One of the most promising applications of nanomaterials is as nanofillers to enhance the properties of polymeric materials. However, the effect of nanofillers on polymers subject to typical environmental stresses, such as ultraviolet (UV) radiation, high humidity, or elevated temperatures, is not well understood. In particular, the degradation mechanisms of nanocomposites and the effect the nanofiller has on surface chemistry are unclear. In this study, multiwall carbon nanotube (MWCNT) epoxy nanocomposite materials were prepared and exposed to carefully controlled UV doses (equivalent of up to ~ 4 years in Florida) under conditions of elevated temperature and humidity. The samples were then analyzed using a suite of techniques to assess changes occurring in the bulk material (gravimetric analysis), surface chemistry (Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy), and surface and sub-surface morphology (scanning electron microscopy, atomic force microscopy, and energy filtered transmission electron microscopy) of the UV-irradiated samples. Overall, the photodegradation process of the epoxy matrix was retarded by the presence of the 3.5 % MWCNT filler suggesting that the MWCNTs may enhance the lifetime of the nanocomposite material. Multiple microscopic and spectroscopic techniques also showed an accumulation of MWCNTs on the nanocomposite surface that grew with increasing UV dose. The presence of MWCNTs on the nanocomposite surface may be significant with regard to the potential risk of MWCNT release during the nanocomposite lifetime. Preliminary tests performed using scratch lithography suggested that the exposed MWCNTs remained attached to the nanocomposite surface.
Citation: ACS Nano
Pub Type: Journals
polymer composite, MWCNT, UV radiation, characterization, accumulation