Exfoliated Graphite Nano-Reinforcements With Surface Modifications to Improve Dispersability

Exfoliated graphite nanoflakes are a potential low-cost source of nano-reinforcement for making polymer composites with unique properties. The chemical nature of the graphitic surface leads to a low-surface energy as produced. This makes the nanoflakes difficult to disperse in polymer resins and makes it difficult to make high-quality composites. To improve nanoflake dispersability in various polymers, two surface treatments were selected to modify the chemical structure of the graphite nanoflakes.

The treatment was scaled up to pilot-plant size, with special emphasis on further scalability to production quantities. For the oxidative plasma treatments, which created carboxyl and hydroxyl
groups that greatly increased the nanoflake surface energy and provided chemical sites for subsequent reactions, a continuously operating RF (radio-frequency) plasma unit was designed, built, and demonstrated. Large-scale bonding of polymer oligomers to the nanoflake surface using reactive coupling agents was achieved with a scalable batch process for coating applications, followed by a continuous heat activation to generate the chemical bond between flake and resin. Different analytical methods, including IGC (Inverse Gas Chromatography), SEM (scanning electron microscope), and XPS X-ray Photoelectron Spectroscopy (XPS), were used to verify the modifications.
The treated flakes were used to create nano-reinforced composites.

This work was done by Ronald E. Allred, Jan-Michael Gosau, Jeremy P. Barlow, and Sheldon P. Wesson of Adherent Technologies, Inc. for Glenn Research Center. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Materials category.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steve Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-18543-1.