SEMISIL 150 Fumed Silica (BET 150 m²/g, Hydrophilic)

SEMISIL 150 is a hydrophilic fumed silica manufactured by Shanghai Semitech New Material Co., Ltd. through the high-temperature flame hydrolysis of chlorosilanes. With a BET surface area of 150 m²/g, it is the lowest surface area grade in the SEMISIL hydrophilic range, offering a cost-effective entry point for thixotropy and anti-sag performance in resin systems where moderate rheology control is required.

Fumed silica particles consist of primary amorphous SiO2 nano-spheres (5–30 nm diameter) that form fused aggregates and loosely bound agglomerates. When dispersed in resin under shear, these structures develop a hydrogen-bonded network with silanol groups on the particle surface, creating pronounced shear-thinning (thixotropic) rheology. SEMISIL 150's moderate surface area produces a good thixotropic response with lower viscosity impact and easier incorporation compared to higher surface area grades.

SEMISIL 150 is widely used in unsaturated polyester resins, epoxy systems, and gelcoats for hand lay-up and spray-up applications where anti-sag on vertical surfaces is required. It improves storage stability of filled resin systems by preventing filler settling. Recommended dosage is 0.3–1.5 phr depending on the required thixotropic index. Always disperse under high shear (cowles dissolver or equivalent) for optimal performance.