Not to be confused with silica fume
"Aerosil" redirects here. Not to be confused with aerosol
Fumed silica with surface area of 130 m2/gFumed 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]
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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.
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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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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]
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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.
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Hydrophilic fumed silica is a nanomaterials with strong hygroscopicity(absorbing moisture). This fluffy white powder is based on high purity amorphous silica. It is can be wetted by water, and dispersed in water forming a suspension.
When it firstly produced from oxyhydrogen flame&#;the moisture content is very low. Take XYSIL200 for example, it is around 0.48 wt%. If exposed into air for about 30 seconds to 180 seconds, this number will be double or even tripled.
Hydrophilic fumed silica is mainly used to provide thixotropic properties in coating and adhesive; to provide reinforcement in silicone rubber. Besides, it acts as free flow and absorbing agent in pharmacy, food and cosmetic products.
Various grades can be divided mainly by hydrophilic fumed silica BET surface area. Take XYSIL fumed silica as example, the 200 in XYSIL 200 comes from the value of BET surface area.
Some manufacturer divides into more grades according to applications. The picture below is Aerosil hydrophilic grades, Aerosil A200 F is the grade for food and Aerosil 300 pharma is obviously for pharma.
Due to its strong tendency of absorbing moisture, the hydrophilic fumed silica requires strictly moisture proof. Three layer kraft paper bag and plastic layer around the pallet meet this need. However, this packing is fragile during transporting.
If the original package is open or broken, the product inside should be used as soon as possible.
For more information, please visit hydrophilic pyrogenic silica.