Preparation And Properties Of Graphene And Its Polyoleifn Based Composites

Graphene has attracted much attention from science and engineering fields thanks to its exceptional electrical, thermal and optical properties. Graphene is widely used to prepare polymer based composites because it can greatly improve the properties of composites at very low loading levels. In this paper, graphene were prepared by in-situ oxidation-exfoliation method (ISOE). X-ray diffraction (XRD) was used to characterize the intercalation reaction during oxidation and the layer exfoliation during ultrasonic treatment. Graphene as preapred was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Thermal properties of graphene were tested by thermogravimetric analysis (TGA). Meanwhile, expanded graphite (EDG) was exfoliated to prepare graphite nanosheets whose morphological structure was investigated. Ethylene-vinyl acetate copolymer/graphene nanosheets composites (EVA/GE) and polyolefin elastomer/modified EDG composites (POE/EDG) were prepared by solution and melt method, respectively. Tensile and electrical properties of the composites were evaluated.The following results are obtained.(1) The XRD results indicate that the ultrasonic treatment during oxidation favors the exfoliation of graphite layers. Graphene of about2nm thickness with5-7carbon atoms layer is successfully prepared by ISOE method. The low thermal stability of graphene is revealed by TG due to oxygenated groups on the surface.(2) After acidification, surface modification and ultrasonic treatment, the layers of EDG can be exfoliated to form graphite nanosheets. Ball milling can further reduce the thickness of nanosheets.(3) Compared with EVA, the tensile properties of composites are little changed with increasing graphene concentration from0.25wt.%to1.00wt.%. The electrical resistivities of the composites are of the same order, suggesting good insulation properties due to isolated dispersion of graphene in EVA observed by SEM.(4) Modification of EDG improves its dispersion in POE EDG modified with sodium dodecyl sulfate (S-EDG) shows better dispersion, whose composites have excellent tensile properties. However, the lower electrical resistivity of the composites with pristine EDG is found, which can be partially attributed to the local conductive path formed by the aggregation of EDG.