Influence of pressure on end corrections in capillary rheometry

The research and modeling of the connection of polymer viscosity and the present pressure level have brought forth a variety of, often contradictory, results. While different machinery setups are used resulting in less comparison of the studies, a combined analytical and experimental approach to apply end corrections at correct pressure levels has not been presented yet. In this work, the effect of pressure on end corrections in die flow is assessed with a combination of a pressure chamber and an orifice die, and applied to capillary rheometry measurements at different pressure levels. The pressure dependence of the end corrections has been found to show good correlations with an applied modified Power-Law model. By comparing the results to regular end corrections, the error in computing the viscosity has been found to be largely independent of the shear-rate. Neglecting the influence of pressure on end corrections yields 0–12 % too high viscosities, depending on the average die pressure.