Binder for refractory materials and fiber products - silica sol

      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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