Headspace solid-phase microextraction - a tool for new insights into the long-term thermo-oxidation mechanism of polyamide 6.6

Low-molecular-mass products formed. during thermo-oxidation of polyamide 6. 6 at 100 degreesC were extracted by headspace solid-phase microextraction a nd identified by GC-MS. A total of 18 degradation products of polyamide 6.6 were identified. In addition some low-molecular-mass products originating from the lubricants were detected. The identified degradation products were categorized into four groups where compounds within each group contain the same structural feature. In groups A, B and C several new thermo-oxidation products of polyamide 6.6 were identified including cyclic imides, pyridin es and structural fragments from the original polyamide chain. 1-Pentyl-2,5 -pyrrolidinedione (pentylsuccinimide) showed the largest increase in abunda nce during oxidation. The cyclopentanones in group D were already present i n the un-aged material. Their amounts decreased during ageing and they are thus not formed during thermo-oxidation of polyamide 6.6 at 100 degreesC. T he identified thermo-oxidation products can be formed as a result of extens ive oxidation of the hexamethylenediamine unit in the polyamide backbone. T he degradation products pattern shows that the long-term thermo-oxidative d egradation, just like thermal degradation and photo-oxidation of polyamide 6.6, starts at the N-vicinal methylene groups. (C) 2001 Elsevier Science B. V. All rights reserved.