Page 411 - Handbook of Properties of Textile and Technical Fibres

384 Handbook of Properties of Textile and Technical Fibres

0.3
DR 2.5 normal
DR 2.5 quenched
DR 3.5 normal
0.2
Estimated ν TT (–) 0.1 DR 4.5 normal
DR 3.5 quenched
DR 4.5 quenched

0.0
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
Fiber modulus (GPa)
Figure 12.19 Relation between initial modulus and the portion of taut tie molecules for PA 6
fibers (according to (Mishra and Deopura, 1982)).

For calculation of the property P, it is therefore necessary to know P c ,P a ,v TT , and
v c . In their work Mishra and Deopura (1982) used the initial modulus E as the
property; for PA 6 they adopted the following values E c ¼ 24.0 GPa and
E a ¼ 0.7 Gpa, and they measured X-rayebased crystallinity. Then they calculated
from the known fiber initial modulus E the corresponding portion of taut tie molecules
v TT .
Results for PA 6 fibers drawn to three draw ratios (25, 3.5, and 4.5) and partially
quenched by a quenching system with a temperature of about 16 C are shown in

Fig. 12.19.
It is interesting that the dependence between E and v TT is practically linear, which
supports the hypothesis that the taut tie molecules play a major role in determining the
properties of PA fibers.
More recently, the portion of taut tie molecules v TT between 0.04 and 0.10 was
estimated from nuclear magnetic resonance results (Zhizhenkov and Egorov, 1984).
One reason for the differences can be probable errors in the equation for the calculation
of v TT using the modulus E.
Assessment of molecular orientation in polyamides is simply based on the bire-
fringence measurement (Lim et al., 1989). Hermans et al. (1946) provided a thor-
ough analysis of the orientation factor, f, and its effects on axial alignment of
macromolecules. Ziabicki and Kedzierska (Lim et al., 1989; Ziabicki and
Kedzierska, 1959, 1962) proved that the birefringence of the as-spun fibers
increases at a monotonic rate with the reciprocal of fiber diameter. Also, Ishibashi
(Lim et al., 1989; Ishibashi et al., 1970) provided an equation that describes how
birefringence decreases with spinning temperature.
A theoretical framework developed by Shigemitsu et al. (1998) can be used for
analyzing intensity of polarized fluorescence in an anisotropic polymer and its direct