Thermal degradation of aliphatic polyamides studied by field ionization and field desorption mass spectrometry

Abstract

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.

Synthesis, characterization and thermal decomposition of poly(decamethylene 2,6-naphthalamide)

“…The pyrolysates were identified by mass spectra and confirmed by comparing their retention times [33][34][35][36][37]. The results of identification, the molecular weight and relative intensity of pyrolysis products Table 2.…”

Pyrolysis‐field ionization mass spectrometry of polyamide copolymers and blends

“…As Novamid 2030 contains mainly PA 6 subunits, the averaged number of PA 6 and PA 66 subunits is very similar between blends 1 and 4. Indeed, the mass spectra of both blends are really very similar.…”

“…Oligomers appear as [M,]+' and [M, + HI+ ions, which are typical of various polyamides. 6 In addition, PA 666 shows abundant mass signals which are absent in the spectra of the two homopolymers PA 6 and PA 66. These mass signals belong to products containing the PA 6 as well as PA 66 subunits.…”

Ambient Characterization of Synthetic Fibers by Laser Ablation Electrospray Ionization Mass Spectrometry

“…13,59−61 Differentiation between, e.g., PA 6 and PA 66 could not be achieved. With FA-APGD, the cyclic monomer ion of PA 66 at m / z 227 could be detected.…”