HDK® pyrogenic silica

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Pyrogenic silica is a mature product that WACKER has produced for over 50 years and is used by customers worldwide with great success. Thanks to our integrated production system with statistical process control and highly efficient reactor dynamics, we produce pyrogenic silica of exceptionally purity.

With HDK® you get not only great product performance, but also tailored customer service. Our specialists can offer you extensive applications support. They will work with you to develop process-focused solutions, providing comprehensive support with optimizing your products and formulations.

Silicon dioxide with branched chains on micro scale

Not to be confused with silica fume

"Aerosil" redirects here. Not to be confused with aerosol

Fumed silica (CAS number -52-5), also known as pyrogenic silica because it is produced in a flame, consists of microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles which then agglomerate into tertiary particles. The resulting powder has an extremely low bulk density and high surface area. Its three-dimensional structure results in viscosity-increasing, thixotropic behavior when used as a thickener or reinforcing filler.[1]

Properties

Fumed silica has a very strong thickening effect. Primary particle size is 5&#;50 nm.[2] The particles are non-porous and have a surface area of 50&#;600 m2/g. The density is 160&#;190 kg/m3.

Production

Fumed silica is made from flame pyrolysis of silicon tetrachloride or from quartz sand vaporized in a  °C electric arc.[3] Major global producers are Evonik (who sells it under the name Aerosil), Cabot Corporation (Cab-O-Sil), Wacker Chemie (HDK), Dow Corning, Heraeus (Zandosil), Tokuyama Corporation (Reolosil), OCI (Konasil), Orisil (Orisil) and Xunyuchem(XYSIL).[4]

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Applications

Fumed silica serves as a universal thickening agent and an anticaking agent (free-flow agent) in powders. Like silica gel, it serves as a desiccant. It is used in cosmetics for its light-diffusing properties. It is used as a light abrasive, in products like toothpaste. Other uses include filler in silicone elastomer and viscosity adjustment in paints, coatings, printing inks, adhesives and unsaturated polyester resins.[5] Fumed silica readily forms a network structure within bitumen and enhances its elasticity.[6]

Health issues

Fumed silica is not listed as a carcinogen by OSHA, IARC, or NTP. Due to its fineness and thinness, fumed silica can easily become airborne, making it an inhalation hazard capable of causing irritation.

See also

References