As we all know, silica sol can remain suspended and stable for a long time, but there are still many factors in the environment that can affect its stability. In particular, you must pay attention to some matters during storage, otherwise irreversible damage will occur. Let’s take a look at the five major factors that affect the stability of silica sol.
Factors affecting stability 1. Freezing
Ordinary silica sol is a water dispersion of nano-silica. When the storage or use temperature of silica sol is too low, it will cause the silica sol to freeze. Once ordinary silica sol freezes, it will cause irreversible damage. Even if it is re-melted, Phenomenon such as flocculation and precipitation may also occur in silica sol. This is because when freezing occurs, the nano-silica particles of the silica sol will be squeezed during the formation of ice crystals, causing their agglomeration, thereby destroying the stability of the silica sol.
Factors affecting stability 2. Electrolyte
Ordinary silica sol is an aqueous dispersion of nano-silica. The surface of the particles is negatively charged and causes repulsion, so agglomeration does not occur. This is the fundamental reason why the silica sol suspension system remains stable. Therefore, during use, polyvalent salts cannot be added to ordinary silica sol, because the silicate radicals on the surface of the silica sol will combine with multivalent metal ions to generate insoluble salts, destroying its surface charge structure, resulting in silica sol gel, Flocculation etc.
Factors affecting stability 3. Cationic substances
Because the surface of silica sol nanoparticles is negatively charged, adding cationic substances (such as cationic emulsifiers, multivalent metal ions, etc.) to the silica sol system will cause silica sol flocculation and irreversible scrapping.
Factors affecting stability 4. Organic macromolecules
If water-soluble organic macromolecules are added to ordinary aqueous silica sol systems, the silica sol will also gradually thicken or eventually gel. This is because organic macromolecules with excessive molecular weight will be adsorbed on the surface of silica sol nanoparticles, covering their surface charges, weakening the charge repulsion between silica sol particles, resulting in silica sol gel.
Factors affecting stability 5. Container exposure
During the use of silica sol, if the container is left open for a long time, the surface water will evaporate and silica crystals (fine needles or sand grains) will precipitate. This phenomenon generally does not affect the stability of silica sol, but it may It will affect the use. When using, you need to use a very fine filter cloth to filter out these solid precipitates.
