Fumed silica

Fumed silica (also known as colloidal silicon dioxide) is a high-purity, amorphous, nano-particle thickening agent used to modify the rheology (flow behavior) of liquid resin systems. When added to epoxy, polyester, vinyl ester, or polyurethane resins, fumed silica creates thixotropic properties – the resin becomes thick and gel-like when静态but flows easily when agitated (shear thinning). This prevents resin from dripping or sagging on vertical surfaces, allows thicker fillets and bond lines, and keeps fillers (glass bubbles, microballoons, chopped fibers) suspended during cure.

Key Features

• Chemical Name: Amorphous fumed silica (SiO₂)

• Appearance: Very fine white powder

• Particle Size: 5 – 50 nanometers (primary particles)

• Surface Area: 150 – 400 m²/g (very high)

• Bulk Density: 40 – 60 g/L (very low – extremely fluffy)

• Purity: ≥ 99.8% SiO₂

• pH (4% slurry): 3.5 – 4.5 (hydrophilic grade)

• Compatibility: Epoxy, polyester, vinyl ester, polyurethane, acrylic, and most solvent-based systems