Exploring the thermal behavior of nitrocellulose used for lacquers by slow heating experiments

This paper studied the spontaneous combustion risks of nitrocellulose used for lacquers by experimental and mathematical methods. The heat generation behavior and kinetic parameters of thermal decomposition of nitrocellulose in different nitrogen contents and of different masses were analyzed, by heating samples with a microcalorimeter at heating rates of 0.5 degrees C min(-1) and lower under both air and inert atmosphere. The effects of heating rate and atmosphere on thermal behavior were identified. The iso-conversional models were used to calculate the kinetics. A critical conversion rate of 0.2-0.3 was identified for nitrocellulose in different contents. When the conversion rate was lower than the critical value, the activation energy increased slightly. After reaching the critical value, the activation energy continued to decrease. The activation energy at the initial decomposition stage was derived by a simplified kinetic algorithm. Based on Semenov model and Frank-Kamenetskii model, the critical ignition temperature and self-accelerating decomposition temperature of nitrocellulose in standard 25 kg, 100 kg and 150 kg packages were derived and compared to typical energetic materials. Nitrocellulose with a higher nitrogen content or in a larger package size had lower apparent activation energy and SADT. Values of SADT could be easily reached with external heat sources, indicating the potential thermal risks of nitrocellulose stored in large sizes under slow heating conditions. [GRAPHICS]