A new method for preparation of functionalized graphene and its epoxy nanocomposites

Abstract Organic solvents are often used to prepare epoxy/graphene nanocomposites. A graphene precursor is developed in this study, which in epoxy at 200 °C is able to directly exfoliate into three classes of graphene platelets: large, single-layer sheets, medium sized sheets with 5.2 ± 1.95 nm in thickness, and smaller 0.5–1.0 nm thick sheets of 200–500 nm in lateral dimension, with a Raman ID/IG ratio of 0.177. The yield of single-layer graphene is 41.45%. Due to oxygen-containing groups on the surface, these sheets are named functionalized graphene platelets. Platelet films of ∼10 μm in thickness have an electrical conductivity of 978.65 ± 79.44 S/cm. A percolation threshold of electrical conductivity is observed at 0.80 vol% for epoxy/graphene nanocomposites. The composites show highly improved mechanical and dynamic thermo-mechanical properties. At 1.03 vol%, the nanocomposite has a fracture energy release rate of 850.78 ± 58.00 J m−2 corresponding to an increase of 170.6% over the neat epoxy.