| 초록 |
In this study, we report experimentally on the linear and nonlinear rheological behaviors of wormlike micelles made of CTAB with NaSal and heptanols. The CTAB concentration was fixed at either 0.05M or 0.005M. The added NaSal salt concentration varied from 0.0005M to 0.5M. We focused on the linear and nonlinear rheological properties as the molar concentration ratio, [NaSal]/[CTAB], from 0.1 to 10.0 at the fixed surfactant concentration. Rheological properties at low molar ratios in steady shear and dynamic oscillatory mode show an similar results of rheo-optical measurements in the point of the time dependent relaxation and Newtonian behavior. As molar ratio increases to 2.0, the micellar solutions are governed by a single relaxation time that means linear viscoelastic model. The rheological data matches Maxwell model prediction at oscillatory mode in both low and high frequency regions. As more molar ratio increases, these behaviors deviate at high frequencies. These results are confirmed by the flow birefringence measurements where the relaxation behaviors of birefringence intensity explain the oscillatory flow results. For the CTAB concentration is low, we can observe a shear thickening effects that affected several parameters, phase volume, particle shape, particle-particle interactions. As the CTAB concentration increases, the micellar solutions show not a shear thickening behavior but a shear thinning behavior in the range of used equipment limit. For investigation of rheological properties of wormlike micelles, we use the viscometry and rheo-optical measurements.
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