DISPERSION STABILITY AND RHEOLOGICAL BEHAVIOR OF SUSPENSIONS OF POLYSTYRENE COATED FUMED SILICA PARTICLES IN POLYSTYRENE SOLUTIONS

Polystyrene coated silica（SiO;@PS） core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface ofγ-methacryloxypropyltrimethoxysilane grafted SiO;nanoparticles of 20-50 nm in diameter.Rheological behavior and dispersion stability of SiO;@PS suspension in 10 wt%PS solution were compared with suspensions of untreated SiO;and silane modified SiO;nanoparticles.Suspensions of the untreated and the silane modified SiO;exhibited obvious shear thinning.The SiO-2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO;at low shear rates.Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions,implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution.