Rheology of fumed hydrophilic and hydrophobic titania suspensions dispersed in silicone oils

The rheological properties of fumed titania particles suspended in various silicone oils were investigated by steady-state viscosity measurements as functions of titania contents and surface properties of the fumed titania particles. Adsorption behavior of the silicone oils and optical microscopy observation were also examined. When the fumed hydrophilic titania particles were dispersed in the silicone oils, the larger amounts of the silicone oils were adsorbed on the titania particles, the larger flocculated structures were formed, and the stronger shear thinning behavior was observed, as compared to the fumed hydrophobic titania suspensions. The difference should be mainly attributed to the interaction between the titania surface and the silicone oils. The relative viscosities of the fumed titania suspensions at the same titania concentration could be superimposed on the master curve by taking into account the Peclet number, irrespective of the silicone oil.