Effect of Surface Treatments on Viscoelastic Measurements of Thread-like Micellar Solutions

Abstract

Thread-like micelles are formed in aqueous solutions of cationic surfactants and a certain type of salts, and for some of these solutions, the strain hardening behavior is observed after inception of shear flow at high shear rates. In the present study, we examined the effect of chemical surface treatments of the cone-and-plate fixture made of glass on measurements of strain hardening behavior of the thread-like micellar solutions. The untreated glass fixture gave significantly weak strain hardening behavior, when compared with the ordinary stainless steel fixture. This could be attributed to the slippage of the solution on the surface of fixture. When the surface of glass fixture was modified with trimethychlorosilane to increase the dispersion component of surface free energy, the pronounced strain hardening was observed. Thus, the surface treatment of rheometer fixtures is very important to examine the nonlinear rheology of thread-like micellar solutions.