T-Jump/FT-IR Spectroscopy: A New Entry into the Rapid, Isothermal Pyrolysis Chemistry of Solids and Liquids

Abstract

The interface of a Pt filament pyrolysis control unit and a rapid-scan FT-IR spectrometer is described that enables the thermal decomposition of a thin film of material to be studied isothermally after heating at 2000°C/s. A model of the heat transfer of the Pt filament as a function of gas atmosphere and pressure is developed to help understand the instrument response. The control voltage of the Pt filament is highly sensitive to the thermochemistry of the thin film of sample. By simultaneously recording the control voltage and the rapid-scan IR spectra of the near-surface gas products, one learns considerable detail about chemical mechanisms relevant to combustion of a bulk material. The application of T-jump/FT-IR spectroscopy is illustrated with rapid thermolysis data for the energetic organoazide polymers azidomethyl-methyloxetane (AMMO), bis(azidomethyl)oxetane (BAMO), and glycidylazide polymer (GAP); the cyclic nitramine, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazacine (HMX); and the nitroaromatic 1,3,5-triamino-2,4,6-trinitrobenzene (TATB).