Origin of cloudiness in PET bottles modified with chain extenders for mechanical recycling
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Toshihiko Kanda
Abstract
Melt viscosity improvers (MVs) are known as chain extenders that increase the intrinsic viscosity of recycled polyethylene terephthalate (PET) by forming covalent bonds with PET molecules. Experimental results showed that MVs accelerate epitaxial crystallization in a direction perpendicular to the orientation of MV agglomerates. Acting as nucleating agents, MVs promote crystallization under tension and the formation of light-scattering structures, resulting in cloudiness. Transmission electron microscopy confirmed the presence of MV agglomerates within PET bottles. Wide-angle X-ray diffraction further revealed that MVs altered the crystal orientation of PET by 90° compared to neat PET. Small-angle X-ray scattering during tensile tests indicated that MV-induced crystals within PET bottles were highly oriented perpendicular to the MV orientation direction, potentially contributing to enhanced mechanical drawability and toughness.
Acknowledgments
We would like to thank Frontier, Inc. (Nagano, Japan) for injection molding and blowing the various formulations of the PET bottles under different conditions, and Kaneka Techno Research Corporation (Osaka, Japan) for obtaining the WAXS patterns and TEM images of the PET bottles. We would like to thank Mr. Kimihide Nishimura and Mr. Tetsunori Mori of Kaneka Corporation (Osaka, Japan) for synthesizing MV polymers and production of PET compounds for injection blow molding. We thank Prof. Masayuki Yamaguchi of JAIST (Ishikawa, Japan) for supportive discussion to elucidate the mechanism of cloudiness effect. We also thank Dr. Noboru Ohta for the X-ray measurements at the beam line of BL40B2 in SPring-8 (Hyogo, Japan).
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Research ethics: Not applicable.
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Informed consent: Informed consent was obtained from all individuals included in this study, or their legal guardians or wards.
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Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.
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Use of Large Language Models, AI and Machine Learning Tools: None declared.
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Conflict of interest: All other authors state no conflict of interest.
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Research funding: None declared.
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Data availability: Not applicable.
References
Alexander, L.E. (1979). X ray diffraction methods in polymer science. Krieger Publishing, New York.Suche in Google Scholar
Asano, T., Flores, A., Tanigaki, M., Mina, M.F., Sawatari, C., Itagaki, H., Takahashi, H., and Hatta, I. (1999). Crystallization of oriented amorphous poly(ethylene terephthalate) as revealed by X-ray diffraction and microhardness. Polymer 40: 6475–6482, https://doi.org/10.1016/S0032-3861(98)00839-8.Suche in Google Scholar
Bakir, K., Aydemir, D., Bardak, T., and Kartal, M.E. (2022). Thermal, morphological, rheological and deformation under mechanical loading analyses of recycled polyethylene terephthalates. Int. Polym. Process. 37: 287–302, https://doi.org/10.1515/IPP-2021-4165.Suche in Google Scholar
Benyathiar, P., Kumar, P., Carpenter, G., Brace, J., and Mishra, D.K. (2022). Polyethylene terephthalate (PET) bottle-to-bottle recycling for the beverage industry: a review. Polymers (Basel) 14, https://doi.org/10.3390/polym14122366.Suche in Google Scholar PubMed PubMed Central
Bubeck, R.A. and Barger, M.A. (2000). Injection blow molding technology for polyethylene terephthalate. Int. Polym. Process. 15: 337–342, https://doi.org/10.3139/217.1616.Suche in Google Scholar
