Condensed Phase Chemistry of Explosives and Propellants at High Temperature: HMX, RDX and BAMO [and Discussion]

T. B. Brill, P. J. Brush, P. Gray, S. A. Kinloch


By studying the behaviour of a thin film of an explosive or propellant it is possible to produce a snapshot of the surface reaction zone that exists during combustion of such explosives as cyclotrimethylene trinitramine (RDX) and cyclotetramethylene tetranitramine (HMX). Rapid heating (2000 K s$^{-1}$) and fast monitoring of the mass and heat-balance are performed simultaneously with fast Fourier transform infrared spectroscopic analysis of gaseous products. Initially, HMX and RDX yield mainly N$_{2}$O at low temperatures or NO$_{2}$ at higher temperatures; the former is quickly followed by CH$_{2}$O and the latter by HCN: these species are formed from the primary residue. These concurrent pathways compensate for one another thermochemically to make this a roughly thermoneutral `initial' stage. Subsequently, a highly exothermic reaction between CH$_{2}$O and NO$_{2}$ leads to CO, NO and H$_{2}$O and constitutes the main source of heat for the condensed phase. The azide polymer bis(azedomethyl)oxetane has also been studied as a prototype of rather different behaviour. For it, ratios of gaseous products are not very dependent on temperature in the range 275 to 390 degrees C.

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