Effect of microwave treatment exposure time on functionalization and purification of multi-walled carbon nanotubes (MWCNTs)

Carbon nanotube (CNT)-reinforced polymer composites are steadily replacing other materials and finding their applications in many structural components. This has been credited to their light weight, ease of processing and extraordinary thermal, mechanical and electrical properties. However, direct addition of CNTs into polymer leads to formation of agglomerates due to strong van der Waals' force of attraction between individual nanotubes. These agglomerates then act as defects and hinder the properties of polymer/CNT composites. As a result, CNTs are functionalized in acids to minimize their tendency to agglomerate and improve dispersion in polymer matrix. The present study focuses on the microwave treatment of CNTs to achieve better functionalization as compared to the conventional ultra-sonication technique. The time of exposure of multi-walled carbon nanotubes (MWCNT) to the microwave radiation is optimized by investigating the structural integrity of different samples with Raman spectroscopy, infrared spectroscopy (FTIR), microscopy and purification effect by X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS). The mechanism of sidewall modification of MWCNTs after functionalization is elucidated schematically as well.