2026-04-21
Published: April 21, 2026
Technical Guide Formulator’s Resource
- Verdict: SemiSIL 200 is a validated 1:1 technical equivalent to AEROSIL 200, sharing the same CAS number…
Verdict: SemiSIL 200 is a validated 1:1 technical equivalent to AEROSIL 200, sharing the same CAS number (112945-52-5) and matching all critical performance parameters.
Key Advantage: Factory-direct supply from China eliminates intermediary markups, reducing procurement costs by 20–35% without reformulation.
Best For: Coatings, adhesives, sealants, silicone rubber, and powder coatings requiring universal thixotropy and anti-settling performance.
Table of Contents
Both grades are synthetic amorphous silicon dioxide (SiO₂) manufactured via flame hydrolysis. The table below compares their certified technical parameters.
Parameter SemiSIL 200 (SEMITECH) AEROSIL 200 (Evonik) Match?
CAS Number 112945-52-5 112945-52-5 ✓ Identical
BET Surface Area 200 ± 25 m²/g 200 ± 25 m²/g ✓ Identical
SiO₂ Content ≥ 99.8% ≥ 99.8% ✓ Identical
pH Value (4% dispersion) 3.6 – 4.5 3.7 – 4.7 ✓ Equivalent
Loss on Drying ≤ 1.5% ≤ 1.5% ✓ Identical
Tapped Density ~50 g/L ~50 g/L ✓ Equivalent
Primary Particle Size ~12 nm ~12 nm ✓ Identical
Surface Chemistry Hydrophilic (Si-OH groups) Hydrophilic (Si-OH groups) ✓ Identical
Data sourced from SEMITECH TDS and Evonik AEROSIL 200 product specification sheet.
The primary function of both grades is to form a reversible 3D hydrogen-bonding network in liquid systems. This network provides thixotropy — the material flows under shear (pumping, brushing) and rebuilds viscosity at rest (preventing sag and settling).
SEMISIL 200
Achieves TI of 4–7 at 2% loading in standard epoxy systems. Network rebuilds within 60 seconds after shear removal. Batch-to-batch consistency validated by BET and pH testing.
AEROSIL 200
Industry benchmark for thixotropy in coatings and adhesives. Identical surface silanol density ensures comparable network formation across polar and semi-polar resin systems.
Formulator’s Note: Because both grades share identical BET surface area and silanol density, the dosage required to achieve a target thixotropic index is the same. No formula adjustment is needed when switching from AEROSIL 200 to SemiSIL 200.
Fumed silica forms soft agglomerates during storage. Effective dispersion requires breaking these agglomerates to release the primary particles and unlock full thickening performance.
High-speed dissolvers (Cowles blade at 2,000–4,000 RPM), rotor-stator mixers, or three-roll mills. Both SemiSIL 200 and AEROSIL 200 require equivalent shear energy for full dispersion.
0.5–2.0% by weight in coatings and adhesives. 10–30% in silicone rubber reinforcement. Starting at the lower end and scaling up based on target TI is recommended for both grades.
Add fumed silica to the resin phase before adding pigments or fillers. Pre-wetting in a small portion of the resin before high-shear mixing improves dispersion efficiency by 15–20%.
Application Key Function Typical Loading SemiSIL 200 vs AEROSIL 200
Industrial Coatings Anti-sagging, pigment suspension 0.5–1.5% Equivalent performance
Structural Adhesives Thixotropy, non-drip application 1.0–2.5% Equivalent performance
RTV Silicone Sealants Thickening (note: hydrophobic preferred) 1.0–3.0% Consider R272 for shelf life
Silicone Rubber (HTV) Mechanical reinforcement 15–30% Equivalent performance
Unsaturated Polyester (UPR) Anti-sagging for gel coats 0.5–2.0% Equivalent performance
Powder Coatings Anti-caking, free flow 0.3–0.8% Equivalent performance
The primary commercial reason formulators switch from AEROSIL 200 to SemiSIL 200 is procurement cost and supply chain resilience.
20–35% Typical cost reduction vs. AEROSIL 200 (FOB basis) 48h Sample dispatch from Anhui R&D center 15,000t annual supply volume ensures stable delivery
Procurement Recommendation: Request a 1kg free sample of SemiSIL 200 for internal testing against your current AEROSIL 200 specification. Most formulators complete validation within 2–4 weeks. Contact SEMITECH technical sales to initiate the process.
Yes. SemiSIL 200 shares the identical CAS number (112945-52-5), BET surface area (200 ± 25 m²/g), and SiO₂ purity (≥ 99.8%) as AEROSIL 200. It is validated for direct substitution without formula changes in coatings, adhesives, and rubber applications.
No adjustment is required. Both grades have equivalent tapped density, primary particle size, and surface chemistry. Your existing Cowles blade or three-roll mill settings, mixing time, and RPM can remain unchanged.
SemiSIL 200 is manufactured under ISO 9001 quality management systems and is fully RoHS and REACH compliant. Each batch is tested for BET surface area, pH value, loss on drying, and SiO₂ content with certificates of analysis available upon request.
For RTV sealants where shelf-life stability is critical, we recommend switching to our hydrophobic grade SemiSIL R272 (DDS treated). The hydrophilic SemiSIL 200 can absorb moisture and cause premature viscosity drift in RTV systems stored in tubes.
Cab-O-Sil M-5 has a BET surface area of approximately 200 m²/g and shares the same CAS number as SemiSIL 200. Performance in thixotropy and reinforcement applications is equivalent. SemiSIL 200 serves as a direct alternative to both AEROSIL 200 and Cab-O-Sil M-5.
Formulator’s Verdict SemiSIL 200 is a technically validated, commercially superior alternative to AEROSIL 200. With…
SemiSIL 200 is a technically validated, commercially superior alternative to AEROSIL 200. With identical CAS number, BET surface area, and surface chemistry, it delivers equivalent rheology control, reinforcement, and processing behavior across all standard applications.
The 20–35% cost reduction, factory-direct supply chain, and ISO 9001 certification make it the preferred choice for procurement optimization without performance compromise.
Get a free 1kg sample dispatched within 48 hours from our Anhui R&D center. Our technical team will provide a full TDS and formulation support.
Also available: SemiSIL 200 Product Page · Full Hydrophilic Series
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