Fumed silica

Description

[Degussa] A colloidal form of Silica that is a very light, fluffy white powder. Fumed silica, also called aerosol silica, is made by hydrogen-oxygen furnace combustion of silicon tetrachloride. This produces tiny spherical particles of varying sizes. Untreated fumed silica is hydrophilic, but many commercial products have been treated to make them hydrophobic. Generally, silanes or siloxanes are used to replace hydroxyl groups on the surface and thus prevent the absorption of moisture. Fumed silica is approved by the U.S. FDA for use in food products.

Synonyms and Related Terms

aerosol silica; colloidal silica; pyrogenic silica; thermal silica;

Commercial products: Aerosil® [Evonik]; Cab-O-Sil [Cabot]; HDK [Wacker Chemie]; Zandosil [Dow Corning]; Reolosil [Tokuyama Corp.]; Konasil [OCI]; Orisil [Orisil]; XYSIL [Xunyuchem]

Applications

• Matting agent
• Thickener
• Filler
• Desiccant to kill insects

Risks

• Inhalation may cause silicosis; used dust mask.
• Integra Chem: SDS

Physical and Chemical Properties

• CAS = 112945-52-5
• Composition = SiO2
• Density = 2.0 - 2.2 g/cm3
• Melting point = 1700 C
• Decomposition = >2000C
• Moisture content = 0.5-2.5 % (Hydrophilic); 0.5% (hydrophobic)
• Adsorbed moisture = 6%
• Refractive index = 1.46
• Particle size = 5-40 nm

Resources and Citations

• Wikipedia: Fumed silica Access July 2023
• George Wypych, 'FILLERS – ORIGIN, CHEMICAL COMPOSITION, PROPERTIES, AND MORPHOLOGY, in Handbook of Fillers (Fourth Edition), 2016Chapter 2.1.79.1 Fumed Silica