Industrial Chemicals & Nano Powders

Both are synthetic amorphous silicon dioxide, but their production routes and properties differ fundamentally:

• Fumed silica (pyrogenic silica): produced by vapour-phase hydrolysis of silicon tetrachloride in a hydrogen/oxygen flame. Results in primary particles of 5–50 nm aggregated into loose agglomerates; extremely high purity (>99.8% SiO₂); high BET surface area (50–400 m²/g); hydrophilic or hydrophobic grades available. Typical uses: thickener and thixotropic agent in coatings, adhesives, and rubber; reinforcing agent in silicone; battery separator coating.
• Precipitated silica: produced by wet chemical reaction of sodium silicate with sulfuric acid. Larger primary particle size (10–100 nm); lower purity; more economical. Typical uses: rubber reinforcement (tyre industry), anti-caking agent, toothpaste abrasive.

Nano TiO₂ (primary particle size <100 nm) performs several functions in coatings that conventional pigment-grade TiO₂ (200–300 nm) cannot replicate:

• UV blocking: the nanoscale particle size shifts the absorption cut-off into the UV range while remaining transparent in the visible spectrum — essential for UV-curable coatings, sunscreen, and anti-UV wood finishes.
• Photocatalytic self-cleaning: nano anatase TiO₂ decomposes organic contaminants under UV light, enabling self-cleaning exterior coatings.
• Antifogging and superhydrophilicity: nano TiO₂ coatings create a superhydrophilic surface that prevents condensation fogging on glass.

Conventional pigment TiO₂ provides opacity but has no UV-transparency or photocatalytic activity at commercial concentrations.

TiO₂ dispersion stability in the PA6 melt or in the caprolactam medium is highly sensitive to processing conditions:

• Temperature: elevated temperatures (>200°C) accelerate sintering between nano-particles, causing irreversible hard agglomeration. Surface coating of the nano TiO₂ (e.g. silane or alumina) is critical to providing a diffusion barrier.
• pH: in aqueous caprolactam (extraction stage), the isoelectric point of TiO₂ is at approximately pH 6–7. Operating near this point gives minimum electrostatic repulsion and maximum agglomeration tendency. A slightly acidic or alkaline pH (away from the IEP) improves colloidal stability. Adding a dispersant that chemisorbs onto the TiO₂ surface is the practical solution.

Zeta potential (ζ) is the key indicator of electrostatic colloidal stability:

• |ζ| > 30 mV: sufficient repulsion to maintain stable dispersion.
• |ζ| < 10 mV: the electrical double layer collapses; van der Waals attraction dominates and rapid agglomeration occurs.

For nano TiO₂ in waterborne systems, a typical target is |ζ| ≥ 40 mV. Measurement is carried out by laser Doppler electrophoresis (Zetasizer). If zeta potential is poor, adjustment strategies include: pH optimisation, addition of anionic or nonionic polymeric dispersant, and ultrasonic pre-dispersion followed by rotor-stator high-shear dispersion.

• Eliminates dust hazards: dry fumed silica powder is extremely light and a severe inhalation hazard; pre-dispersed suspension removes this risk entirely.
• Ready to incorporate: the suspension can be metered directly into the formulation without a separate dispersion step — reduces process time and eliminates costly dispersion equipment at the customer site.
• Consistent quality: BONAFEI controls particle size distribution and solids content at the point of manufacture, ensuring batch-to-batch consistency.
• High solids content: suspensions up to 60% SiO₂ solids are available, reducing transport volume and cost.

Yes. BONAFEI's nano TiO₂ and fumed silica products are manufactured under ISO-9001 quality management systems and comply with REACH regulation (EC 1907/2006):

• SDS (Safety Data Sheet): available in Chinese and English for all product grades; further language versions on request.
• TDS (Technical Data Sheet): covering particle size, BET surface area, pH, purity, loss on ignition, and other specification data.
• Nano-specific registration: nano-form TiO₂ registration under REACH Annex VI is in place for EU export grades.

Documents can be provided upon request during the enquiry or ordering process.