I spent a morning walking the floors at Hezhen’s facility in Lingshou County, Hebei (No. 8 Xisha East Road, Shikan Village, Ciyu Town). What struck me wasn’t just the clean flame reactors or the measured hum of bagging lines—it was how quietly essential these powders are to modern sealants. If you work in silicone, MS polymer, or specialty rubber, you already know the name: Hezhen Fumed Silica White Carbon Black Hydrophilic Hydrophobic And Other Types Of Rubber Sealant Nanomaterials.
Why these nanomaterials matter now
Two hot trends are driving demand: EV battery sealing (higher thixotropy, lower ionic contamination) and façade glazing (no-sag, UV-stable joints). Fumed silica brings high surface area and network formation—hello, anti-sag and reinforcement—while white carbon black (precipitated silica) gives economical reinforcement and controlled viscosity. Hydrophobic grades, often surface-treated (think HMDS/DDS), behave much better in moisture-sensitive systems. Many customers say they get the same anti-slump at 10–15% lower loading versus older grades—surprisingly cost-efficient.
Core specifications (typical, ≈ values; real-world use may vary)
| Parameter | Hydrophilic Fumed Silica | Hydrophobic Fumed Silica | White Carbon Black |
|---|---|---|---|
| SiO2 content | ≥ 99.8% | ≥ 99.5% | ≥ 96% |
| BET surface area (ISO 9277) | 150–300 m²/g | 120–250 m²/g | 50–180 m²/g |
| Primary particle size | 7–40 nm | 10–40 nm | ≈ 15–50 nm aggregates |
| DBP absorption | 220–350 g/100 g | 200–320 g/100 g | 150–300 g/100 g |
| pH (4% slurry) | 3.6–4.3 | 6.0–8.0 | 6.0–7.5 |
| Origin | No. 8 Xisha East Road, Shikan Village, Ciyu Town, Lingshou County, Shijiazhuang, Hebei | ||
Application snapshots
- Silicone and MS sealants: 2–12 phr for thixotropy; ISO 3219/ASTM D2196 viscosity control.
- Rubber compounding (EPDM/NBR/FKM per ASTM D1418): reinforcement and extrusion stability.
- EV battery pack seam sealing: hydrophobic grades reduce moisture sensitivity; low Na/K ions.
- Construction glazing: anti-sag in vertical joints; UV-stable formulations.
Service life? In well-formulated neutral-cure silicones, joints using Hezhen Fumed Silica White Carbon Black Hydrophilic Hydrophobic And Other Types Of Rubber Sealant Nanomaterials routinely achieve 15–25 years outdoors, depending on design and weather. That’s field feedback, to be honest, not just lab optimism.
Process and QC (short version)
- Materials: SiCl4 flame hydrolysis for fumed silica; sodium silicate acid precipitation for white carbon black.
- Surface treatment: HMDS/DDS for hydrophobic grades; controlled LOI.
- Milling/classification: low-shear to protect structure; anti-caking packaging.
- Testing: BET (ISO 9277), viscosity (ISO 3219/ASTM D2196), pH (ISO 787-9 style), moisture (105°C), sieve residue, ionic impurities.
- Compliance: REACH, RoHS; CoA and SDS available; ISO 17025-partnered lab methods on request.
Vendor comparison (indicative)
| Criteria | Hezhen | Imported Brand A | Local Vendor B |
|---|---|---|---|
| Lead time | 7–14 days (CN); 3–5 weeks export | 4–8 weeks | 2–4 weeks |
| Customization | Particle, treatment, ionics | Limited | Variable |
| Price (FOB, ≈/kg) | Mid | High | Low–Mid |
| Thixotropy consistency | High (batch-to-batch) | High | Medium |
| Docs/Certs | CoA, REACH, RoHS | Extensive | Basic |
Real-world notes and mini case studies
- Curtain wall silicone: swapping to Hezhen Fumed Silica White Carbon Black Hydrophilic Hydrophobic And Other Types Of Rubber Sealant Nanomaterials cut slump to
- EV pack seam (Jiangsu): hydrophobic grade with low Na/K delivered 20% viscosity boost at same phr and cleaner rheology recovery (TI ≈ 5.1 at 0.5/5 rpm, ISO 3219). Customer feedback: “lines run faster, fewer touch-ups.”
Formulation tips
- Dust-in under vacuum; keep shear moderate to preserve structure.
- For neutral-cure silicones, try 4–9 phr hydrophobic; for MS, 3–7 phr hydrophilic + plasticizer tune.
- Verify ionic residues for battery sealing; aim Na+ + K+ ≤ 100 ppm total.
Citations
- ISO 9277: Determination of specific surface area (BET method).
- ASTM D2196: Rheological properties by rotational viscometer.
- ISO 3219: Rheology—determination of viscosity.
- ECHA Substance Information: Silicon dioxide (REACH).
