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Amorphous silica is a non-crystalline form of silicon dioxide with a disordered three-dimensional silicon-oxygen network.
Amorphous silica provides adsorption, reinforcement, rheology control, matting, anti-caking, flow improvement, and moisture-management functions.
Amorphous silica is available as fumed silica, precipitated silica, silica gel, hydrous silica, colloidal silica, fused silica, and silica fume.
CAS Number: 7631-86-9 is commonly used; form-specific identifiers include 112945-52-5 for pyrogenic silica, 112926-00-8 for precipitated silica and silica gel, and 69012-64-2 for silica fume
EC Number: 231-545-4 for silicon dioxide
Molecular Formula: SiO₂
Molecular Weight: 60.08 g/mol
SYNONYMS
Amorphous Silica, Silica Amorphous, Amorphous Silicon Dioxide, Non-Crystalline Silica, Noncrystalline Silica, Silicon Dioxide Amorphous, Synthetic Amorphous Silica, SAS, Silicon Dioxide, Silica, Silicic Anhydride, Silicic Acid Anhydride, Dioxosilane, Hydrated Silica, Hydrous Silica, Anhydrous Silica, Colloidal Silica, Colloidal Silicon Dioxide, Silica Colloidalis Anhydrica, Pyrogenic Silica, Fumed Silica, Pyrogenic Amorphous Silica, Fumed Amorphous Silica, Highly Dispersed Silica, High-Surface-Area Silica, Precipitated Silica, Precipitated Amorphous Silica, Wet-Process Silica, Silica Gel, Amorphous Silica Gel, Xerogel Silica, Hydrogel Silica, Aerogel Silica, Silica Aerogel, Fused Silica, Vitreous Silica, Silica Glass, Quartz Glass, Silica Fume, Amorphous Silica Fume, Microsilica, Micronized Silica, Fine Silica Powder, Porous Silica, Mesoporous Silica, Synthetic Silica, White Carbon, E551, Silicon Dioxide E551, Food-Grade Silicon Dioxide, Pharmaceutical Colloidal Silicon Dioxide, Rubber Reinforcing Silica, Coating Matting Silica, Rheology-Control Silica, Desiccant Silica Gel, CAS 7631-86-9, EC 231-545-4, SiO₂
APPLICATIONS
Amorphous silica serves as a reinforcing filler in tire compounds containing natural rubber, synthetic rubber, and compatible silane coupling systems.
Amorphous silica can improve tensile properties, abrasion resistance, wet traction, and rolling behavior when dispersion and filler-polymer interaction are optimized.
Amorphous silica functions as a reinforcing filler in silicone-rubber compounds requiring increased tensile strength, tear resistance, and dimensional stability.
Amorphous silica creates a filler network whose performance depends on surface area, surface treatment, moisture, dispersion, and polymer compatibility.
Amorphous silica contributes to industrial rubber products such as hoses, belts, seals, footwear components, rollers, and molded elastomer articles.
Amorphous silica can modify hardness, modulus, tear strength, abrasion behavior, electrical properties, and compound processing.
Amorphous silica serves as a thixotropic rheology modifier in solvent-borne, waterborne, and solvent-free coatings.
Amorphous silica helps reduce sagging and settling by forming reversible particle networks within compatible liquid formulations.
Amorphous silica functions as a matting agent in paints, varnishes, lacquers, wood finishes, and industrial coatings.
Amorphous silica creates microscopic surface irregularity that reduces specular reflection and lowers the apparent gloss of the dried film.
Amorphous silica contributes to printing inks by controlling rheology, pigment suspension, rub resistance, and surface appearance.
Amorphous silica must be selected according to the printing process because particle size and oil absorption influence flow, transfer, and gloss.
Amorphous silica supports adhesives and sealants requiring thixotropy, anti-sag behavior, reinforcement, or controlled extrusion.
Amorphous silica can improve bead stability and filler suspension in epoxy, polyurethane, silicone, acrylic, and other compatible binder systems.
Amorphous silica functions as a reinforcing or functional filler in thermosetting resin composites.
Amorphous silica can modify viscosity, shrinkage, hardness, thermal expansion, electrical behavior, and mechanical performance in compatible resin systems.
Amorphous silica contributes anti-blocking and surface-slip performance to compatible plastic films and polymer compounds.
Amorphous silica creates microscopic surface roughness that reduces direct contact between adjacent film layers.
Amorphous silica supports free-flowing powder formulations by absorbing surface moisture and reducing cohesion between particles.
Amorphous silica can improve dosing, conveying, packaging, blending, and storage behavior in compatible dry products.
Amorphous silica serves as an anti-caking agent in legally authorized powdered food products under the E551 designation.
Amorphous silica prevents dry food particles from adhering strongly to one another by managing surface moisture and particle contact.
Amorphous silica functions as a processing and stabilization aid in authorized beverage and brewing applications.
