Chemistry Reference
In-Depth Information
The anhydrides react with traces of moisture or with pendant hydroxyl groups first. This opens the
anhydride groups and frees the carboxylic acids for reactions with the epoxy rings:
O
COOH
+
1.
O
H
2
O
O
COOH
O
OH
COOH
2.
+
O
O
O
O
O
OH
O
O
O
O
When only epoxy and hydroxyl groups are present, very little reaction takes place even at elevated
temperatures, as high as 200
C. Proton donors, however, catalyze the reaction [
139
]. When
anhydrides are present in the reaction mixtures, diesters form as a result of termolecular transition
states. Kinetic data support that [
136
]:
O
OH
O
+
+
O
O
O
H
O
O
O
O
O
O
OH
O
O
Tertiary amines are very effective in catalyzing reactions of anhydrides with epoxies:
O
O
O
O
+
R
3
N
O
O
NR
3
O
O
O
O
O
O
O
O
O
O
O
O
