High density polyethylene-exfoliated graphene nanoplatelet nanocomposites for automotive fuel line and fuel tanks applications

High density polyethylene - exfoliated graphene nanoplatelet (GnP) composites were produced by melt extrusion and injection molding. Bulk specimens were manufactured for mechanical testing (tensile, flexural and Izod impact tests) and films were produced for the measurement of the permeation to oxygen and fuel. 3 different grades of graphene nanoplatelets with different diameters (from 15 to 0.3 micron), thicknesses (from 6 to 2 nm, respectively) and surface areas (from 100 to 750 m2/g, respectively) were investigated over a range of concentrations from 0.2 wt. % to 7.5 wt. %. The stiffness of the GnP nanocomposites was greatly improved without a loss of the strength. The impact resistance decreased. A clear decrease of the permeation to both oxygen and fuel was measured. An increase of the crystallinity was induced by the nucleation sites provided by the surface of the platelets. The thermal stability was also notably improved. The maximum concentration of platelets tested in this study did not result in any increase in electrical conductivity. The percolation threshold was not reached because of the limited dispersion of the particles in the polymer melt. The evolution of the properties depended on the type of platelets, their concentration and their dispersion.