Low Energy Monopropellants Based on the Guanylurea Cation
Résumé
Reaction of cyanoguanidine (3) with hydrochloric, sulphuric, nitric or perchloric acids yielded guanylurea chloride (4), sulphate (5), nitrate (6) and perchlorate (7). 4 and 5 were reacted further to form a new family of energetic salts based on the guanylurea cation and azide (8a), 5-nitrotetrazolate (9), 5-aminotetrazolate (10), picrate (11) and 5,5´-azotetrazolate (12a) anions. The water of hydration in compounds 8a and 12a was eliminated by heating under vacuum yielding the anhydrous salts 8b and 12b. All materials were characterized by means of elemental analysis, mass spectrometry (MS) and vibrational (IR, Raman) and NMR (1H, 13C, 14/15N and 35Cl) spectroscopy. Additionally, the crystal structures of 4, 7, 8a and 10 were determined by low temperature X-ray measurements (4, 7 and 8a: Monoclinic, P21/c; 10: Monoclinic, P21). The thermal behavior of 6–12 was assessed by DSC measurements and their heats of formation was calculated on the basis of the electronic energies of the ions using the MP2 method. In addition, the sensitivity to shock, friction and electrostatic discharge of all materials was measured by submitting the compounds to standard (BAM) tests. The detonation pressures (P) and velocities (D) were calculated from the energies of formation using the EXPLO5 code (6: P = 17.4 GPa, D = 7004 m s–1; 8a: P = 20.6 GPa, D = 7880 m s–1; 8b: P = 16.9 GPa, D = 7289 m s–1; 9: P = 20.3 GPa, D = 7439 m s–1; 10: P = 18.4 GPa, D = 7530 m s–1; 11: P = 19.7 GPa, D = 7152 m s–1; 12a: P = 24.3 GPa, D = 8222 m s–1 and 7: P = 23.3 GPa, D = 8115 m s–1). Lastly, the long term stability of 12a was assessed and the ICT code was used to predict the decomposition gases. Most materials decompose giving large amount of environmentally friendly gases and their performance values classify them as new insensitive low-energy monopropellants.
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