Shear-thickening rheological response of PCC/PEG suspensions

Abstract

The steady and dynamic rheological behaviors of precipitated calcium carbonate (PCC) suspension in polyethylene glycol (PEG) were investigated on a TA AR2000ex rheometer. Under steady shear consistency index K and flow exponent N of suspensions with different volume fractions were determined. The shear-thinning and the discontinuous shear-thickening behavior were observed at different constant frequencies from 10 to 100 rad/s. The relationship between the complex viscosity and the constant frequency were determined. As the volume fraction increases, flow exponent N shows a rapid increase, and it increases dramatically when the discontinuous shear-thickening takes place, while consistency index K decreases. Dynamic oscillatory shear experiments were conducted at constant strain amplitude and constant frequency, respectively. For the frequency sweep, the system shows viscous property in entire range of the frequency investigated, and the complex viscosity shows discontinuous jump at a critical frequency of 10 rad/s. For the strain sweep, on the other hand, at low strain the elastic modulus is strongly dependent on the strain, and the viscous modulus is independent of the strain. But at the critical strain point both of the moduli show an abrupt jump and the system transits from elastic to viscous at a strain of 0.1.