Carbon nanotubes (CNTs) are becoming increasingly prevalent in consumer products, especially when embedded in polymer matrices. These CNT-polymer nanocomposites are attractive because they utilize relatively low loadings of CNTs by weight (< 5 weight %) to increase strength, thermal stability, and/or electrical conductivity of a given polymer. However, the fate of these products during their lifecycle, following consumer use, remains unclear. Specifically, there remains much to be studied regarding nanocomposite degradation pathways and the degree to which nanoparticles are released into the environment as their polymer matrix degrades. One of the principal means of polymer degradation in the environment occurs as a result of photolysis. Consequently, our research has focused on studying the photodegradation behavior of CNT-polymer nanocomposites under accelerated aging conditions.  CNT-polymer nanocomposite samples composed of various polymers (e.g. polystyrene) and containing different single walled CNT loadings were irradiated under aqueous conditions with light of various wavelengths, UVC through visible, for different exposure times. CNT-polymer nanocomposites were removed from the light reactor at intervals to assess mass loss, image physical transformations on the surface with scanning electron microscopy (SEM) and analyze chemical changes in the composite with attenuated total reflectance infrared spectroscopy (ATR- IR). To complement these studies on the composite, the supernatant was analyzed with SEM and transmission electron microscopy (TEM) to characterize released particles. Using residual metal catalysts impurities within CNTs as a proxy, the quantity of released CNTs was determined by single particle- inductively coupled plasma- mass spectrometry (sp-ICP-MS). With his technique, particle concentrations in the parts-per-billion to parts-per-trillion range can be accurately measured. By combining the information gained from these various analytical techniques, insights into the photodegradation mechanism(s) of CNT-polymer nanocomposites and quantitative information on released particle concentration were obtained. This information will be important in determining the ultimate fate of CNT-nanocomposites in the environment.

Photodegradation and CNT release from polymer nanocomposites

248th National Meeting (2014)

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