Development of Green Energetic Oxidizers for Solid Propellant Applications: Present Status

The quest for new high‐energy materials (HEMs) with superior performance properties compared to conventional HEMs has opened up a new area of research and has resulted in the synthesis of many novel molecules. The challenge is to balance superior performance with stability while adopting an environmentally benign approach during synthesis, use, and disposal. This multipoint challenge has united theoretical, experimental, and applied researchers toward achieving this goal. Oxidizers are HEMs that possess stoichiometric excess of oxygen, which is used to oxidize the binder‐fuel and solid fuel additives in solid propellants. Ammonium perchlorate (AP), a commonly used oxidizer in solid propellants, needs replacement due to environmental and performance concerns. The demand for new “green energetic oxidizers” has led to the synthesis of dinitramide and trinitromethane salts, polynitroazoles, and strained‐ring compounds. Some of these compounds can be effectively used as energetic fillers to improve the overall performance of the solid propellants. This review assesses AP and ammonium nitrate in propellant applications and the performance challenges associated with the use of ammonium dinitramide (ADN), hydrazinium nitroformate, trinitroazetidine, and hexanitrohexaazaisowurtzitane (CL‐20) in propellant formulations. The synthetic feasibility of these new oxidizers, their decomposition behaviour, performance, compatibility in propellant formulations, and ways to overcome these difficulties are discussed. Evaluation of the theoretical performance of these molecules indicated that the ADN − Glycidyl azide polymer is a promising combination. However, ADN is highly hygroscopic, and an anti‐hygroscopic strategy needs to be developed. Finally, this review examines the possible identification of practical oxidizers for application purposes.