Effects of different processing parameters on covalent functionalization of straight and helical carbon nanotubes for nanocomposite applications
Carbon nanotubes (CNTs), as one of the carbon allotropes, have been extensively investigated during the past two decades, due to their unique and extraordinary mechanical, thermal, and electrical properties. They exist in various structural/geometrical configurations and have varying dimensions, purities, and characteristics. Based on their unique properties, CNTs have been used and investigated in a number of high-tech industries such as aerospace, pharmaceutical, biomedical, energy storage, and electronics. Among the various forms of CNTs, helical CNTs (HCNTs) have great potential for high-performance structural applications. Compared to straight CNTs, their spiral shape can be used as reinforcement to significantly increase certain mechanical properties of nanocomposites. To investigate the effect of adding HCNTs in different resin systems, their uniform dispersion throughout the resin is quite necessary. Here, a chemical (covalent) functionalization process can be a suitable solution to increasing the dispersion uniformity and bonding CNTs to polymer molecules. This study provides an investigation of three different chemical routes for covalent functionalization of HCNTs. In addition, the effect of different parameters influencing the quality and severity of CNT functionalization has been explored. Overall, considering the parameters of the chemical routes, 62 methods for functionalizing HCNTs have been devised. Then, the functionalized HCNTs have been characterized, and the obtained results have been evaluated and compared in order to investigate the extent of functionalization. Here, different suggested mechanisms that can influence the entanglement and dispersion of HCNTs during chemical functionalization are presented. Finally, based on characterization results, the best functionalization methods and processing parameters are identified and recommended for chemical functionalization of HCNTs.
Thesis (Ph.D.)-- Wichita State University, College of Engineering, Dept. of Mechanical Engineering