NMR ANALYSIS OF UV-AGED AND HEAT-AGED NYLON-6,6

Samples of Nylon-6,6 were analyzed by 1-D and 2-D NMR techniques to de termine the degradation structures resulting from UV exposure of Nylon films and heat aging of Nylon pellets. The dominant degradation struc ture in all cases was the terminal methyl group which was attributed t o chain scission reactions. Further evidence for chain scission was fo und through the presence of aldehyde and formamide structures upon UV exposure and heat aging (in the presence of air) and terminal vinyl st ructures upon UV exposure. The presence of oxygen during UV exposure r esulted in OH substitution adjacent to the amide group and at the end of a cleaved alkyl chain. Terminal amide groups were observed in the s tarting material and did not increase in concentration upon heat aging or UV exposure. In heat-aged samples, no evidence was found for olefi nic or hydroxyl-containing structures in nitrogen, but hydroxyl struct ures were observed. A degradation mechanism was proposed to account fo r the structures observed in our work.