Page 32 - Carbon Nanotube Fibres and Yarns

Yarn production from carbon nanotube forests 25

The twisting-untwisting operation can be accomplished in one contin-
uous operation, known as false-twisting. In a false-twist setup, as illustrated
in Fig. 2.9C, turns of twist are present only in the region before the yarn
reaches the false-twisting device [40]. This temporary twist disappears after
the yarn passes the twisting device (thus called false twist). As false twist can
be inserted into yarns without rotating a heavy yarn package or the feed-
stock, the method is used to process yarns at high speeds, as in the produc-
tion of false-twist textured nylon yarns that are used in fine-gauge elastic
fabrics, such as socks, tights, and leggings.

2.3.1.4 Core-spun yarns
A core-spun CNT yarn consisting of a fine metal filament core and a CNT
sheath was constructed for application in two-ply yarn supercapacitors
(see Chapter 10) to take advantage of the high electrical conductivity of
the metal filament in the core and the large specific surface area of the
nanotubes in the sheath [41]. The core/sheath-structured CNT yarn can
be manufactured on a flyer spinner, as shown schematically in Fig. 2.10A.

Fig. 2.10 Core-spun yarns: (A) schematic of core-spun yarn process and (B) cross-sectional
view of core-spun CNT yarn [41]. (Reprinted with permission from D. Zhang, M. Miao, H. Niu,
Z. Wei, Core-spun carbon nanotube yarn supercapacitors for wearable electronic textiles, ACS
Nano, 8 (5) (2014) 4571–4579.)