Predicting High-Density Polyethylene Melt Rheology Using a Multimode Tube Model Derived Using Non-Equilibrium...

Area of Science:

• Non-equilibrium thermodynamics
• Polymer rheology
• Constitutive modeling

Background:

• Existing models had limitations regarding thermodynamic laws and predicting complex rheological phenomena like stress undershoot.
• The Generalized bracket (or Beris-Edwards) formalism provides a foundation for advanced rheological models.

Purpose of the Study:

• To extend and validate a recently proposed differential constitutive model for polymer melts and solutions.
• To assess the model's predictive capabilities for industrial polymer systems, specifically High-Density Polyethylene (HDPE).

Main Methods:

• Development of a multiple-mode version of the differential constitutive model.
• Comparison of model predictions with experimental rheological data for HDPE resins.
• Validation across different flow conditions: Small Amplitude Oscillatory shear, start-up shear, and start-up uniaxial elongation.

Main Results:

• The multiple-mode model successfully predicts rheological responses, including transient stress undershoot.
• The model demonstrates good agreement with experimental data for HDPE across various shear and elongation tests.
• The enhanced model overcomes limitations of previous versions concerning the convective constraint release parameter and thermodynamic consistency.

Conclusions:

• The validated multiple-mode constitutive model is a promising tool for studying the rheology of entangled polymer systems.
• The model's ability to accurately predict industrial polymer behavior enhances its practical applicability in material science and engineering.