Factors Affecting the Stability of Silica Sol
Release date:
2025-07-22
Silica sol can maintain suspension stability for a long time, but in real-world environments, many factors can still affect its stability. In particular, during storage, certain precautions must be taken; otherwise, irreversible damage may occur.
Silica sol can maintain suspension stability for a long time, but in real-world environments, many factors can still affect its stability. In particular, certain precautions must be taken during storage; otherwise, irreversible damage may occur. The common factors are as follows:
Stabilizing factor 1: Freezing
Silica sol is an aqueous dispersion of nano-sized silicon dioxide. When the storage or usage temperature of silica sol is too low, it can freeze. Once ordinary silica sol freezes, it suffers irreversible damage—even if it is subsequently thawed, phenomena such as flocculation and sedimentation will occur within the silica sol. This is because, during the freezing process, the formation of ice crystals exerts pressure on the nano-sized silicon dioxide particles in the silica sol, causing them to agglomerate and thereby disrupting the stability of the silica sol.
Stabilizing Factor 2: Electrolyte
Ordinary silica sol is an aqueous dispersion of nano-sized silicon dioxide. The particles carry negative charges on their surfaces, which generate repulsive forces and prevent agglomeration. This is the fundamental reason why silica sol suspensions remain stable. Therefore, during use, ordinary silica sol must not be mixed with polyvalent salts, as the silicate ions on the surface of the silica sol will bind with polyvalent metal ions to form insoluble salts, disrupting the surface charge structure and thereby causing gelation or flocculation of the silica sol.
Stabilizing factor 3: Cationic substances
Since the surface of silica sol nanoparticles carries a negative charge, adding cationic substances (such as cationic emulsifiers or polyvalent metal ions) to a silica sol system will cause the silica sol to flocculate, resulting in irreversible scrap.
Stabilizing factor 4: Organic macromolecules
If water-soluble organic macromolecules are added to a conventional aqueous silica sol system, the silica sol will gradually thicken or eventually gel. This is because excessively large molecular-weight organic macromolecules adsorb onto the surface of the silica sol’s nanoparticles, masking their surface charges and thereby weakening the electrostatic repulsion between the silica sol particles, which in turn leads to gelation of the silica sol.
Stabilizing factor 5: Open containers
During the use of silica sol, if the container is left open for an extended period, surface moisture will evaporate, causing silica crystals (in the form of fine needles or sand-like particles) to precipitate out. This phenomenon generally does not affect the stability of the silica sol, but it may impact its usability. Therefore, when using the silica sol, it is necessary to filter out these solid precipitates using a very fine filter cloth.
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