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

A new slit-radial die capable of simultaneously obtaining steady state shear viscosity η(γ) and the average first normal stress difference coefficient <Ψ$_{1}$(γ)> via capillary rheometry has been developed. The steady state shear viscosity η(γ) and average first normal stress difference coefficient <Ψ$_{1}$(γ)> are calculated in the slit part and radial part of the die, respectively. The steady state shear viscosity η(γ) from the slit part of the slit-radial die is compared to shear viscosities η(γ) obtained from a capillary die and also the magnitude of the complex viscosity |η*(ω)| obtained from oscillatory shear experiment. The average value of first normal stress difference coefficient <Ψ$_{1}$(γ)> which is calculated in the radial part of the slit-radial die is compared to first normal stress difference coefficient Ψ$_{1}$(γ) 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 <Ψ$_{1}$(γ)> obtained from the radial part of the slit-radial die is discussed. ... mehrAs this die has the shape of the city map of Karlsruhe it is named as Karlsruhe die.