engleski

Combined thermal - and UV - degradation of polyethylene terephthalate - characterization of aged material

Increasing pollution from microplastics (MPs), i.e. polymer particles smaller than 5 mm, is one of the most recent environmental concerns worldwide. A study has shown that approximately 0.4 particles of microplastics per 1 L can be detected in the environment.[1] Among detected MPs polyethylene terephthalate (PET) is very common. Degradation due to weathering and aging of commercial PET is inevitable despite anti-UV and anti-hydrolysis additives. Degradation of PET leads to change in micro- and macro-scale properties.[2] The aim of this work was to establish the nature and extent of changes which occurred in samples of shredded PET bottles (PET/B/C) and commercial films (PET/F/C) during cyclical exposure to thermal and hydrolytic degradation, namely: (i) at 70 °C for 18 hours without moisture addition, (ii) -18 °C for 2 h without moisture addition and (iii) at 70 °C with moisture. The cycles were repeated for 14, 28 and 42 days. Furthermore, the effects of UV aging on shredded bottles (PET/B/UV) and films (PET/F/UV) during periods of 14, 28 and 42 days were investigated. The UV degradation experiments were carried out in a Suntest CPS (Heraeus, Germany) solar simulator. The samples were characterized by the following methods: Fourier- transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), contact angle and differential scanning calorimetry (DSC). The experimental results indicate that there is little to no change in the structure of the thermally aged samples in comparison to the UV- aged samples in which structural changes are more obvious.

polyethylene terephthalate ; microplastics ; thermal aging ; UV aging

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