Simulation of microstructure evolution for polymer using the phase field method: Crystallization induced by temperature

Abstract

Mechanical properties of polymers highly depend on microstructure and the thermal and/or mechanical histories during the forming process have an important influence on the final microstructure. For example, crystallized polyethylene terephthalate (PET) highlights different mechanical properties than amorphous PET and to be able to predict the microstructure of polymers is a scientific goal. In this article, we propose to model the crystallization of PET at the mesocopic scale of spherulite by using the phase field method coupled to finite element method. We first present a simulation of the PET crystallization under thermal conditions where spherulite growth is modeled by the phase field method. The phase variable governing equation describes the state (amorphous and crystallized) in the material as a function of space and time. Coupled to the thermal equations, the problem can be solved without tracking the interface. Parameters of the phase field model are adjusted from the experimental results in order to reproduce accurately the growth of one spherulite, and the crystallization kinetic of PET at different temperature. Second, a multiphase field version is implemented and the influence of the germs positions and initial radius is discussed using a stochastic approach.