Summary: Nano SiO2 builds a thixotropic hydrogen-bond network that resists settling and sagging while matting and hardening the film.
Mechanism
Nanoparticles (5-100 nm) form a weak 3D network: stable at rest (anti-settle), fluid under shear for easy application.
Key data
- Fumed SiO2 specific surface ~50-380 m²/g; higher area = stronger effect per dose.
- Typical loading ~0.5-4% on solids; above it viscosity and yield rise sharply.
- Hardness and abrasion rise; excess reduces gloss and recoat adhesion.
Selection by type
| Type | System | Role |
|---|---|---|
| Fumed hydrophobic | Solventborne | Strong anti-settle, clear matte |
| Precipitated | Waterborne industrial | Cost-effective matte / anti-settle |
Defects & fixes
- Roughening/agglomeration: raise shear or change dispersant.
- Excess gloss loss: cut dose or use gel-type silica.
- Settling: add hydrophobic fumed or blend bentonite.
FAQ
Why is nano silica a thickener?
Its particles form a hydrogen-bond network that builds structure at rest and breaks under shear.
Why is too much bad?
Over the window the network is over-strong, raising viscosity/yield, hurting gloss, flow and recoat adhesion.
Rheology and matting of fumed/precipitated silica (public literature).
Kexin New Materials (Guangdong) Co., Ltd. · 2026-09-17