Paper Number
SM23                         My Program 

Session
Polymer Solutions, Melts and Blends

Title
An elasto-viscoplastic approach to polymer rheology

Presentation Date and Time
October 21, 2025 (Tuesday) 1:30

Track / Room
Track 3 / Coronado + DeVargas

Authors (Click on name to view author profile)

  1. Winters, Arturo (ETH Zurich, Department of Materials)
  2. Vermant, Jan (ETH Zurich, Department of Materials)
  3. Tervoort, Theo A. (ETH Zurich, Department of Materials)

Author and Affiliation Lines (in printed abstract book)
Arturo Winters, Jan Vermant and Theo A. Tervoort
Department of Materials, ETH Zurich, Zurich, Switzerland

Speaker / Presenter 
Tervoort, Theo A.

Keywords
experimental methods; theoretical methods; non-Newtonian fluids; polymer melts; polymer solutions; rheometry

Text of Abstract
This presentation explores the rheology of polymer melts and solutions through the lens of a standard elasto-viscoplastic Maxwell model. This simple one-mode building block emphasizes the role of recoverable strain—a tensorial measure of the elastic deformation stored in the material, which would be recovered upon removal of all external forces.

Building on the GENERIC (General Equation for the Non-Equilibrium Reversible-Irreversible Coupling) framework, we derive thermodynamically consistent evolution equations grounded in this recoverable strain concept [1]. From this foundation, we propose a particularly simple closed-form evolution equation for the stress tensor. Despite its simplicity, the model captures key nonlinear rheological behaviors using only linear material input data.

Analytical solutions are presented for stationary states under common flow conditions. The multi-mode version of the model is evaluated against experimental data from elongational, shear, and superposed flows of polymer melts. We benchmark its performance against established nonseparable constitutive models, particularly the Leonov model, which shares structural similarities, and we discuss the relation of our model to the well-known empirical Cox-Merz relation.

To enhance adaptability, we introduce two optional non-linear parameters to tailor the model to specific material responses. We also discuss thermodynamically consistent modifications, highlighting the model’s flexibility and extensibility.

This work demonstrates that using recoverable strain as a central concept allows strongly nonlinear effects—such as shear thinning and strain hardening—to be incorporated within a framework that uses only linear viscoelastic input parameters.

References:
1. Markus Hütter and Theo A. Tervoort, J. Non-Newtonian Fluid Mech., 152 (2008), 53–65.