Abstract: The rheological properties of dispersions of silica in polyethylene glycol (PEG) have been studied under steady and oscillation stress shear performed on AR2000 stress controlled rheometer. The system shows shear thinning and reversible shear thickening behavior. Under steady stress shear, when the stress is less than the critical stress 9.99 Pa(σ＜σ_c^s), the system shows shear thinning, while, the system shows shear thickening when σ＞σ_c^s. Under oscillatory stress shear, when the shear stress is less than the critical stress 15.85 Pa(σ＜σ_c^o)、storage modulus(G′) decreases, loss modulus(G″), and the complex viscosity(η*) almost remain unchanged; but when σ＞σ>_c^o, G′、G″ and η* increase synchronously. The magnitude of G″ is larger than the magnitude of G′ in the range of stress studied. The higher frequency used in the experiment leads to the larger value of the critical stress. The systems almost have the same values of the σ>_c^o as the SiO₂ mass fraction increasing, but the shear thickening phenomena are more obvious. Compared with the dispersion in PEG200, the dispersion in PEG400 shows lower complex viscosity before the critical point and a more sharp increase in the viscosity beyond the point, but has the same value of the critical stress (σ>_c^o) and comparative viscosity at high stresses.

Key words: Silica, Polyethylene glycol, Non-Newtonian flow, Rheological property, Shear-thickening