Chemistry Reference
In-Depth Information
O
Δ
OH
othre fragments
+
O
The main differences that were observed between amine-cured and anhydride-cured resins are
[
511
]:
1. The amine cross-linked resin generated more water and hydrogen, because they contained more
-CH
2
-CHOH-CH
2
- groups.
2. Scissions of anhydride-reacted resins tend to regenerate the anhydride and release CO and CO
2
in
large quantities
3. The aliphatic segments of the amine cross-linked resins yield more acetaldehyde than acetone. The
reverse is true of the anhydride-cured resins. This is thought to be due to preferential rupture of
carbon-nitrogen bonds [
511
]:
2H
O
N
O
H
+
N
O
O
2H
H
O
+
O
O
O
The anhydride-cured compositions may tend to break up symmetrically instead:
O
O
O
OH
+
+
HO
O
9.9.5 Thermal Degradation of Polyimides, Polyoxidiazoles,
and Polyquinoxalines
The technique mentioned in the previous section of pyrolysis and radiochemical gas chromatogra-
phy was also applied in a study to thermal degradation of
[
512
]. Aromatic
polyimides are more stable thermally than previously discussed polymers and require higher
temperature for decomposition. Based on the experimental results, the following mechanism was
proposed [
512
]. Initially, hydrogen radicals form. They come from various places of the polymer
backbone during the pyrolytic decomposition. Also, decomposition of amic acid may yield water
(see Chap.
6
).
aromatic polyimides
