In order to investigate the influence of the type of sample container on the thermal behavior of nitrocellulose (NC) mixed with an acid solution (H2SO4, HNO3, or HCl), differential scanning calorimetry and heat flux calorimetry were carried out for NC/acid mixtures in sealed and open containers. The results revealed no significant difference in the thermal behavior of NC/HCl under the sealed and open conditions ; the stability (evaluated from the decomposition temperature under controlled ramp heating conditions and the induction time to exothermic decomposition under isothermal conditions) of this system was the same as that of NC alone. In contrast, the thermal behavior of the NC/H2SO4 and NC/HNO3 mixtures varied depending on the conditions used. Specifically, the thermal stability of NC/H2SO4 was lower in the open system than in the sealed system, whereas NC/HNO3 showed the opposite behavior. The phenomenon observed in NC/H2SO4 is thought to be attributed to an increase in the concentration of H2SO4 under open conditions due to evaporation of the solvent (water) from the H2SO4 solution and the low volatility of H2SO4. In contrast, in the case of more volatile HNO3, it was suggested that water and HNO3 both evaporated to the outside of the system upon heating in an open container, which led to high stability under open conditions. These results may also indicate that the thermal decomposition of NC/HNO3 under the sealed conditions was caused by the reaction between NC and gaseous HNO3.
nitrocellulose, nitric acid ester, spontaneous ignition, thermal stability, calorimetry