The mechanical, electrical, and thermal properties of a polymer can be improved by the incorporation of carbon nanotubes. This has driven the manufacture of carbon nanotube/polymer nanocomposites (CNT/PNCs) for use in consumer products. With increasing consumer use and eventual product disposal, the degradation properties of CNT/PNCs and the potential environmental health and safety risks CNT/PNCs may pose at different stages of their life cycle still require investigation. Currently, the available techniques to measure changes in CNT/PNCs at different stages of degradation have not yet been systematically evaluated for trend comparisons, biases, and limitations. For this reason, multi-wall carbon nanotube (MWCNT)/epoxy nanocomposites were prepared at two different mass loadings (0.3 % and 1 % by mass fraction of epoxy) for exposure to accelerated weathering. Neat epoxy specimens were also prepared as controls. Weathering was conducted in the NIST SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) using highly collimated ultraviolet (UV) light under controlled temperature and humidity conditions. The specimens were irradiated at (159 ± 2) W/m<sup>2</sup> (average of 24 spots) for various exposure times ranging from (0 – 24) d at 55 °C, 75 % relative humidity. Specimens were analyzed with confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) at different stages of exposure. CLSM and SEM were used to qualitatively assess the accumulation of carbon nanotubes observed at the surface of the CNT/PNC. The choice of using CLSM versus SEM for imaging in transformation studies will be discussed. X-ray photoelectron spectroscopy and Raman spectroscopy were used to measure the change in the MWCNT content at the CNT/PNC surface/sub-surface during degradation. Method limitations will be discussed, including the fluorescence background increase associated with Raman spectroscopy as well as the presence of differential charging using XPS. General trends of CNT/PNC photodegradation as a function of exposure time will be described for different MWCNT loadings.

Methods to assess the environmental degradation of carbon nanotube/polymer nanocomposites

254th National Meeting (2017)

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