Modification of nanosilica particles with hydrophobic modifier bis[3-(triethoxysilyl)propyl]tetrasulfide by using micro-injection in aqueous solutions

Effective modification of nanosilica particles in aqueous solution with the hydrophobic modifier bis[3-(triethoxysilyl)propyl]-tetrasulfide (Si69) was developed. The modification was carried out through the route of aqueous mixing, spray drying, and thermal treatment. The Si69 hydrolysate was maintained at a low concentration by using micro-injection and well mixed with the nanosilica particles to increase the hydrolysate grafting density on the particle surfaces. Precipitated, fumed, and colloidal silica particles were modified up to a high grafting density of 2.96 nm(-2) , 3.07 nm(-2) and 3.25 nm(-2) , respectively. The dispersibilities of the Si69modified nanosilica particles were improved significantly. The modification performances of the three kinds of nanosilica particles are different, which result from the silanol characteristics and the Bronsted/Lewis acid sites present on the particle surfaces.