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 degrees C and 170 degrees 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 E-a of 159.4 kJ mol(-1) and lnA of 34.74 s(-1) were obtained at the lag phase, whereas an average E-a 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 degrees 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 degrees 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.

Automated summary

The isothermal decomposition of N-guanylurea dinitramide (FOX-12) was studied, revealing a long lag phase and acceleration period. Kinetic parameters showed that the activation energy of the acceleration period was lower than that of the lag phase. Model-fitting results confirmed that FOX-12 decomposition at 120-160 degrees C follows a reaction order of n = 1/4. The estimated time for 0.1% extent of reaction at ambient temperature (25 degrees C) was about 9.8 years.