The surface modification of fumed silica was achieved by batch and continuous spray drying process. To quantify the hydrophobicity of modified silica particles, ethanol volume ratio on water and contact angle were measured. Fourier Transfer IR(FT-IR) and Thermogravimetric Analysis(TGA) were used to determine the degree of surface modification. Scanning Electron Microscopy(SEM) and Transmission Electron Microscopy(TEM) were used to study the morphology of modified silica particles.
As the concentration of octyltriethoxysilane(OTES, Aldrich, 96%) increased, the degree of surface modification was also increased in the batch process. The modified silica particles were agglomerated severely. Ultrafine particles formed by the reaction of unreacted octyltriethoxysilane caused agglomeration of silica particles.
To overcome the agglomeration of particles and increase hydrophobicity of silica, the surface of silica particles was modified by the continuous spray drying process. The modified silica particles in the continuous spray drying process showed improved hydrophobicity and morphology. Agglomeration of surface modified silica particles was reduced because unreacted octyltriethoxysilane inducing agglomeration of silica particles in the batch process was vaporized in the continuous spray drying process. The unreacted OTES was found to be completely removed according to the Thermogravimetric Analysis(TGA) and Fourier Transfer IR(FT-IR) measurement.