Chang, S., Sheu, M.F., and Chen, S.M. (1983). Solid-state polymerization of poly(ethylene terephthalate). J. Appl. Polym. Sci. 28: 3289–3300, https://doi.org/10.1002/app.1983.070281023.Suche in Google Scholar
Chen, F.C., Griskey, R.G., and Beyer, G.H. (1969). Thermally induced solid state polycondensation of nylon 66, nylon 6-10 and polyethylene terephthalate. AIChE J. 15: 680–685, https://doi.org/10.1002/aic.690150510.Suche in Google Scholar
Demirel, B. (2011). Crystallization behavior of PET materials. In: BAÜ Fen Bilimleri Enstitüsü Dergisi Tech. Papers, pp. 26–35.Suche in Google Scholar
Ganapathi, A., Abdelwahab, M.A., and Rabnawaz, M. (2024). Achieving bottle-grade poly(ethylene terephthalate)-like properties from blends of bottle-grade and thermoform-grade poly(ethylene terephthalate). Polym. Int. 73: 625–630, https://doi.org/10.1002/pi.6633.Suche in Google Scholar
Gazzano, M., Gualandi, C., Zucchelli, A., Sui, T., Korsunsky, A.M., Reinhard, C., and Focarete, M. (2015). Structure-morphology correlation in electrospun fibers of semicrystalline polymers by simultaneous synchrotron SAXS-WAXD. Polymer 63: 154–163, https://doi.org/10.1016/j.polymer.2015.03.002.Suche in Google Scholar
Jabarin, S.A. (1982). Optical properties of thermally crystallized poly(ethylene terephthalate). Polym. Eng. Sci. 22: 815–820, https://doi.org/10.1002/pen.760221305.Suche in Google Scholar
Karayannidis, G.P., Kokkalas, D.E., and Bikiaris, D.N. (2003). Solid-state polycondensation of poly(ethylene terephthalate) recycled from postconsumer soft-drink bottles. II. J. Appl. Polym. Sci. 56: 405–410, https://doi.org/10.1002/app.1995.070560311.Suche in Google Scholar
Kim, T.Y., Lofgren, E.A., and Jabarin, S.A. (2003). Solid-state polymerization of poly(ethylene terephthalate). I. Experimental study of the reaction kinetics and properties. J. Appl. Polym. Sci. 89: 197–212, https://doi.org/10.1002/app.11903.Suche in Google Scholar
Kitabatake, S., Janchai, K., and Yamaguchi, M. (2024). Pronounced shear-induced crystallization of polypropylene by addition of poly(methyl methacrylate). Polymer 307: Article 127260, https://doi.org/10.1016/j.polymer.2024.127260.Suche in Google Scholar
Kwon, D. (2023). Three ways to solve the plastics pollution crisis. Nature 616: 234–237, https://doi.org/10.1038/d41586-023-00975-5.Suche in Google Scholar PubMed
Lee, C., Jang, Y.-C., Choi, K., Kim, B., Song, H., and Kwon, Y. (2024). Recycling, material flow, and recycled content demands of polyethylene terephthalate (PET) bottles towards a circular economy in Korea. Environments 11, https://doi.org/10.3390/environments11020025.Suche in Google Scholar
Mahendrasingam, A., Fuller, W., MacKerron, D.H., Harvie, J.L., Oldman, R.J., and Riekel, C. (2000). Influence of temperature and chain orientation on the crystallization of polymers. Polymer 41: 7803–7813, https://doi.org/10.1016/S0032-3861(00)00129-4.Suche in Google Scholar
Mykhaylyk, O.O., Chambon, P., Impradice, C., Fairclough, J.P.A., Terrill, N.J., and Ryan, A.J. (2010). Control of structural morphology in shear-induced crystallization of polymers. Macromolecules 43: 2389–2405, https://doi.org/10.1021/ma902495z.Suche in Google Scholar
Standau, T., Nofar, M., Dörr, D., Ruckdäschel, H., and Altstädt, V. (2021). A review on multifunctional epoxy-based Joncryl® ADR chain extended thermoplastics. Polymer Rev. 62: 296–350, https://doi.org/10.1080/15583724.2021.1918710.Suche in Google Scholar
Szymczak, P., Dziadowiec, D., Andrzejewski, J., and Szostak, M. (2023). The efficiency evaluation of the reactive extrusion process for polyethylene terephthalate (PET): monitoring of the industrial foil manufacturing process by in-line rheological measurements. Appl. Sci. 13: Article 3434, https://doi.org/10.3390/app13063434.Suche in Google Scholar
Supplementary Material
This article contains supplementary material (https://doi.org/10.1515/ipp-2025-0043).
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