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Amorphous silica is a non-combustible solid.
Generally unreactive chemically.
Incompatible with fluorine, oxygen difluoride, chlorine trifluoride.
CAS: 112945-52-5
MF: O2Si
MW: 60.08
EINECS: 231-545-4
Synonyms
acticel;SILICA GEL 7G;SILICA GEL 8-20 MESH;SILICA GEL 12-28 MESH;SILICA GEL 100;SILICA GEL 60;SILICA GEL 30;SILICA GEL 60 G
Soluble in molten alkalis and reacts with most metallic oxides at high temperature.
Amorphous silica is a silicon oxide made up of linear triatomic molecules in which a silicon atom is covalently bonded to two oxygens.
Amorphous silica may be synthesized by high temperature hydrolysis of SiCl4 in O2(N2)/H2 flame.
Amorphous silica is amorphous in nature and possesses very high specific area.
The micro droplets of amorphous silica fuse into a branch and form a chain like agglomerate.
Amorphous silica, 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.
Amorphous silica's three-dimensional structure results in viscosity-increasing, thixotropic behavior when used as a thickener or reinforcing filler.
Amorphous silica, also known as silica fume or pyrogenic silica, finds wide-ranging industrial applications due to its unique properties.
Amorphous silica is a versatile submicroscopic material characterized by its small particle size and large surface area, making it ideal for a variety of applications across pharmaceuticals, cosmetics, and food industries.
Amorphous silica significantly enhances the flow properties of dry powders, which can be crucial in processes like tableting and capsule filling.
In formulations, Amorphous silica serves as a stabilizing agent for emulsions and as a thickening and suspending agent in gels and semisolids, with the capacity to form transparent gels when combined with other ingredients of similar refractive index.
Amorphous silica's impact on viscosity is mainly influenced by the liquid's polarity and remains stable across different temperatures, although pH changes can alter the viscosity.
In aerosol formulations, Amorphous silica prevents hard settling, promotes particulate suspension, and prevents spray nozzle clogging.
Amorphous silica's also utilized as a tablet disintegrant, adsorbent dispersing agent, and in suppository formulations to enhance viscosity and control release rates.
Additionally, Amorphous silica serves as a thickening agent for topical applications and plays a role in the freeze-drying of nano-suspensions and the preparation of wax microspheres.
Amorphous silica, identified by the CAS number 112945-52-5, is a non-crystalline form of silicon dioxide (SiO2) produced through the combustion of silicon tetrachloride in an oxygen-rich environment.
Amorphous silica is characterized by its fine particle size, high surface area, and low density, which contribute to its unique properties.
Amorphous silica is typically a white, fluffy powder that is hydrophobic, meaning it repels water, and it exhibits excellent adsorption capabilities.
Amorphous silica is widely used as a thickening agent, anti-caking agent, and reinforcing filler in various applications, including paints, coatings, adhesives, and cosmetics.
Amorphous silica's high surface area enhances its effectiveness in these roles, providing improved texture and stability.
Additionally, Amorphous silica is chemically inert and does not react with most substances, making it suitable for use in a variety of industrial and consumer products.
Safety considerations include avoiding inhalation of dust, as Amorphous silica can cause respiratory irritation.
Overall, Amorphous silica is a versatile material with significant utility across multiple industries.
Amorphous silica Chemical Properties
Melting point: >1600°C
Density: 2.3 lb/cu.ft at 25 °C (bulk density)(lit.)
Refractive index: n20/D 1.46(lit.)
Solubility: Practically insoluble in organic solvents, water, and acids, except hydrofluoric acid; soluble in hot solutions of alkali hydroxide. Forms a colloidal dispersion with water. For Aerosil, solubility in water is 150 mg/L at 258℃ (pH 7).
Form: powder
Specific Gravity: 2.2
Hydrolytic Sensitivity 5: forms reversible hydrate
InChI: InChI=1S/O2Si/c1-3-2
InChIKey: VYPSYNLAJGMNEJ-UHFFFAOYSA-N
CAS DataBase Reference: 112945-52-5(CAS DataBase Reference)
EPA Substance Registry System: Amorphous silica (112945-52-5)
Amorphous silica, the noncrystalline form of SiO2, is a transparent to gray, odorless, amorphous powder.
Colloidal silicon dioxide is a submicroscopic Amorphous silica with a particle size of about 15 nm.
Amorphous silica is a light, loose, bluish-white-colored, odorless, tasteless, amorphous powder.
Uses
Amorphous silica has interesting thickening and thixotropic properties, and an enormous external surface area.
Amorphous silica is produced by a vapor phase hydrolysis process using chlorosilanes or substituted silanes such as, silicon tetrachloride in a flame of hydrogen and oxygen.
Amorphous silica is formed and collected in a dry state.
Amorphous silica contains no detectable crystalline silica.
Amorphous silica has a very strong thickening effect.
Primary particle size is 5–50 nm.
The particles are non-porous and have a surface area of 50–600 m2/g.
The density is 160–190 kg/m3.
Amorphous silica serves as a universal thickening agent and an anticaking agent (free-flow agent) in powders.
Like silica gel, Amorphous silica serves as a desiccant.
Amorphous silica is used in cosmetics for its light-diffusing properties.
Amorphous silica 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.
Amorphous silica readily forms a network structure within bitumen and enhances its elasticity.
Amorphous silica can be widely used in various coatings, plastics, adhesives and sealants, and used as a reinforcing agent in rubber; Used as dehumidifying desiccant, dehydrating agent, moisture-proof agent and air humidity regulator.
Also used for gas drying.
Amorphous silica is also used as catalyst and catalyst body, reinforcing agent of silicone rubber, and sizing agent used in textile industry.
Pharmaceutical Applications
Amorphous silica is widely used in pharmaceuticals, cosmetics, and food products.
Amorphous silica's small particle size and large specific surface area give it desirable flow characteristics that are exploited to improve the flow properties of dry powders in a number of processes such as tableting and capsule filling.
Amorphous silica is also used to stabilize emulsions and as a thixotropic thickening and suspending agent in gels and semisolid preparations.
With other ingredients of similar refractive index, transparent gels may be formed.
The degree of viscosity increase depends on the polarity of the liquid (polar liquids generally require a greater concentration of colloidal silicon dioxide than nonpolar liquids).
Viscosity is largely independent of temperature.
However, changes to the pH of a system may affect the viscosity1.
In aerosols, other than those for inhalation, Amorphous silica is used to promote particulate suspension, eliminate hard settling, and minimize the clogging of spray nozzles.
Amorphous silica is also used as a tablet disintegrant and as an adsorbent dispersing agent for liquids in powders.
Amorphous silica is frequently added to suppository formulations containing lipophilic excipients to increase viscosity, prevent sedimentation during molding, and decrease the release rate.
Amorphous silica is also used as an adsorbent during the preparation of wax microspheres; as a thickening agent for topical preparations; and has been used to aid the freeze-drying of nanocapsules and nanosphere suspensions.
Production Methods
Amorphous silica is prepared by the flame hydrolysis of chlorosilanes, such as silicon tetrachloride, at 18008℃ using a hydrogen–oxygen flame.
Rapid cooling from the molten state during manufacture causes the product to remain amorphous.
Purification Methods
Purification of silica for high technology applications uses isopiestic vapour distillation from concentrated volatile acids and is absorbed in high purity water.
The impurities remain behind.
Preliminary cleaning to remove surface contaminants uses dip etching in HF or a mixture of HCl, H2O2 and deionised water.
