LAUSR

Abstract We considered the gelation and its relaxation mechanism of a shear-induced bentonite / heptaethylene oleyl ether (abbreviated as C18:1E7) aqueous suspension based on the analysis of Rheo-SALS. When bentonite / C18:1E7 aqueous suspension formed the shake-gel, the concentration of bentonite was greater than or equal to the critical concentration of c* = 1.3 wt% where hydrodynamic interactions occur. The relationship between the time ts when the shear thickening occurs and the bentonite / surfactant concentration (c - cs) can be described by the first-order reaction equation, and ts can be further reduced with the applied shearing. The gel formation time and the relaxation time were affected by the shear hysteresis. We found that the formation and the relaxation (breakdown) of gels comprising bentonite particles did not follow the same pathway. Thus, Shear induced gel formation is due to the percolation transition by the infinite network structure in which the anisotropic orientation of bentonite particles grows. In contrast, the relaxation (breakdown) of the gel proceeds by the isotropic diffusion of individual bentonite particles forming the network structure.