Fumed silica

Fumed silica (CAS 112945-52-5) is a synthetic amorphous silicon dioxide produced by flame hydrolysis of silicon tetrachloride. It is commercially available under trade names including CAB-O-SIL M-5, AEROSIL, and DAVISIL, and is distinct from crystalline silica forms in both structure and regulatory classification.

In coatings and adhesives, fumed silica builds thixotropic flow by forming hydrogen-bonded particle networks that resist sagging under static load but break down under shear. In sealants and elastomers, it reinforces the polymer matrix and controls extrusion rate. Personal care formulators use it as a dry-feel agent and to suspend pigments in anhydrous systems.

Fumed silica is supplied in untreated hydrophilic and surface-treated hydrophobic grades, with surface area typically ranging from 90 to 380 m2/g. It falls under REACH registration requirements within the EU and is available in multi-wall paper bags and bulk containers. Pharmaceutical-grade material may comply with Ph.Eur. monograph standards.