Effect Of Humidity On Thermal Stability Of Red Pyrotechnic Composition

Fireworks gives off heat because of chemical reaction under certain humidityatmosphere, Thermal explosion accidents will happen when the heat accumulate to a certaindegree. Therefore, it is of vital importance investigating effect of ambient humidity on thethermal stability of red pyrotechnics. This paper studied thermal decomposition, kinetics,thermal stability and compatibility of red pyrotechnics in ambient humidity atmosphere.This paper obtained different thermal decomposition curves using five kinds of heatingrates and four kinds of ambient humidity by simultaneous TG-DSC. Non-isothermalthermal decomposition kinetic models of Kissinger method was used to study the kineticparameter. The critical temperature of thermal explosion and the acceleratingdecomposition temperature was calculated to evaluate the thermal stability of this redpyrotechnics. The results shows that thermal characteristic decomposition temperaturereduced with the increase of relative humidity, and the activation energy shows a firstdecrease and then increase trend. Meanwhile, The critical temperature of thermal explosionand the accelerating decomposition temperature both declined with the relative humidityincreasing. Therefore, thermal hazard increased under the promoting of ambient humidity.The influence of pre-wetting time on thermal safety of red pyrotechnics wasinvestigated by DSC method. The decomposition curves shows that the exothermic peaktemperature and peak temperature of DTG both decreased with the pre-wetting time longer.AKTS simulation method was used to get activation energy under different pre-wettingtime, and it consistent with calculated value, verifying the feasibility and certainty ofsimulation method. Meanwhile, the critical temperature of thermal runaway in24hours andself-accelerating temperature were calculated by the same method. The conclusion is thatthe possibility of accident happen is biggest when the relative humidity is60%andpre-wetting time is24hours. The corresponding thermal runaway temperature in24h andself-accelerating temperature were both smallest.The DSC tests were carried out after red pyrotechnics pre-wetted and owned certainmoisture content by constant temperature and humidity. The ambient relative humiditywhen testing was the same as the humidity pre-wetting. The stability and compatibility ofmoisture content red pyrotechnics were studied. The system stability was evaluated byextrapolation starting temperature of the heating rate tends to zero. The systemcompatibility was evaluated by quantity changes of decomposition peak temperature and rate of activation energy, separate system relative to the mixed system. The conclusion isthat the higher the water content, the worse the thermal stability is, and the level ofcompatibility became higher.