Understanding cure and interphase effects in functionalized graphene‐epoxy nanocomposites

Abstract

AbstractAgglomerations effects of graphene‐based nanofillers are often reported in the literature to be the main reason on the deterioration of the mechanical properties, especially at high filler loadings. In our study, we focused on the correlated effects of plasma‐treated graphene nanofillers on the curing reaction and mechanical properties of an epoxy matrix. Specifically, we explored the effect of dispersion state, planar size, filler content, surface functionalization and stoichiometric ratio on the epoxy curing process. The surface of the treated graphene nanofillers were studied in detail by X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy and X‐ray diffraction (XRD). The results indicated greater presence of oxygen containing groups with the crystallinity to be unaffected after the plasma process. Dynamic Mechanical Analysis (DMA) was used to assess the changes in both the Tg and the mechanical properties of graphene‐epoxy nanocomposites. Rheological and microscopic data showed that a well‐dispersed material was achieved at high filler loadings with the use of calendaring and plasma functionalization. Although, a well‐dispersed material was achieved on the bulk composite, no further mechanical reinforcement was observed at high filler loadings. The adsorption of epoxy groups onto the graphene nanofillers' surface, leading to a stoichiometric imbalance between the epoxy chains and hardener molecules, was proposed to explain the results.