(119e) Transient Shear Rheology of Dilute Particle Suspensions in Polymer Solutions and Entangled Polymer Melts

Previous studies on rheology of suspensions in dilute polymer solutions have focused on steady shear measurements both in numerical simulations and experiments. However, since this response typically takes 10-100 shear strain to achieve, the time dependent response is of great practical and fundamental interest as well. In this work, we present time-dependent evolution of shear stress in viscoelastic suspensions using complete 3D numerical simulations over a range of shear Weissenberg number. We also show the evolution of first normal stress difference of suspensions with time and understand how the presence of particles changes the response of suspending polymeric fluid to shear. Note that of principal interest is the time scale to steady state and the time scales involved in the response. We compare our numerical results with experimental measurements of varying volume fraction suspensions in Boger M1 fluid upto 20%. We use Oldroyd-B and Giesekus constitutive equations in single and multi-mode forms to model the suspending fluid.

In a second related study, we present the transient shear rheology of dilute particle suspensions in highly entangled polymer melts. We model the melt using the single and multi-mode Rolie-Poly equation and solve for the shear stress of suspension as a function of time. Viscometric functions in polymer melts such as shear viscosity and first normal stress difference show interesting non-monotonic approach to steady state in shear flow. We study the effect of adding particles to the transient melt behavior as a function of shear strain numerically for a range of Weissenberg number based on Rouse time in system. If time permits, we will contrast the response of the melt suspension to the solution suspension.