Rheological Behavior of Polymer Systems in Processing Applications

Polymers in melt or solution form exhibit complex flow and deformation characteristics that underpin virtually all industrial shaping processes, from extrusion and injection moulding to fibre spinning and additive manufacturing. Their rheological behaviour arises from the interplay of molecular weight distribution, chain architecture and entanglement density, which together govern shear‐ and extensional viscosities, viscoelastic relaxation and non‐Newtonian responses such as shear thinning and strain hardening. In shear flows, polymer melts often display a reduction in viscosity with increasing shear rate, facilitating high‐speed processing, while in elongational flow they may exhibit pronounced strain hardening that stabilises filament stretching and reduces melt fracture. Advanced constitutive models—ranging from tube‐based frameworks to slip‐link and mesoscopic simulations—have been developed to predict nonlinear stress growth and steady‐state viscosities. Control of rheological parameters through molecular design, temperature and processing conditions ensures product uniformity, dimensional accuracy and energy efficiency. Recent advances in multiscale characterisation have further elucidated the microscopic origins of flow instabilities, enabling more reliable process design and the development of sustainable polymer formulations.

Research from Nature Portfolio

Recent studies have introduced a predictive model that links the extensional viscosity and strain hardening behaviour of branched polymer melts directly to their molecular architecture. By synthesising polystyrene “pom-pom” systems with systematically varied arm and backbone molecular weights, researchers identified four distinct regimes of extensional response—from linear viscoelasticity to strong strain hardening—and demonstrated that the maximum hardening factor depends solely on arm number. This framework offers a route to tailor branched polymers with predictable flow stability in high‐speed elongational processes, advancing the rational design of materials for fibre spinning and film blowing.

Rheological Behavior of Polymer Systems in Processing Applications publication trend

The graph below shows the total number of articles in rheological behavior of polymer systems in processing applications across all publications each year (not limited to Nature Index journals).

Technical terms

Viscoelasticity: The time‐dependent combination of viscous flow and elastic deformation exhibited by polymer melts and solutions.

Extensional viscosity: The resistance of a polymer fluid to uniaxial stretching, often exhibiting strain hardening at high deformation rates.

Strain hardening: Increase in extensional viscosity with accumulated strain, stabilising filament draw and delaying fracture.

Melt instability: Surface or flow defects (e.g., stick-slip, sharkskin, gross melt fracture) arising at high shear rates during extrusion.

Polydispersity: Measure of the molecular weight distribution in a polymer sample, influencing flow uniformity and processability.

Weissenberg number (Wi): Dimensionless ratio of elastic to viscous forces, defined as product of characteristic relaxation time and deformation rate.

References

1. Predicting maximum strain hardening factor in elongational flow of branched pom-pom polymers from polymer architecture. Nature Communications (2024).
2. Microstructural Dynamics of Polymer Melts during Stretching: Radial Size Distribution. Polymers (2023).
3. Melt Instability Identification Using Unsupervised Machine Learning Algorithms. Macromolecular Materials and Engineering (2023).
4. Modelling elongational viscosity overshoot and brittle fracture of low-density polyethylene melts. Rheologica Acta (2022).
5. Review on tube model based constitutive equations for polydisperse linear and long-chain branched polymer melts. Journal of Rheology (2019).
6. Entangled Polymer Dynamics in Equilibrium and Flow Modeled Through Slip Links. Annual Review of Chemical and Biomolecular Engineering (2014).
7. Slip Spring-Based Mesoscopic Simulations of Polymer Networks: Methodology and the Corresponding Computational Code. Polymers (2018).