Rheological Properties of Polyethylene Materials

Polyethylene encompasses a family of thermoplastic polymers widely used in packaging, automotive and construction. Their rheological properties – encompassing shear and extensional flow behaviours – govern processing performance in extrusion, moulding and film blowing. These properties arise from molecular factors such as molar mass, branching architecture and distribution, which dictate viscosity, elasticity and flow instabilities. Non-Newtonian characteristics, such as shear thinning and strain hardening, emerge from polymer chain entanglements and long-chain branches, influencing melt strength and surface quality. Precise rheological characterisation enables optimisation of processing parameters, quality control of recyclate streams and design of novel grades with tailored performance. Recent advances leverage simulation techniques, in situ microscopy and advanced constitutive models to link molecular structure with macroscopic flow, supporting circular economy strategies and bespoke manufacturing. This overview highlights key developments in the elucidation and control of polyethylene flow behaviour.

Research from Nature Portfolio

Recent studies have established a rheology-based framework for defining degradation in recycled high-density polyethylene. By simulating chain scission and branching during extrusion and oxygen exposure, researchers identified a degradation parameter correlating molecular changes with viscosity evolution, enabling rapid assessment of recyclate quality. Another investigation applied atomic force microscopy to directly visualise long-chain branches in low-density polyethylene at nanometre resolution. This approach quantified branch lengths and spacing along individual chains, providing unprecedented insight into how branch distribution impacts melt elasticity and processing stability. Together, these works bridge nanoscale architecture and bulk rheology, advancing methodology for quality control and molecular design of polyethylene materials.

Rheological Properties of Polyethylene Materials publication trend

The graph below shows the total number of articles in rheological properties of polyethylene materials across all publications each year (not limited to Nature Index journals).

Technical terms

Shear viscosity: Resistance of a polymer melt to flow under applied shear stress, dependent on molecular entanglements and branching.

Extensional viscosity: Measure of resistance to deformation under stretching flows, critical for film blowing and fibre spinning.

Zero-shear viscosity: Viscosity value at very low shear rates, reflecting intrinsic molecular weight and branching effects.

Long-chain branching: Polymer architecture featuring branches of significant length on the main chain, enhancing melt elasticity and strain hardening.

Molar mass distribution: Spread of polymer chain lengths in a sample, influencing flow uniformity and viscoelastic response.

Non-Newtonian fluid: Fluid whose viscosity varies with applied shear rate rather than remaining constant.

References

1. Defining quality by quantifying degradation in the mechanical recycling of polyethylene. Nature Communications (2024).
2. Direct Observation of Long-Chain Branches in a Low-Density Polyethylene. Scientific Reports (2019).
3. Coupling Effect of LDPE Molecular Chain Structure and Additives on the Rheological Behaviors of Cable Insulating Materials. Polymers (2023).
4. Characterization of industrial low-density polyethylene: a thermal, dynamic mechanical, and rheological investigation. Rheologica Acta (2022).
5. Modelling of Elongational Flow of HDPE Melts by Hierarchical Multi-Mode Molecular Stress Function Model. Polymers (2021).
6. Irradiation processing to modify HDPE molecular architecture: Correlation with irradiation conditions and polymer grade. Materials Today Communications (2022).