Page 79 - Carbon Nanotube Fibres and Yarns

72 Carbon Nanotube Fibers and Yarns

Fig. 5.1 Scheme of the structures of textile fiber, high-performance fiber, and ideal fibers [1].
(Source: H.G. Chae, S. Kumar, Making strong fibers, Science 319 (5865) (2008) 908–909.)

ultra-high-molecular-weight polyethylene (UHMW-PE, Dyneema and
Spectra) in 1980s [2]; the development of new spinning technology, such as
dry-jet wet spinning for Kevlar fibers and gel spinning for high-performance
PE and poly(vinyl alcohol) (PVA) fibers. Combining the developments of
new materials and spinning technologies, fiber performances have been dra-
matically improved.
A schematic representation of various fiber structures based on their ten-
sile performances is shown in Fig. 5.1. The tensile properties of a particular
polymer fiber depend on its physical structures and defects (chain entangle-
ments, chain ends, foreign particles, and voids) [1]. For a particular polymer,
the developments of fiber structures rely on its spinning method and con-
ditions. For example, the development of gel spinning for UHMW-PE and
PVA fibers has led to revolutionary improvements of fiber performances
over traditional wet spinning. The optimization of spinning conditions and
polymer structures has continuously improved the tensile performances of
the resultant fibers. For example, the tensile strength of polyacrylonitrile
(PAN)-based carbon fibers has been improved from 3 to 7 GPa since the
late 1970s.
Spinning technology may be regarded as a top-down method for con-
trolling the chain structures in fibers, because it is difficult to tune the chain
structures in nanoscale. Toward the end of the 20th century, technology
developments made it possible to produce nano-sized materials. Due to
size and quantum effects, these nano-materials exhibit unique and supe-
rior properties over their bulk materials. Among them, nano-sized carbon
allotropies, including carbon nanotubes (CNTs) [2] and graphene [3], have