Preparation And Electrical Conductivity Of Graphene Oxide/Polyamide 6 Nanocomposites

Graphene is the name given to a flat monolayer of carbon atoms tightly packed into a two-dimensional (2D) honeycomb lattice. It is a basic building block for graphitic materials of all other dimensionalities, which can be wrapped up into OD fullerenes, rolled into 1D nanotube or stacked into 3D graphite. Graphene has a large theoretical specific surface area, high Young's modulus, good thermal conductivity and electrical conductivity.These unique properties make it a choice as inorganic fillers to improve electrical, thermal and mechanical properties of composite materials.In this paper, graphene nanosheets were prepared by thermal exfoliation and reduction of the graphite oxide, which is prepared by complete oxidation of pristine graphite. The structure and morphology of graphite oxide as well as graphene were studied by XRD, XPS, FT-IR and SEM.After that, electrically conductive and thermally stable polyamide 6 nanocomposites were prepared through one-step in situ polymerization ofε-caprolactam monomer in the presence of electrically insulating and thermally unstable graphene oxide nanosheets. These nanocomposites show a low percolation threshold of～0.41 vol% and high electrical conductivity of～0.028 Sm-1 with only～1.64 vol% of graphene oxide. TGA and XPS results of the graphite oxide before and after thermal treatment at the polymerization temperature indicate that the graphene oxide was partially reduced in situ during the polymerization process. XRD, SEM and TEM observations confirm the exfoliation and uniform dispersion of the graphene oxide in the polyamide 6. In addition, although graphene oxide has a poor thermal stability, its polyamide 6 nanocomposite is thermally stable with a satisfactory thermal stability similar to those of neat polyamide 6. Such a one-step in situ polymerization and thermal reduction method shows significant potential for the mass production of electrically conductive graphene oxide/polymer nanocomposites. For comparison, polyamide 6/graphene nanocomposites were also prepared using the same experimental procedure and conditions.The another highlight in this paper is that ID-carbon nanotubes and 2D-graphene were combined to prepare a series of hybrid graphitic nanofillers, and synergistic effect between the graphene and carbon nanotubes in the enhancement of the electric conductivity of nylon 6 composites was observed. In comparison with individual carbon nanotube or graphene fillers the 0D point contact geometry along the filler network was substituted by a 1D linear contact with significantly increased area of interface junctions within the hybrid filler network. This may be considered as the major reason for the observed synergistic effect of the 1D and 2D hybrid fillers.