Review on Promising Insensitive Energetic Materials
Central European Journal of Energetic Materials
During the last twenty years military explosives, and energetic materials in general, have changed significantly. Worldwide, research and development programs are active in developing promising insensitive HEMs with higher performance. This has been due to several factors, which include new operational requirements such as Insensitive Munitions (IM), but it is also due to the availability of new materials and to new assessment and modelling techniques. The present review focuses on the basic
... a and necessity for IM, and the conditions, technical requirements and tests for IM. The review also explains the various promising insensitive high explosives, their synthesis and formulation used in different propellants. The slow cook-off, fast cook-off, and bullet impact tests for munitions were well defined in the past as they had been performed as part of the WR-50  tests. There were however no documented tests or procedures for fragment impact, sympathetic detonation, and sensitivity to electromagnetic radiation. These were new requirements  . DOD-STD-2105 required tests on only two munitions per stimulus, i.e. two for slow cook-off, two for fast cook-off, etc. To minimize the costs and provide additional information for use in IM assessments, NAVSEAINST 8010.5 stated the following: in addition to the requirements of , new energetic materials will undergo testing in munition-size hardware such as described in [16, 17] . The following data are required: 1. Slow Cook-off − The requirement to test for a slow increase in the thermal environment such as a fire in an adjacent magazine, store or vehicle. These types of incidents require exposure to a gradually increasing thermal environment at a rate of 6 °K/h. 2. Fast Cook-off − The requirement to test for a fast heating hazard comes from the ignition of liquid fuel fires such as burning aircraft fuel on a flight deck or burning diesel fuel from a truck as a result of a transportation accident. These types of incidents thus require exposure of the test item configuration to heat fluxes generated within the incandescent flame envelope of a large liquid hydrocarbon fuel fire. 3. Sympathetic Detonation − The requirement for this test is to determine if a sympathetic reaction response results when a detonation of an adjacent munition occurs as a result of an accident or hostile event. 4. Multiple Bullet Impact − The requirement to test for bullet impact threat from small arms during terrorist or combat events. These events require the test item to be impacted by a three-round burst of 0.50 caliber AP projectiles. 5. Multiple Fragment Impact − The requirement to test comes from combat or terrorist events where bombs, artillery shells or IEDs are detonated. These types of events thus require the test item to be subjected to the effects of a high-velocity impact of a calibrated fragment representative of a bomb or artillery fragment. 6. Shaped Charge Jet Impact Testing − The requirement to test for a shaped charge jet threat comes from combat or terrorist events where rocket propelled grenades, land mines, airborne bomblets or guided weapons are deployed. These types of events thus require the test item to be subjected to a direct hit from a representative shaped charge jet. These tests will provide the reliable data necessary to assess the relative synthesis of nitrogen heterocycles. Thus, this compound is a potential candidate for LOVA (Low Vulnerability Ammunition)  . RDX is considerably cheaper than FOX-7, however increasing demand for low vulnerability explosives (LOVEX) for IMs  has led to the initiation of exhaustive applied research on high explosive formulations based on FOX-7, reported by many researchers to be a promising candidate. Lochert et al.  has reported that FOX-7 is significantly less sensitive than RDX, particularly to impact and friction stimuli and is compatible with TNT-based, melt-cast compositions. The velocity of detonation and detonation pressure of FOX-7 charges are marginally higher than those for RDX charges, the detonation pressure showing a 5% increase  . Wild and Teipel  have also reported that the performance of FOX-7 is better than that of TNT and close to those of nitramines, with relatively insensitive characteristics. A plastic bonded explosive (PBX) formulation of FOX-7 with a polyGlyn binder has been reported by Karlsson et al. . This formulation does not detonate up to a diameter of 25 mm in large-scale detonation and small-scale slow cook-off tests. The composition ignites at 220 °C on slow heating (3.3 °C/h) and burns without damage to the container  . A new formulation based on FOX-7 and HMX (called FOF-5), with the same theoretical performance as Composition B, has been developed by FOI Weapons and Protection Division, Swedish Defense Research Agency  . This composition has been tested with respect to its low sensitivity properties by applying fast heating, slow heating and bullet impact tests. The response of a FOF-5 loaded 40 mm gun munition (with an HNS II-based fuse) in the fast heating test was Type IV (deflagration), Type V/IV (fire/deflagration) in the slow heating test, and Type V (fire) in the bullet impact test. Composition B shows a detonation response in all of the above tests. The loading of FOX-7 in these formulations has been restricted to a maximum of 30% by weight in non-aluminized formulations and a maximum of 25% by weight in aluminized formulations. Melt cast formulations  based on FOX-7 and TNT showed that these formulations will find application as insensitive high explosive formulations for future applications in insensitive munitions. Guanylurea dinitramide (GUDN or FOX-12) Energetic dinitramides are interesting high energy materials for present and future demands  . N-Guanylurea dinitramide (GUDN or FOX-12) is a stable salt of dinitramidic acid, with good thermal stability and low water absorbency  . It does not respond to mechanical stimuli, which makes it an excellent component for many insensitive energetic material applications.