High-temperature interaction mechanisms of typical igniting pyrotechnics with cellulose as the packing material

Abstract

In order to study the effect of cellulose shell on the thermal behavior including pyrolysis gaseous products, ignition and combustion characteristics of typical pyrotechnics, three composites of pyrotechnics/cellulose were prepared in this paper. Various characterization techniques were used to investigate the prepared composites and their combustion condensed products (CCPs), including scanning electron microscopy (SEM), simultaneous thermal analysis (DSC-TG-FTIR), X-ray diffraction (XRD), bomb calorimetry, and home-made combustion diagnostic system. The results showed that the overall heat release of the black powder and Mg/PTFE decreased from 3108 J·g−1 and 1157.4 J·g−1 to 1045.4 J·g−1 and 810.4 J·g−1 in the presence of 33.3% cellulose, respectively. Moreover, the FTIR spectra showed that the cellulose did not change the reaction pathways of black powder and Mg/PTFE, which mainly include H2O, CO2, NO2 for the black powder, and HF, H2O, CO2, CF2 for Mg/PTFE. However, the condensed products of cellulose would interact with B/KNO3 at a higher temperature, so that the heat release was largely increased by 339%. The cellulose has obviously impact on the energy release rate of Mg/PTFE in comparison to the other two composites. Moreover, the negative impact on ignition of Mg/PTFE composite is significant, when the content of cellulose reaches over 33.3%, resulting in difficult self-sustainable combustion at ambient pressure. The cellulose can largely reduce the maximum flame temperature of the black powder and Mg/PTFE, whereas it has little effect on B/KNO3. The CCPs of the involved igniting pyrotechnics and their cellulose-based composites have different phases due to their strong thermal interactions with cellulose.