Explosive behavior of nitroguanidine

Abstract

In studying the explosive behavior of nitroguanidine, a high-bulk density (NQ-h) and a low-bulk density (NQ-1) form of this material were used. Determination of failure limits in the charge diameter-density (ϱ0) plane showed that both behave as a Group 1 explosive (critical diameter decreasing with ϱ0 increasing) at ϱ0<1.63 g/cc, but that NQ-h exhibits “dead-pressing” and, thus, behaves as a Group 2 explosive at higher densities. NQ-h has a large critical diameter, about three times that of NQ-l, in the range of their detonability. That aids in studying the subcritical region of NQ-h, where a strong shock produces a subdetonation, supersonic constant-velocity front. This pseudo-detonation (or LVD) has failure limits similar in trend to the detonability limits of Group 2 materials. Shock sensitivity tests show that NQ-l and NQ-h differ less in this property than in critical diameter. Both forms are much less shock sensitive than other common explosives; this is attributed to the relatively low ignitability of NQ. The trend of the failure curves combined with the power of the LVD reactions can explain (1) a hump in the shock sensitivity curve of NQ-h, and (2) a reversal in the apparent shock sensitivity rating of NQ-h and NQ-l when tested on large- and small-scale gap tests. It is suggested that the reversal in the trend of the detonability curve, the ability to support LVD, and the unusual shock sensitivity results are behaviors that might be exhibited by any explosive under appropriate experimental conditions. The observation of them in NQ-h is attributed to the fact that the appropriate conditions are much more accessible than those for other explosives.