Ammonium perchlorate (AP) has applications in munitions, primarily as an oxidizer for solid rocket and missile propellants. It is also used as an air-bag inflator in the automotive industry, in fireworks, and as a component of agricultural fertilizers. Because of these uses and AP’s high solubility, chemical stability, and persistence, it has become widely distributed in surface water and groundwater systems particularly in the southwestern United States.

The objective of this SERDP Exploratory Development (SEED) project was to explore the chemical synthesis of possible replacements for AP as an oxidizer in tactical missile rocket motors. Researchers investigated the synthesis, sensitivities, thermal stability, binder compatibility, and decomposition pathways of these new high oxygen materials.

This project synthesized oxygen-rich trinitroethyl derivatives, which are high-oxygen compounds (oxidizers) but not necessarily high-nitrogen species (explosives). Full characterization of these alternatives included X-ray diffraction, multinuclear NMR spectroscopy, mass spectrometry, vibrational (IR and Raman) spectroscopy, elemental analysis, and differential scanning calorimetry. Sensitivities towards impact, friction, and electrostatic discharge were measured by BAM methods and a small-scale electrostatic discharge device. Heats of formations were computed by the atomization method (CBS-4M enthalpy based). With these values and the X-ray densities, several combustion and detonation parameters were calculated from pure and composited oxidizers.

2,2,2-trinitroethyl nitrocarbamate (TNC-NO₂) is quite stable with potential to be used as a high energetic oxidizer. The synthesis of TNC-NO₂ was carried out directly in nitro-sulfuric acid. The reaction leads to almost essential pure product. TNC-NO₂ crystallizes in the monoclinic space group P21/c with four formula units per unit cell and a density of 1.725 g cm^–3. The sensitivities towards impact, friction and electrostatic discharge of TNC-NO₂ are comparable to RDX. The compound melts at 109 °C, is stable up to 153 °C, and is compatible with fine aluminum powder. Long-term stability testing has yet to be performed. TNC-NO₂ was the most promising compound evaluated in this work, and it has been scaled up to 10 g for additional testing.

The results of this project provide the Department of Defense (DoD) an environmentally benign (chlorine- and perchlorate-free) oxidizer as a potential replacement for AP.  Alternative oxidizers that perform as well as or better than AP would not only reduce DoD’s environmental burden but also allow soldiers to continue to train as they fight, thus maintaining mission readiness.