Water induced thermal decomposition of pyrotechnic mixtures – Thermo kinetics and explosion pathway

• Fireworks tip mixture is susceptible to thermal decompositions at ambient conditions.
• Mixture has the potential to trigger accidents on iso-aging at ambient conditions.
• The thermal decomposition contributes to substantial rise in system pressure.
• In practice accidental conditions can be attained by thermal and mechanical stimulus.
• Thermo kinetic studies revealed that the mixture follows first order Arrhenius kinetics.

Pyrotechnic mixtures are susceptible to explosive decompositions. The aim of this paper is to generate thermal decomposition data for flowerpot tip, which is a mixture used in the tip of flowerpot fireworks for easy ignition. Several accidents were reported by using this mixture. The mixture is prepared by mixing barium nitrate, potassium nitrate, aluminum (666) and dextrin in a slurry manner with water. In the manufacturing process 40% water wt/wt is added to the mixture. The thermal characteristics of pure sample and water added sample were studied. Differential Scanning Calorimeter is used for screening tests and Accelerating Rate Calorimeter is used for detailed studies in adiabatic and isothermal mode. The self heat rate data obtained showed onset temperature for pure sample at 170.62 °C and the sample with water showed a much earlier onset at 95.71 °C in adiabatic mode. Also it gets decomposes even at 40 °C and starts exothermic characteristics with a substantial rise in system pressure of 32 bar in isothermal mode. The heats of exothermic decomposition and Arrhenius kinetics were computed.