Using of DSC for identification of polyethylene terephthalate (PET) waste of various origin and composition for physical recycling

abstract

English

Physical recycling of polymers is among the important strategies of circular economy. It is also implemented into EU legislation, which aims to dictate the content of recycled polymers in new products. PET (polyethylene terephthalate) is one the mostly used polymers in packing industry. The methods of its physical recycling are relatively simple, they include separation of waste plastics, shredding (mostly bottles to flakes) and washing. The resulting PET pieces are then extruded and re-granulated. The key problem for successful recycling and re-granulation is various types of PET including already recycled PETs, bottles with additives, preforms, regranulates or virgin PET. Each of these types may have different properties that affect their suitability for recycling process. In this study, we present DSC as a method for the identification of these different types of PET. In principles, the method uses the simple parameters obtained from a DSC run such as temperatures and enthalpies of melting, crystallization and glass transitions of the first and second heating and cooling cycles. We collected 79 samples of different types of PET, which included virgin PET, preforms, regranulates, bottles with varying content of rPET (recycled PET) and so called bioPET, bottles with additives, recycled products, PET-G and controllably degraded samples at high temperatures. The method is based on the assumption that thermal history, composition and degree of recycling would affect the DSC parameters of the PET. Glass transition, crystallization and melting behavior of PET were used as primary parameters for advanced statistical analysis, which allowed to distinguish the samples into groups according to their history and properties. In particular, principal component analysis (PCA) showed the possibility to distinguish several groups i) virgin PET (before, but also after controlled degradation); ii) PET affected by high temperature or the addition of other substances (degraded samples, bottles with additives and products from rPET); iii) rPET, bioPET and PET-G; iv) preforms, bottles and PET flakes. To sum it up, simple DSC run can be used to distinguish PET materials of different origins and recycling degree based on the interrelationship between thermophysical properties.

PET, DSC, recycling

ŠUDOMOVÁ, L.; DOLEŽALOVÁ WEISSMANNOVÁ, H.; KUČERÍK, J.

20. 7. 2021

Central and Eastern European Committee for Thermal Analysis and Calorimetry (CEEC-TAC)

Rumunsko

978-606-11-7861-2

Book of abstracts of the 6th Central and Eastern European Conference on Thermal Analysis and Calorimetry (CEEC-TAC6) and 15th Mediterranean Conference on Calorimetry and Thermal Analysis (Medicta2021).

89

89

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http://www.ceec-tac.com/download.php?f=../download/BoA%20CEEC-TAC6%20Medicta2021.pdf