Exfoliated graphite nano-platelets (xGnP) are new types of

nanoparticles A nanoparticle or ultrafine particle is a particle of matter 1 to 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At ...

made from

graphite Graphite () is a Crystallinity, crystalline allotrope (form) of the element carbon. It consists of many stacked Layered materials, layers of graphene, typically in excess of hundreds of layers. Graphite occurs naturally and is the most stable ...

. These nanoparticles consist of small stacks of

graphene Graphene () is a carbon allotrope consisting of a Single-layer materials, single layer of atoms arranged in a hexagonal lattice, honeycomb planar nanostructure. The name "graphene" is derived from "graphite" and the suffix -ene, indicating ...

that are 1 to 15 nanometers thick, with diameters ranging from sub-micrometre to 100 micrometres. The X-ray diffractogram of this material would resemble that of graphite, in that the 002 peak would still appear at ~26^o 2 theta. However, the peak would appear considerably smaller and broader. These features indicate that the interplanar distance in exfoliated graphite is similar to that of the parent graphite, but the stack size (of graphene layers) is small. Since xGnP is composed of the same material as

carbon nanotubes A carbon nanotube (CNT) is a tube made of carbon with a diameter in the nanometre range (nanoscale). They are one of the allotropes of carbon. Two broad classes of carbon nanotubes are recognized: * ''Single-walled carbon nanotubes'' (''SWC ...

, it shares many of the electrochemical characteristics, although not the tensile strength. The platelet shape, however, offers xGnP edges that are easier to modify chemically for enhanced dispersion in polymers. Composite materials made with

polymers A polymer () is a substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeating subunits derived from one or more species of monomers. Due to their broad spectrum of properties, b ...

, like

plastics Plastics are a wide range of synthetic or semisynthetic materials composed primarily of polymers. Their defining characteristic, plasticity, allows them to be molded, extruded, or pressed into a diverse range of solid forms. This adaptab ...

nylon Nylon is a family of synthetic polymers characterised by amide linkages, typically connecting aliphatic or Polyamide#Classification, semi-aromatic groups. Nylons are generally brownish in color and can possess a soft texture, with some varieti ...

, or

rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Types of polyisoprene ...

, can be made electrically or thermally conductive with the addition of small amounts of xGnP. These nanoparticles can change the fundamental properties of plastics, enabling them to perform more like metals with metallic properties. These new nanoparticles also improve barrier properties, modulus, and surface toughness when used in composites.

Properties

Graphene Graphene () is a carbon allotrope consisting of a Single-layer materials, single layer of atoms arranged in a hexagonal lattice, honeycomb planar nanostructure. The name "graphene" is derived from "graphite" and the suffix -ene, indicating ...

is extremely electrically conductive material. In turn, xGnP has a percolation threshold for conductivity of 1.9 wt% in thermoplastic matrix. At densities of 2–5 wt%, conductivity reaches sufficient levels to provide electromagnetic shielding. xGnP can also be combined with glass fibers or other matrix materials to provide sufficient conductivity for electrostatic painting or other applications requiring electrical conductivity. xGnP significantly outperforms most other forms of carbon in terms of thermal conductivity when used at densities of 20 wt% in control resins. At these densities, xGnP also confers significant electrical conductivity as well as improved mechanical properties to most thermoplastic, thermoset, or elastomeric systems. At lesser densities, xGnP adds thermal stability to a variety of matrix materials. As opposed to materials like

carbon black Carbon black (with subtypes acetylene black, channel black, furnace black, lamp black and thermal black) is a material produced by the incomplete combustion of coal tar, vegetable matter, or petroleum products, including fuel oil, fluid cataly ...

, xGnP improves mechanical properties of most composites, particularly stiffness and tensile strength. Elastomeric compounds have been shown to experience increased life and reduced surface wear when reinforced with xGnP. Because of the platelet shape, xGnP significantly improves the impermeability of composites when used at densities of ~3 wt% or greater. xGnP particles can be aligned using electric field, although alignment is not necessary for use in most extrusion systems. Because xGnP also imparts electrical conductivity at these densities, the resulting composites offer attractive cost savings for applications like fuel lines or fuel tank linings.

References

{{reflist Allotropes of carbon Refractory materials