Aerosil 300 Silicium dioxide 112 945-52-5 Degussa Extenders / Fillers >> Silica Rheology Modifiers / Thickeners >> Mineral >> Fumed Silica Rubber - Elastomer (Chloroprene, Butyl …) Silicones (Si) Aerosil 300 is a hydrophilic fumed silica. The high specific surface area gives a pronounced thickening and thixotropic effect, if sufficiently well dispersed. An important application is in the reinforcement of HTV silicone rubber. Aerosil 300 is a hydrophilic fumed silica. Has athickening and thixotropic effect.