A new slit‐radial die for simultaneously measuring steady state shear viscosity and first normal stress difference of viscoelastic liquids via capillary rheometry

Abstract

AbstractA new slit‐radial die capable of simultaneously obtaining steady state shear viscosity and the average first normal stress difference coefficient via capillary rheometry has been developed. The steady state shear viscosity and average first normal stress difference coefficient are calculated in the slit part and radial part of the die, respectively. The steady state shear viscosity from the slit part of the slit‐radial die is compared to shear viscosities obtained from a capillary die and also the magnitude of the complex viscosity obtained from oscillatory shear experiment. The average value of first normal stress difference coefficient which is calculated in the radial part of the slit‐radial die is compared to first normal stress difference coefficient obtained from transient shear experiment in a cone‐plate geometry and the molecular stress function model predictions. The effect of variation of power law fitting parameters (consistency index, k and power law index, n) on average value of the first normal stress difference coefficient obtained from the radial part of the slit‐radial die is discussed. As this die has the shape of the city map of Karlsruhe it is named as Karlsruhe die.