Page 404 - Handbook of Properties of Textile and Technical Fibres

The chemistry, manufacture, and tensile behavior of polyamide fibers 377

(a) (b)
110
002
200
a
C
001 C O
C O H N
H N
C O 020
CO
H N
H N C O H N C O
NH
c O N H O C N
NH C O C N H O C
O C
NH
NH O H N C O H N
C C O H N C O
O C
b c
a b
100 202
010

Figure 12.10 Unit cell of (a) PAD 66 and (b) PAD 6 (a form) (Source: Yang, 2006).

(a) α form (monoclinic) (b)
γ form c sin β
c c
C b
a a sin β
O
b b
N
H

Van der
H-bonds
b- c plane
waals
Van der waals
b- c plane
H-bonds
a- b plane a- b plane
Figure 12.11 Sheet arrangement in the (a) a form (monoclinic) and (b) g form crystal lattices of
PA 6 (according to Millot, 2015).
the greater proportion of the g form. Annealing the filaments at elevated temperatures
converts the g form to the more stable a form.
In the g form the polymer chains are slightly distorted. The amide group rotates by
30 degrees with respect to the eCH 2 e backbone and the hydrogen bonds are formed