Chemistry Reference
In-Depth Information
Several polyamide-imides are available commercially. Two are based on trimellitic anhydride and
methylene dianiline. They are, however, prepared by two different processes. In the first one, the
polymer is formed from the anhydride and a diamine:
O
O
HO
+
H
2
N
O
O
NH
2
O
O
N
N
n
H
H
COOH
O
H
O
N
N
n
O
In the second one, trimellitic anhydride is reacted with a diisocyanate:
O
HOOC
n
+
O
n
O
N
NO
O
O
O
+
N
CO
2
n
N
O
n
H
Another polyamide-imide is formed through a reaction of trimellitic anhydride, isophthalic acid,
and diisocyanate. It has the following structure:
H
O
O
O
N
O
N
N
N
n
H
H
O
Most polyamide-imides are not as heat-resistant as are the polyimides discussed in the next
section. They are, however, easier to process. The polyester-imides might be considered as
“upgraded” polyesters, though properties vary, depending upon chemical structure [
86
].
