Advances in techniques to determine extensional rheology from capillary measurements

摘要

Flow through an abrupt contraction has been analyzed experimentally and theoretically through FEM simulations using the modified White-Metzner model. The results show that the 'entrance viscosity η{sub}ENT ' (entrance pressure drop divided by the shear rate) strongly depends on the shape of the steady extensional viscosity, the L/D ratio of the orifice die and it can be properly described by the newly proposed model. A 'Trouton Correction' was proposed and successfully tested to improve the capability of the entrance techniques to properly predict extensional viscosity at low extensional rates. It is demonstrated that the proposed improvements in this work help to more effectively evaluate extensional rheology from capillary measurements.