126 Effect of concentration ratio of surfactant and counter ion on planar elongation induced structure change
Details
Cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) in de-ionized water forms worm-like micelles at a certain concentration and shows remarkable viscoelastic property such as polymer solution. CTAB/NaSal aqueous solution causes flow induced structure change when both shear rate and strain are higher than a certain value in start-up behavior of Couette flow. Though the fluid is originally transparent, it turns out to be opaque in this state. In this report, the flow-induced structure in step-elongation behavior of squeezing flow was investigated. The occurrence condition of the planar elongation induced structure in the middle plane of the flow cell was measured concerning the solutions which have different concentration of NaSal. The relaxation time and the elastic modulus of one-mode Maxwell model were evaluated by dynamic viscoelastic test. The relationship between the critical planar elongation strain and Debora number based on the relaxation time is collapsed on a single curve independent of the molar concentration ratio of detergent and salt.
