Rheological characterisation of ammonium polyacrylate dispersed, concentrated alumina suspensions

The effect of low-molecular weight ammonium polyacrylate (NHPA) dispersant on high solids content alumina suspensions has been rheologically characterised. The viscosity exhibited a strong dependence on the solid concentration, a relationship that could be accurately represented by the modified versions of Eilers and Chong equations from which the maximum packing fraction was found to be 0.655. When subjected to shear sweep investigations, the suspensions demonstrated shear-thinning and thixotropic behaviour as a result of changes to the suspension microstructure. Application of the Ostwald de Waele model successfully characterised the shear-dependent behaviour of the suspensions over a wide range of shear rates. The viscoelastic properties of the suspensions were found to be functions of both frequency and solids loading with the viscous component dominating over the elastic component under the conditions investigated.