Molecular Beam Sampling Mass Spectrometry of High Heating Rate Pyrolysis:Description of Data Acquisition System and Pyrolysis of HMX in a Polyurethane Binder.

摘要

The data acquisition capability of the time-of-flight mass spectrometer used with the molecular beam sampling system has been expanded. An oscilloscope intensity-modulated raster technique using negative film scanned by a microdensitometer provides simultaneous semi-quantitative time-resolved mass spectra of all masses up to 160 amu with time resolution down to 10 ms. A system of parallel sample/hold channels which follow predetermined masses with time resolution near that of the spectrometer cycle time has been assembled and shown to have good dynamic range, adequate mass resolution, and provide good reproducibility. This system has been used to study the products of low pressure pyrolysis of nitrocellulose and cyclotetramethylene tetranitramine/polyurethane binder. Using a carbon dioxide laser for heating the samples up to 5000 deg/s heating rate effects are clearly demonstrated for NC but are not observed for HMX/PU. Relative amounts of the major decomposition species observed for the HMX/PU were nitrous oxide, 100; nitrogen dioxide, 54; hydrogen cyanide, 42; formaldehyde, 39; and nitric oxide, 27. The large amounts of nitrogen dioxide is compatible with the breaking of the N-N bond as the first step of the thermal decomposition of HMX. (Author)