THE EFFECT OF TRACE WATER ON NON-AQUEOUS SILICA DISPERSIONS

Spherical monodisperse silica particles, of 401 nm diameter, were prepared and sterically stabilized using a non-ionic surfactant. The particles were dispersed in a low dielectric constant organic medium. The effect of trace amounts of water added to the system was investigated by studying the electrophoretic mobility of the particles, the consolidation of the sedimented bed and the rheology of the dispersion. The changes in these three measurements was attributed to the change in surface charge of the silica particles due to the presence of the added water. The theoretical justification for the variable rheology, as exemplified by the high frequency limit of the storage modulus, is qualitatively discussed.