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Comparison of EI and metastable atom bombardment ionization for the identification of polyurethane thermal degradation products
Authors:M Boutin  J Lesage  C Ostiguy  M J Bertrand  
Institution:

a Institut de recherche Robert-Sauvé en santé et en sécurité du travail, 505 De Maisonneuve Ouest, Montreal, Quebec, Canada H3A 3C2

b Regional Center for Mass Spectrometry, Department of Chemistry, University of Montreal, Montreal, Canada H3C 3J7

Abstract:Polyurethanes are widely used in the manufacture of commercial products such as foams and paints. During combustion, these polymers can generate isocyanates, which induce adverse health effects. Polymer pyrolysis (Py) hyphenated with mass spectrometry (MS) allows the investigation of polymer thermal degradation over time/temperature. A diphenylmethanediisocyanate (MDI) polyurethane foam was analyzed with electron ionization (EI) and metastable atom bombardment (MAB) ionization at a pyrolysis temperature of 400 °C. The recently introduced MAB ionization source uses discrete energy stored in metastable atoms of gases to ionize the analytes. This characteristic allows modulation of the ionization energy by simply changing the ionization gas. The extensive fragmentation of molecular ions observed using EI 70 eV is not totally eliminated with EI 10 eV. However, only molecular ions are observed with MAB using N2 as the ionization gas. Temperature gradients were used to separate the products generated during the thermal degradation of a 1,6-hexamethylenediisocyanate (HDI) polyurethane paint. The analysis of mass spectra was facilitated owing to a selective desorption of pyrolysis products. Furthermore, changing the MAB ionization gas allows elucidation of the structure of the pyrolysis products by controlling the extent of their fragmentation. During these experiments, isocyanic acid, methyleneisocyanate, ethyleneisocyanate, propylisocyanate and butylisocyanate were detected.
Keywords:Metastable atom bombardment ionization  MAB  EI  Pyrolysis  Mass spectrometry  Polyurethane  Diphenylmethanediisocyanate  MDI  Hexamethylenediisocyanate  HDI  Acrylic polyol  Thermal degradation
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