Thermal Decomposition of Energetic Materials. 3. Temporal Behaviors of the Rates of Formation of the Gaseous Pyrolysis Products from Condensed-Phase Decomposition of 1,3,5-Trinitrohexahydro-S-Triazine

Through the use of simultaneous thermogravimetry modulated beam mass spectrometry (STMBMS) measurements, time-of-flight (TOF) velocity-spectra analysis, and 2H, 13C, 15N, and 18O labeled analogues of 1,3,5- trinitrohexahydro-s-triazine (RDX), the thermal decomposition products of RDX have been identified as H2O, HCN, CO, CH2O, NO, N2O, NH2CHO, NO2, HONO, (CH3) NHCHO, oxy-s-triazine (OST), and 1nitroso-3,5-dinitrohexahydro-s-triazine (ONDNTA) and all of their gas formation rates have been measured as a function of time. From these results the primary reaction pathways that control the decomposition of RDX in both the solid and liquid phases have been discovered. Four primary reaction pathways control the decomposition of RDX in the liquid phase between 200 and 215 deg C. Two pathways are first-order reactions solely in RDX. One produces predominantly OST, NO, and H2O and accounts for approximately 30% of the decomposed RDX, and the other produces predominantly N2O and CH2O with smaller amounts of NO2, CO, and NH2CHO and accounts for 10% of the decomposed RDX. The third pathway consists of formation of ONDNTA by reaction between NO and RDX, followed by the decomposition of ONDNTA to predominantly CH2O and N2o. The fourth reaction pathway consists of decomposition of RDX through reaction with a catalyst that is formed from the decomposition products of previously decomposed RDX. ONDNTA is the only product that appears to be formed during the early stages of decomposition of RDX in the solid phase.