In¯uence of silane coupling agents on surface properties of precipitated silicas

Silicas of highly dispersion degree were obtained. This process includes formation of silica particles and their aggregation. The ethylene glycol solution was used in precipitation process, resulting in a partial blocking of the silica surface hydroxyl groups (silanol groups) and, thus, in a decreased hydrophilicity of silica. Studies on the surface modi®cation of silicas using silane coupling agents are described. The best modi®ers were selected, which inducted a change of the silica surface from hydrophilic to hydrophobic. Basic physicochemical analyses of the obtained silicas were performed. The methods of evaluating the degree of surface modi®cation of the silica were presented. Near infrared spectroscopy (NIR) was used to determine the degree of condensation of the silica surface silanol groups. The degree of hydrophobization of silica surface was determined by a calorimetric method. Moreover, studies on morphology and microstructure using transmission electron microscopy (TEM) were performed. Size distribution of primary particles and aggregates and agglomerates structures were determined by ZetaPlus instrument using dynamic light scattering (DLS) method. # 2001 Elsevier Science B.V. All rights reserved