Polymeric suspensions in shear flow: Relaxation and normal stress differences

- Relaxation of polymeric suspension is studied as a function of volume fraction.
- A relaxation model for polymeric suspension in shear is developed.
- Normal stress differences are studied based on this model.

Viscometric properties of non-colloidal polymeric suspensions are investigated, showing a longer relaxation time with increasing volume fraction of the particulate phase, due to the influence of particles that form a pairwise close-contact microstructure. This results in a shift of the onset of the shear thinning to a lower shear rate, with a corresponding shift in the first normal stress difference. The effective relaxation time derived from the first normal stress difference and the shear stress is investigated as a function of the particle volume fraction. The relative relaxation time (normalized by the relaxation time of pure polymeric fluid) is independent of the polymeric suspending mediums used in our experiment (various silicone oils of different molecular weights).