Reactive Extrusion of Long-Chain Branched Polymers

Reactive extrusion is a versatile, continuous processing technique in which chemical reactions and polymer shaping occur simultaneously within an extruder. When applied to linear polyolefins such as polypropylene, the introduction of long-chain branches transforms molecular architecture, enhancing melt strength, extensional viscosity and strain-hardening behaviour. These macromolecular modifications enable advanced processing routes—film blowing, thermoforming and foaming—while also offering routes to upcycle post-consumer and post-industrial waste. By carefully controlling initiator levels, residence time and temperature profile, reactive extrusion permits tailored branching densities without extensive chain degradation. This approach addresses both performance demands in high-engineering applications and circular-economy goals by restoring or elevating the rheological properties of recycled polyolefins. Recent advances have explored diverse branching chemistries, from peroxide-driven radical grafting to copolymer-mediated side-chain formation, and have refined extruder screw designs for optimal mixing and reaction control. The global significance of this technology spans packaging, automotive components and additive manufacturing feedstocks, demonstrating how molecular-level design within reactive extrusion can unlock new material functionalities while reducing environmental impact.

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Reactive Extrusion of Long-Chain Branched Polymers publication trend

The graph below shows the total number of articles in reactive extrusion of long-chain branched polymers across all publications each year (not limited to Nature Index journals).

Technical terms

Reactive extrusion: A continuous process integrating chemical modification and shaping in a single extrusion step.

Long-chain branching (LCB): Introduction of pendant macromolecular chains onto a polymer backbone to alter rheological and mechanical properties.

Melt strength: The ability of a polymer melt to resist deformation under extensional stress, essential for stable film and foam formation.

Extensional rheology: Study of polymer melt behaviour under tensile deformation, revealing strain-hardening and flow stability characteristics.

References

1. Towards effective recycling routes for polypropylene: Influence of a repair additive on flow characteristics and processability. Polymer Degradation and Stability (2024).
2. A pragmatic approach to analyze the ability of ethylene‐octene copolymer in the long chain branching of polypropylene in molten and solid state. SPE Polymers (2023).
3. Influence of Different Types of Peroxides on the Long-Chain Branching of PP via Reactive Extrusion. Polymers (2020).