Two 380 m²/g hydrophilic fumed silica grades compared on specs, thixotropy efficiency, and total cost of ownership for formulators.
Two 380 m²/g hydrophilic fumed silica grades compared on specs, thixotropy efficiency, and total cost of ownership for formulators.
The 380 m²/g surface area creates a denser silanol network — roughly 2.5 Si-OH groups per nm² — that forms stronger hydrogen-bonded particle networks in liquid media compared to 200 m²/g grades. Formulators typically achieve target viscosity with 15–25% less loading by weight when switching from a 200-grade to a 380-grade. In unsaturated polyester resins, 1.0% SEMISIL 380 delivers comparable sag resistance to 1.3–1.5% of a 200 m²/g grade. Both SEMISIL 380 and AEROSIL 380 show equivalent thixotropic index (TI 3.5–4.5 at 1% in epoxy) when dispersed under identical high-shear conditions (tip speed ≥ 20 m/s). Differences in lot-to-lot aggregate structure may shift the optimal dispersion time by 1–3 minutes.
High-BET fumed silica at 380 m²/g is selected when formulators need maximum thixotropic efficiency at minimum loading. Core applications include silicone sealants (RTV-1 and RTV-2), high-solids epoxy adhesives, gel-coat resins, and lithium-ion battery electrode slurries where every fraction of a percent of additive affects energy density. In anti-settling applications for solvent-borne industrial coatings, 380-grade silica keeps TiO₂ and heavy pigments suspended at 0.5–1.0% loading. For transparent systems — clear coats, optical gels — the finer primary particle size (7 nm vs 12 nm for 200-grade) reduces haze. Neither grade suits applications requiring hydrophobic surface treatment; both need post-treatment or a pre-treated variant like SEMISIL 380-TS.
AEROSIL 380 typically commands a 20–35% price premium over SEMISIL 380 on a per-kilogram basis, driven by brand positioning and European manufacturing costs. However, per-kilogram price is the wrong metric for 380-grade silica — cost per unit of viscosity increase matters more. Because both grades perform equivalently in controlled dispersion tests, the total cost of ownership favors the lower-priced material when qualification testing confirms no performance gap. Freight economics also matter: fumed silica ships at low bulk density (~50 g/L), so a 10-kg bag occupies roughly 200 liters of volume. Regional sourcing from Chinese producers like SEMISIL eliminates trans-Pacific or intra-European logistics markups, which can add 8–15% to landed cost.
SEMISIL 380 and AEROSIL 380 target the same performance envelope — a BET surface area of 380 ± 30 m²/g produced by…
SEMISIL 380 and AEROSIL 380 target the same performance envelope — a BET surface area of 380 ± 30 m²/g produced by hydrogen-flame hydrolysis of silicon tetrachloride. Both deliver primary particles of approximately 7 nm, a tapped density near 50 g/L, and SiO₂ content ≥ 99.8%. pH in 4% aqueous dispersion falls within 3.6–4.5 for both grades. The manufacturing route is identical in principle: SiCl₄ is vaporized, mixed with hydrogen and air, and combusted at roughly 1800 °C. Differences emerge in aggregate structure and moisture content — parameters that affect dispersion behavior rather than chemistry.
| Parameter | SEMISIL 380 | AEROSIL 380 |
|---|---|---|
| BET Surface Area | 380 ± 30 m²/g | 380 ± 30 m²/g |
| Primary Particle Size | ~7 nm | ~7 nm |
| SiO₂ Content | ≥ 99.8% | ≥ 99.8% |
| Tapped Density | ~50 g/L | ~50 g/L |
| pH (4% Dispersion) | 3.7–4.3 | 3.7–4.5 |
| Loss on Drying (2 h, 105 °C) | ≤ 1.5% | ≤ 1.5% |
| Loss on Ignition (2 h, 1000 °C) | ≤ 1.0% | ≤ 1.0% |
The table below consolidates physical, chemical, and performance parameters for both grades. All values represent typical ranges from published technical data sheets. Formulators should request a certificate of analysis for lot-specific values before qualification trials.
| Property | SEMISIL 380 | AEROSIL 380 | Test Method |
|---|---|---|---|
| BET Surface Area | 380 ± 30 m²/g | 380 ± 30 m²/g | ISO 9277 |
| Primary Particle Size | ~7 nm | ~7 nm | TEM |
| Tapped Density | ~50 g/L | ~50 g/L | DIN EN ISO 787-11 |
| SiO₂ Content | ≥ 99.8% | ≥ 99.8% | Gravimetric |
| pH (4% in Water) | 3.7–4.3 | 3.7–4.5 | DIN EN ISO 787-9 |
| Loss on Drying | ≤ 1.5% | ≤ 1.5% | 2 h at 105 °C |
| Loss on Ignition | ≤ 1.0% | ≤ 1.0% | 2 h at 1000 °C |
| Sieve Residue (45 µm) | ≤ 0.05% | ≤ 0.05% | DIN EN ISO 787-18 |
| HCl Content | ≤ 250 ppm | ≤ 250 ppm | Titration |
SEMISIL 380 matches AEROSIL 380 across every critical specification — BET, particle size, purity, and pH. For formulators already qualified on 380 m²/g fumed silica, switching to SEMISIL 380 reduces material cost by 20–35% with no reformulation required once dispersion equivalence is confirmed.
Both SEMISIL 380 and AEROSIL 380 have a BET surface area of 380 ± 30 m²/g, measured per ISO 9277. This high surface area produces primary particles of approximately 7 nm and delivers greater thixotropic efficiency per gram than lower-grade 200 m²/g fumed silica.
A 380 m²/g grade typically requires 15–25% less loading by weight to achieve the same viscosity build. In epoxy systems, 1.0% of a 380-grade matches the sag resistance of 1.3–1.5% of a 200 m²/g grade, reducing additive cost and preserving formulation solids.
SEMISIL 380 matches AEROSIL 380 on all published specifications including BET, purity, and pH. A direct substitution is feasible after confirming equivalent dispersion behavior and viscosity build in your specific system — typically a 4–8 week qualification cycle.
Higher BET surface area requires finer flame control and lower throughput in the hydrolysis reactor, reducing yield per unit time. The 380-grade also demands tighter quality control on aggregate size distribution, adding to production cost — typically 30–50% more per kg than 200-grade.
Applications needing maximum thixotropy at minimum loading favor 380 m²/g: RTV silicone sealants, high-solids structural adhesives, gel-coat resins, and lithium-ion battery electrode slurries. Clear coatings also benefit because the 7 nm particle size minimizes haze compared to 12 nm particles in 200-grade.
SEMISIL 380 is typically 20–35% lower in per-kilogram price than AEROSIL 380, depending on volume and region. Regional sourcing from China further reduces landed cost by eliminating 8–15% in trans-Pacific or intra-European freight markups on this low-density material.
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