the Anti-aging properties. So as to achieve the purpose of comprehensively improving the performance of resin-based materials.
In the plastics industry, the use of white carbon black to transmit light and small particle size can make plastics more dense. Not only improve its transparency, strength, toughness, but also waterproof performance, anti-aging performance and hardness, finish is also significantly improved. For example: the use of nano-silica to modify the ordinary plastic polypropylene, the main technical indicators (water absorption, insulation resistance, compression residual deformation, flexural strength, etc.) have reached or exceeded the performance indicators of engineering plastic nylon 6, to achieve The use of polypropylene railway fittings instead of nylon 6 has greatly reduced the product cost, and its economic and social benefits are very significant.
In the rubber industry, carbon black is usually added to the rubber compound to improve strength, abrasion resistance and aging resistance, but the products are all black due to the addition of carbon black. For example, after adding a small amount of nano-silica to ordinary rubber, the strength, wear resistance and aging resistance of the product reach or exceed that of high-grade rubber products, and the color can remain unchanged for a long time. Tires are usually black, but the tires produced with nanomaterials are not only bright in color, but also greatly improved in performance.
In color TV and other home appliances, because carbon black is added to the material for electrostatic shielding, the home appliances are generally black, which is called black home appliances. By using nano-silica, electrostatic shielding coatings can be developed, and the color of the coatings can be further controlled, and black home appliances will become color home appliances.
In the coatings industry, nano-silica modified coatings have changed the deficiencies of previous products and greatly improved such as poor suspension stability, poor thixotropy, poor weather resistance, and poor scrub resistance. [1] 
In the pigment and dye industry, it can overcome the shortcomings of organic pigments (dyes) that have bright colors and strong tinting strength, but generally have poor light resistance, heat resistance, solvent resistance and migration resistance. The surface modification treatment of organic pigments (dyes) by adding nano-silica not only greatly improves the anti-aging properties of pigments (dyes), but also improves the brightness, hue and saturation to a certain extent. Dadi has broadened the grade and application range of organic pigments (dyes).
Silica has strong ability to reflect ultraviolet rays and good stability, and will not decompose or discolor after being irradiated by ultraviolet rays, nor will it react with other components in the formula. Therefore, it can be used in advanced cosmetics, new plexiglass for UV protection, etc.