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Environmental Degradation of Polymer Nanocomposite: release, detection, and toxicity of nano-fragments
Citation:
Sahle-Demessie, E., C. Han, AND E. Varughese. Environmental Degradation of Polymer Nanocomposite: release, detection, and toxicity of nano-fragments. American Chemical Society, San Diego,CA, August 25 - 29, 2019.
Impact/Purpose:
As industries find new and useful ways to use nanocomposites, the release of engineered nanomaterials (ENMs) into the environment over the life-cycle will increase. Scientists and engineers are assessing ENMs properties that determine the fate transport, and effects of ENMs, to better understand the potential impacts of released ENMs on organisms, ecosystems, and human health. This presentation summarizes EPA/ORD/NRMRL studies on the release and implications of nano-composites when they are exposed to environmental stress.
Description:
Polymeric materials, such as epoxy and polypropylene, that are filled with multiwalled carbon nanotube (MWCNT) are used for a wide applications. To determine their lifecycle impacts sample plates were aged in an accelerated weathering chamber that simulates cycles of solar irradiation and rainfall were evaluated during for release of pollutants and potential risks. The changes in physicochemical properties modulated by sample thicknesses and the added MWCNTs during the weathering process were investigated. The results revealed that surface oxidation increased in crystallinity causing the surface to become brittle during the weathering process. This loss of elasticity resulted in crack formation and further degradation of the thinner samples. Oxidation penetrated selectively into the polymer structure forming surface cracks and chemical changes. When the aged composites were placed in sonication water-bath fragments of polymer, CNT and metals were released. The release of nanomaterials from the composites was investigated with high-resolution transmission microscopy (HR-TEM), dynamic light scattering (DLS), and single particle-inductively coupled plasma (SP-ICP) analysis. The metal ions in released MWCNTs were quantified with a single particle-ICP analysis. The toxicity of released particles was investigated. Combined toxicity assessment using cell viability and activity (MTS assay), oxidative stress measuement via detection of reactive oxygen species. The results demonstrated the toxicity of the released MWCNT-embedded polymer to A594 adenocarcinomic human alveolar basal epithelial cells. Epoxy composite show a significant amount of nickel in the wash water that has toxicity. The results of this study will be useful for human exposure and health risk assesment of to engineered nanoparticles that arer released from consumer products.