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FAQ

AEROSIL® fumed silica is manufactured by a continuous flame hydrolysis process of silicon tetrachloride SiCl4. During this process, SiCl4 is converted into the gas phase and then reacts spontaneously and quantitatively in an oxyhydrogen flame with the intermediately formed water to produce the desired silicon dioxide. 2 H2 + O2 -----> 2 H2O
SiCl4 + 2 H2O -----> SiO2 + 4 HCl
2 H2 + O2 + SiCl4 -----> SiO2 + 4 HCl
During this chemical reaction a considerable amount of heat is released, which is eliminated in a cooling line. The only by-product is gaseous hydrogen chloride which is separated from the AEROSIL® fumed silica solid matter.
 
For example, in the case of AEROSIL® R 972, freshly-produced hydrophilic AEROSIL® 130 is converted with dimethyldichlorosilane (DDS) in a fluid-bed reactor. The silane reacts with the silanol groups primarily with the formation of Si-O-Si (CH3)2 units, and as a result the material acquires a hydrophobic character. The number of silanol groups is reduced during the treatment to about 30% of the initial value. Analogous reactions can also be carried out with other silanes and other hydrophilic grades.
 
AEROSIL® fumed silica is a white, fluffy powder.
 
The BET method, according to Brunauer, Emmett and Teller is used to determine the specific surface of highly dispersed materials by means of the adsorption of gases, especially nitrogen.
 
The thixotropic index is defined as the quotient from two viscosity values obtained at different speeds. Rotational speed n1 and n2 are usually in an approximate ratio of 1:10
 
USP/NF: Colloidal Silicon Dioxide; EP: SILICA, COLLOIDAL ANHYDROUS; FCC: Silicon Dioxide; JECFA: SILICON DIOXIDE, AMORPHOUS.
 
AEROSIL® grades can be surface-treated to be functionalized and/or hydrophobic, i.e. water-repellant. This is denoted with the letter "R" (repellant) within their name. Prominent hydrophobic AEROSIL® grades (aftertreated with organosilanes) are e.g. AEROSIL® R 202, AEROSIL® R 972, AEROSIL® R 812 S, AEROSIL® R 8200.
 
Most handling techniques to keep the process dust free are described in our Technical Bulletin Fine Particles 28 “Handling of synthetic silica and silicate”. The engineers of our Handling Technology Department can recommend equipment and methods for dust-free handling of AEROSIL® products and consults customers in questions concerning handling and packaging.
 
Most handling techniques to keep the process dust free are described in our Technical Bulletin Fine Particles 28 “Handling of synthetic silica and silicate”. The engineers of our Handling Technology Department can recommend equipment and methods for dust-free handling of AEROSIL® products and consults customers in questions concerning handling and packaging.
 
AEROSIL® fumed silica is supplied in multi-ply 10 kg paper bags, or in 10 lb multi-ply paper bags within the NAFTA region.
 
Because of its X-ray amorphous structure, AEROSIL® fumed silica inhalation does not cause silicosis.
 
The above mentioned product is a pure substance. During the production process we do not intentionally use or add any ingredients usually mentioned to be allergens -according to EU-Directive 2000/13/EC and amendments
-according regulation (EU) No 1169/2001 - Food information to consumers
-according to the ALBA-list.
Cereals containing gluten (e.g. Wheat, Rye, Barley, Oat, Spelt, Kamut), Maize, Crustaceans, Molluscs, Egg, Fish, Milk, Lactose, Ox, Pig, Hen/Chicken, Peanuts, Soybeans, Almonds, Hazelnut, Walnut, Cashew nut, Pecan nut, Brazil nut, Pistachio, Macadamia nut, Queensland nut, Celery, Mustard, Sesame, Lupines, Leguminous plants, Cinnamon, Vanilla, Coriander, Cocoa, Sulphur dioxide, Sulphites. Yeast, Glutamate (E620 – E625), Benzoic acid (E210 – E219) Azo-colorants/pigments.
-Other additives, preservatives, flavors/fragrances or latex.

Since testing of these substances is not part of our standard routine quality control and production testing procedures, we therefore cannot warrant or guaranty the absence of these substances in this product.
 
In the production process of the above mentioned product we do not use any genetically modified organisms (GMO). The above mentioned product is no GMO, it does not contain any GMO and has not been in contact with any GMO. Therefore the Regulations (EC) No 1829/2003 (as amended) and No 1830/2003 (as amended) are not applicable.
 
Origin – TSE / BSE and Materials of animal or plant origin The above mentioned product is chemically produced. In the product process we do not use any raw material of animal or plant origin ( as mentioned in EMEA / 410/01, current version). In our manufacturing facilities we generally do not use any material of animal or plant origin. Our product is not contaminated with any animal - or plant – based material when it leaves the manufacturing sites and warehouses of the manufacturing company.
 
