Study on thermal decomposition of polymers by evolved gas analysis using photoionization mass spectrometry (EGA-PIMS)

Photoionization mass spectrometry (PIMS) with vacuum ultraviolet (VUV) light source provides an efficient and fragmentation-free method for the soft ionization of gaseous compounds, in order to facilitate an understanding of thermal decomposition behavior and chemical composition of polymeric materials. The PIMS was applied to the evolved gas analysis (EGA) system equipped with a skimmer interface which is constituted based upon a jet separator principle between a vacuum MS chamber and an atmospheric sample chamber in a furnace. A photoionization source with a deuterium (D₂) lamp was closely installed to the vacuum ionization chamber of a mass spectrometer to improve the ionization efficiency. The thermal decomposition of typical polymers in inert gas atmosphere was investigated by the EGA-PIMS and the resulting PI mass spectrum was characterized satisfactorily by only the parent ions with no contribution as a result of fragmentation during the ionization. The results suggested that the EGA-PIMS was an especially powerful and desirable in situ thermal analysis method for polymeric materials which evolve organic gases simultaneously and concurrently. The combination of EGA equipped with skimmer interface with no change of evolved gaseous species and PIMS with fragmentation-free during the ionization is described briefly, and the effective results are presented by comparing with EGA using conventional electron impact ionization mass spectrometry.