Shear thickening in a solution undergoing inverse melting

Abstract

Rheological measurements on a solution undergoing inverse melting are presented as a function of temperature and concentration. Under shear, this solution exhibits the phenomenon of shear thickening; i.e. an increase in apparent viscosity with increasing shear rate . In particular, a shear-thickening transition happens at a critical shear rate , which increases with increasing concentration. It defines two different regimes: at low shear rates , the fluid shows Newtonian behaviour, while at shear rates , a transition from the Newtonian to the shear-thickening regime is observed. This behaviour is interpreted on the basis of a relaxation process activated by the shear and characterised by a relaxation time. In the thickening region, the viscosity data are well fitted with a power-law model , with n = 1.8. The temperature and concentration behaviour of the zero shear viscosity, the power-law exponent and the critical shear rate are discussed.