Development of Scalable Dispersion Technique of Graphene Nanoplatelets into Polymer Matrix to Improve Electrical and Thermal Conductivities

Fiber reinforced polymer (FRP) composites have exceptional advantage over traditional materials. A primary limitation of these composites for aircraft application is its susceptibility to lightning strike due to poor electrical, thermal properties. First step of this research was to develop processing method for graphene/epoxy nanocomposites. The most attractive property of graphene nanoplatelets is its high electrical conductivity. This conductive graphene may significantly enhance the electrical conductivity of the composites when used it as filler materials in the insulating polymer matrix. The fundamental criteria used for process development was electrical conductivity, process repeatability and scale up to a larger batch of material. The materials chosen in this study are graphene nanoplatelets (xGnP-25), epon 828 epoxy resin. Three types of exfoliation and dispersion techniques were investigated: conventional mechanical mixing, sonication and three-roll mill. The study showed that three-roll mill dispersion is most repeatable, consistent and scalable to larger batches. The optimized process consists of three gap settings (40, 30 and 25 µm) at 200 rpm and three passes for each gap setting. The percolation thereshold of xGnP graphene in epon 828 epoxy was found to be 1.0 wt. %. The xGnP/epon 828 nanocomposites showed an increase of eight log cycles in electrical conductivity, 93 % in thermal conductivity and 34 % in fracture toughness over the base epon 828.