Thermal decomposition behavior of nitrocellulose in the presence of nitric acid solution

Abstract. Nitrocellulose (NC) is extensively used as a raw material in explosives, paints, and various industrial applications. However, it is susceptible to spontaneous decomposition even at room temperature, potentially leading to spontaneous ignition due to the accumulation of decomposition heat. In our previous studies, we conducted thermal analyses under constant-rate heating conditions using a Calvet-type calorimeter to examine the thermal decomposition behavior of NC in the presence of reactive substances such as oxygen, nitrogen dioxide, and nitric acid, which are known to accelerate decomposition. Among these substances, nitric acid exhibited the most significant effect, greatly enhancing the decomposition rate. Notably, NC mixed with nitric acid decomposed at a relatively low temperature (approximately 100 °C) with rapid heat release. In this study, we visually observed 2 g of NC mixed with nitric acid under isothermal conditions at 95 °C using a custom-made glass apparatus. Simultaneously, we monitored temperature changes with a K-type thermocouple. The observations revealed that NC emitted a brownish gas, likely NO2, followed by a sudden temperature increase in the sample after approximately 10 hours. The induction time prior to the heat release and the observed temperature profile were consistent with the estimated thermal behavior derived from differential kinetic analysis based on the thermal analysis.