Rheological and structural characterization of organo-hectorite dispersions: Influence of the organoclay loading

Abstract

The complex behavior of organoclay dispersions is influenced by the structure and the intermolecular interactions between clay platelets. The confinement of the clay particles is seen to be the main reason of this complex behavior because of the presence of surfactants with long alkyl chains on clay surfaces. The rheological properties of organo-hectorite (OHt) dispersed in gasoil were studied using a controlled stress rheometer. Commercial organoclay surfaces were modified with dimethyldialkyl quaternary ammonium cations. It was found that all the dispersions exhibit yield stress with a shear thinning behavior. Flow curves were correlated using both the Herschel-Bulkley phenomenological model and the Carreau-Yasuda structural model, in order to describe, respectively, the macroscopic and the microstructural behaviors of the dispersions (3 to 10 wt%). The parameters of the Carreau-Yasuda model showed the existence of a critical concentration of 6 wt%. Furthermore, frequency sweep tests showed that the dispersions start to have a fully developed gel behavior with a more pronounced solid-like structure at loadings greater than the critical concentration.