Environmentally compatible next generation green energetic materials (GEMs).

A novel energetic cocrystal predicted to exhibit greater power and similar sensitivity to that of the current military standard explosive 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) is presented. The cocrystal consists of a 2:1 molar ratio of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), a powerful explosive too sensitive for military use, and HMX. A predicted detonation velocity 100 m/s higher than that of β-HMX, the most powerful pure form of HMX, was calculated for the cocrystal using Cheetah 6.0. In small-scale impact drop tests the cocrystal exhibits sensitivity indistinguishable from that of β-HMX. This surprisingly low sensitivity is hypothesized to be due to an increased degree of hydrogen bonding observed in the cocrystal structure relative to the crystals of pure HMX and CL-20. Such bonding is prevalent in this and other energetic cocrystals and may be an important consideration in the design of future materials. By being more powerful and safe to handle, the cocrys...

High Power Explosive with Good Sensitivity: A 2:1 Cocrystal of CL-20:HMX

Recent advances in new oxidizers for solid rocket propulsion

Enhanced performance of propellants and explosives is the most sought-after attribute for ambitious research programs in the field of high energy materials. Convergence of defence and space sector priorities has always kept research and development efforts in the area of propellants to the forefront. With the diminishing boundaries between rocket and gun propellants, as well as explosives, the possibility of low-vulnerable munitions with high performance potentials and spin-off advantages of research on rocket propellants are also emerging on the forefront. At the same time, an increasing predominance of missiles in today’s military warfare, as well as the space sector, has brought the issue of pollution by chlorine-containing combustion products of modern ammonium-perchlorate-based propellants into focus. A drastic transformation of high energy material technology is in offing. Research and development efforts made in this direction have brought an array of new materials into prominence. This paper reviews the recent work done in the frontier areas of advanced novel high energy materials. This paper covers the global scenario in the development of oxidizers, binders, plasticizers, high energy density materials, and insensitive high energy materials.

Emerging trends in advanced high energy materials

Two energetic compounds, [Pb(Htztr)2(H2O)]n (1) and [Pb(H2tztr)(O)]n (2), were synthesized and then structurally characterized (N% = 39.4% for 1, N% = 27.2% for 2), where Htztr represents 3-(tetrazol-5-yl)triazole. Structural analysis revealed that both compounds have reticular two-dimensional structures. Remarkably, thermogravimetric measurements demonstrated that the compounds possess excellent thermostabilities with high decomposition temperatures up to 340 °C for (1) and 318 °C for (2). The kinetic parameters of exothermic processes were studied by the Kissinger's and Ozawa–Doyle's methods. The standard molar enthalpies of formation were obtained from the determination of constant-volume combustion energies. The calculated detonation properties showed that compound (1) can be used as a potential explosive. Sensitivity tests revealed that the compounds are extremely insensitive. In addition, two compounds were examined for use as additives to promote the thermal decomposition of ammonium perchlorate and hexahydro-1,3,5-trinitro-1,3,5-triazine.

High-energy-density materials with remarkable thermostability and insensitivity: syntheses, structures and physicochemical properties of Pb(II) compounds with 3-(tetrazol-5-yl) triazole

This study was undertaken to see the effect of the replacement of picrite by 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) (5, 10, and 15%) in triple-base gun propellants. Experimental results of a closed-vessel test at a loading density of 0.2 g/cm 3 indicate improvement in energetics of the CL-20-incorporated compositions. The force-constant values obtained were 1046, 1071, and 1095 J/g for 5, 10, and 15% CL-20-based formulations, compared with 1028 J/g for conventional picrite composition as the control. Similar trends were observed for linear burning-rate coefficient β 1 values. The selected energetic plasticizers N-(n-butyl)-N-(2-nitroxyethyl) nitramine (Bu-NENA) and bis-2,2 dinitro propyl formal/acetal (BDNPF/A) were also evaluated for their effectiveness in CL-20-containing gun-propellant compositions. Thermal analysis was carried out using differential scanning calorimeter and thermogravimetric analyzer. Replacement of picrite by CL-20 resulted in an increase in AH values (by differential scanning calorimeter) compared with that of control composition. Weight-loss data (from thermogravimetric analyzer) showed a similar trend. The CL-20-based compositions were found relatively more sensitive to friction stimuli (12-17 kg) compared with control composition (19.2 kg).

Closed-Vessel and Thermal Studies on Triple-Base Gun Propellants Containing CL-20

Studies on thermal stability, autoignition and stabilizer depletion for shelf life of CMDB propellants

Studies on Advanced CL-20-Based Composite Modified Double-Base Propellants

Tetrakis-(4-Amino-1,2,4-Triazole) Copper Perchlorate: A Novel Ballistic Modifier for Composite Propellants

This paper reports the effect of replacement of non -energetic plasticizer diethyl phthalate (DEP) by nitroplasticizer [1:1 mixture of bis (2,2 dinitro propyl) formal (BDNPF) and bis (2,2 dinitro propyl) acetal (BDNPA)] on burning rates and Isp of nitramine (RDX) / ammonium perchlorate (AP) based composite modified double base (CMDB) propellants. Addition of BDNPF/A led to overall 9–46% increase in burning rates, as well as gain in Isp to the order of 5–10 s in both the systems. Inclusion of copper chromite (C.C.) led to further improvement in burning rates. A typical aluminized (17.5%)- ecofriendly RDX (12.5%)-CMDB formulation gave burning rates of the order of 8–22 mm/s in the pressure range of 2.9–10.8 MPa with Isp (theoretical) of 264 s. Aluminized AP-CMDB propellant with low pressure combustion limit of 1.9 MPa and burning rates of 15–31 mm/s was also realized during this work. Superior oxygen balance and heat of formation of BDNPF/A compared to DEP appear to play contributory role in this r...

C. N. Divekar

Papers

Closed-Vessel and Thermal Studies on Triple-Base Gun Propellants Containing CL-20

Studies on thermal stability, autoignition and stabilizer depletion for shelf life of CMDB propellants

Studies on Advanced CL-20-Based Composite Modified Double-Base Propellants

Tetrakis-(4-Amino-1,2,4-Triazole) Copper Perchlorate: A Novel Ballistic Modifier for Composite Propellants

Studies on effect of incorporation of BDNPF/A on burning rates of RDX/AP/AI filled CMDB propellants