A simple chemical treatment for easy dispersion of carbon nanotubes in epoxy matrix for improving mechanical properties

Carbon nanotubes have considerable potential for use as reinforcements in high-performance polymer composites, but their large-scale application has been hindered by their poor processability. Here, we report an extremely simple and scalable method for the chemical treatment of single-wall carbon nanotubes (SWNTs) to enable easy dispersion in an epoxy matrix. The treatment involves stirring SWNTs in a concentrated solution of sodium hydroxide in ethanol. The chemicals used can be recovered and re-used. The treated SWNTs show greater ease of exfoliation into organic solvents without the need for high-intensity ultrasonic probe treatment. Raman spectroscopy shows that the treatment does not create any noticeable defects or functional groups on the SWNT walls. As a result of the treatment, the SWNTs could be dispersed in epoxy with minimal, low-power ultrasonic treatment. The resulting composites showed increased fracture toughness and tensile strength at SWNT loadings as low as 0.5 weight percent, when compared with neat epoxy. The enhancement in properties of the composites does not decrease with increased SWNT loading, implying that the SWNTs do not re-aggregate.