(653f) Slip-Link Modeling of a Crystallizing Entangled Polymer Melt

Modeling of polymer processing is a subject of continuing industrial and theoretical interest. Many industrial polymer melts are entangled and undergo crystallization during processing. Experimental data for the rheology of crystallizing entangled polymers are available in a number of published studies on this topic. In the literature, suspension-based models have been used with considerable success to describe the evolution of the mechanical modulus at a given frequency during crystallization. Meanwhile, over the past few years, slip-link models have been demonstrated to be very capable for describing the rheology of entangled melts under a variety of non-linear deformation conditions, including shear, extension, and start-up. These models are attractive for their physically measurable parameters, and for their ability to represent distributions of composition, molecular weight and branching architecture. In this work, we present a modification of the slip-link model to capture the rheology of an entangled melt undergoing crystallization. Partially crystallized melts are represented by blends of linear or short-chain-branched chains with crosslinked, bridge-like chains that resemble the tie molecules between developing crystallites. The model simultaneously captures the evolution of viscosity and elasticity over the whole range of frequencies in the linear regime. Experimental data for several polymer chemistries, including industrial-grade materials, are well represented by this model. The model is able to describe effects of molecular architecture and molecular weight distribution. However, the main advantage of this approach is the capability to predict the effects of on-going crystallization during non-linear deformation.