  We study the Rolie-Poly model for entangled polymers, using a singular
perturbation analysis for the limit of large relaxation time. In this limit, it
is shown that the model displays the characteristic features of thixotropic
yield stress fluids, including yield stress hysteresis, delayed yielding and
long term persistence of a decreased viscosity after cessation of flow. We
focus on the startup and cessation of shear flow. We identify dynamic regimes
of fast, slow and yielded dynamics, and show how the combination of these
regimes can be used to describe the flow.
