The dependence of deflagration reaction properties on initiation method*

Deflagration reactions are very complicated; efforts to model temperature, pressure and chemistry are underway with the aim of simulating the reaction under a range of conditions. In the current study, deflagration of the explosive HMX was initiated using a BAM impact tester, as well as a Split Hopkinson pressure bar (SHPB), to investigate the dependence of reaction conditions on the initiation method. The BAM impact tester initiated reaction at 0.6 GPa, whereas the SHPB required a pressure of 1 GPa to initiate. Under higher pressure, SHPB deflagration had a lower reaction temperature of 2900 ± 200 K compared to 3900 ± 400 K in BAM impact, with optical spectroscopy also indicating the presence of more solid particles compared to the BAM impact. Use of a mass spectrometer showed the two reactions occupy different areas in products-temperature space; they have different ‘typical’ chemical pathways, or at least the same multiplicity of reactions in differing proportions. As such, deflagration cannot be considered to have the same chemistry across our experiments; the overall ‘ideal’ reaction, and therefore other properties such as temperature, are dependent on initiation method and the prevailing local environment.