A differential scanning calorimetry (DSC) approach for assessing the quality of polyethylene terephthalate (PET) waste for physical recycling: a proof-of-concept study

Physical recycling of plastics is among the most important approaches of circular economy. The efficiency of the recycling is influenced by many factors including the number of recycling cycles, composition of plastics, chemical modifications, additives and others. Currently, however, there are no methods enabling to distinguish the quality of plastics for recycling. In this work, we address this issue and suggest a new method based on the correlation of solely thermophysical properties of polyethylene terephthalate (PET) waste obtained using differential scanning calorimetry (DSC) during repeated heating and cooling. The combination of results of differential scanning calorimetry and advanced statistical methods enabled to separate 76 PET samples into six groups according to their origin, chemical modification, degradation and suitability for recycling. The discriminant analysis enabled to suggest a model which uses for the discrimination a combination of temperatures and enthalpies of melting and crystallization. The approach illustrates that thermophysical properties, which can be obtained using a single DSC experiment, can be used to distinguish the polymers of various origin and quality.