engleski

The effect of hot melt extrusion on the thermal properties of post-consumer PET bottles

Poly(ethylene terephthalate) (PET) is one of the most important thermoplastic used for a broad range of applications, from drinking bottles to textile fibers. The first recycling effort of post- consumer PET bottles in the world was in 1977. [1] Since the price of virgin PET remains high, new and cheaper technologies for recycling PET are beneficial to the PET recycling industry. Hence, the physical recycling of PET by melt reprocessing is very important ; it is relatively simple, requires low investments, utilizes established equipment, is flexible in terms of feedstock volume, and has little adverse environmental impact. [1] Among other operations, recycling of PET includes the re-extrusion for the production of new PET products. [1] However, re-extrusion process at high temperatures could cause changes in PET structure and properties. [2] In this work post-consumer PET bottles were gathered, separated from other materials, washed, dried, cut out to smaller pieces and extruded at 235 °C. PET samples (PET - bottle and rPET - re-extruded) were characterized by FTIR spectroscopy to investigate the effect of re-extrusion on the structure of PET. Likewise, differential scanning calorimetry (DSC) was utilized in order to determine characteristic thermal transitions ; glass transition, crystallization and melting. Finally, thermogravimetric analysis (TG) was used in order to evaluate the effect of extrusion on the thermal stability of samples. Position and intensity of PET characteristic groups (peaks) remained almost unchanged upon extrusion. DSC results indicated the influence of re-extrusion on melting and crystallization temperatures of PET. TG analysis revealed that thermal stability of the investigated PET samples wasn’t affected by the re-extrusion process.

extrusion, poly(ethylene terephthalate), recycling, thermal properties

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