Effects of Wet-Pressing and Cross-Linking on the Tensile Properties of Carbon Nanotube Fibers

Abstract

To increase the strength of carbon nanotube (CNT) fibers (CNTFs), the mean size of voids between bundles of CNTs was reduced by wet-pressing, and the CNTs were cross-linked. Separate and simultaneous physical (roller pressing) and chemical methods (cross-linking) were tested to confirm each method’s effects on the CNTF strength. By reducing the fraction of pores, roller pressing decreased the cross-sectional area from 160 μm2 to 66 μm2 and increased the average load-at-break from 2.83 ± 0.25 cN to 4.41 ± 0.16 cN. Simultaneous injection of crosslinker and roller pressing augmented the cross-linking effect by increasing the infiltration of the crosslinker solution into the CNTF, so the specific strength increased from 0.40 ± 0.05 N/tex to 0.67 ± 0.04 N/tex. To increase the strength by cross-linking, it was necessary that the size of the pores inside the CNTF were reduced, and the infiltration of the solution was increased. These results suggest that combined physical and chemical treatment is effective to increase the strength of CNTFs.

Selective Interbundle Cross-Linking for Lightweight and Superstrong Carbon Nanotube Yarns

“…Wet-spun CNTY of CSA doping has also been reported for further densification with controlled orientation. − The CNTY exhibited high strength and high electrical conductivity through a high-density structure in which van der Waals interactions between CNTs were maximized. To achieve higher strength beyond the record, covalent or ionic bonds, which are up to 10 times stronger than van der Waals interactions, − should be introduced in the internal structure of a CNTY. These advances can be realized by the chemical cross-linking of the CNT surface through the infiltrated binding materials, such as polymer or small organic molecule, thereby preventing pullout failures. − Nevertheless, the performance of the resulting materials has been disappointing ,,− because of inefficient cross-linking from a lack of understanding of the assembled CNTY structure and its load-bearing systems.…”

“…To achieve higher strength beyond the record, covalent or ionic bonds, which are up to 10 times stronger than van der Waals interactions, − should be introduced in the internal structure of a CNTY. These advances can be realized by the chemical cross-linking of the CNT surface through the infiltrated binding materials, such as polymer or small organic molecule, thereby preventing pullout failures. − Nevertheless, the performance of the resulting materials has been disappointing ,,− because of inefficient cross-linking from a lack of understanding of the assembled CNTY structure and its load-bearing systems. Recently, the unique hierarchical structure of CNTY has been highlighted, and interbundle sliding was pointed out as the main hurdle to the fabrication of high-performance CNTY rather than intertubular slippage. ,, Therefore, CNTs inside the bundles can be assumed to be bound by intrabundle interactions, which are ideally composed of CNT stabilization energy and van der Waals interactions.…”