Fumed Silica Modified by Hexamethyldisilazane

Fumed silica was modified with hexamethyldisilazane (HMDS) in a fluidized bed reactor, and then the structure and morphology of it were characterized by TEM, FTIR etc. The results indicate that the agglomeration of fumed silica is restrained by HMDS modification. The pH value of fumed silica and its carbon content in fumed silica increase and silanol groups on its surfaces decrease with the increasing modification time, temperature and HMDS partial pressure. The coating rate of HMDS is high at the first 15min, and then decreases rapidly with coating time. The coating rate is strongly dependent on the reaction temperature and HMDS partial pressure when the modification temperature and HMDS partial pressure is less than 250°C and 7.9kPa respectively.