煙霧シリカの単純分散媒中での分散性

概要

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Dispersion of fumed silica powders having specific surface areas (S_<BET>) of 50-500 m^2.g^<-1> was investigated based on the optical absorption (τ) in the wavelength (λ) range of 460-700 nm. Light scattering index (n) was evaluated by using the equation τ=αλ^<-n>. In the fumed silica-water disperse system, n and τ at λ=700 nm changed rapidly to reach n^* and τ^*_<700nm>, respectively, in the steady state under strong ultrasonic agitation conditions. n^* and τ^*_<700nm> were found to be more useful than S_<BET> as a dispersibility index of fumed silica. In general n^* tended to increase as S_<BET> increased, indicating that aggregated silica particles became filler in water as the size of primary silica particles decreased. Dispersion behavior of fumed silica was also well correlated with τ^*_<700nm>. The fumed silica having a larger τ^*_<700nm> easily reached an ultimate dispersion state in water under mild ultrasonic agitation, while that having small τ^*_<700nm> started dispersion as rather grossy particles, which were subsequently divided into finer pieces to reach a very fine dispersion state eventually. Fumed silica was dispersed similarly in other polar media such as methanol and acetone but not in nonpolar or poorly polar media such as n-hexane and toluene.
1993-06-01