Page 430 - Handbook of Properties of Textile and Technical Fibres

The chemistry, manufacture, and tensile behavior of polyamide fibers 403

12.4.7.6 PA 7

PA 7 fibers are spun from polyheptanoamide (polyenanthamide). PA 7 has a melting
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point of 225 C, a density of 1100 kg/m and a moisture regain of 3% at 65% RH and
16% at 100% RH (amorphous) (Aharoni, 1997; Cook, 2001). Raw materials are either
carbon tetrachloride and ethylene that are run over 7-chlorheptanic acid. Melt spinning
may be carried out without difficulty. Under equilibrium conditions, nylon 7 contains
only a very small proportion (about 1.5%) of monomer and other low-molecular-
weight materials.
While the physical properties of these fibers are generally similar to those of PA 6
and PA 66, there are differences in certain characteristics that could be of commercial
significance (Cook, 2001). PA7 has the well-suited properties for textile and technical
applications: a tenacity of 37 cN/dtex; relative wet tenacity of about 90%; tenacity
approximately equal to PA 6 or PA 66; breaking elongation of 14%e16%; initial
modulus 46e49 cN/dtex; boiling shrinkage of 10%, and good thermal stability. PA
7 fibers have completely disappeared from the market, because the synthesis of the
raw material is not economically viable; ε-amino u-enanth acid was produced in
1950 in the USSR (Polymer properties database). PA 7 has superior wash-and-wear
characteristics due to the increased initial modulus and low moisture absorption.
12.4.7.7 PA 8

PA 8 fibers are spun from polyacrylamide and can be synthesized by using butadiene
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or acetylene. PA 8 has a melting point of 200 C, a density of 1090 kg/m and a mois-

ture regain of 2.9% at 65% RH and 10% at 100% RH (amorphous) (Aharoni, 1997;
Cook, 2001). Capryllactam polymerizes readily to PA 8 polymer similar to capro-
lactam. The polymer contains only a very small proportion of oligomers (0.5e2.5
extractable with water). It may be melt spun without difficulty.

12.4.7.8 PA 9
PA 9 fibers are spun from polynonanoamide. PA 9 has a melting point at 200 C, a den-

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sity of 1090 kg/m , and a moisture regain 2.5% at 65% RH (Aharoni, 1997; Cook,
2001). These fibers have been produced commercially and known as Telargon. Self-
polycondensation of 9-amino-nonanoic acid takes place readily. The polymer contains
only a very small proportion of oligomers at equilibrium (about 0.5%e1.5% extract-
able with water). It may be melt spun as readily as PA 6. The molten polymer is
thermally stable as long as it is protected from atmospheric oxygen.
12.4.7.9 PA 11

PA 11 is produced by polymerization of 11-aminoundecanoic acid. PA 11 has a
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melting point of 190 C, a density of 1040 kg/m and a moisture regain of 1.2% at
65% RH and 5% at 100% RH (amorphous) (Aharoni, 1997; Cook, 2001). The starting
material is castor oil. Polycondensation takes place in a water suspension with all the

necessary additives and forms polymer at 265 C. Molten PA 11 polymer is very stable

at the temperature used during melt spinning (about 215 C), and it may be stored for