Silica Particles Characterization and Properties

Aerosil particles from Degussa are fumed silica, a synthetic amorphous silicon dioxide manufactured by continuous flame hydrolysis of silicon tetrachloride. Siloxane and silanol groups are present on the surface of unmodified Aerosil particles, where silanol groups account for the hydrophilic behavior. Reactions of the silanol groups with various organosilanes and siloxanes can chemically modify the surface ofthe particles. Aerosil 200, Aerosil 7200 and Aerosil 972 were used in this study. Aerosil 200 is an unmodified silica, while Aerosil 7200 is a structure modified (3-methacryl-oxypropyl-trimethoxysilane) product based on Aerosil 200. The hydro-phobic Aerosil 972 is a fumed silica after-treated with dimethyldichlorosilane. Table 12.2 summarizes the properties of these three products. Importantly, the 

T)etermined from the freezing point depression of benzene. 

Product After-treated with Specific surface area (BET) Tapped density (gL- ) Primary particle size (nm) 

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