- Time:Mar 28, 2023
Silica sol is a binder prepared by physical and chemical treatment of sodium silicate or silicon organic compounds, also known as silicic acid sol. Silicic acid sol is a colorless or milky white transparent colloidal solution, which is formed by dispersing SiO2 colloidal particles in aqueous solution, and has good cementing properties. Silica sol is a very important binder for the production of fiber products. There are 5 ways to prepare silica sol;
1. Hydrolysis with ethyl silicate;
2. It is prepared by electrolysis, dialysis and electrodialysis with sodium silicate (water glass) solution;
3. It is prepared by metal silicon powder reaction method;
4. Prepared by interacting sodium silicate with glyoxal and aqueous hydrochloric acid;
5. It is obtained by ion exchange with sodium silicate solution.
However, it is widely used to remove Na+ and CT from sodium silicate solution by ion exchange. The performance of silica sol can be adjusted according to the application. The content of SiO2 in the sol fluctuates greatly, from 15% to 50% %. However, the content of SiO2 in silica sol generally used as a binder for refractory materials is 25%~30%, the content of Na2O is ≤30%, the density is 1.1~1.25g/cm3, the viscosity is 0.005-0.03Pa.s, and the pH value is 8.5-9.5. Silica sol has strong adsorption performance and good bonding performance t. Silica sol has a wide adaptability as a binder for refractory materials. It can be used for acidic, neutral and alkaline refractory materials without adding other admixtures. However, when used as a binder for aluminum silicate ceramic fiber boards and special-shaped parts, cationic starch is generally added to improve the retention effect of silica sol and increase the normal temperature strength and high temperature strength of the product.
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