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Stuctural transformations of 1,1‐diamino‐2,2‐dinitroethene (FOX‐7) were investigated in the temperature range 298–513 K by means of DSC, TG, isothermal calorimetry, PXRD, IR spectroscopy, and electron microscopy. The data obtained confirm the existence of the high‐temperature δ‐FOX‐7 polymorph stable above 480 K. The heat effect of the γ→δ transformation is − 4.6 J g−1 (−680 J mol−1). Metastable γ‐phase formed in the reverse process δ→γ has a perfect crystal structure and is stable towards thermal decomposition. Possible mechanisms of sharp deceleration of thermal decomposition of FOX‐7 at the 40 % conversion are discussed.

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Kinetic regularities of thermal decomposition of dinitramide in aqueous and sulfuric acid solutions were studied in a wide temperature range. The rate of the thermal decomposition of dhaitramide was established to be determined by the rates of decomposition of d~Xferent forms of dinitramide as the acidity of the medium increases: first, N(NO2)-anions, then HN(NO2)2 molecules, and finally, protonated H2N(NO2)2 + cations. The temperature dependences of the rate constants of the decomposition of N(NO2)-(kan) and HN(NO2) 2 (k'ac) and the equilibrium constant of dissociation of HN(NO2)2 (Ka) were determined: knn = 1.7" 1017 exp(-20.5-103/73, s -l, k'ae = 7.9" 1016 exp(-16.1 9 103/73, s -1, and Xa = 1.4" t0 exp(-2.6-103/73. The temperature dependences of the decomposition rate constant of H2N(NO2)2 § (kd) and the equilibrium constant of the dissociation of H2N(NO2)2 + (Ka) were estimated: k s = 1012 exp(-7.9-103/73, s -1 and K a = 1.I exp(6.4-103/7). The kinetic and thermodynamic constants obtained make it possible to calculate the decomposition rate of dinitramide solutions in a wide range of temperatures and acidities of the medium.

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