Pyrolysis-field ionization mass spectrometry of polyamide copolymers and blends

Nylon foils of PA 6, PA 66, PA 69, PA 12, the copolymer PA 666, and nine blends based on these polymides have been investigated by in-source pyrolysis (Py)–field ionization mass spectrometry (FIMS). These polymers and blends can be distinguished by characteristic molecular ions of oligomers, protonated amines and nitriles, and products terminated by olefinic end groups. Series of ions are formed differing in the number of additional monomeric units. Thus, polymers containing different chemical subunits were easily distinguished from each other in the spectra of the blends. Mass signals, only expected for copolymers, were found in the integrated blend spectra, indicating that amide exchange reactions occur under the experimental conditions employed. This observation was confirmed by pyrolysis of mixtures of pure polymers in the same crucible and under the same experimental conditions. Hence, the distinction by Py–MS alone between blends and copolymers with an identical averaged number of identical chemical subunits is not possible.