A Comparison Between the Densification Kinetics of Colloidal and Polymeric Silica Gels

ABSTRACTSilica gels were prepared by three methods in which the original silicate species varied from extended linear or randomly branched polymers to more highly crosslinked clusters to colloidal particles of anhydrous silica. During isothermal sintering experiments, the viscosities of the two polymer gels increased significantly (up to 3 orders of magnitude) while the isothermal viscosity of the colloidal gel was constant. Viscosity increases were explained by crosslinking and structural relaxation of the polymeric gels.