Upcycling Poly(Ethylene Terephthalate): Identification of the Recovered Poly(Ethylene Terephthalate) by Thermogravimetry Analysis

Abstract

The production and utilization of disposal merchandise made of poly(ethylene terephthalate) (PET) continue to increase with an annual rate of ∼2%. The post-consumer PET (PC-PET), accumulated as waste, creates a pseudo-renewable resource which generates opportunities for reusing and recycling. The recycling of PC-PET saves energy and reduces the burden that the waste plastics in landfills and storage facilities impose on the environment. The polymer of this study (PET-R) was purified from PC-PET by a solvent extraction method and was characterized by thermogravimetric analysis (TGA) via five different linear temperature programs. The TGA curves of PET-R showed three distinct regions: the vaporization of the adsorbed volatile organic chemicals (VOCs) at temperatures 60–220 °C, the fast decomposition of the purified PET (PET-R) 350–500 °C, and the slow pyrolysis of the remains at temperatures >500 °C. The values of decomposition energy barrier (E_a), preexponential of the Arrhenius equation (lnA) and the mechanism of decomposition expressed by f(α), for both VOCs and PC-PET, were evaluated by isoconversional methods according to the Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall methods; the results of the two methods were very close to each other for each of the factors in each of the stages. The values of E_a, and lnA of the VOCs decreased with the increase of the extent of the reaction since they were related to the availability of the VOCs. The values of E_a, and A of PET-R were relatively constant with standard deviations of ±4 kJ/mol. The thermal properties of PET-R were close to the properties reported for the pure PET samples. This proves that pure PET can be extracted and purified from PC-PET by solvent extraction for industrial applications and upcycling wastes.

Keywords:

• activation energy
• Kissinger-Akahira-Sunose method
• Ozawa-Flynn-Wall method
• poly(ethyl benzene-1
• 4-dicarboxylate)
• poly(oxyethyleneoxyterephthaloyl)
• pyrolysis
• recycling
• upcycling PET

Acknowledgements

We acknowledge the supports of Dr. L. Whitesides and Dr. J. Salley and their teams in South Carolina State University.

Declaration

Any opinions, findings, and conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect those of the Funding Agency.

Additional declarations

In this study there is no-involvement of humans and/or animals

Conflicts of interest

All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript.

Data availability

The TGA unprocessed data are available upon request from the corresponding author.

Additional information

Funding

This work was supported by the U.S. Department of Agriculture, National Institute of Food and Agriculture, Evans-Allen project number SCX-311-21-17 and SCX-311-29-21.