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Hydrophobic Colloidal Silica

    Synonyms: Aerosil R972; silica dimethyl silylate; silica hydrophobica colloidalis; silicic acid, silylated; silicon dioxide, silanated.

    Description:  Hydrophobic colloidal silica occurs as a light, fine, white or almost white amorphous powder, not wettable by water.

    Chemical Name: Silane, dichloro-dimethyl-, reaction products with silica

    Anticaking agent; emulsion stabilizer; glidant; suspending agent;
    thermal stabilizer; viscosity-increasing agent.

    • Hydrophobic colloidal silica has nano-sized primary particles and a large specific surface area, which provide desirable flow characteristics in dry powders used in tableting and capsule filling.

    • The hydrophobic grades absorb less moisture and may offer an advantage in moisture-sensitive formulations.

    • Hydrophobic colloidal silica is also used to thixotropically control viscosity, to thicken and stabilize emulsions, or as a suspending agent in gels and semisolid preparations.

    • Hydrophobic colloidal silica has a less pronounced effect on solution viscosity but can thicken and stabilize the oil phase of a water–oil emulsion.

    • With other ingredients of similar refractive index, transparent gels may be formed.

    • Generally, the uses and ranges of hydrophobic colloidal silica are similar to the concentrations used of the standard hydrophilic colloidal silicon dioxide.

    Use of the hydrophobic colloidal silica Aerosil R972 reduces the strength of starch-based tablets

    The safety profile of hydrophobic colloidal silica is the same as for the hydrophilic silica types, as the modified silica surface does not significantly alter the toxicological properties.

    Observe normal precautions appropriate to the circumstances and quantity of the material handled. Eye protection and gloves are recommended. Considered to be a nuisance dust. Inhalation of hydrophobic colloidal silica dust may cause irritation to the respiratory tract but it is not associated with fibrosis of the lungs (silicosis), which can occur upon exposure to crystalline silica

    Colloidal silicon dioxide.