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 degrees C were extracted by headspace solid-phase microextraction and 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, pyridines and structural fragments from the original polyamide chain. 1-Pentyl-2,5-pyrrolidinedione (pentylsuccinimide) showed the largest increase in abundance during oxidation. The cyclopentanones in group D were already present in the un-aged material. Their amounts decreased during ageing and they are thus not formed during thermo-oxidation of polyamide 6.6 at 100 degrees C. The identified thermo-oxidation products can be formed as a result of extensive oxidation of the hexamethylenediamine unit in the polyamide backbone. The degradation products pattern shows that the long-term thermo-oxidative degradation, just like thermal degradation and photo-oxidation of polyamide 6.6, starts at the N-vicinal methylene groups.
Gröning
M
M
Department of Polymer Technology, The Royal Institute of Technology (KTH), Stockholm, Sweden. minna@polymer.kth.se
Hakkarainen
M
M
D002209:Caprolactam / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D010084:Oxidation-Reduction; D011108:Polymers / Q000737:chemistry / Q000302:isolation & purification*; D013696:Temperature
D011108:Polymers; C009916:nylon 6; D002209:Caprolactam