Silica Sol

Oct 20, 2020

Silica sol is a colloidal solution, odorless and non-toxic. Silica sol is a dispersion of nano-scale silica particles in water or solvent. Since the SiO2 in the silica sol contains a large amount of water and hydroxyl groups, the silica sol can also be expressed as SiO2.nH2O.
Silica sol inorganic polymer coatings have been developed in recent years. The key technology for preparing the coating is
Silica sol
Use a special method to remove the water-soluble sodium ions in the water glass. Generally, it can be achieved by ion exchange, acid neutralization, water decomposition, electrodialysis and other methods to produce a very fine silica ultrafine colloidal aqueous solution with a particle size of 580nm (generally 800-1000nm for emulsion particles). The content of Si2O is 20%-30%, the content of Na2O is 0.3%￥, and the ratio of silicon oxide and sodium oxide is above 40%. Using this silicon solution/glue as a base material, with pigments and various additives, a silica sol inorganic polymer coating is made. When the silicon solution loses water, the monomer silicic acid gradually polymerizes into high-polymer silica gel. As the water evaporates, the colloidal molecules increase, and finally form -SIO-O-SIO- coating film: IO-SI-OH+HO-SI- Because of the low content of OH in silica sol, silica sol has a certain amount of film-forming and dissolving characteristics, and its water resistance and heat resistance are obviously better than organic coatings. The coating film is dense and hard, does not generate static electricity, and all kinds of dust in the air are difficult to adhere. In architectural coatings, its anti-pollution ability is strong.
The fine particles have strong penetrating power to the base layer, can penetrate into the base layer through the capillary, and can react with the calcium hydroxide in the concrete base layer to form calcium silicate, so that the coating has strong adhesion.
However, the volume of silica sol shrinks greatly during the film forming process, and the coating film is easy to crack. Silica sol can be arbitrarily compatible with emulsions such as acrylic ester and vinyl acetate. The characteristics of the two complement each other, and organic and inorganic composite coatings with excellent performance can be formulated.
Traits
Silica sol is a colloidal solution, odorless, non-toxic, and its molecular formula can be expressed as mSiO2nH2O.
1. Because the colloidal particles are fine (10-20nm) and have a large specific surface area, the particles themselves are colorless and transparent, and do not affect the natural color of the covered object.
2. The viscosity is low, and water can penetrate wherever it can penetrate, so the dispersion and permeability are very good when mixed with other substances.
3. When the water in the silica sol evaporates, the colloidal particles firmly adhere to the surface of the object, forming a silicon-oxygen bond between the particles, which is a good adhesive.
use
1. Used as a binder for various refractory materials, with strong adhesion and high temperature resistance (1500°C-1600°C), etc.
2. Used in the coating industry, it can make the coating firm, and can resist dirt, dust, aging, fire and other functions.
3. It is used for precision casting of thin shells, which can make the shell strong and smooth. Its molding quality is better than that of sodium silicate molding, instead of ethyl silicate molding, it can reduce costs and improve operating conditions.
4. Silica sol has a higher specific surface area and can be used for catalyst manufacturing and catalyst carrier.
5. Used in the paper industry, it can be used as a cellophane anti-sticking agent, photo paper pretreatment agent, cement bag anti-skid agent, etc.
6. Used as a sizing agent in the textile industry. It can be used together with an oil agent to treat the spinnability of wool and rabbit hair, reduce end breakage, prevent flying, increase the yield and increase economic benefits.
7. Used as silicon steel sheet treatment agent, picture tube dispersant, floor wax anti-slip, etc.