The Formation of Colored Impurities in Triaminoguanidine Nitrate and Related Incompatibility Problems in Gun Propellants

摘要

A mechanism has been proposed for the formation of colored impurities in triaminoguanidine nitrate. It is suggested that the rate determining step for color formation is the production of the free base, triaminoguanidine, from triaminoguanidine nitrate. The multitude of colored impurities arise either from the metal ion induced oxidation or the aerial oxidation of triaminoguanidine or subsequent reactions of these oxidation products. The aerial oxidation processes are enhanced in the presence of bases. The aerial oxidation process is also strongly catalyzed by metal ions. It is recommended that purification and storage of triaminoguanidine nitrate is best carried out in acidified water in non-metallic apparatus. The optimum conditions for the synthesis of triaminoguanidine nitrate, such that the production of colored impurities is minimized, would appear to involve an aqueous medium kept free of metal ions, minimal alkaline conditions and the absence of atmospheric oxygen. Propellants containing contaminated triaminoguanidine can undergo various color changes during manufacture which may cause porosity in the propellant, leading to enhanced and erratic burning rates. Strategies to minimize introduction of impurities which may cause incompatibility problems during the formulation of propellant are discussed.