Significance of Predicting the First Normal Stress Difference and the Dynamic Moduli from the Steady‐Flow Viscosity

Based on the integral constitutive equation and using a specific functional form of the response function which is shear rate dependent, the dynamic moduli and the first normal stress difference are quantitatively predicted from the steady‐flow viscosity for linear polyethylene melts of varying molecular weight and molecular weight distribution. No arbitrary constant is involved in the procedure. The significance of the prediction is that at least for linear polyethylene melts, the elastic properties are obtained exclusively from knowing the manner in which the viscous parameter, namely the steady‐flow viscosity, changes with shear rate.