Recycling and Properties of Polyethylene Terephthalate
Summary
Polyethylene terephthalate (PET) is a semi-crystalline polyester renowned for its combination of mechanical strength, thermal stability and barrier performance, making it indispensable in packaging, textile fibres and engineering materials. Its high melt viscosity and well-defined crystalline morphology ensure excellent processability in extrusion and moulding operations. However, repeated melt processing and exposure to moisture and oxygen induce chain scission, leading to declines in molecular weight, viscosity and mechanical integrity. Recycling strategies encompass mechanical reprocessing, which grinds and remelts post-consumer waste, and chemical depolymerisation routes that reclaim monomers. Recent innovations aim to mitigate degradation by controlling the processing atmosphere, incorporating reactive extrusion techniques and deploying sustainable chain extenders that rebuild molecular weight without residual catalysts. Characterisation methods such as differential scanning calorimetry, size exclusion chromatography and rheological analysis link thermal transitions, molecular mass distribution and mechanical behaviour. By tailoring crystallinity and macromolecular architecture, recycled PET is being elevated from bulk packaging to high-value applications in composites, textiles and food-contact materials. Global efforts now focus on closing the loop through energy-efficient monomer recovery, biodegradable enzymatic processes and additive-free approaches that enhance circularity while preserving the intrinsic properties that underpin PET’s widespread utility.
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Recycling and Properties of Polyethylene Terephthalate publication trend
The graph below shows the total number of articles in recycling and properties of polyethylene terephthalate across all publications each year (not limited to Nature Index journals).
Technical terms
Melt viscosity: A measure of a polymer melt’s resistance to flow under applied shear at processing temperatures.
Chain scission: The cleavage of polymer backbone bonds, leading to reduced molecular weight and altered mechanical properties.
Chain extension: A chemical modification process that reconnects or lengthens polymer chains to restore or increase molecular weight.
Crystallinity: The proportion of ordered, crystalline regions within a polymer, influencing stiffness, barrier properties and thermal behaviour.
Reactive extrusion: A processing technique combining chemical reactions (e.g. chain extension) with melt extrusion to tailor polymer structure in situ.
Differential scanning calorimetry (DSC): A thermal analysis method that measures heat flow associated with material transitions such as melting and crystallisation.
References
- Understanding poly(ethylene terephthalate) degradation using gas-mediated simulated recycling. Resources Conservation and Recycling (2023).
- Catalyst free PET and PEF polyesters using a new traceless oxalate chain extender. Green Chemistry (2024).
- Degradation of PET – Quantitative estimation of changes in molar mass using mechanical and thermal characterization methods. Polymer Testing (2023).
- Recycled Poly(Ethylene Terephthalate) from Waste Textiles with Improved Thermal and Rheological Properties by Chain Extension. Polymers (2022).
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