Characterization of drag-reducing surfactant systems by rheology and flow birefringence measurements /

Dilute surfactant solutions can be effective in drag reduction and show unique rheological characteristics. Rheological and flow birefnngence measurements are performed to characterize these drag reducing surfactant systems. Application studies on separation of surfactants and stability of drag reducing additives are also described. Counterion structure affects drag reduction and the rheological behavior of surfactant systems. The Arquad 16-50 (5 mM) / 2-Cl-benzoate (12.5 mM) system has no drag reduction, low apparent extensional viscosity, no viscoelasticity and spherical micelles. The 4-Cl-benzoate with the same surfactant has a thread-like micellar network, is drag reducing and viscoelastic, and has high apparent extensional viscosity. The 3-Cl system is similar to the 4-Cl system at 30°C. These differences are caused by the different positions of the chlorine group at the micelle-water interface. A stress induced precipitation phenomenon is observed at 20°C for the 3-Cl system, which may have one of three different microstructures: thread-like micelles, vesicles or precipitation, depending on external forces. A schematic diagram is proposed to describe this phenomenon.