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Assessing polymer weathering in aquatic environmental systems
Citation:
Zepp, R., Brad Acrey, Mary J. Davis, W. Wohlleben, AND E. Sahle-Demessie. Assessing polymer weathering in aquatic environmental systems. Presented at SETAC North America National Meeting, Portland; N/A (virtual), Oregon, November 14 - 18, 2021.
Impact/Purpose:
Global plastic waste generation is estimated to reach 35.8-90 Mt by 2030 under business as usual assumptions. ( ADDIN EN.REFLIST Borrelle, S. B., et al (2020). "Predicted growth in plastic waste exceeds efforts to mitigate plastic pollution." Science 369(6510): 1515-1518) Sunlight has been shown to be an important determinant of risk associated with exposure to plastic residues present in aquatic environments. Energy provided by absorption of solar photons can initiate a wide range of reactions, including direct and indirect photolysis that results in the weathering of polymers. Inputs of trash represent a recurring opportunity for contamination of aquatic and terrestrial environments by plastic-derived compounds. Here we present data based on the simulated environmental weathering of different polymeric nanocomposites, (epoxy, polyamide, polypropylene, low density polyethylene) filled with organic (multiwalled carbon nanotube, graphene, carbon black) and inorganic (WS2, SiO2, Kaolin, Fe2O3, Cu-Phthalocyanines) nanomaterials. Weathering of these polymers results in fragmentation to micro- and nano-sized particles. Multiple techniques were employed to evaluate the effects of weathering of the polymers on fragmentation products: ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), optical microscopy, contact angle measurements, gravimetric analysis, analytical ultracentrifugation (AUC), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Raman spectroscopy. Wavelength studies demonstrated that the short-wavelength component of simulated sunlight was most effective in inducing weathering of the low density polyethylene- nanosilica matrix with added pro-oxidant.
Description:
Sunlight has been shown to be an important determinant of risk associated with exposure to polymer residues present in aquatic environments. Energy provided by absorption of solar photons can initiate a wide range of reactions, including direct and indirect photolysis that results in the weathering of polymers. Inputs of trash represent a recurring opportunity for contamination of aquatic and terrestrial environments by polymer-derived compounds. Here we present data based on the simulated environmental weathering of different polymeric nanocomposites (epoxy, polyamide, polypropylene) filled with organic (multi-walled carbon nanotube, graphene, carbon black) and inorganic (WS2, SiO2, Kaolin, Fe2O3, Cu-Phthalocyanines) nanomaterials. Sunlight plays a major role in the weathering of these polymers, which results in dramatically different fragmentation to micro- and nano-sized particles. Multiple techniques were employed to evaluate the effects of weathering of the polymers on fragmentation products: ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), optical microscopy, contact angle measurements, gravimetric analysis, analytical ultracentrifugation (AUC), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Raman spectroscopy. This work aimed to elucidate the extent to which weathering protocols (i.e. wet vs. dry) and array of filler characteristics modulate fragment release and polymer matrix degradation. Other studies of weathering of low-density polyethylene-nanosilica composites also were conducted. The polymer was modified by addition of a pro-oxidant to stimulate transformation of the polymer matrix to more biodegradable forms. Polymer degradation was followed by Fourier-transform-infrared spectroscopy (FTIR) and changes in tensile mechanical properties. Addition of the pro-oxidant accelerated deterioration of mechanical strength by an order of magnitude compared to controls. Wavelength studies demonstrated that the short-wavelength component of simulated sunlight was most effective in inducing photodegradation of the matrix with added pro-oxidant. Action spectra based on these wavelength studies were used to evaluate the effects of sunlight over space and time on photodegradation of this polymer.
