In the materials industry, silica sol, as a new material, has attracted attention for its excellent fire resistance and acid resistance. After the silica sol prepared by reacting sulfuric acid with silicic acid containing 24% of silica mass fraction is treated with ceramic acid-resistant containers, it will not be leached and can increase the pressure resistance. The thin shell made by using small-particle silica sol instead of ethyl silicate has high strength and good finish, which can greatly improve the quality and dimensional precision of castings, reduce costs and improve operating conditions. Adding silica sol to CO2 type coating agent can improve ductility and increase sand mold strength.
Silica sol can also be used as a binder for acid-resistant cement, various thermal insulation materials and silicate materials. It has the characteristics of strong adhesion, acid resistance and high temperature resistance, and is widely used in ceramic and refractory industries.
A big problem on the surface of cast steel is that a small amount of steel ingots often stick to the mold and the bottom plate, which affects the quality of metal products. If silica sol is mixed with refractory powder (such as silicon oxide, aluminum oxide, zirconium oxide, iron oxide, etc.) and coated on the surface of heat-resistant and corrosion-resistant containers such as steel ingot molds and iron molds, this high-temperature protective layer coating can withstand high temperatures of 1570~1630℃, can protect the working surface of the mold and the bottom plate, greatly reduce the loss of the mold, and make it demold well.
If silica sol is mixed with amines, thiourea, zinc powder and other materials to make a coating, it can be used as a steel surface protection material, and its performance, especially the anti-rust performance, greatly exceeds that of lithium silicate zinc powder coating.
As early as the 1970s, Japan began to use silica sol in architectural coatings, especially exterior wall coatings. For example, a composite exterior wall coating composed of silica sol as the main film-forming material, synthetic emulsion (such as styrene acrylic emulsion, vinyl acetate resin emulsion) as an auxiliary film-forming agent, and pigments, fillers, and additives, is not attached to the surface of the material as a general coating, but the result of penetration and hardening. It has the advantages of both inorganic and organic coatings. Silica sol is used as the base material of building exterior wall coatings. It can make the coating firm, have good adhesion performance, and has the functions of anti-fouling and dustproof, aging resistance, and fire resistance. However, silica sol will generally freeze below 0°C and cannot be restored after melting. This irreversibility causes the significant defect that silica sol coating cannot be constructed in winter.
If one or more long-chain diols with more than 3 carbon atoms and water-soluble melamine are added to silica sol, the silica sol coating can be constructed in winter and has low-temperature storage stability. It can be sprayed, rolled or brushed without organic solvents. It does not need to be heated and dried after coating. It is particularly suitable for the interior and exterior walls of concrete, mortar and slate buildings. The coating film has good hardness, no cracks, and excellent performance.