Page 395 - Handbook of Properties of Textile and Technical Fibres

368 Handbook of Properties of Textile and Technical Fibres

Silk and cotton were quickly replaced by this more durable and easy-care product.
Nylon soon found its way into other end uses. In parachutes and fishing line, nylon
provided a moisture and mildew-resistant replacement for silk. In protective vests,
nylon offered a strength and durability previously unattainable for protection against
shell fragments. When used as aircraft tire reinforcement, nylon enabled heavy
bombers to land safely on improvized air strips. DuPont, as the global leader in nylon
polymer, offers a wide range of PA 66 polymer types for use in industrial, textile, and
furnishing/floor covering applications (Deopura et al., 2008; Yang, 2006). Another
important development is the use of polyamides to make safety airbags (Yang, 2006).
Initially, the textile industry focused primarily on aeronautical and military equip-
ment and then extended their use to consumer applications. To this end, a series of new
synthetic textiles and techniques for processing textiles have been developed.
Other commercial polyamides like polyamides 11, 12, and 610 are mostly used as
engineering plastics, for example, in cars, and for making films for food packaging.
They are used in films for their good balance between mechanical strength and barrier
properties against oxygen, smells, and oils (Aharoni, 1997).
Northeast Asia continues to be the centre of the world’s nylon fiber manufacturing
industry. In 2015, Asia accounted for nearly two-thirds of the world’s nylon fiber
output. In the past 5 years, production of nylon fiber in China has increased by about
7.6% per year. The only other region to exhibit positive growth over the same time
frame was Southeast Asia. Most other Asian countries, such as Japan, South Korea,
Taiwan, and India, experienced no growth or even declining production (Yang,
2006). As nylon-producing regions, North America and Western Europe are expected
to remain, at best, stable. Both are important nylon fiber consumers, but both regions
are growing at below-average rates. Regions with above-average annual growth rates
for fiber consumption include the Indian subcontinent (about 3%), Northeast Asia
(3%), and Southeast Asia (2.5%). Major regions with below-average annual growth
rates include North America (0.6%) and Western Europe (0.6%) (Yang, 2006).
Technical polyamide fibers have usually enhanced mechanical properties (initial
modulus and tenacity), chemical resistance, and thermal stability. High-modulus,
high-tenacity technical polyamide fibers are abbreviated as HM-HT fibers (Najafi
et al., 2017b). They can be prepared by the modification of polymeric chain lengths;
their distribution; and process of spinning, drawing, and thermal treatment.

12.2 Polyamide types

Polyamides are polymers that contain repeating amide (peptide) linkages eCOeNHe,
in so called u positions where the number of carbons in the backbone between subse-
quent amide groups is maximal. Proteins have amide groups in so-called a positions
i.e., separated by only one carbon in the backbone. Due to the partial double-bond
character of the eCOeNHe this group is planar. This is manifested in a shortening
of the bond from 0.146 to 0.133 nm (Puffr and Kubanek, 1991a). Regular positions of
eCOeNHe groups in the polymeric chains are responsible for their ordering (in crys-
talline regions) and their ability to form intra and intermolecular hydrogen bonds. The
hydrogen bonds are formed between hydrogen of one NH group and the oxygen of