Graphite Nanoplatelets to Improve Mechanical, Electrical and Thermal Properties of Polymers and Composites

Many research efforts have been focusing on exfoliated clay systems, the same nanoreinforcement concept can be applied to another layered material, graphite. The key to utilizing graphite as a platelet nanoreinforcement is in the ability to exfoliate this material. If the appropriate surface treatment can be found for graphite, its exfoliation and dispersion in a polymer matrix will result in a composite with not only excellent mechanical properties but electrical properties as well, opening up many new structural applications as well as non-structural ones where electromagnetic shielding and high thermal conductivity are required. In this research, a special thermal treatment was applied to the graphite flakes to produce exfoliated graphite reinforcements. Intercalated natural crystalline graphite compounds [GICs] were formed followed by exfoliation and milling to produce sub-micron graphite flakes. SEM and TEM images showed that the average size of graphite became 0.86 um with a thickness of around 5 nm. With the proper surface treatment, the graphite nanoplatelets in polymeric matrices showed better flexural strength than composites with other carbon materials. Impedance measurements have shown that the exfoliated graphite plates percolate at below 3 vol % and the composites showed resistivity close to 101 ohm*cm. The cost of this new nano-size graphite material was estimated to be around $5/lb or less. Since exfoliated graphite has superior mechanical, electrical, thermal properties and cost effectiveness, this material has been shown to be a superior potential reinforcement for polymer nanocomposites for many applications including fuel cells, batteries and composites for electrical shielding