Improved exfoliation of surface-functionalized graphene oxide by epoxy monomer and enhanced mechanical properties of epoxy nanocomposites

The surface functionalization of graphene oxide (GO) provides an efficient way to improve the dispersion of GO in matrix and the interfacial properties of nanocomposites. In this contribution, GO grafted by bifunctional, trifunctional and tetrafunctional epoxy monomers (E51, AFG90, AG80) was designed and three epoxy-functionalized GO (EFGO) samples were acquired and utilized as fillers for epoxy nanocomposites. The chemical, structural and morphological characteristics of EFGO samples were studied. The exfoliation and dispersion state of EFGO in epoxy matrix were characterized. Mechanical properties of the nanocomposites at room temperature (RT), liquid nitrogen temperature (LNT) and after thermal cycling were comprehensively investigated. Results showed that the interlayer distance of EFGO was enlarged with the increase in functionality degree of the grafted epoxy monomers. AG80-functionalized GO (AGGO) with the largest interlayer distance showed the best exfoliation and dispersion in the nanocomposites, while E51-functionalized GO (EGO) showed the worst. Correspondingly, AGGO/epoxy nanocomposites exhibited the highest mechanical properties at RT, LNT and after thermal cycling. The toughening mechanisms of EFGO for epoxy resin were disclosed to better understand the role of epoxy monomers grafted to GO surfaces in the nanocomposites.

Automated summary

The functionalization of graphene oxide with epoxy monomers improved the dispersion in matrix and interfacial properties of nanocomposites. Results showed that functionalized GO with larger interlayer distance exhibited better dispersion and mechanical properties in epoxy nanocomposites, suggesting potential toughening mechanisms for epoxy resins.