Influence of shear-induced crystallisation on the rheological behaviour of polyethylene

This paper presents a numerical simulation for the influence of shear-induced crystallisation on the rheological behaviour. The effect of flow on crystallisation is considered through the mathematical relationship between the additional number of nuclei induced by shear treatment and the first normal stress difference. Avrami model is used to describe the crystallisation kinetics. Normalised viscosity, orientation factor and extra stress are simulated with the development of crystallinity. It is found that the short-term shear treatment has a great effect on the crystallisation dynamics of polyethylene, and a small amount of crystallinity cause a strong increase of shear viscosity. Beyond a specific shear strain the stress increases dramatically, which indicate the solidification of the material and the locking-in of stresses.