Computational fluid dynamics of polymer flow-induced crystallization using the polySTRAND model

A computational model for predicting regions of flow-induced crystallization (FIC) during processing of a polydisperse polymer melt is presented. Flow produces local alignment of polymer segments that reduces the energy barrier for nucleation, which can lead to a dramatic increase in the rate of formation of crystal nuclei. However, simulating FIC in a complex flow geometry is challenging due to the need to couple a molecular-level description of chain configuration to the macroscale flow dynamics. This is compounded in polydisperse melts as the most marked flow-induced effects occur from the long-chain species at low undercooling. In this work, we use the Rolie-Double-Poly (RDP) model [Boudara et al., J. Rheol. 63, 71–91 (2019)] in combination with the polySTRAND model [Read et al., Phys. Rev. Lett. 124, 147802 (2020)] to create a computationally viable method for modeling FIC. This model is used to examine flow-induced crystallization in a contraction-expansion geometry, where previous experiments [Scelsi et al., J. Rheol. 53, 859–876 (2009)] found a highly localized region of crystal formation at and downstream of the wall of the constriction.