Page 16 - Carbon Nanotube Fibres and Yarns

8 Carbon Nanotube Fibers and Yarns

The production of CNT fibers continuously from the furnace provides an
effective method for production scaling up. The direct spinning method
will be reviewed in Chapter 3, including the synthesis of the nanotubes,
assembly of a continuous CNT network, and formation of a final fiber.
Chapter 4 provides an overview of the wet spinning of neat or nearly
neat CNT fibers from bulk-grown CNTs. Premade CNTs are dissolved
into a solvent (usually a strong acid) or in a suspension with the aid of sur-
factant, which is then formed into a fiber using wet-spinning methods that
are similar to the high-throughput extrusion of textile fibers from polymers.
Because the synthesis of the CNTs is separated from the formation of fi-
bers, the wet-spinning method provides the opportunity to optimize both
processes independently.
Instead of dissolving in a solvent, bulk-produced CNTs, usually a
small percentage, can be dispersed in a polymer and then extruded us-
ing traditional textile fiber spinning methods. This approach is discussed in
Chapter 5. Because of their superior properties and one-dimensional (1D)
cylindrical geometry, CNTs are ideal fillers for reinforcing polymeric fibers.
The reinforcement effect is beyond the rules-of-mixture effect because of
the development of an interphase between the CNTs and the polymer. In
this chapter, the structure development and property enhancement of such
interphase are discussed in detail.
Many treatments have been proposed to improve the mechanical, elec-
trical, and thermal properties of neat and composite CNT fibers, including
further densification treatments based on twist insertion, lateral compres-
sion, rubbing, liquid evaporation, purification, cross-linking treatments by
irradiation and polymer infiltration, and combinations of two or more of
these treatments. Chapter 6 reviews the principles and procedures of these
post-spinning treatments and their effects on CNT fiber properties.
Despite tremendous progresses in the last two decades, the properties of
the CNT fibers and yarns produced around the world are far behind that
of their constituent nanotubes. The challenge has been to organize CNTs
into yarns with the best possible properties. Part 2 discusses the structures,
properties, and methodology for improving the structure and properties of
CNT fibers and yarns based on experiments and computational mechanics.
Unlike conventional textile yarns, the strength of final CNT fibers and
yarns can be rarely related back to the strength of their constituent nano-
tubes, mainly due to the complex nature of direct testing of individual
nanotubes. Geometry of CNT yarn structure, such as nanotube alignment
and packing density, is mainly investigated by adjusting the conditions of