The thermal hydrolysis of nylon 6,6 between 338 and 398 K was investigated using solution O-17 NMR spectroscopy. By performing the hydrolysis with isotopically O-17-enriched H2O, it is possible to easily identify the non-volatile oxygen-containing degradation products formed during the hydrolysis of nylon. For the aging temperature range investigated, the dominant oxygen-containing degradation species are carboxylic acids, consistent with the hydrolytic cleavage of the amide bond. These O-17 NMR studies allowed the temperature variation for the hydrolysis of the amide bond in nylon 6,6 to be determined with of the initial rate of carboxylic acid concentration production giving an energy of activation of similar to87 +/- 1 kJ/mol. (C) 2003 Elsevier Ltd. All rights reserved.