Shear exfoliation of graphite into graphene nanoflakes directly within polyetheretherketone and a spectroscopic study of this high modulus, lightweight nanocomposite

This research demonstrates a general approach to produce graphene enhanced polymer matrix composites (G-PMCs) using in situ shear exfoliation of mined graphite directly within molten thermoplastic polymer. It is found that shear exfoliation of 35 wt % graphite within polyetheretherketone (PEEK) after multipass processing creates graphene nanoflakes (GNFs) that are uniformly distributed and bonded to PEEK, resulting in a nearly 400% increase in tensile modulus. Morphology images show surface crystallization of PEEK on GNF surfaces, very good planar adhesion, and size reduction of GNFs in both the c-axis direction and in diameter due to fracture across the basal plane. Spectroscopic analysis from Raman and XPS spectra indicate in-situ formation of chemical bonding between created GNFs and PEEK. This shear exfoliation melt-mixing method allows high GNF concentration, intimate particle-matrix interaction, in situ functionalization, and provides a platform changing technology for lightweight, stiff PMCs with low raw materials costs, tunable properties, and simple part fabrication methods.