Large Scale Processing of Carbon Nanotubes Using Microfluidizer® High Shear Fluid Processors Dispersion/deagglomeration - Conductivity of polymer composites - Length –Purification - Functionalization
Microfluidics Intl, US
Keywords: dispersion, carbon nanotubes, nanocomposites,microfluidizer, electrical conductivity, purification
Abstract:For many carbon nanotube (CNT) applications, paramount performance can be achieved if the CNTs get deagglomerated, frequently shortened, and uniformly dispersed in liquid media. Microfluidizer high shear fluid processors were used successfully to disperse single- and multi- wall CNTs in various liquid media including polymer resins, organic solvents and water at concentrations in the range of 0.3-6 wt%. Processing deagglomerated the CNTs and caused them to form networks inside the liquid media. Length reduction of CNTs was possible and controlled based on the processing conditions. During processing, CNTs detached from the catalyst substrate, facilitating purification. Finally, the electrical resistivity of polymer/CNT composites was measured as a function of CNT concentration. For samples processed with the Microfluidizer® processor, the volume resistivity of the composites decreased by seven orders of magnitude as the CNT concentration increased from 0.008wt% to 0.06wt%. There was no change in resistivity for the baseline samples. The heart of the technology is the interaction chamber which consists of “fixed geometry” microchannels. Flow through the chamber is characterized by high fluid velocities (up to 500 m/s) and subsequent impingement of fluid jets to the chamber walls or to one another. Under these conditions, mixing of fluids (miscible or immiscible) takes place at the nanometer scale, and solid agglomerates disperse or break to give submicron particles. Parallel arrays of identical channels inside these chambers ensure that each volume of fluid is processed under identical conditions on the small and large scale. The scalability of the technology has been demonstrated up to tens of liters per minute. Some of the current largest scale machines have production rates of over 50 liters/minute.