Influence of the temperature on the rheological properties of bentonite suspensions in aqueous polymer solutions

Dispersions of clay particles in aqueous polymer solutions generally exhibit complex rheological behaviours depending on the mechanical history of the material. In this paper, the effect of the temperature on the rheological properties of bentonite dispersions in aqueous carboxymethylcellulose solutions is examined. The bentonite concentration was fixed to 5% w/w while the polymer is 0.5 or 1% w/w. For stresses lower than a yield stress, the systems behaved as a gel and, above the yield stress, they flowed as liquids. The samples were characterized both in permanent and oscillatory shear flow. In the liquid like regime, the viscosity of the fluids decreased as the temperature increased. In the solid like regime, when the temperature increased, the experimental results displayed unusual behaviours of the viscosity and of the shear moduli. The increase of the chain mobility induced by the Brownian motion combined with a dissociation of the aggregates of particles could result in the formation of an elastic network with more crosslinks. This could explain why a dramatic increase of the solid-like character of the dispersions was observed.