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The thermal degradation of aromatic polyamides such as poly-(1 ,Cphenyleneterephthalamide) (Kevlar) and poly-(l,3-phenylene-isophthalamide) (Nomex) was studied by pyrolysis-field ionization mass spectrometry (Py-FIMS) and pyrolysis-gas chromatography (Py-GC). In Py-FIMS, the thermal degradation products were recorded which were formed in the ion source of a double focusing mass spectrometer. Usually a temperature range from 50 to 75OOC and a heating rate of 1.2OC/s were employed. Various common and characteristic products for the two samples, respectively the corresponding para-or meta-isomers, were observed up to m/z 500 with significant differences in intensity. The main products observed were produced by both radical homolytic and hydrolytic decompositions.On the other hand, in flash Py-GC the instantaneous thermal degradation products at 720 "C were gas-chromatographically separated by a fused-silica capillary column and detected both by a flame ionization detector and a mass spectrometer with electron ionization @I). Although many of the degradation products were identical with those observed by Py-FIMS, the former almost entirely consisted of the fragments formed through radical homolytic degradation. In general, the differences between the samples with Py-GC were much less than those observed in Py-FIMS. ZUSAMMENFASSUNG:Der thermische Abbau von aromatischen Polyamiden wie Kevlar (Poly-l,4-(phenylen-terephthalamid)) und Nomex (Poly-( 1,3-phenylen-kophthalamid)) wurde mit Pyrolyse-Feldionisation-Massenspektrometrie (Py-FIMS) und Pyrolyse-Gaschromatographie (Py-GC) untersucht. Bei den Messungen mit Py-FIMS wurden die Proben in der Ionenquelie eines doppel-fokussierenden Massenspektrometers im Tempe-raturbereich von 50°C bis 750°C bei einer Heizrate von 1,2 "C/s pyrolysiert. Zahlreiche gemeinsame und charakteristische Abbauprodukte der beiden Proben, bzw. der entsprechenden para-und meta-Isomeren, wurden im Massenbereich bis m/z 500 gefunden, allerdings mit erheblichen Intensitiitsunterschieden. Die Hauptprodukte wurden durch homolytische Reaktionen sowie durch Hydrolyse gebildet .Andererseits wurden die bei 720 "C gebildeten thermischen Abbauprodukte gaschromatographisch mit einer gebundenen Silicagel-Siiule getrennt. Der Nachweis erfolgte sowohl durch einen Flammenionisations-Detektor als auch durch Elektronen-stol3-@I)-Massenspektrometrie. Obwohl viele der Abbauprodukte mit denen der bei den Py-FIMS Messungen gefundenen iibereinstimmten, setzten sich erstere vorwiegend aus solchen Produkten zusammen, welche durch radikalische, homolytische Reaktionen gebildet werden. Die Unterschiede zwischen der Zusammensetzung der thermischen Abbauprodukte der beiden Proben waren allgemein mit Py-GC erheblich geringer, als bei Py-FIMS beobachtet wurde.

Linear polyesters of the lactone and the diol-dicarboxylic acid types have been pyrolyzed in the ion source of a mass spectrometer. The gaseous degradation products were softly ionized by means of field ionization. Oligomers were the dominant products observed as protonated species. In contrast to the general experience with soft ionization mass spectrometry, with polyesters distinct mass spectrometric fragmentation occurs forming singly charged and doubly charged carboxonium and hydroxonium ions, respectively. Single fragments are formed with high intensity when the simultaneous formation of several double bonds is possible with the structural subunits present. In addition, cyclic six-membered transition states and the possibility of the formation of stable cyclic fragments increase the degree of fragmentation. Finally, a fundamental interpretation of the processes of polyesters in pyrolysis-field ionization mass spectrometry is given.

The aliphatic polyamides nylon 6.6, 6.9, 6.10, 6.12, 12.6, 12.10, and 12.12 of the diamine dicarboxylic acid‐type were pyrolyzed in the ion source of a double‐focusing mass spectrometer and the thermal degradation products were recorded by field ionization (FI) and field desorption (FD) mass spectrometry (MS). In the FI mode, several series of thermal degradation products differing in the number of polymer repeating units were detected up to 1000 Daltons. The main products were oligomers and, in addition, protonated dinitriles and various protonated nitriles are formed in large amounts except for nylon 6.6 and nylon 12.6. These two polymers form, in contrast to all other samples, large amounts of protonated amides and diamines. The technique employed allows distinction between oligomers already present in the original polymer and oligomers formed by thermal fission of bonds in the polymer chain. Reaction mechanisms are given that explain the products observed. High resolution experiments and accurate mass measurements were performed to confirm the proposed structures. In the FD mode, cationized oligomers (attached mostly to a sodium cation) were observed below 200°C with the dimers being the base peak for most samples. In contrast to the FI results, the monomers were only detected at very low intensities. Similarly, only weak signals for additional thermal degradation products were registered except for nylon 12.6. At higher temperatures the FD mass spectra gave protonated and doubly protonated oligomers in the high mass range up to 2000 Daltons, which resulted in complementary structural information about the polymers.