Amorphous silica can adsorb selected haze-forming proteins during beer clarification when a suitable food-grade material and validated process are used.
Amorphous silica serves as a glidant in pharmaceutical powders intended for tablet or capsule manufacturing.
Amorphous silica improves powder flow by reducing interparticle friction and absorbing small quantities of surface moisture.
Amorphous silica supports pharmaceutical tablets, capsules, granules, suspensions, and semisolid formulations as an adsorbent or processing excipient.
Amorphous silica requires the appropriate pharmacopoeial grade, purity documentation, particle specification, and regulatory acceptance for the intended route.
Amorphous silica functions as a mild abrasive and thickening component in toothpaste formulations.
Amorphous silica grade selection allows cleaning performance, transparency, rheology, fluoride compatibility, and enamel abrasivity to be adjusted.
Amorphous silica contributes absorbency, mattifying performance, texture modification, and oil control to compatible cosmetic powders.
Amorphous silica can improve sensory properties in facial powders, color cosmetics, dry shampoos, and oil-control products.
Amorphous silica supports creams, lotions, gels, antiperspirants, sunscreens, and anhydrous personal-care formulations.
Amorphous silica can increase viscosity, stabilize suspended ingredients, absorb oils, and modify the feel of the applied product.
Amorphous silica functions as a structural component in antifoam formulations containing compatible oils and hydrophobic ingredients.
Amorphous silica helps destabilize foam films when its surface treatment, particle dispersion, carrier composition, and dosage are appropriate.
Amorphous silica gel serves as a desiccant in packaging, storage, laboratory, pharmaceutical, electronic, and industrial applications.
Amorphous silica gel adsorbs water vapor within its porous structure without dissolving or becoming a liquid under normal use conditions.
Amorphous silica functions as a stationary-phase material and support in chromatography and separation technologies.
Amorphous silica surface silanol groups can be chemically modified to control polarity, selectivity, pore characteristics, and analyte interaction.
Amorphous silica serves as a catalyst carrier or catalyst-support precursor in chemical and petrochemical processes.
Amorphous silica provides high surface area, thermal stability, adjustable porosity, and accessible sites for supported catalytic species.
Amorphous silica aerogel supports thermal-insulation systems requiring very low density and low thermal conductivity.
Amorphous silica aerogel can be incorporated into blankets, panels, coatings, and specialty insulation composites after suitable dust and durability controls.
Amorphous silica fume functions as a supplementary cementitious material in concrete, mortar, grout, and repair compositions.
Amorphous silica fume reacts pozzolanically with calcium hydroxide and can improve density, strength, permeability resistance, and interfacial structure.
Amorphous silica contributes to microporous separator formulations used in selected electrochemical battery systems.
Amorphous silica can provide porosity, electrolyte wettability, dimensional structure, and filler reinforcement in compatible separator matrices.
Amorphous silica functions as a carrier, absorbent, flow aid, or dispersing support in agricultural and industrial formulations.
Amorphous silica must be selected according to purity, particle size, dust behavior, adsorption capacity, environmental requirements, and final-product authorization.
DESCRIPTION
Amorphous silica is silicon dioxide in which silicon and oxygen atoms do not form the long-range repeating arrangement found in crystalline silica.
Amorphous silica has the nominal chemical formula SiO₂ and a formula weight of approximately 60.08 g/mol.
Amorphous silica is chemically related to quartz but differs substantially in atomic organization, particle structure, surface behavior, and occupational hazard profile.
Amorphous silica should therefore not be described as respirable crystalline silica unless crystalline phases are actually present.
Amorphous silica is a broad category that includes synthetic and naturally derived materials produced through different processes.
Amorphous silica forms commonly include fumed silica, precipitated silica, silica gel, hydrous silica, colloidal silica, fused silica, and silica fume.
Amorphous silica commonly uses CAS Number 7631-86-9, but modern substance records also apply form-specific identifiers.
Amorphous silica identity should be matched to the exact production process, surface treatment, hydration state, and commercial grade.
Amorphous silica consists of interconnected silicon-oxygen tetrahedra arranged without long-range crystalline order.
Amorphous silica surfaces commonly contain silanol groups that interact with water, polymers, surfactants, pigments, proteins, and other polar substances.
Amorphous silica produced by flame hydrolysis is commonly described as pyrogenic or fumed silica.
Amorphous silica made by this high-temperature route normally forms very small primary particles fused into branched aggregates.
Amorphous silica produced through wet precipitation can be manufactured with controlled particle size, porosity, surface area, and oil absorption.
Amorphous silica gel is also produced by wet chemistry and develops a porous network during gel formation, washing, drying, and particle processing.
Amorphous silica normally appears as a white, odorless, lightweight powder, granule, bead, gel, monolith, or colloidal dispersion.
Amorphous silica appearance and bulk density vary widely because highly porous grades contain substantial internal void volume.
