Abstract
In geometries capable of producing uniform shear stress across the gap such as cone–plate, it is a
challenge to study the nonlinear rheology of well-entangled polymers without wall slip and edge
fracture. The task to obtain meaningful steady-state information is particularly daunting. Significant
insights are required in the design of experiments and choice of reliable apparatuses that could fulfill
the objective to determine the constitutive behavior. In a recent published article, Hu J. Rheol.
54, 1307–1323 (2010) reported particle-imaging velocimetric measurements of two highly
entangled polybutadiene solutions with a cocylinder geometry. One of the solutions was prepared
and provided to Hu by Ravindranath from the University of Akron. Rheological and particletracking
velocimetric studies have been carried out on the same sample in our laboratory. In this
letter, we will compare Hu’s results with our own measurements, clarify a few misrepresentations,
and discuss several important issues concerning shear banding in entangled polymers.
