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

Organic solvents are often used to prepare epoxy/graphene nanocomposites. In this study a graphene precursor is developed, which in epoxy at 200 degrees 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 I-D/I-G 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 similar to 10 mu m 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 170.61% over neat epoxy.