Amorphous silica can possess high specific surface area and strong adsorption capacity.
Amorphous silica surface area, pore volume, particle aggregation, moisture content, and surface chemistry determine performance more strongly than formula alone.
Amorphous silica builds rheology by hydrogen bonding and particle-particle interaction within compatible liquids.
Amorphous silica adsorbs water, oils, flavors, active substances, pigments, and formulation ingredients according to pore structure and surface treatment.
Amorphous silica is noncombustible and provides high thermal and chemical stability in many applications.
Amorphous silica can react with strong alkalis and hydrofluoric acid and can undergo surface or structural changes during extreme thermal treatment.
Amorphous silica is practically insoluble in water as a bulk material but can disperse as colloidal particles.
Amorphous silica can dissolve slowly to form soluble silicic species depending on particle size, pH, temperature, and aqueous chemistry.
Amorphous silica quality is commonly controlled through silicon-dioxide content, moisture, loss on drying, surface area, particle size, pore volume, pH, bulk density, and crystalline-silica content.
Amorphous silica food, pharmaceutical, cosmetic, rubber, coating, construction, and analytical grades are not automatically interchangeable.
Amorphous silica is distinct from crystalline silica under occupational silica standards, but airborne amorphous silica dust should still be minimized.
Amorphous silica grades containing crystalline impurities require additional exposure assessment because crystalline contamination can materially change the respiratory hazard.
PROPERTIES
Chemical Name: Silicon Dioxide
Chemical Class: Non-Crystalline Inorganic Oxide
Common CAS Number: 7631-86-9
EC Number: 231-545-4
Molecular Formula: SiO₂
Molecular Weight: 60.08 g/mol
Physical Form: Powder, Granule, Gel, Bead, Monolith, or Colloidal Dispersion
Appearance: Commonly White and Odorless
Water Solubility: Practically Insoluble; Colloidally Dispersible in Suitable Grades
True Particle Density: Commonly Approximately 2.2 g/cm³
Surface Area: Grade Dependent
Porosity: Nonporous to Highly Porous, Grade Dependent
Primary Functions: Reinforcement, Rheology Control, Matting, Adsorption, Anti-Caking, and Flow Improvement
Main Uses: Rubber, Coatings, Food, Pharmaceuticals, Cosmetics, Desiccants, Construction, and Chemical Processing
Storage: Cool, Dry, Tightly Closed, and Protected from Moisture and Contamination
FIRST AID
Inhalation
Move the person exposed to amorphous silica dust or aerosol into fresh air and allow comfortable breathing.
Obtain medical attention if amorphous silica exposure causes persistent coughing, throat irritation, chest discomfort, wheezing, or breathing difficulty.
Skin Contact
Wash skin contaminated with amorphous silica thoroughly using soap and water.
Obtain medical attention if amorphous silica causes persistent dryness, redness, irritation, or another adverse skin response.
Eye Contact
Immediately rinse eyes exposed to amorphous silica with clean running water for at least 15 minutes while holding the eyelids open.
Remove contact lenses when easy to do and obtain medical attention if amorphous silica irritation, pain, redness, or visual disturbance persists.
Ingestion
Rinse the mouth after accidental ingestion of amorphous silica and drink water in small amounts when the person is conscious.
Obtain medical advice after substantial amorphous silica ingestion or whenever choking, gastrointestinal discomfort, or other symptoms develop.
Note to Physicians
Treat amorphous silica exposure symptomatically and provide appropriate supportive care.
Assess amorphous silica exposure according to particle size, dust concentration, crystalline-silica content, surface treatment, quantity, route, and symptoms.
HANDLING AND STORAGE
Handling
Handle amorphous silica using enclosed transfer, low-dust charging, and careful powder-management methods wherever practical.
Avoid generating amorphous silica dust and prevent unnecessary contact with the eyes, skin, clothing, food, and drink.
Ventilation
Provide effective general ventilation and local dust extraction wherever amorphous silica is opened, transferred, weighed, milled, or blended.
Use suitable particulate respiratory protection when engineering controls cannot adequately control airborne amorphous silica dust.
Storage
Store amorphous silica in tightly closed and moisture-resistant containers within a cool, dry, and well-ventilated area.
Protect amorphous silica from humidity, contamination, damaged packaging, strong alkalis, hydrofluoric acid, and incompatible chemicals.
Spill and Leak Procedures
Collect spilled amorphous silica using suitable filtered vacuum equipment or another recovery method that minimizes airborne dust.
Avoid compressed air and uncontrolled dry sweeping and prevent amorphous silica from entering drains or surface water in bulk quantities.
Handling Precautions
Wear suitable gloves, protective clothing, and tightly fitting safety goggles while handling amorphous silica.
Review the grade-specific Safety Data Sheet and verify crystalline-silica content before transporting, processing, or disposing of amorphous silica.
