The thermal decomposition behavior of nitrocellulose (NC) and its mixtures with acid solutions (H2SO4 or HNO3) was studied in various sample containers having different internal volumes, using differential scanning calorimetry (DSC) and heat flow calorimetry (C80). The thermal stability of NC and its acid mixtures was evaluated from the decomposition temperature observed by DSC under controlled heating conditions, and the induction time before heat release measured by C80 under isothermal conditions. The thermal stability of NC alone remained unchanged, regardless of the sample container volume. In contrast, the thermal stability of the NC/H2SO4 decreased slightly with increasing container volume, suggesting that the solvent water in H2SO4 could be easily vaporized in a large-volume or open container and that the H2SO4 solution condensed to a greater extent in large containers than in smaller containers. NC/HNO3 was the most destabilized when an intermediate-volume container was used, although the DSC data were largely scattered even under the same conditions. Assuming that the HNO3 solution (liquid phase) stabilizes NC by absorbing the reaction heat and that the vaporized HNO3 shows high reactivity with NC, the sample is the most destabilized in a certain volume of the container by the balance between the concentration of gaseous HNO3 and the amount of remaining liquid, which is possibly reflected in the experimental results.
nitric acid ester, nitrocellulose, spontaneous ignition, DSC, heat flow calorimetry