POLYMER RHEOLOGY
The science of polymer melt flow — viscosity, viscoelasticity, shear-thinning behavior, die swell, and melt fracture. Essential for understanding and troubleshooting all polymer processing operations.
“Rheology is the language of molten polymers under shear and stress.”
— Polymer Rheology · PolymerHub
9 Lessons
Non-Newtonian Rheology: Power-Law & Carreau-Yasuda Models for Polymer Melts
Polymer melt rheology, shear-thinning pseudoplasticity, Ostwald-de Waele Power-Law model, Carreau-Yasuda model, zero-shear viscosity, and power-law index n.
Time–Temperature Superposition, WLF Shifts & Rheological Master Curves
Time-Temperature Superposition (TTS), Williams-Landel-Ferry (WLF) shift factors, reduced frequency, and rheological master curves for G' and G''.
First Normal Stress Difference, Recoverable Strain & Polymer Melt Elasticity
Melt elasticity, First Normal Stress Difference N1, Weissenberg effect (rod climbing), extrudate die swell, and recoverable shear strain.
Polymer Melt Rheology, Viscosity & Shear Flow Fundamentals
Newtonian vs non-Newtonian fluids, viscosity definition, and why understanding melt flow is essential for every processing engineer.
Shear-Thinning and the Power Law Model
How polymer viscosity decreases with shear rate, the power law (Ostwald-de Waele) model, flow behavior index n, and practical implications for injection moulding and extrusion.
Viscoelasticity — The Memory of Polymer Melts
Elastic recovery, die swell (Barus effect), Weissenberg effect, Maxwell and Kelvin-Voigt models, and why polymer melts behave like both liquids and solids.
Capillary Rheometry and Viscosity Measurement: Flow, Corrections & Shear Kinetics
How capillary rheometers measure viscosity at processing shear rates, Rabinowitsch correction, Bagley correction, and interpreting viscosity curves for material selection.
Melt Fracture, Sharkskin, and Flow Instabilities: Physics, Diagnostics & Mitigation
Flow instabilities in extrusion — sharkskin, gross melt fracture, slip-stick oscillation — their causes, critical shear stress values, and industrial solutions.
Rheology in Practice: Selecting and Processing Polymer Grades
Using rheological data for grade selection, how MFI relates to the viscosity curve, time-temperature superposition, WLF equation, and practical processing window determination.
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