Fate of graphene in polymer nanocomposite exposed to UV radiation

Graphene is increasingly incorporated in polymers to enhance their mechanical, thermal and electrical properties. However, organic polymers are prone to degrade when exposed to UV radiation. Therefore, graphene in polymer nanocomposites could eventually be released into the environment during their life cycle, which might have a negative impact on the environment and thus presents a roadblock to their use. This study investigates the degradation of a graphene/polyurethane composite and characterizes the graphene concentration at the nanocomposite surfaces during exposure to UV radiation. The polyurethane was a one-component, water-borne polyurethane and graphene material was graphene oxide (GO) sheets. GO/WBPU composites having a thickness between 105 μm and 150 μm were exposed to 75% RH, 50 deg. C, and UV radiation between 290 nm and 400 nm in a NIST-developed UV chamber. Chemical degradation, mass loss, and surface morphology were measured at specified exposure time using FTIR, gravimetry, SEM, AFM and LCSM techniques. Results showed that, when exposed to UV radiation having wavelengths similar to those of the sunlight, the polyurethane matrix underwent photodegradation, subsequent mass loss and accumulation of a large amount of graphene on the composite surface.