Composites of Epoxy and Graphene-Related Materials: Nanostructure Characterization and Release Quantification

Due to their good electrical and mechanical properties, composites of epoxy and graphene-related materials (GRMs) are applied in sports equipment or gasoline containers. During the use phase, wear and tear may induce the release of composite fragments, which might have different effects on human health than pristine GRMs that have shown to increase inflammatory response when they are inhaled into the trachea bronchus and the alveoli of the respiratory system. Our study aims to determine the fraction of released (protruding and freestanding) GRMs on abraded composite fragments using qualitative, semi quantitative and quantitative methods and to evaluate how the GRM size, the inter-layer strength between graphene sheets and the interaction between the GRM and the epoxy affect the GRM release. Using lead as a marker of GRMs, the release of lead-labeled GRMs was qualitatively evaluated via energy-dispersive X-ray-scanning electron microscopy (EDX-SEM) mapping. Moreover, semi-quantitative evaluation of the GRM surface coverage via Raman spectroscopy mapping and quantitative assessment of the released GRM fraction via inductively coupled plasma-optical emission spectrometry (ICP-OES) showed that the release of GRM depended strongly on the GRM size, the inter-layer strength between graphene sheets and the interaction between the GRM and the epoxy. The detected GRM surface coverage values were comparable to the release fractions determined using ICP-OES. This implies that Raman spectroscopy mapping can be used as a first appraisal to determine the fraction of released GRM, which would accelerate the exposure and risk assessment of GRM-enabled composites.