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

Abstract

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 0 at low temperatures or NO 2 at higher temperatures; the former is quickly followed by CH 2 0 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°C.