Influence of sample container volume on the thermal behavior of nitrocellulose/acid mixtures

摘要

Thermal stability of nitrocellulose (NC) has been reported to decrease in the presence of sulfuric acid and nitric acid [1]. In this study, we investigated the thermal behavior of NC containing acid solution (NC/nitric acid or NC/sulfuric acid) in sample containers of various volumes using differential scanning calorimetry (DSC) and a high sensitivity calorimeter (C80). The volume of the containers used in this study was 15, 50 and 100 uL for DSC and 1.2, 3.2 and 4.0 mL for C80 measurement. In the case of NC/sulfuric acid solution, the thermal stability, estimated by using the heat release temperature or the elapsed time before heat release, decreased with increasing container volume. This behavior indicated that in large-volume containers, the solvent water was more rapidly vaporized and sulfuric acid solution was more concentrated than that in other containers. The NC/nitric acid showed the highest destabilization when the medium sized containers (50 μL and 3.2 mL) were used. In a previous study [2], it was reported that gaseous nitric acid or NO_x derived from nitric acid promotes the decomposition of NC, whereas solution of nitric acid in liquid phase prevents it by absorbing the reaction heat. Therefore, it can be concluded that the behavior of the NC/nitric acid is perhaps caused by interaction between gaseous and liquid nitric acid that remain in the solution after heating.