Relationship between Mechanical and Electrical Properties of Continuous Polymer-Free Carbon Nanotube Fibers by Wet-Spinning Method and Nanotube-Length Estimated by Far-Infrared Spectroscopy

Neat carbon nanotube (CNT) fibers produced by wet spinning methods offers a potential for high-strength and electrically conductive lightweight materials. For improving their performances, it is necessary to understand how each manufacturing process affects the raw CNTs and implicates the effects in the fiber properties. Recently, we found that the lengths of the clean CNT channels can be estimated by far-infrared (FIR) spectroscopy based on the plasmon resonance model. In this paper, the relationship between the mechanical properties and electric conductivities of the neat CNT fibers, and the lengths of the constituent CNTs are systematically studied by using different types of single-walled CNTs (SWCNTs) with various diameters and different dispersing times. Irrespective of the type of CNTs or the tube diameters, Young moduli, fracture strengths, and electric conductivities of the CNT fibers were found to be related to the CNT lengths estimated from the FIR spectra. The results prove that the evaluation of CNT length by the FIR spectroscopy is a highly useful method to optimize the processing conditions as well as to select the proper CNTs for fabricating high-performance CNT-based materials.