MECHANISTIC ASPECTS OF THE STABILIZATION OF POLYAMIDES BY COMBINATIONS OF METAL AND HALOGEN SALTS

For aliphatic polyamides the most effective stabilizers against the long-term thermooxidative degradation are synergetic combinations of metal (mainly Cu and Mn) and halogen (mainly Br and I) salts. Their mechanism of action is still a topic of discussion. Experiments with a model compound for polyamide 46 (PA46) confirm that the combination of metal and halogen salts results in a synergetic mixture. It is shown that radical scavenging only cannot be responsible for the stabilizing action of mixtures of metal and halogen salts. The mechanism of action of combinations of metal and halogen salts is probably based on the metal ion catalyzed decomposition of hydroperoxides by the halogen salt.