Information concerning the safety of this product is listed in the corresponding Safety Data Sheet, which will be sent with the first delivery or upon updating. Such information is also available from Evonik Industries AG, Product Safety Department, E-MAIL sds-im@evonik.com or can be download from this website (Services/Safety data sheets). We recommend to read carefully the safety data sheet prior to the use of our product.
 
All hydrophilic synthetic amorphous silica of type AEROSIL® are in line with the quality requirements for food additive E 551 in Europe. However, only the products AEROSIL® 200 F and AEROSIL® 380 F ex our plant Antwerp / Belgium are produced according to HACCP principles as defined in VO (EU) 852/2004.
 
Extrudability is the amount of sealant pressed out of a putty gun with an air pressure of about 0.6 N/ mm2, contained in a cartridge through a circular nozzle of approx. 6 mm diameter into a calibrated vessel. The quantity in weight per time unit (g/min) is determined in accordance with CGSB 19-GB-5 or ASTM D 2452-69 T. The higher the compound's viscosity, the lower the extrudability.
 
The tendency of a material, under the force of gravity, to flow. The test bead is measured in millimeters, from the lower edge, in accordance with ASTM D 2202-88.
 
AEROSIL® R 202 and AEROSIL® R 805 are very effective thixotropes for structural adhesives based on epoxy resins or polyurethanes.
 
Through the use of AEROSIL® fumed silica in coatings, the settling of pigments and fillers can be prevented or reduced. Standard amount used is in the range between 0.4 - 0.8 % AEROSIL® 200 related to the total formulation. In special cases such as zinc dust paints, additions of up to 1.5% are possible or required.
 
In addition to its effect as a suspension aid in anti-corrosive paints, AEROSIL® fumed silica also brings an improvement in the corrosion resistance. 0.5 - 1.5 % of AEROSIL® R 972 and R 974 are recommended.
 
AEROSIL® fumed silica can be used in all kinds of coatings, e. g. solvent, water-based, UV-curing coatings and powder coatings.
 
Usually a pearl mill or ball mill is recommended. A dissolver can be sufficient in non-glossy systems.
 
Yes , through the use of AEROSIL® fumed silica, the rheological characteristics of the mill base are positively changed. The favorable influence on viscosity and thixotropy results in an improvement of the dispersibility.
 
The most important applications of AEROSIL® fumed silica are rheology control, thickening, thixotropy, anti-settling of pigments and fillers and anti-sagging of coatings on vertical substrates.
 
A concentration of 0.5 - 1.0% of AEROSIL® fumed silica calculated on total formulation is usually sufficient.
 
Some additives like bifunctional liquids (e.g. polyethylene glycol, polypropylene glycol) may significantly enhance the thickening behaviour of fumed silicas.
 
For the thickening of UPE lamination resins 0.8 - 1.3 % of AEROSIL® 200 is recommended.
 
For thickening and thixotropy effects, gel coats normally contain 2.0 - 3.0 % of AEROSIL® 200 and in special cases up to 4 %.
 
For the proper dispersion of AEROSIL® fumed silica in UPE gel coats high speed dissolver are recommended.
 
For the dispersion of AEROSIL® fumed silica in UPE lamination resins ultrasonic sonolators or in line rotor-stator mixer are recommended. High speed dissolvers are used as well.
 
AEROSIL® 200 is the most commonly used grade for the thickening of UPE lamination resins and gel coats.
 
AEROSIL® R 202 is the most commonly used grade for the thickening of VE resins.
 
The tear resistance steadily improves as a function of the increasing BET surface area of the AEROSIL® products. To achieve good tear resistance, it is advisable to apply a grade of AEROSIL® fumed silica with a higher surface area (e.g. AEROSIL® R 812 S).
 
LSR (engl. = Liquid Silicone Rubber) is processed using LIMS (engl. Liquid Injektion Moulding System).
 
AEROSIL® R 8200 has a distinctly lower structure than previously known AEROSIL® product grades. Its properties include: extremely low thickening effect, excellent reinforcing properties at high filler loading levels and good processiability due to its high tapped density. It is therefore suitable for all polymer systems requiring a very high filler loading level and/or extremely low thickening effect e.g. liquid silicone rubber, self leveling or high tear resistance silicone formulations, or two component silicone rubber.
 
AEROSIL® R 974 or AEROSIL® R 106 should be used to achieve this effect or AEROSIL® R 812 S if highly transparent formulations are required.
 
AEROSIL® 200, AEROSIL® 300 and AEROSIL® 380 are the most frequently used AEROSIL® grades. These hydrophilic grades need a treatment with functional silanes during the compounding process (the so called "in-situ treatment"). Additionally we recommend special hydrohobic grades like AEROSIL® R 8200 and AEROSIL® 812 S, which can be used directly by simple just mix (the in-situ treatment is not necessary).
 
AEROSIL® 150 and AEROSIL® R 972 are the most frequently used grades.