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Upgrading and Enhancement of Recycled Polyethylene Terephthalate with Chain Extenders: In-Depth Material
Christian W Karl1, Bjørnar Arstad2, Madina Shamsuyeva3
1SINTEF Materials and Nanotechnology, Polymer and Composite Materials Group, P.O. Box 124 Blindern, 0314 Oslo, Norway.
Industrial & Engineering Chemistry Research
|July 24, 2024
Summary
Joncryl is a more effective chemical chain extender (CE) for recycled polyethylene terephthalate (PET) than pyromellitic dianhydride (PMDA). This leads to improved rheological properties and higher storage modulus in recycled PET materials.
Area of Science:
- Polymer Science
- Materials Science
- Chemical Engineering
Background:
- Recycled low-molecular-weight polyethylene terephthalate (PET) often requires property restoration.
- Chemical chain extenders (CEs) are utilized to enhance the molecular weight and performance of recycled polymers.
- Industrial PET waste from bottles and trays presents unique challenges for recycling and reprocessing.
Purpose of the Study:
- To investigate the impact of Joncryl and pyromellitic dianhydride (PMDA) as CEs on recycled PET.
- To evaluate the influence of CE type and concentration on rheological properties, particularly viscosity.
- To compare the effectiveness of Joncryl versus PMDA for chain extension in a mixed recycled PET stream.
Main Methods:
- Characterization using differential scanning calorimetry, viscometry, and cone plate rheometry.
- Advanced analysis via pyrolysis-gas chromatography-mass spectroscopy and spectroscopy (FTIR, 13C SSNMR, 1H NMR).
- Molecular weight determination using size exclusion chromatography.
Main Results:
- Joncryl demonstrated superior chain extension efficiency compared to PMDA in recycled PET.
- PET samples extended with Joncryl exhibited significantly higher storage modulus values.
- PMDA's effectiveness was potentially hindered by water formation, accelerating PET degradation.
Conclusions:
- Joncryl is a more suitable CE for enhancing the properties of recycled PET, especially mixed streams.
- The choice of CE significantly impacts the rheological performance and stability of recycled PET.
- Understanding CE mechanisms is crucial for effective PET recycling and upcycling.
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