Scalable, solvent-less de-bundling of single-wall carbon nanotube into elastomers for high conductive functionality

Abstract

Composite fabrication techniques predominantly involve wet-synthetic protocols with organic solvents. While the resulting composite exhibits good electrical properties, their mass-production have been severely hindered due to use of excessive organic solvents. In contrast, dry-compounding methods are well-suited for industrialization but result in composites with lower electrical properties. This mutually exclusivity between (a) the fabrication process, (b) the composite properties and (c) the industrial scalability has been a major road-block for their commercialization. Addressing this obstacle, we report an electrically conductive polymer composite with long single-wall carbon nanotubes (SWCNT) as conductive fillers. The SWCNT/polymer composite possesses superior electrical properties to those achieved previously with other fillers or CNTs, obtained through dry-processes. The method involved efficient loosening of long SWCNT bundles through a biaxial shear force and subsequent kneading into the rubber matrix. The structural damage to SWCNTs was thereby minimized, as indicated by Raman spectroscopy and optical microscopy. Consequently, we achieved a SWCNT/polymer composite exhibiting ∼200 fold higher electrical conductivity than composite materials made by conventional dry-compounding methods. Finally, we demonstrate the industrial scalability of the process through the continuous, batch-production of the SWCNT-polyurethane composite sheet (12 m long and 60 mm wide) with uniform electrical conductivity (1.5 S/cm).