Industrial Grade Fumed Silica for Silicone Rubber and Sealants

Fumed silica has a very wide range of applications, mainly covering rubber and plastics (reinforcing agent), adhesives and sealants (thickening and thixotropic agent), coatings and inks (anti-settling, thickening, matting agent), food and pharmaceuticals (anti-caking agent, carrier), cosmetics (thickening, thixotropy), electronics and new energy (CMP polishing, battery separators), and more.

Hydrophilic grade is untreated with a large number of silanol groups on the surface, strongly polar, suitable for waterborne and polar solvent systems, with relatively lower price. Hydrophobic grade is surface-modified, where organic groups replace silanol groups, reducing polarity and enhancing compatibility with non-polar systems (e.g., oil-based coatings, non-polar resins), with better moisture resistance. Selection guideline: Choose hydrophilic for polar s

The core differences lie in production process and performance. Fumed silica is produced by the fumed process (high-temperature hydrolysis) with primary particle size of 7-40nm, specific surface area of 50-450 m2/g, high purity (SiO2 >= 99.8%), excellent thickening, thixotropic and reinforcing effects, higher price, suitable for high-performance applications. Precipitated silica is produced by wet chemical precipitation with coarser particle size (micron level), lower specific surface area, lowe

Addition level is typically 0.5%-3% of total formulation, adjusted based on thickening, thixotropy, anti-settling requirements. Dispersion process: High-speed disperser or three-roll mill is recommended to ensure thorough deagglomeration. Hydrophilic grade disperses more easily in polar systems; hydrophobic grade disperses better in non-polar systems. Dispersion temperature should be controlled below 50C to avoid high temperature affecting performance.

Higher BET (e.g., >= 300 m2/g) provides stronger thickening and thixotropic effects, higher transparency, and better reinforcement, but dispersion becomes more difficult. Lower BET (e.g., <= 100-150 m2/g) offers easier dispersion and better flowability, suitable for systems with lower viscosity and transparency requirements. Common BET specifications include 150 m2/g, 200 m2/g, 380 m2/g, each corresponding to different application focuses.