Model for flow-induced crystallization of industrial-grade LLDPEs

Flow-induced crystallization (FIC) is ubiquitous in the manufacturing of semi-crystalline plastic products. Generally speaking, polymer crystallization and polymer rheology operate on very different time and length scales. Therefore, modeling FIC requires a multi-scale approach.
In this work, we combine information from atomistic molecular dynamics simulations, mesoscale slip-link modeling, rheo-Raman measurements and fast scanning chip calorimetry to build a model for flowing LLDPE melts undergoing crystallization. Analysis of non-equilibrium molecular dynamics simulations motivate the use of the conformation tensor as a suitable order parameter with which to correlate FIC. The conformation tensor can be tracked during flow using a mesoscale computational model that incorporates the physics of slip-links, cross-links and suspensions to capture linear viscoelasticity and its dependence on polydispersity, entanglement dynamics and crystallinity. Crystallinity in turn evolves according to a kinetic model that depends on the conformation tensor. The combination of models is parametrized from the experimental rheo-Raman and calorimetry data and is shown to be suitable for multi-level modeling of an industrial blown-film process.