whereas another species had an excitation maximum at 390 and 420 nm and could
not be isolated. The latter one was reported to be associated with the presence of a-
ketoimide structures formed during thermal oxidation of nylon 66. Extracted
products were separated by TLC and analyzed using GC-mass spectrometry. They
confirmed the presence of cyclic enone dimer and dienone trimer of cyclopentanone
amongst other products.