This grant provides funding for creating a scaleable and continuous processing method that leads to carbon single-walled nanotube (SWNT)/polymer composites with exfoliated nanotube bundles. Development of such a technique is important because in order to optimize the properties of SWNT/polymer composites, the SWNTs must be separated from the bundles. The approach to meeting this critical goal is to use supercritical CO2 assisted twin-screw extrusion to achieve separation and dispersion of SWNTs. In order to achieve wetting between the supercritical fluid and the SWNTs, the surface of the SWNT bundles will be chemically altered such that the supercritical fluid will preferentially migrate to the surface of the SWNT bundles. Upon exiting the extruder/pressure chamber, the supercritical fluid will expand, as it becomes gas.
If successful, the processing method will promote the use of SWNTs and thus increase demand that is necessary to reduce the price. The process will allow the production of commercial scale quantities and broader scale testing of composite properties. In addition, this is a solvent free process that is environmentally friendly. This project will also contribute to the fundamental understanding of the thermodynamics of CO2 solubility in heterogeneous systems, as well as our understanding of the role of aspect ratio and surface area in controlling nanocomposite properties. Finally, the understanding gained through the analysis of surface modification (interface), miscibility and solubility, and processing conditions will increase our ability to control and create future materials. As we address the challenge of a commercial scale process that achieves excellent dispersion in a manner that is inexpensive and environmentally friendly, one of the broader societal impacts will be to improve the properties of potential products and enable the manufacture of new products containing SWNTs.
