REPTATE rheology software: Toolkit for the analysis of theories and experiments

We present a new, free, and open source reptate (rheology of entangled polymers: toolkit for analysis of theory and experiment) software package for viewing, exchanging, and analyzing rheological and associated data. The main idea of reptate is to propose a powerful and user-friendly platform, which can be installed on the same computer as, e.g., the rheometer and which makes comparing experiments with classical, or latest, theories easy—without the need for a theoretician. The new reptate software offers full compatibility with different operating systems (Windows, Mac, and Linux). We demonstrate the use of reptate by reproducing predictions of recently published articles, from entangled, monodisperse, and polydisperse linear chains to branch-on-branch polymer systems in linear and nonlinear rheology regimes

Advances in modeling transport phenomena in material-extrusion additivemanufacturing: Coupling momentum, heat, and mass transfer

Material-extrusion (MatEx) additive manufacturing involves layer-by-layer assembly ofextruded material onto a printer bed and has found applications in rapid prototyping.Both material and machining limitations lead to poor mechanical properties of printedparts. Such problems may be addressed via an improved understanding of thecomplex transport processes and multiphysics associated with the MatEx process.Thereby, this review paper describes the current (last 5 years) state of the art modelingapproaches based on momentum, heat and mass transfer that are employed in aneffort to achieve this understanding. We describe how specific details regardingpolymer chain orientation, viscoelastic behavior and crystallization are often neglectedand demonstrate that there is a key need to couple the transport phenomena. Such acombined modeling approach can expand MatEx applicability to broader applicationspace, thus we present prospective avenues to provide more comprehensive modelingand therefore new insights into enhancing MatEx performanc

Nonlinear rheology of polydisperse blends of entangled linear polymers: Rolie-Double-Poly models

While there has been much success in modeling the linear and nonlinear rheology of monodisperse entangled linear polymers, progress in the constitutive modeling of polymeric materials continues to lag behind the needs of industry. Industrially sourced polymers are typically polydisperse (comprising a broad distribution of molecular weights), making their rheology more suitable for processing but also more difficult to predict. To date, there are no molecular-based constitutive models that are practically suitable for describing industrially relevant polymers in industrially relevant flows. In this article, we extend but strongly simplify the model of Read et al. [J. Rheol. 56, 823–873 (2012)], which is able to predict the linear and nonlinear rheology of bidisperse blends but is prohibitively complex for industrial use. We propose a pair of simplified tube models for polydisperse melts of entangled linear polymers that combine the success of the double reptation approximation [des Cloizeaux, Europhys. Lett. 5, 437–442 (1988)] in the linear regime with the success of the Rolie-Poly constitutive equation [Likhtman et al., J. Non Newtonian Fluid Mech. 114, 1–12 (2003)] in the nonlinear regime. We first review the key concepts of the double reptation approximation and the original (monodisperse) Rolie-Poly constitutive model. Subsequently, we provide the details of our approximate models for the particular case of a bidisperse blend and show that these models naturally identify the effects from couplings between constraint release and chain retraction (i.e., the so-called “enhanced stretch relaxation time”). Finally, we generalize to a multicomponent (polydisperse) model, based on the same underlying principles. Along the way, we also show that both of our models are in qualitative, and largely quantitative, agreement with experimental data for bidisperse and polydisperse melts of entangled linear polymers

Modelling contraction flows of bi-disperse polymer blends using the RoliePoly and Rolie-Double-Poly equations

The flow of a bi-disperse polymer melt through a hyperbolic contraction is simulated using the recently proposed Rolie-Double-Poly constitutive model (Boudara et al., 2019). This simplified tube model takes account of the nonlinear coupling between the dynamics of the long and short-chains in a bi-disperse blend, in particular it reproduces the enhancement of the stretch relaxation time that arises from the coupling between constraint release and chain retraction. Flow calculations are performed by implementing both the Rolie-Double-Poly and multimode Rolie-Poly models in OpenFOAM using the RheolTool library. While both models predict very similar flow patterns, the enhanced stretch relaxation of the Rolie-Double-Pol models results in an increase in the molecular stretch of the long chain component in the pure extensional flow along the centre-line of the contraction, but a decrease in the stretch in shear-flow near the channel walls