Flow-Induced Crystallization in Polymeric Materials

Flow-induced crystallization (FIC) is the phenomenon whereby polymer chains, subjected to shear or extensional deformation, align and form ordered crystalline domains at rates and temperatures distinct from quiescent conditions. This alignment reduces the free energy barrier to nucleation, accelerates growth kinetics and gives rise to unique morphologies—such as oriented fibrils or shish-kebab structures—that impart enhanced mechanical, thermal and barrier properties. FIC underpins advanced processing techniques in extrusion, injection moulding and fibre spinning, where control over flow history enables tuning of crystallinity, orientation and ultimately performance. Recent progress has deepened understanding of the interplay between chain architecture, flow profile and phase behaviour, revealing pathways to tailor polymer microstructure for applications ranging from high-strength composites to biodegradable packaging. By integrating rheological characterisation, in-situ scattering and phenomenological modelling, researchers are establishing quantitative frameworks to predict and optimise FIC across diverse polymer classes and industrial processing regimes.

Research from Nature Portfolio

Recent studies have combined extensional rheology with in-situ synchrotron X-ray scattering to construct non-equilibrium phase diagrams of polyethylene under flow, delineating melt, metastable δ and stable hexagonal and orthorhombic regimes. This work clarifies how transient pre-ordered phases guide final crystalline structures and informs precise control of processing conditions. In parallel, investigations into long-chain branched polylactides have demonstrated that increasing branching degree broadens relaxation spectra, enhances nucleation density under shear and induces a systematic shift from spherulitic to highly oriented morphologies. These foundational insights reveal how molecular architecture modulates flow-enhanced kinetics and morphology evolution, laying the groundwork for structure-property tailoring in semicrystalline polymers.

Research from all publishers

A 2023 study on polypropylene integrated differential scanning calorimetry, optical microscopy and oscillatory shear rheology to develop a phenomenological model relating transient storage and loss moduli to spherulitic microstructure throughout crystallization and remelting cycles. The findings highlight the necessity of microstructural descriptors beyond crystalline fraction for accurate rheological prediction. In 2021, rheological experiments on polyamide 11 under precisely controlled shear rates identified a critical shear threshold for nuclei formation, revealing a transition from space-filled spherulitic superstructures to random and then aligned fibrillar crystals as shear intensity increased. Complementary work on polyethylene examined the effect of flow duration on shish-kebab development, quantifying shish core growth rates and demonstrating that extended flow times stabilise the core sufficiently to nucleate successive kebab lamellae, thereby influencing final morphology and mechanical response.

Flow-Induced Crystallization in Polymeric Materials publication trend

The graph below shows the total number of articles in flow-induced crystallization in polymeric materials across all publications each year (not limited to Nature Index journals).

Technical terms

Flow-Induced Crystallization (FIC): Crystallization process accelerated and directed by polymer chain alignment under applied flow.

Spherulite: Radially ordered aggregate of lamellar polymer crystals formed under quiescent or weak-flow conditions.

Shish-Kebab Structure: Hierarchical morphology featuring an extended central fibre (“shish”) with perpendicular lamellar overgrowths (“kebabs”) formed under strong flow.

Extensional Rheology: Characterisation of a material’s response to stretching flows, critical for analysing how deformation rate influences crystallization pathways.

References

1. The non-equilibrium phase diagrams of flow-induced crystallization and melting of polyethylene. Scientific Reports (2016).
2. Shear-induced enhancements of crystallization kinetics and morphological transformation for long chain branched polylactides with different branching degrees. Scientific Reports (2016).
3. Viscoelastic Properties of Polypropylene during Crystallization and Melting: Experimental and Phenomenological Modeling. Polymers (2023).
4. Shear-induced crystallization of polyamide 11. Rheologica Acta (2021).
5. Flow-Induced Crystallization in Polyethylene: Effect of Flow Time on Development of Shish-Kebab. Polymers (2020).