Degradation and Nanoparticle Release of Epoxy/Nanosilica Composites Exposed to Solar UV Radiation
B. Pellegrin, T. Nguyen, L. Mermet, A. Shapiro, X. Gu, J. Chin
Keywords: nanoparticle, release, nanocomposites, nanosilica, UV radiation
Abstract:Nanoparticles are increasingly incorporated in polymers to enhance multifunctional properties. However, polymers are prone to undergo photodegradation under UV exposure, resulting in a liberation of nanoparticles from the polymer nanocomposites during their life cycle. The release of nanoparticles might have a negative effect to the environment and presents a roadblock to their potential uses in many industries, such as construction and automobile. This study investigates changes of nanosilica concentration at the surface, release rate of nanosilica, and degradation of epoxy/nanosilica composites during their exposures to solar UV radiation. The polymer matrix was a stochiometric mixture containing a diglycidyl ether of bisphenol A epoxy and an aliphatic tri-amine. The nanosilica was a pretreated, 7 nm diameter material. Epoxy nanocomposite films containing 1% and 5 % nanosilica having a thickness of 75 μm 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 the NIST-developed environmental chamber. Exposed samples were removed for measurements of photodegradation, mass loss, surface morphology, and nanosilica release rate using FTIR, SEM, and AFM techniques. The amount and rate of nanosilica release was estimated by thermogravimetry (TGA), which can separate nanosilca loss from epoxy degradation. The results show that epoxy/nanosilica composites exposed to UV radiation undergoes rapid photodegradation of the epoxy matrix, which results in a substantial mass loss and gradual increase of nanosilica concentration at the composite surface with exposure time.