Shear-thinning behaviour of dense, stabilised suspensions of plate-like particles. Proposed structural model.

• A model describing the shear-thinning behaviour of kaolin suspensions is proposed.
• The effect of solids volume fraction and dispersant content is taken into account.
• Structural assumptions are considered.
• The results confirm the validity of the model.

A structural model was developed to describe the shear-thinning behaviour of dense, stabilised suspensions of plate-like particles. The model is based on the following main assumptions: the particles are distributed in more or less compact layers, oriented parallel to the flow; the particles are assumed to behave as hard disks, disk thickness being the sum of crystal thickness plus twice the Debye length; when the shear stress increases, the orientation of the plate-like particles in the flow direction also increases, thus increasing layer compactness. In order to test the proposed model, a kaolin was selected and characterised. The kaolin was used to prepare more than 40 aqueous suspensions, modifying the solids volume fraction between ϕ = 0.20 and ϕ = 0.475 and the dispersant (sodium silicate) content between Xs = 0.075 and Xs = 0.225 mg dispersant/m2 solid. The flow curves of all suspensions were determined in the quasi-steady state. The results confirmed the validity of the model to satisfactorily describe the combined effect of ϕ and XS on the flow curves in the shear-thinning range.