Chemically modified carbon nanotube (CNT) fibers and CNT yarns prepared by a simple twisting method, both result in weak mechanical properties limiting their practical application. Therefore, in this paper, the interfacial properties of CNT yarn have been improved remarkably by introducing a two-stage strategy, i.e., by inter-tube cross-linking and densification of CNTs within CNT yarn. For this purpose, multiwall carbon nanotube film was chemically modified using acid and alcohol to induce ester bonds among CNTs, and then further densified by the wet compression method using acetone as a lubricant. After cross-linking and densification, a compact structure was observed by the SEM and TEM techniques. The product CNT yarn showed significant enhancements in mechanical properties due to the strong chemical interactions among the CNTs. The tensile strength and Young’s modulus of the CNT yarn increased from 131 to 991.5 MPa and 0.7 to 6.0 GPa, respectively. The interactions induced by inter-tube cross-linking and densification were confirmed by TGA, FTIR, and XPS analyses and further quantified by the extent of functionalization. In addition, the interfacial shear strength of the cross-linked and densified CNT yarn was increased from 15 to 60 MPa compared with the pristine CNT yarn. Therefore, the enhanced mechanical strength of CNT yarns indicates their promising potential in a variety of applications.
Graphical abstract
Keywords: Carbon nanotubes yarn; Chemical modification; Cross-linking; Interfacial properties; Densification