Page 187 - Carbon Nanotube Fibres and Yarns

Carbon nanotube yarn structures and properties 177

Now, if future commercial CNT yarns can utilize their theoretical
strength to the same level as the commodity textile fibers, they can be ex-
pected to achieve a specific strength in the range of 1.5–2.5 N/tex, which
have already been reported by a number of research groups. If the utilization
ratio can be increased to that of the high-performance fibers, future CNT
yarns may be expected to reach specific strength between 4.3 and 7 N/tex
and specific modulus between 161 and 325 N/tex. These values translate into
3
7.7–12.6 and 290–585 GPa, respectively, based on a density of 1.8 g/cm .
These strength and modulus are higher than the mechanical performance
achieved by any commercially manufactured fibers.

7.7 Summary and future prospect

CNTs possess very high mechanical properties combined with excellent
electrical and thermal conductivity. Fiber and yarn are the most efficient
structures known to researchers for utilization of these properties. The CNT
fibers and yarns of today have utilized only a small fraction of the mechan-
ical, electrical, and thermal properties of the constituent CNTs. The struc-
tural mechanics of conventional textile yarns is well understood and in many
cases provides useful clues for understanding the relationship between the
structure and properties of CNT yarns. The strong van der Waals force, the
geometrical disorder of as-synthesized CNTs and the unique nanotube in-
terfacial properties present challenges as well as opportunities for the research
and development of higher performance CNT fibers and yarns. Maximizing
densification and alignment of the CNTs are two widely used tools to im-
prove the load transfer efficiency and conductivity between nanotubes in
CNT fibers and yarns. Lessons from textile industry tell us that CNT fiber
has a good prospect to become the strongest fiber we have ever had.

References

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