Effect of aminosilane adsorption on rheology of silica powders in nonaqueous media

Abstract

An aminosilane,N-(3-acryloxy-2-hydroxyl propyl)-3-amino-propyltriethoxysilane (AHAS), was used to disperse and stabilize Stober silica suspensions via steric stabilization in nonaqueous media. The effect of variables, such as the calcination temperature of the silica, the water content of the solvents, the physicochemical properties of solvent media, the particle size distributions of the silica, and the proportions of mixed solvent were studied. Viscosity measurements were conducted to assess the dispersion behaviour of the silica suspensions. Fourier transform-infrared analysis was used to deduce the mechanism of AHAS adsorption on the silica surface. The effect of the water content in the silica suspension was found to be highly dependent upon the degree of silica surface hydration before AHAS addition and also upon the kind of solvent medium used. It was observed that electrostatic contribution to the silica stabilization was appreciably greater than anticipated and was found to be a function of the relative acid-base nature of the organic solvent. Analyses of rheological data and infrared spectra were used to explain the behaviour of the silica suspensions.