Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) was used to determine the structure of the molecules produced in the thermo-oxidative degradation of Nylon 6 and Nylon 66, at 180°C and 250°C in air. The MALDI spectra of the thermo-oxidized nylons provide information on the structure and end groups of the oligomers produced in the oxidation process. Our results show that the thermo-oxidation of both Ny6 and Ny66 proceeds through a hydrogen abstraction and subsequent formation of hydroperoxide intermediates. The latter decompose, yielding oligomers containing aldehydes, amides and methyl terminal groups. The aldehydes undergo further oxidation to produce carboxylic end groups. The formation of cyclopentanone terminal groups is also observed in the case of Nylon 66. Oligomers with structures deriving from Norrish-type degradation processes were not detected here for either Ny6 or Ny66.

Keywords: MALDI-ToF MS, thermal oxidation products, Nylon 6, Nylon 66