Abstract: Shear thickening implies that the viscosity of a fluid increases with increasing rates of shear. In the past work reported, all shear thickening phenomena were observed in concentrated solid/liquid colloidal suspension. In this paper, the shear thickening was observed in colloidal dispersion gel, with very lower volume fraction, of partially hydrolyzed polyacrylamide(PHPA)/aluminum citrate. Colloidal dispersion gels are made of low concentrations of polymer and crosslinker. Polymer mass fractions normally range from 0.01% to 0.12%. In this concentration regime, there is not enough polymer to form a continuous network, so a conventional bulk type gel cannot form. Instead of a solution of separate gel bundles forms, and it is a mixture of predominantly intramolecular and minimaLIntermolecular crosslinks. In the work reported here, the colloidal dispersion gels are made of PHPA of 0.03%, KCl of 0.5%, thiourea of 0.1% and Al³⁺with a mass fractions range of 0-0.003%, the Al³⁺:PHPA mass ratio changes from 0 to 0.1. The critical shear rates(CSR) for the onset of shear thickening are about 200 s^-1for all CDGsystems studied, i.e ., the Al³⁺:PHPA mass ratio don't affect the CSR. In the lower shear regime than CSR shear thinning was observed and in the higher shear regime than CSR the shear thickening was observed. The shear thickening may be explained with cluster-formation mechanism.

Key words: Partially hydrolyzed polyacrylamide, Aluminum citrate, Shear thickening, Colloidal dispersion gel, Colloid