Prediction of dynamic and transient rheological properties of polystyrene and high‐density polyethylene melts from the molecular weight distribution

A model relating the steady‐shear melt viscosity and elasticity to the molecular weight distribution in HDPE and polystyrene melts has been extended to predict the dynamic viscosity, modulus, and loss modulus. Limitations in the model as applied to the dynamic properties are discussed. The model is also applied to the transient response of stress growth during steady shearing. This application is considered useful because it may help describe nonsteady‐state flow of polymer melts in short dies and cyclic operations as employed in commercial molding equipment.