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  • Fumed silica is also known as pyrogenic silica because it is produced in flame pyrolysis of silicon tetrachloride or from quartz sand vaporized in a 3000 °C electric arc. Fumed Silica consists of microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles, agglomerating into tertiary particles. The resulting powder has an extremely low bulk density of 2.5-11.8 lbs/ft3 (40–190 kg/m3), a primary particle size of 5–50 nm (smaller than the average p Fumed silica is 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. It is also used in producing cat litter box fillers and as a core material in produc Fumed silica is an artificial substance, so it’s no surprise that it’s known by multiple names—Diatomaceous earth, Diatomaceous silica, Diatomite, Silicon dioxide (amorphous), and Vitreous silica, at least. In fact, before 1989, its official name was silica (amorphous). Today, however, industry and regulators tend to call the substance fumed silica—not to be confused with silica fume, which is an industrial byproduct quite different from fumed silica. Fumed silica is a beneficial industrial chem The benefits of fumed silica and silica fume in the manufacturing and construction industries are well known. While the two terms seem similar, the products have apparent differences. Unfortunately, most people use the terms interchangeably. Here is everything you need to know about fumed silica and silica fume. Fumed silica or pyrogenic silica is a multi-purpose silica-based additive commonly used to manipulate viscosity and rheology and enhance the functionality of existing polymer matrices. I What is Fumed Silica?Fumed Silica is a form of silicon dioxide, or silicon, with the molecular formula SiO2 and a molecular weight of 60.0843 g/mol. Fumed silica is also known as pyrogenic silica. It is an odorless white powder consisting of droplets of fused silica cooled by forming three-dimensional chains. These are organized into particles of amorphous matter of very low apparent density and very high specific surface area. Fumed silica is insoluble in water. Fumed silica (CAS number 112945- The Aerosil® 200 silica used by the invention, with a BET surface area, differs from the known Aerosil® 300, which has a surface area of 300 m2/g, not only in the surface size but also in the average primary particle size. The Aerosil® 300 has an average primary particle size of 7 nm. Based on these differences, these silicas have different performance properties. The fumed silica of the invention contains no hydrophobic fractions. Despite this, the silica of the invention shows no propensity to The prior art can only prevent deagglomeration if the hydrophilic silica is mixed with 3% by weight of hydrophobic silica and if this mixture is ground utilizing an air-jet mill or a pinned-disc mill (EP 0 076 377 B1). In this case, for a fumed silica having a BET surface area of 200 m2/g, even after compaction to 73 or 107 g/l, a goniometer value of 35 is achieved. For a fumed silica with a BET surface area of 300 m2/g, adding hydrophobic silica before grinding produces a goniometer value of 10 A known procedure is to render fumed silica hydrophobic, grind it in a pinned-disc mill, and then classify it (U.S. 2004/0110077 A1). This known silica is used as an external additive in toner mixtures. Reducing the agglomerate size by dispersing outside a liquid system, in other words, in practice, in the air, or by grinding in the conventional sense, is possible only to a limited extent since in the case of material with a given propensity to agglomerate the comminution is followed immediately The primary particles and aggregates of a fumed silica agglomerate form larger assemblies whose size is generally in inverse proportion to the primary particle size or proportion to the specific surface area. The agglomerate size also increases with the extent to which the fumed silica is compacted. The binding forces holding these agglomerates together are relatively weak. Nevertheless, a certain shearing energy is required when these agglomerates are incorporated into and broken down in a liqu Fumed silica having a BET surface area of 200±15 m2/g, a goniometer value of less than 30 μm, and a median value by PCS of 65 to 85 nm are prepared by grinding a fumed silica having a surface area of 200±25 m2/g, and silicone rubber containing this silica. This application is a continuation of Ser. No. 12/095,840 filed Jun. 2, 2008, a U.S. National Stage Filing of international No. PCT/EP2006/068889 filed Nov. 24, 2006, which claims priority from EP 051125334 filed Dec. 20, 2005, which all are b

The shear strength enhancement as a result of fumed silica addition is even more striking

The shear strength enhancement due to fumed silica addition is even more striking. Adhesive shear strength typically increases more than a thousand-fold compared to films without particle reinforcement. The chemical bond formation in these adhesive films caused by adding fumed silica dispersions is currently being investigated, as this enhancement level was unexpected. Regardless of the shear strength enhancement source, the film cohesive strength increase is significant. The peel strength of th

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Pressure Sensitives of Fumed Silica

Significant improvements have been observed in cohesive shear strength and thermo-mechanical properties of waterborne pressure-sensitive adhesives (PSAs) due to the incorporation of highly dispersed fumed silica. Adhesive films with fumed silica content ranging from 0 to 15 weight % (dry weight) were formulated from water-based acrylic emulsions designed for PSA applications. The films were formed by drawing down the emulsions on Mylar backing and drying the wet films in a ~ 110°C oven for 20-40

