Numerical investigation of the crystallization and orientation behavior in polymer processing with a two-phase model

• The morphology variation during solidification is mathematically modeled with a two-phase model.
• The amorphous phase and semi-crystalline phase are approximated as FENE-P fluid and rigid rods.
• The Schneider approach is used to distinguish between thermal and flow effect on crystallization.
• The penalty FE–FD model of the nonlinear governing equations is derived.
• The crystallization and orientation behavior in polymer processing are successfully predicted.

The crystallization and orientation behavior of a polymeric material can significantly influence the performance of products in practical processing. In this study, the variations in morphology that occur during solidification in polymer processing are mathematically modeled using a two-phase model. The amorphous phase is approximated as a finite extensible nonlinear elastic dumbbell with a Peterlin closure approximation (FENE-P) fluid, and the semi-crystalline phase is modeled as rigid rods oriented within the flow field. The crystallization and orientation behavior are numerically investigated using the penalty finite element–finite difference method with a decoupled algorithm. The evolution of the crystallization process is described by Schneider's equation, which differentiates between the effects of thermal and flow states. The hybrid closure approximation is adopted for the calculation of the three-dimensional orientation tensor. The discrete elastic viscous split stress (DEVSS) algorithm, which incorporates the streamline upwind scheme, is introduced to improve calculation stability. The variations in morphology during polymer processing are successfully predicted using the proposed mathematical model and numerical method. The influence of processing conditions on the crystallization and orientation behavior is further discussed.