Creep Tests, Flow Birefringence Measurements, and Flow Visualization of Aqueous Solutions of CTAB and NaSal in Shear Flow between Parallel Plates

Abstract

Creep tests, flow birefringence measurements, and flow visualization experiments in shear flows between parallel plates were carried out for aqueous solutions of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) with excess of NaSal. The mol concentration of CTAB was fixed to 0.030 mol/l and the concentration ratio of NaSal to CTAB was varied. The creep tests indicate that it requires long time to develop micellar network structures for low to moderate concentrations at low shear stresses. Under conditions of shear rate at which the shear-thickening property in viscosity is observed in a flow curve, periodical changes in flow birefringence and shear stress occur and these frequencies are almost the same as that of the emergency of white turbidity observed in the flow visualization. These results indicate that relatively large structures of micellar network are induced by the shear flow and repeatedly appear and disappear.

Keywords

• surfactant solutions
• creep test
• flow birefringence
• turbidity
• wormlike micelles
• ctab/nasal
• shear flow