Network Aggregation of CNT at the Surface of Epoxy/MWCNT Composite Exposed to UV Radiation
T. Nguyen, B. Pellegrin, L. Mermet, A. Shapiro, X. Gu, J. Chin
Keywords: nanoparticle, release, nanocomposites, life cycle, CNT
Abstract:CNTs are increasingly incorporated in polymers to enhance their mechanical and other properties. However, organic polymers are prone to degrade under UV radiation. Therefore, CNTs in a polymer nanocomposite will eventually be released into the environments during their life cycles, which might have a negative impact to the environment and presents a roadblock on their potential uses. This study investigates the degradation of epoxy/CNT composites and changes of CNT concentration at the nanocomposite surfaces during exposure to UV radiation. An amine-cured diglycidyl ether of bisphenol A epoxy and multi-walled CNTs pre-dispersed in the epoxy resin were used as the polymer matrix and CNT, respectively. Epoxy/MWCNT composite films of approximately 100 micron were prepared by drawdown technique. Specially-designed cells containing nanocomposite specimens were exposed to 75 %RH, 50 oC, and UV radiation of between 295 nm and 400 nm in a NIST-developed environmental chamber. Exposed samples were removed for measurements of polymer chemical degradation, mass loss, and surface morphology using FTIR, SEM, and AFM techniques. The results show that the epoxy in the nanocomposite containing 1 % (mass) MWCNTs undergoes rapid photodegradation under UV environment, resulting in a large concentration increase and network aggregation of MWCNT at the nanocomposite surface with exposure time (Figure 1). Postulated degradation pathways of amine-cured epoxy under UV and model of CNT network aggregation at the nanocomposite surface will be presented.