Impact of temperature and humidity on the thermal decomposition behavior and the ignition characteristics of Si-based pyrotechnic delay composition

This study focuses on analyzing the degradation, ignition, and combustion behavior of a silicon (Si)-based pyrotechnic delay mixture. A comparative analysis is conducted between a fresh sample and one exposed to accelerated aging conditions at a constant temperature of 65 °C and 85% relative humidity for 120 days. The findings indicate that the average burning rate decreases by factors of 1.3 and 2.2 for the thermally aged and moisture-exposed samples, respectively. Furthermore, in comparison to the unaged composition, the total energy output is reduced by 38.5% and 66% for the thermally aged and moisture-affected samples, respectively. TG analysis shows that humidity and thermal aging act as catalysts, accelerating the decomposition reactions and reducing the decomposition onset temperature by approximately 1–4 °C. TGA/DTG analysis reveals a multiple-stage reaction process, including binder decomposition, oxidizer pre-decomposition, and combustion of the pyrotechnic composition. Thermal analysis, incorporating the peak deconvolution technique, identified sub-reactions occurring within the primary exothermic process, including #1 (Si and Pb3O4), and #2 (Si, Pb3O4, and BaCrO4). The activation energy (Ea) of the second combustion stage displays a slightly higher value for the aged samples compared to the fresh composition.