Authors: T. Nguyen, B. Pellegrin, P. Stutzman, A. Shapiro, E. Byrd, X. Gu, J. Chin
Affilation: NIST, United States
Pages: 724 - 727
Keywords: nanoparticles, release, UV radiation, life cycle
Nanoparticles are increasingly used for enhancing multiple properties of polymers in many industries including construction, automobile, and aerospace. However, recent research suggests that nanoparticles might have negative effects on the environments and health safety. Since organic polymers are susceptible to photodegradation by solar UV radiation, nanoparticles imbedded in a polymer nanocomposite will eventually be released into the environments during their life cycles. Such a release of nanoparticles might have an effect to the environments and present a roadblock on their potential uses. This study investigates the release of nanoparticles from polymer nanocomposites during their exposures to UV radiation having wavelengths similar to that of terrestrial sunlight. The polymer matrix (typically used in composites and coatings) was a stochiometric mixture containing a diglycidyl ether of bisphenol A epoxy and a tri-amine curing agent. The nanoparticles were pretreated nanosilica having a 7 nm diameter. Epoxy nanocomposite films having a thickness of between 100 μm and 150 μm containing 1%, 5%, and 10 % mass fraction of nanosilica were prepared by drawdown technique. Specially-designed cells containing nanocomposite specimens were exposed to UV radiation between 295 nm and 400 nm, at 75 %RH and 50 oC temperature in a well-controlled NIST-developed environmental chamber. Released silica nanoparticles were collected in a container placed at the bottom of the exposure cell. Samples were removed at specific times for measurements of photodegradation, mass loss, surface morphology, and nanosilica release using a variety of analytical techniques. The results show that the epoxy matrix underwent extensive photodegradation, resulting in substantial mass loss, large increase in nanosilica concentration at composite surface, and release of silica nanoparticles to the environment.