Page 125 - Carbon Nanotube Fibres and Yarns

Post-spinning treatments to carbon nanotube fibers 117

of the polymers [17, 56, 57]. There are various types of polymers that
can be used for the treatment, such as PVA, polyethyleneimine (PEI),
and epoxy [56, 58]. Liu et al. [22] compared the tensile strength of the
CNT fibers experiencing three types of treatments: twisting, twisting and
shrinking, and PVA infiltration, as shown in Fig. 6.7A. According to their
results, the CNT/PVA composite fibers could reach a high strength of
1.95 GPa, which was 255% higher than that of the simple twisting fibers
and 103% higher than the value of the CNT fibers subjected to twist-
ing and shrinking treatment. As shown in Fig. 6.7B, the high strength
of the infiltrated fibers could be attributed to two main factors: (1) the
decrease of fiber diameter due to high wettability between CNTs and
dimethyl sulfoxide (DMSO) and (2) the increase of tensile load due to
improved load transfer efficiency between the CNTs after the infiltration
treatments.
Wang et al. [55] introduced graphene oxide (GO) into the CNT fiber
structures to enhance their interfacial shear strength (Fig. 6.8). Because the
sizes of GO and the void within the fibers matched closely, the CNT bun-
dles were interlocked, therefore enhancing their shear interactions. Thus,
the GO-infiltrated CNT fibers showed significant improvements of 100%
in Young’s modulus, 110% in yield strength, 56% in tensile strength, and
30% in energy to failure.

PVA(2500)/DMSO
2.0 Twisting&shrinking Diameter (µm) 1.95
Tensile load (mN)
Simply twisting
Tensile strength (GPa)
1.5
Stress (GPa) 1.0 1.16

0.5 0.54 188 230
152
19.0
14.4 12.3
0.0
–0.5 0.0 0.5 1.0 1.5 2.0 2.5 Twisting Twisting&shrinking SACNT/PVA
(A) Strain (%) (B) Types of yarns
Fig. 6.7 (A) Stress-strain curves of a typical CNT/PVA fiber and two types of pure CNT
fibers and (B) comparison of the diameter, tensile load, and tensile strength of a simply
twisting, a twisting, and shrinking (by DMSO), and a CNT/PVA fiber. (Reproduced with
permission from K. Liu, Y. Sun, X. Lin, R. Zhou, J. Wang, S. Fan, et al., Scratch-resistant, highly
conductive, and high-strength carbon nanotube-based composite yarns, ACS Nano 4 (2010)
5827–5834.)