Composition B (Comp-B) is a melt-castable explosive formulation incorporating TriNitroToluene (TNT) and 1,3,5-trinitro-1,3,5,7-triazacyclooctane (RDX). Both of these components have undesirable environmental impacts from production and use. The desired outcome of this work was the selection of an explosive material to replace Comp-B that would preserve the beneficial attributes of that explosive without the negative environmental ramifications.

This project combined synthesis of energetic materials, thermal testing, sensitivity testing, melt casting, and performance testing. Due to the large number of candidate energetic ingredients, the only practical path forward was to begin with compatibility testing at small scale, down-select for sensitivity testing, and then further down-select for performance testing. Thermal stability of mixtures was initially measured using Differential Scanning Calorimetry (DSC) or Thermogravimetric Analysis (TGA), however in the interest of conserving time and money a simple optical melting point apparatus was employed. Sensitivity testing at Los Alamos National Laboratory (LANL) involves type 12B drop hammer, aluminum magnesium boride (BAM) friction testing, and Electrostatic Discharge (ESD) testing. Army Development, Research and Engineering Center, Picatinny NJ (ARDEC) additionally performed gap testing on selected materials. Performance measurements focused on detonation velocity, critical diameter, and detonation pressure.

During this project, the researchers investigated a number of energetic materials both old and new and determined that most of them were unsuitable due to safety or sensitivity reasons. Unsuccessful coformulants include 1,3,3-Trinitroazetadine (TNAZ) and Bis(NitroFurazanyl)Furoxan (BNFF) for volatility reasons, and Diaminoazoxyfurazan (DAAF) due to thermal compatibility issues. The powerful explosive 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) became a focus of the work in later stages as it conferred excellent power while being commonly available in well-regulated particle size lots and is chemically compatible in the melt with many coformulants. Ultimately three preferred formulations emerged from this work: a formulation tested on large scale by ARDEC involving N-propyl-N’-nitroguanidine (PrNQ) and HMX; a formulation tested at ARDEC and LANL using a nitrate salt eutectic and HMX; a formulation tested at LANL using 3-(4-nitro-1,2,5-oxadiazol-3-yl)-1,2,4-oxadiazol-5-amine (LLM-201) and HMX.

Several candidate materials were identified by this project, however cost to produce is a significant barrier. Holston Army Ammunition Plant (HSAAP) manufactures approximately 9 million pounds of RDX per year compared to only 1 million pounds of HMX at roughly twice the cost per pound. Switching from RDX to HMX would benefit the environment and performance of the munition but at cost and with a limit to scale. The explosive formulations manufactured on the highest scale are actually mining explosives such as ammonium nitrate based blasting media and these do not have adequate power for military use. Existing military production capacity in the United States is insufficient, with contracts going to Polish producers of TNT, and the variety of High Explosive (HE) available from Continental United States (CONUS) sources places a sever limitation on the production of new formulations.