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One Component Polyurethane of Fumed Silica

High-surface-area carbon blacks and fumed silica are more efficient on an equal-weight basis as reinforcing agent than other rheology-control additives. Carbon black is used to build viscosity, provide sag resistance, and increase the cohesive strength of automotive windshield adhesives. Coated precipitated calcium carbonates (PCCs) are used for rheology control of STP and polyurethane adhesives and sealants. Those PCCs with hydrophobic coatings (e.g., fatty acid or stearic acid) do yield shear-

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Formulators using hydrophilic fumed silicas in moisture curing systems

Formulators using hydrophilic fumed silicas in moisture curing systems, such as STP or polyurethane, must address premature curing of these systems due to the large water adsorption capacity of hydrophilic silica. Several options are available to solve this challenge, including adding process steps (e.g., pre-drying hydrophilic silica or removing water during compounding via heat and vacuum) or adding additional components (e.g., chemical dryers). A better option is replacing the hydrophilic sil

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Understanding the Role of Fumed Silica in Adhesives

Formulators use particles to enhance the functionality of existing polymer matrices for adhesive and sealant products. Fumed silica is commonly used as a rheology control additive to provide sag resistance, anti-settling of fillers, and shear-thinning viscosity. The generic term “fumed silica” defines a range of products with different surface chemistries—from hydrophilic to hydrophobic. These products have differing compatibility with polymer systems, which enable formulators to fine-tune rheol

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About Fumed Silica

What is Fumed Silica?Since its first production in the early forties of this century, fumed silica has found widespread use in industrial applications. Due to its pyrogenic manufacturing process by combustion of silicon tetrachloride in an oxygen-hydrogen flame, fumed silica offers a variety of fascinating properties. It consists of finely dispersed amorphous silicon dioxide, and its surface is covered by highly reactive silanol groups, which are available for chemical reactions. Additionally, f

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Can you get silicosis from fumed silica

Breathing in dust from silica-containing materials can lead to Silicosis. Silica dust particles become trapped in lung tissue, causing inflammation and scarring. The particles also reduce the lungs' ability to take in oxygen. Many products use fumed silica (silicon dioxide) as a filler or flow control additive. Many other metal oxides including TiO2, ZnO, and Fe2O3 are produced as particulate solids with a primary particle size below 100 nm. Fumed silica powder has a high surface area. It is ext

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Is fumed silica an oil thickener

In addition to providing good thickening and stability and allowing the system to exhibit elasticity to large strains, fumed silica can also be used as a thickening additive in formulated greases. As an additive to formulated greases, fumed silica can provide an additional level of rheological tailoring. Fumed silica has a chain-like particle structure that bonds together to trap liquid, thereby increasing viscosity. Add to thicken and increase the transparency of the paint. Stirring or brushing

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What precautions should be taken during fumed silica

What is Fumed silica?Fumed silica, or pyrogenic silica, is an amorphous, synthetic silica produced by vapor phase hydrolysis of chlorosilanes in a hydrogen-oxygen flame. Primary particles are fused into branched, three-dimensional secondary particles or aggregates in the flame process. Silica fume is added to Portland cement concrete to improve its properties, particularly its compressive strength, bond strength, and abrasion resistance. The silica particles then alter the surface of its host ma

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What material is fumed silica

What is Fumed silica?Fumed silica can be defined as finely divided amorphous silicon dioxide particles produced by high temperatures in an oxygen-hydrogen flame. Fumed silica, also known as pyrogenic silica because it is produced in a flame, consists of microscopic amorphous silica fused into branched, chainlike, three-dimensional secondary particles, which agglomerate into tertiary particles. The resulting powder has an extremely low bulk density and high surface area. Its three-dimensional str

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Does fumed silica absorb water

While small quantities of Silica are not thought to threaten health, having Silica contaminated water can create problems around your home. Like hard water minerals, Silica can create a scale that can impact the performance of your water-using appliances and fixtures. The resulting fumed Silica has a highly porous and sponge-like structure. It also has a larger surface area than other forms of Silica, such as ground silica and precipitated Silica. The surface area makes fumed Silica highly react

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Is fumed silica hydrophobic

Aggregated fumed Silica can be applied to large surfaces to render them hydrophobic. Micro and nanoscale structures, resembling ball and block-like forms, are attributed to the hydrophobic characteristics. They enable silicone to be used safely in ovens and direct contact with food. And we also offer a further special feature: AEROSIL® fumed Silica enables you to manufacture colorless, highly transparent silicone rubber used in medical applications. Silica fume, a by-product of the ferrosilicon

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