Multi-method analysis of multiwall carbon nanotube polymer nanocomposite samples after photodegradation E. J. Petersen, * T. F. Lam, ** J. M. Gorham, *** K. Scott, *** C. J. Long, **,***** R. Sharma, ** L. P. Sung, **** and J. A. Liddle ** , T. Nguyen **** * Biosystems and Biomaterials Division, Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 ** Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899 *** Materials Measurement Science Division, Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 **** Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 ***** Maryland Nanocenter, University of Maryland, College Park, MD 20742 ABSTRACT Nanomaterials can be used as nanofillers to enhance the properties of polymeric materials. However, the effect of weathering on nanocomposites and the potential for nanomaterial release is not yet well understood. Multiple analytical methods are needed to address these issues. Multiwall carbon nanotube (MWCNT) epoxy nanocomposite materials at two concentrations (3.5 % and 0.72 %) were exposed to carefully controlled ultraviolet (UV) doses (equivalent of up to ≈ 4 years in Florida). These samples were analyzed with a suite of optimized gravimetric, spectroscopic, and microscopic techniques. The presence of MWCNTs at both loadings retarded the photodegradation of the nanocomposite samples, and multiple techniques showed the accumulation of MWCNTs on the sample surface. The analytical methods developed in this study provide important information on the life-cycle impacts of polymer nanocomposites. Keywords: carbon nanotube, polymer composites, UV, degradation, analytical methods. 1 INTRODUCTION One exciting potential application of nanotechnology is incorporating nanoscale fillers into polymer composites. When the fillers have one or more characteristic dimensions between 1 nm and 100 nm, they are referred to as nanofillers. While the incorporation of nanofillers may dramatically improve the properties of composite materials (e.g., increased strength, fire resistance, etc.) [1-4], it is not well understood how the presence of the nanofillers affect the degradation of the composite, and the extent to which nanoparticles may be released during use, either by physical (e.g., abrasion) or environmental (e.g., ultraviolet radiation, moisture) processes. There have recently been several studies by our group at National Institute of Standards and Technology (NIST) [5-12] and others [13-15] to investigate these questions. Multiwall carbon nanotube (MWCNT) is one of the main nanofillers that is being tested for application by a large number of industries. There have been a few studies that have tested nanoparticle (NP) release from MWCNT polymer nanocomposites [8,10,13-18]. However, the effect of natural environmental processes, such as degradation by sun light, on the structure of MWCNT polymer nanocomposites has not yet been thoroughly studied, partly as a result of a lack of optimized analytical methods. Epoxy nanocomposites at two MWCNT loadings (3.5 % and 0.72 % by mass) were exposed to controlled ultraviolet (UV) doses using the NIST SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) [19]. These samples were then analyzed using multiple analytical methods. Results from the 3.5 % MWCNT nanocomposite samples using gravimetry, Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy filtered TEM (EFTEM) were described in a recent publication [12]. To provide an overview of the effects observed during photodegradation of the MWCNT polymer nanocomposites by UV irradiation, XPS results from that publication will be included here, as well as unpublished AFM results from the same samples. Preliminary, qualitative results from the 0.72 % samples will also be described. 2 EXPERIMENTAL Epoxy MWCNT composites were processed from MWCNTs supplied commercially as a 1 % and 5 % mass fraction (based on the mass of the epoxy resin) pre- CTSI-Cleantech 2014, www.ct-si.org, ISBN 978-1-4822-5819-6 266