Fumed Silica Resources: Technical Data, Safety, and Selection Tools
Central hub for fumed silica technical documents, safety data, certifications, and practical selection tools used by chemical formulators worldwide.
Technical Data Sheet Library
Every fumed silica grade ships with a TDS that specifies BET surface area, tamped density, pH (4% suspension), SiO₂ content, and loss on drying. Our TDS library covers hydrophilic grades (BET 150–380 m²/g) and hydrophobic grades treated with DDS, HMDS, or silicone oil — each treatment shifting the carbon content and moisture pickup profile. Formulators use TDS data to match thickening efficiency curves: a 200 m²/g hydrophilic grade delivers roughly 2× the viscosity build of a 150 m²/g grade at equal loading in unsaturated polyester. Browse by grade family or surface area range.
- Hydrophilic TDS — Covers SEMISIL 150, 200, 300, 380 — BET, pH, tamped density, SiO₂ ≥99.8%
- Hydrophobic TDS — DDS-treated and HMDS-treated grades — carbon content 0.8–3.5%, moisture uptake <0.5%
- Comparison tables — Side-by-side spec comparison across all grades for quick screening
Safety Data Sheet Library
Fumed silica is amorphous (non-crystalline), but correct handling still matters. Our SDS library provides GHS-classified hazard information, exposure limits (typically 2–6 mg/m³ TWA for respirable dust depending on jurisdiction), first-aid protocols, and storage guidance. Each SDS follows REACH and GBT 16483 formatting. Hydrophobic grades carry additional notes on organic surface treatment decomposition above 300 °C. Formulators integrating fumed silica into food-contact or pharmaceutical applications will find regulatory cross-references in each SDS linking to relevant FDA 21 CFR and EP/USP monographs.
- GHS classification — Eye irritation Cat 2, STOT SE 3 — standard for all amorphous silica grades
- Exposure limits — OEL varies: 2 mg/m³ (DE), 4 mg/m³ (CN), 6 mg/m³ (US OSHA PEL for amorphous)
- Storage — Keep sealed, dry, below 40 °C — moisture absorption degrades hydrophilic grades over time
Certifications and Compliance
Grade selection in regulated industries depends on certifications as much as specs. Our certifications page details ISO 9001 and IATF 16949 production-site credentials, REACH registration numbers, FDA 21 CFR 172.480 (food-grade indirect contact), and EP/USP monograph compliance for pharmaceutical excipient grades. For electronics-grade fumed silica used in CMP slurries, we document trace metal content (Fe <1 ppm, Na <1 ppm, Al <1 ppm) verified by ICP-OES. Each certificate links to the specific grade family it covers — not all grades carry all certifications.
- ISO / IATF — Production certified ISO 9001:2015 and IATF 16949 for automotive supply chain
- Food & pharma — Select grades meet FDA 21 CFR 172.480, EP 0434, USP-NF monograph
- Electronics purity — CMP-grade silica: Fe, Na, Al each <1 ppm by ICP-OES
Grade Selection Guide
Choosing the right fumed silica grade starts with three questions: what is the polarity of your system, what rheology profile do you need, and what is the target loading? Hydrophilic grades (untreated, silanol-rich surface at 2–3 SiOH/nm²) work best in polar systems — epoxies, polyesters, aqueous dispersions — delivering thixotropy via hydrogen-bond networking. Hydrophobic grades (DDS or HMDS treated, carbon content 0.8–3.5%) suit non-polar systems — silicone sealants, alkyd paints, PVC plastisols — where untreated silica would clump. Higher BET means more thickening per unit weight but also higher dust and harder dispersion. The table below maps common applications to recommended grades.
| Application | System Polarity | Recommended Grade | BET (m²/g) | Typical Loading (%) |
|---|---|---|---|---|
| Epoxy adhesive thixotropy | Polar | SEMISIL 200 | 200 | 3–5 |
| Silicone sealant reinforcement | Non-polar | SEMISIL H200-DS | 200 | 6–10 |
| UPE gel coat anti-sag | Polar | SEMISIL 150 | 150 | 1.5–3 |
| Aqueous coating anti-settling | Polar | SEMISIL 300 | 300 | 0.5–2 |
| PVC plastisol flow control | Non-polar | SEMISIL H150-HM | 150 | 2–4 |
| CMP slurry (electronics) | Aqueous | SEMISIL 380-E | 380 | 10–30 |
FAQ
What is the difference between hydrophilic and hydrophobic fumed silica?
Hydrophilic fumed silica has an untreated surface rich in silanol groups (2–3 SiOH/nm²) that hydrogen-bond in polar media. Hydrophobic grades are surface-treated with DDS or HMDS, replacing silanols with methyl groups, lowering surface energy, and enabling dispersion in non-polar systems like silicones and alkyds.
How do I choose the right BET surface area grade?
Higher BET surface area means more thickening efficiency per unit weight. A 200 m²/g grade gives roughly twice the viscosity build of a 150 m²/g grade at equal loading in polyester resin. However, higher BET also means finer primary particles (7–12 nm), more dust, and harder dispersion — balance efficiency against processability.
Where can I find the TDS for a specific fumed silica grade?
The TDS library on this site organizes all technical data sheets by grade family and surface area range. Each TDS includes BET, tamped density, pH, SiO₂ purity, and loss on drying. Visit the TDS library page and filter by hydrophilic or hydrophobic.
What safety precautions apply when handling fumed silica?
Fumed silica is amorphous and not classified as a carcinogen. Key precautions: use local exhaust ventilation, wear P2/N95 respiratory protection, and keep workplace dust below the OEL (2–6 mg/m³ depending on jurisdiction). Consult the SDS library for grade-specific handling details.
Does fumed silica meet food-contact or pharmaceutical regulations?
Select grades comply with FDA 21 CFR 172.480 for indirect food contact and EP/USP monographs for pharmaceutical excipient use. Not all grades carry these certifications — check the certifications page for the specific grade you intend to use.
What typical loading levels are used for thixotropy in epoxy systems?
Most epoxy formulators achieve target thixotropy at 3–5 wt% loading with a 200 m²/g hydrophilic grade. Higher BET grades (300 m²/g) can reduce loading to 1.5–3% but require higher shear dispersion equipment such as a three-roll mill or high-speed dissolver above 10 m/s tip speed.