Chemistry Reference
In-Depth Information
O
COOH
H
2
O
N
X
+
H
2
NX
O
COOH
H
O
X
N
X
CO
N
+
H
H
+
CO
H
2
N
CO
+
+
H
2
N
X
CN
+
H
2
N
X
CN
or
Another study of thermal degradation of aromatic polyimides led to similar conclusions [
513
].
At lower temperatures, the degradation of polyimides proceeds by a hydrolytic mechanism that is
greatly influenced by presence of uncyclized units. At higher temperatures, the degradation is mainly
by decarbonylation of the imide ring and breaking down of the polymer chain through “weak” bonds.
The thermal
was shown to proceed mainly through the heterocyclic
rings that are apparently the weak spots [
514
,
515
]:
degradation of polyoxidiazoles
NC
CN
O
O
O
2
+
CO
2
+
O
O
N
N
N
N
H
2
N
NH
2
N
2
+
N
N
H
H
The process by which aromatic polyquinoxalines decompose is random. At 500-600
C, it involves
the opening of the heterocyclic ring with loss of fragment [
516
]:
N
N
Δ
+
N
N
+
+
+
C
20
H
10
N
3
(CN)
2
HCN
