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Introduction. Polymer nanocomposites are of scientific and commercial interest because of their potential for enhanced properties compared to neat polymer. 1-18 For example, improvements in mechanical properties are expected when highaspect-ratio nanofillers are well-dispersed or exfoliated in polymer; 7, 8 prototypical nanofillers include layered silicates (clay) 9-14 and carbon nanotubes. 15-18 A carbon-based material of intense, recent focus in nanotechnology is graphite. 19 Despite its natural abundance and use since the Middle Ages, 19 graphite and its derivatives have only recently emerged as a nanomaterial of choice, as exceptional mechanical and electrical properties are observed when the sp2-hybridized carbon layers termed “graphene sheets” are isolated or in “paper” form. 20-23 Chemically similar to carbon nanotubes and structurally analogous to layered silicates, graphite has the potential to be an outstanding nanofiller in the form of individual graphene layers or nanoscale layered stacks.

Despite potential advantages, there are relatively few reports of graphite-based polymer nanocomposites. 23-37 This is because effective dispersion or exfoliation of graphite is practically impossible with melt processing. Most polymer-graphite hybrids are made from chemically or thermally pretreated graphite, eg, graphite oxide, expanded graphite, or thermally exfoliated graphite oxide. 23-36 Even with pretreatment, nanocomposite production by conventional processing is challenging due to thermodynamic and/or kinetic limitations, sometimes leading to limited property enhancement. Here we employ solid-state shear pulverization …