Process development, friction insensitivity improvement and compatibility studies of tetranitroacetimidic acid

Herein, nitration of 1,1-diamino-2,2-dinitroethene (FOX-7) using concentrated nitric acid was studied in detail to establish a process for the preparation of tetranitroacetimidic acid (TNAA), an environmentally benign oxidizer. Nitration has also been studied in the presence of various solvents that facilitate liquid–liquid reactions. The products have been characterized by thermal and spectroscopic techniques. The process was kinetically evaluated, and a second order rate with respect to the concentration of FOX-7 was observed. Friction insensitivity of TNAA improved to 196 N by altering the particle size and shape after precipitation in various alkanes. The improvement of the TNAA crystal shape was observed via a scanning electron microscope (SEM). Brunauer–Emmett–Teller (BET) analysis indicates sub-micron particle size and large surface area of TNAA. Compatibility of TNAA with composite propellant ingredients, mainly toluene diisocyanate (TDI) and hydroxyl-terminated polybutadiene (HTPB), was assessed by monitoring the Fourier transform infrared spectroscopy (FTIR) spectra. Thermogravimetric analysis (TGA) of TNAA with ammonium perchlorate was also studied to observe the decomposition pattern in view of partial replacement of ammonium perchlorate in propellant formulations. Overall, this study has revealed the process development outcomes, methodology of improving the friction insensitivity of TNAA, and applicability of TNAA in composite propellant formulations.