Isothermal decomposition and mechanism of N -guanylurea dinitramide

The isothermal decomposition of a new material with high energy, namely N-guanylurea dinitramide (FOX-12), was studied by a self-established isothermal decomposition gas metering device. The gas pressure versus time curves of the isothermal decomposition of FOX-12 were obtained at temperature intervals within 120 °C and 170 °C. An extremely long lag phase and acceleration period were found in the decomposition process of FOX-12. The kinetic parameters of FOX-12 were obtained by the Arrhenius equation and model-fitting method. Results of the two methods were consistent, and the activation energy of the acceleration period was smaller than that of the lag phase. With an average Ea of 159.4 kJ mol−1 and lnA of 34.74 s−1 were obtained at the lag phase, whereas an average Ea of 125.6 kJ mol−1 and lnA of 26.97 s−1 were noted at the acceleration period. The model-fitting method further proved that isothermal decomposition at 120–160 °C conformed to no. 28 corresponding to the reaction order n = 1/4, whether at the lag phase or acceleration period. The time required for decomposition was estimated to be 9.8 years when the extent of reaction reached 0.1% at ambient temperature (25 °C). The residual phase after FOX-12 decomposition was analyzed by Fourier transform infrared spectroscopy, and gases were analyzed by gas chromatography, and the possible decomposition process was proposed.