Observations of the influence of Taylor-Couette geometry on the onset of shear-banding in surfactant wormlike micelles

Rheo‐NMR in food science—Recent opportunities

“…A number of different cylindrical concentric TC geometries were used in Brox et al They consist of an outer cup and a smaller concentric inner bob that leaves a gap between the radius of the inner wall r i (i.e., the radius of the bob) and outer wall r o (i.e., the inner radius of the cup). The gap holds the sample and it can be sheared, for instance, by rotating the bob while holding the cup stationary.…”

“…The NMR coupled bulk rheometry shows that the stress plateau begins at approximately 2 s −1 for the device with κ = 0.89 (∘) and just before 1 s −1 for the geometry with κ = 0.67 (⋆). Reprinted with permission from Brox et al Copyright (2016), The Society of Rheology…”

“…The influence of the shear geometry dimensions on the onset of shear banding in a cetylpyridinium chloride/sodium salicylate in brine wormlike micelle (WLM) systems was recently investigated with Rheo-NMR. [22] This material has been extensively studied in the past two decades. It is considered a model system to illustrate nonlinear mechanical response under steady shear flow conditions.…”

“…Although the shear rates in the low and high shear rate band are considered to be constant under the assumption of the lever rule, more recent work suggests that this may not be always the case. [51][52][53][54] A number of different cylindrical concentric TC geometries were used in Brox et al [22] They consist of an outer cup and a smaller concentric inner bob that leaves a gap between the radius of the inner wall r i (i.e., the radius of the bob) and outer wall r o (i.e., the inner radius of the cup). The gap holds the sample and it can be sheared, for instance, by rotating the bob while holding the cup stationary.…”

“…The bobs used with the torque sensor drive-shaft had a bottom that was tapered into a cone ( = 5 • ); Equation 2 includes a correction factor to account for the torque generated on this conical surface. Most NMR measurements presented in Brox et al [22] were performed on a Bruker Super Wide Bore superconducting magnet at a proton frequency of 300 MHz with an Avance III spectrometer, a three axis imaging gradient system (0.37 T m −1 maximum gradient), and a 60 mm resonator coil. In the case of simultaneous NMR-torque experiments, measurements were performed on a Bruker wide bore superconducting magnet at a proton frequency of 250 MHz with an Avance III spectrometer, a Micro2.5 three axis imaging gradient system (1.5 T m −1 maximum gradient), and a 25 mm birdcage resonator coil.…”