Low-temperature pyrolysis products from a polyether-based urethane

The pyrolysis products from a polyether-based polyurethane were analyzed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), direct probe chemical ionization mass spectrometry (CI-MS), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Pyrolysis of the urethane was found to ensue about 250degreesC in inert atmosphere. The initial degradation products (similar to250-275degreesC) may be explained by three decomposition pathways. Dissociation to isocyanate and alcohol yields as pyrolyzates diphenylmethane diisocyanate, an 'amine-isocyanate', 1,4-butanediol, and hydroxyl-terminated polyurethane and polyether oligomers. Dissociation to amine, olefin, and carbon dioxide is less prevalent initially; this produces an amine-isocyanate, methylene dianiline, and butenyl-terminated polyurethane and polyether oligomers. 'Intramolecular exchange' produces cyclic urethane oligomers. At about 300degreesC, more oligomeric pyrolyzates are observed with aromatic amine and/or buteryl end groups. These indicate that contributions from dissociation to amine, olefin, and carbon dioxide increase with increasing degradation temperature. Also at about 300degreesC, some oligomeric pyrolyzates are observed that have alkyl and/or aldehyde end groups. These are formed via free radical processes. By 325degreesC, all nitrogen-containing oligomeric pyrolyzates have decomposed. The remaining nitrogen is in the form of methylene dianiline (MDA) or methylated MDA. (C) 2002 Elsevier Science B.V. All rights reserved.