Page 429 - Handbook of Properties of Textile and Technical Fibres

402 Handbook of Properties of Textile and Technical Fibres

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260 C in water. PA 610 has a melting point of 215 C and a density of 1070 kg/m . The
moisture absorption of PA 610 is lower than that of either PA 6 or PA 66. PA 610 fi-
bers are unusually resilient. Costly sebacic acid makes major scale production a distant
possibility. This polymer is used for the production of monofilaments by extrusion or
mixed into PA 6 or PA 66 especially for fishing nets and fishing lines (Fourné, 1999).

12.4.7.3 PA 3

PA 3 poly(b-alanine) is highly crystalline, with a melting point of 340 C, a density of
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1330 kg/m , and a moisture regain of 7.7% at 65% RH and 41% at 100% RH
(amorphous). It is made by the self-condensation of the b propiolactam. Because of
the high density of the hydrogen bonds, PA 3 is insoluble in common organic solvents.
The glass transition temperature is higher than that of PA 6 (Morgenstern and Berger,
1992). Decomposition tends to occur at the high temperatures needed in melt spinning.
PA 3 solutions have been prepared using mixtures of methanol and calcium thiocya-
nate, and fibers have been wet-spun from these solutions (Cook, 2001).

12.4.7.4 PA 4

PA 4 fibers are spun from polypyrrolidone or butyrolactam. PA 4 has a melting point
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of 256 C, a density of 1250 kg/m , and a moisture regain of 7.7% at 65% RH and 33%
at 100% RH (amorphous). It has a reduced tendency for a build-up of static electricity
and has improved fabric comfort. Nylon 4 is susceptible to oxidation and is sensitive to
hypochlorite bleaches. Fabrics are easy to launder and dry easily.
PA 4 may be obtained by polymerization of 2-pyrrolidone in the presence of an
alkali catalyst. It has a higher melting point and it tends to decompose readily at tem-
peratures above 265 C. Melt spinning is quite difficult, because the melting point is

only about 2e3 C under the decomposition temperature. The production is also too

expensive; the yarn has a very low elastic modulus; it fibrillates during washing and
texturing does not provide sufficient stability (Aharoni, 1997; Cook, 2001). PA 4
composed of a repeating unit of g-aminobutyric acid (GABA) is a biobased and
biodegradable polymer since it can be synthesized from renewable material. GABA
is produced by decarboxylation of glutamate using glutamate decarboxylase, which
is produced by some microorganisms (Saskiawan, 2008).

12.4.7.5 PA 5
PA 5 fibers are spun from poly valerolactam. These fibers of high quality have prop-
erties similar to PA 66. Commercial scale production of PA 5 will depend on the
economics of monomer production (Aharoni, 1997; Cook, 2001).
Valerolactam may be made from cyclopentadiene and may be polymerized in a

manner similar to caprolactam at a temperature of about 280e290 C. The polymer
produced in this way (molecular weight about 15,000e16,000) is in equilibrium
with some 15% of low molecular weight cyclic oligomers. Poly valerolactam may
also be melt spun. Fibers of up to 8.39 cN/dtex may be produced. They have an initial
modulus higher than and creep less than PA 66.