Condensed phase chemistry of explosives and propellants at high temperature: HMX, RDX and BAMO

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 N20 at low temperatures or NO2 at higher temperatures; the former is quickly followed by CH20 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 CH2O and NO2 leads to CO, NO and H2O 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°C.