SemiSIL 200 vs AEROSIL 200: A Complete Technical Comparison for Formulators
Published: April 21, 2026 Technical Guide Formulator’s ResourceExecutive Summary
- 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.
- 1. Side-by-Side Specifications
- 2. Rheology & Thixotropy Performance
- 3. Dispersion & Processing
- 4. Application Performance by Industry
- 5. Cost & Supply Chain Analysis
- 6. Frequently Asked Questions
- 7. Conclusion & Recommendation
1. Side-by-Side Specifications
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.
2. Rheology & Thixotropy Performance
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 200Thixotropic Index
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 200Thixotropic Index
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.
3. Dispersion & Processing
Fumed silica forms soft agglomerates during storage. Effective dispersion requires breaking these agglomerates to release the primary particles and unlock full thickening performance.
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Recommended Equipment
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.
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Typical Dosage Range
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.
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Addition Sequence
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%.
4. Application Performance by Industry
| 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 |
5. Cost & Supply Chain Analysis
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 deliveryProcurement 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.
6. Frequently Asked Questions
Is SemiSIL 200 a certified drop-in replacement for AEROSIL 200? 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. Do I need to adjust my dispersion process when switching to SemiSIL 200? 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. What quality certifications does SemiSIL 200 carry? 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. Which grade should I choose for RTV silicone sealants? 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. How does SemiSIL 200 compare to Cab-O-Sil M-5? 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-5.7. Conclusion & Recommendation
Formulator’s Verdict
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.
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Request Free Sample Also available: SemiSIL 200 Product Page · Full Hydrophilic Series