2022 Volume 50 Issue 2 Pages 245-252
The dominant responsible factor for the disappearance of shear-induced structure, SIS, in aqueous wormlike micelle solutions is examined. It has been reported that the of SIS is accompanied by a spatial distribution of micelle concentration as the micelle structure changes, which generates on a much larger scale than the size of the micelles. Therefore, the time required for the heterogeneity caused by the SIS formation to be completely eliminated was determined by a continuous step shear test with a constant interval time. The time required for the stress behavior in the second step to completely match that in the first step was defined as the SIS disappearance time. The SIS disappearance time evaluated in this experiment is 3.7 times longer than the relaxation time for micelle entanglement, regardless of the molar concentration ratio, and can be predicted by a simple relaxation curve. The critical conditions for the onset of SIS in the start-up behavior of accelerated shear flow, in which the rheological properties are determined by the balance between the formation and disappearance of SIS, were determined, and it was shown that the maximum value of viscosity normalized by zero shear viscosity can be characterized by the product of the rate of increase of shear rate and the square of the SIS structure disappearance time. It was confirmed that the SIS resolution time is one of the important rheological properties in the SIS formation state.
