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 (Ea), 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 Ea, 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 Ea, 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.