ABSTRACT
In recent years, there has been much interest in polymers reinforced by fillers of nanometer dimension because of their improved chemical, physical, and mechanical properties compared with neat polymers. The incorporation of nanofillers into polymers can significantly increase the tensile strength and stiffness, decrease gas permeability and flammability as well as enhance the thermal stability. The most interesting nanofillers include layered silicates, graphite nanoplatelets, inorganic nanoparticles, and carbon nanotubes (CNTs).
Among these nanofillers, graphite nanosheets and CNTs can further improve the electrical conductivity of polymer resins. Graphite is of particular interest because of its low cost and its ready availability. Conventional electrical conductive polymer composites reinforced with metal and carbon black particles have found widespread applications in industrial sectors such as materials for the electromagnetic interference shields, self-lubricated materials, etc. However, such microcomposites require rather high filler loading in order to achieve satisfactory electrical characteristics. This leads to poor processability and inferior mechanical performances of the microcomposites. In this regard, the incorporation of graphite nanoplatelets or nanosheets with large aspect ratio into insulating polymers can lead to the formation of nanocomposites with enhanced chemical, electrical, and thermal properties. The electrical conductivity is derived from the formation of continuous conduction paths in the composites. The critical filler content or percolation threshold needed to form conductive pathways in the polymer-graphite nanocomposites is relatively much smaller compared to that of the microcomposites. The properties of nanocomposites depend greatly on the chemistry of polymer matrices and the processing techniques such as in situ polymerization, solution, and melt intercalation. The dispersion of graphite nanoplatelets in the polymers is rather poor due to their large surface-to-volume ratio. The uniform dispersion of nanofillers in the polymer matrices is a general prerequisite for achieving desired chemical, mechanical, and physical characteristics.
