On the mechanism of polyamide degradation in chlorinated water

Experiments were performed in an attempt to identify the reactive intermediate(s) involved in the degradation of a polyamide. Nylon 66, in chlorinated water. According to previous studies. N-chlorination is certainly one reaction that ultimately contributes to polyamide degradation. In this case. the intermediates involved could either be Cl, or HM. Available information also indicates that, for many polymers, singlet molecular oxygen (a(l)Delta (L)). chemically generated from HClO. could likewise be involved as an intermediate in a degradation reaction. Thus. tests were undertaken to specifically address this latter issue with respect to polyamide degradation. The degradation of Nylon 66 was monitored under a variety of conditions by FT-IR spectroscopy. The rate of degradation was pH-dependent, and degradation was most pronounced at pH < 5. Characteristic tests for the intermediacy of singlet oxygen, however. were negative. Rather, the data strongly pointed to Cl, as the key intermediate in the degradation. The presence of compounds capable of being oxidized by Cl, arrested the degradation reaction. These results should be pertinent in an attempt to stabilize polymers exposed, e.g., to water that has been chlorinated to kill bacteria (i.e., drinking water).