Study on the spontaneous ignition mechanism of nitric esters (III)

The spontaneous ignition mechanism of three types of smokeless powders such as cellulose nitrate/potassium sulfate (SB), cellulose nitrate/glycerin trinitrate/potassium sulfate (DB), and cellulose nitrate/glycerin trinitrate/nitroguanidine/potassium sulfate (TB) were analyzed in terms of the thermal behavior and the pressure change during the isothermal storage at 393 K in various gases. The heat release of SB and DB was suppressed in the atmosphere without O2 and even in 4.5 vol.% NO2/N2. However, in 4.7 vol.% NO2/air, the exothermic reaction was accelerated compared to that in dry air. In addition, the total pressure decreased during the storage in the presence of O2. This nature of the behavior of SB and DB indicated that autoxidation, which was propagation with O2 and radical species derived from NC, was involved in the exothermic reaction. And, NO2 contributed not to the autoxidation but to the initiation process before the autoxidation occurred. On the other hand, the exothermic reaction of TB might be different from that of SB and DB because TB released the reaction heat in no O2 atmosphere such as 4.5 vol.% NO2/N2. TB would react with NO2 without O2 and release the reaction heat when NO2 was excessively present in the system. This specific nature would be due to the presence of 50 wt.% of nitroguanidine which was not nitric ester.