Robust Model-Fitted Kinetics of the Thermal Decomposition of Nitroguanidine: Comprehensive Validation Across Diverse Conditions

Nitroguanidine (NQ), a critical energetic material used in both civilian and defense applications, requires rigorously validated kinetics to predict its thermal decomposition. Reliable predictions are essential for ensuring safety at every stage—from production to storage, handling, and use—while also maintaining performance integrity. However, existing kinetics remain largely unvalidated beyond their original calibration ranges. In this work, we derive the kinetics of the thermal decomposition of NQ by fitting a two-step model—comprising a reaction-order step and an autocatalytic step—to conversion data from thermogravimetric (TG) measurements in simultaneous TG/DSC (differential scanning calorimetry) experiments at heating rates of 5, 10, and 20 °C/min. The resulting kinetics accurately reproduce conversion profiles from additional TG/DSC experiments under both isothermal (210–230 °C) and dynamic (15–40 °C/min) conditions. Independent validation is performed via high-performance liquid chromatography (HPLC) on samples subjected to isothermal treatments (150–220 °C, 10 min–7 h), as well as on a separate sample exposed to a complex, time-varying temperature profile fluctuating between 30 and 210 °C over more than 5 h. The validated kinetics capture the pronounced acceleration in decomposition near an apparent threshold of 160 °C, in agreement with literature findings, and enable long-term stability predictions—such as a shelf life of approximately 40 years at 25 °C (for a limiting conversion of 0.1%)—that closely match those from the classical, but far more time- and resource-intensive, Berthelot method. The demonstrated consistency across diverse conditions underscores the robustness and practical applicability of the proposed kinetics, providing an extrapolation-ready tool for NQ and establishing a framework relevant to other energetic materials. • Kinetics of the thermal decomposition of nitroguanidine from TG/DSC measurements. • A two-step model—reaction-order and autocatalytic steps—fits conversion data. • Kinetic predictions reproduce additional isothermal and dynamic TG/DSC experiments. • Validation via HPLC confirms accuracy under isothermal and time-varying conditions. • Kinetics enable shelf-life predictions consistent with the Berthelot method.