Physicochemical alterations on UV aged polymers leading to microplastics formation: A multi-tiered study of polyester, polycarbonate and polyamide

Plastic, once a revolutionary material, has progressively converted into a global environmental threat possessing ubiquitous distribution, with microplastics (MPs) pollution being in the center of intense multidisciplinary research. Within the framework of the present study, we systematically investigated the physicochemical properties of three widely used commercial polymers, namely poly(ethylene terephthalate) (PET), polycarbonate (PC) and polyamide (PA) after UV exposure for certain intervals, as to enlighten the aging processes of these polymer types and ameliorate the understanding of their performance through a couple of analytical techniques. The studied polymers were UV -B aged for specific time periods and the photodegradation was initially evaluated by Fourier -transform Infrared Spectroscopy (FTIR), proving signs of oxidation, while the crystallinity and thermal properties' modifications during the weathering were also assessed by X -Ray diffraction (XRD) and Differential Scanning Calorimetry (DSC) analyses. Additionally, Scanning Electron Microscopy (SEM) and water contact angle measurements demonstrated the significant morphological and hydrophilicity differences of the irradiated samples compared to the pristine ones, while mechanical performance deterioration was displayed as evidence that UV irradiation induces the reduction of plastics performance and their progressive fragmentation, possibly inducing the MPs formation. The relative abundance of the pyrolysis products fluctuated throughout the UV exposure experiments as determined by Pyrolysis -Gas Chromatography/Mass Spectrometry (Py-GC/MS) analysis, while the quantity of the pyrolytic marker compounds for the investigated polymers extensively utilized nowadays in MPs analysis also changed with the time of photo -aging, suggesting the imperative further exploration of aging processes on the well-known polymeric types, since severe risk exists with the reliability of MPs quantification in real environmental samples.