SEMISIL 300 Fumed Silica (BET 300 m²/g, Hydrophilic)

SEMISIL 300 is a high surface area hydrophilic fumed silica produced by Shanghai Semitech New Material Co., Ltd., with a BET surface area of 300 m²/g. This premium grade delivers significantly stronger thixotropic performance per unit weight compared to standard 200 m²/g grades, making it the preferred choice for demanding applications requiring high gel strength, strong anti-sag, or anti-settling performance at minimum filler dosage.

The elevated surface area of 300 m²/g means SEMISIL 300 contains more reactive silanol groups per gram, enabling the formation of a denser, stronger three-dimensional hydrogen-bonded network in polar and semi-polar solvents and resins. This translates to a higher thixotropic index at equal dosage: where SEMISIL 200 at 1.0 phr achieves TI ~4, SEMISIL 300 can achieve TI 5–7 at the same loading. Alternatively, SEMISIL 300 can achieve equivalent thixotropy at 25–35% lower dosage compared to SEMISIL 200, which may be beneficial when dosing precision is important or when total silica content must be minimized.

SEMISIL 300 is particularly recommended for epoxy paste adhesives, two-component PU sealants, high-performance gelcoat systems, and any application where strong gel structure at rest is required alongside free-flowing behavior under shear. Direct equivalent to Evonik Aerosil 300 and equivalent grades from Wacker (HDK® N20) and Cabot.