Wet ball milling was used to exfoliate graphite platelets into graphenes in a liquid medium. Multi-layered graphite nanosheets with a thickness of 30 to 80 nm were dispersed into N,N-dimethylformamide (DMF) and exfoliated by shear-force-dominated ball milling carried out in a planetary mill. After high-speed centrifugation, irregular shaped single- and few-layer graphene sheets (≤3 layers) having a thickness around 0.8–1.8 nm were found from the supernatant. The graphenes were identified and characterized using transmission and scanning electron microscopy, electron diffraction, atomic force microscopy and Raman spectroscopy. The electrical conductivity of the graphene powder was ∼1.2 × 10³ S m⁻¹ at room temperature.

A one-step method for the preparation of polystyrene (PS)-functionalized graphene nanosheets, homogeneously dispersed in a PS matrix and forming electrically conductive graphene/PS nanocomposites, via in situ peeling of graphite nanoplatelets into graphene nanosheets in the presence of a PS solution, is presented in this paper. The resulting PS-functionalized graphene sheets displayed a fluff-like nano-structure. The backbones of PS stacked onto the basal plane of graphene sheets under strong π–π interactions with the grafted ratio up to 85 wt%. The chains of PS could effectively prevent the graphene sheets from aggregating and the prepared graphene/PS nanocomposites, with homogeneously dispersed mono- and few-layer graphene, exhibit an extraordinary electrical property, with a percolation threshold of about 2.7 wt%, far outstripping the starting graphite or carbon black as counterpart.

In this work, single and few-layer graphene sheets have been successfully peeled from natural graphite through continuous mechanical exfoliation by a three-roll mill machine with a polymer adhesive. The inspiration takes root in the “Scotch tape” method. Characterizations show that the thickness of the resultant graphene sheets is 1.13–1.41 nm. The presented scalable process can be effective for the high-yield and low-cost production of graphene sheets or in situ fabrication of polymer/graphene nanocomposites.