Viscoelastic Behavior and Ability of Dissipating Energy of SiO2 Dispersions under Stress Shear

The viscoelastic behavior and the ability of dissipating energy of fumed silica dispersions in ethylene glycol, propylene glycol, and butylene glycol have been studied under oscillation stress shear. The systems show linear viscoelastic, shear thinning, and shear thickening behaviors as the shear stress (σ) increases. In linear viscoelastic region, the storage modulus (G′) and loss modulus (G″) remain unchanged; in shear thinning region, G′ decreases and the sequence of the decreasing degree of G′ is EG/SiO2>PG/SiO2> BG/SiO2; however, G″ remains unchanged with σ increasing; in shear thickening region, both G′ and G″ increase as σ increases. The magnitude of G″ is larger than that of G′ over the studied range of stress, indicating that the dispersions mainly possess viscous property, and the energy dissipated is larger than the energy stored. The dissipated energies (Ed) of EG/SiO2, PG/SiO2, and BG/SiO2 dispersions increase with the maximum strain (γ0) increasing in a second power relation under low shear stress; however, in the shear thickening region, the Ed of EG/SiO2, PG/SiO2, and BG/SiO2 dispersions show an exponential increase with γ0 increasing by the exponents of n=2.79, 4.93, and 4.88, respectively.