High shear rate rheology in microcapillary flow with SANS*

The rheology of shear-banding wormlike micelle solutions, which exhibit polymeric viscoelasticity, is investigated at high shear rates using capillary rheometry, particle-streak velocimetry, and small-angle neutron scattering (SANS). The capillary entrance flow was examined so that results of fully developed flow are reported. Such results show shear-thinning power-law behavior for all channel geometries from shear rates of 1,000 /s to nearly 1,000,000 /s. Two distinct power-law behaviors with increasing shear rate indicate a structural change with corresponding broadening of neutron scattering. The transition between these two power laws shifts with changing surfactant concentration and temperature.