Flow behaviour of titanium dioxide dispersions in the presence of 2-hydroxyethyl cellulose

Abstract

The effects of 2-hydroxyethyl cellulose (HEC) of weight-average molecular weight 15,000, 90,000 and 7,20,000 on the rheological properties of TiO2 dispersions were evaluated. For all three HECs, the maximum yield stress, τymax, (occurred at zero zeta potential), decreased with increasing HEC concentration. Interestingly, the largest reduction in τymax was observed with the HEC with the highest molecular weight. This reduction was attributed to steric interaction arising from adsorbed HEC. Adsorbed high-molecular-weight HEC formed an effectively thicker steric barrier because of its larger size and higher adsorption capacity. Bridging interactions that were expected to be important for the high-molecular-weight HEC were found to be unimportant here. In the flocculated regime, HEC enhanced the shear-thinning characteristics of the TiO2 dispersions.