| HMX has been widely used as a high-energy single-mass explosive with high comprehensive performance,but there are still many safety issues in its production,transportation and use.Therefore,it is necessary to carry out an in-depth study on its safety performance.This paper mainly studies the explosion characteristics and thermal decomposition process of HMX,analyzes the experimental results,and provides theoretical basis for evaluating its safety performance.Firstly,STA449F3 synchronous thermal analyzer,QMS403D mass spectrometer are used to test the thermal decomposition mechanism of HMX with a particle size of 35μm under different heating rate.The thermal decomposition curves are analyzed and the thermodynamic parameters are calculated according to the experimental data.The research achievements indicate that:（1）The thermal decomposition of HMX is a continuous process,and as the heating rate increases,the decomposition initiation temperature,peak temperature and decomposition termination temperature of HMX are all increase.The decomposition peak temperatures of HMX are 277.2°C,281.9°C,285.5°C,288.5°C,when the heating rate are 5°C/min,10°C/min,15°C/min,20°C/min.（2）When the heating rate is 10K/min,there is a endothermic peak at 194°C because of the process ofβ-HMX conversion toδ-HMX.The endothermic peak at 280.2°C is the melting process of HMX,285.7°C.The apparent exothermic peak is the process of thermal decomposition,and the temperature of the endothermic and exothermic peaks increases as the heating rate increases.（3）The HMX is a typical melt-decomposable substance.The decomposition process is a liquid-solid heterogeneous reaction process,it is also accompanied by the change of phase state,and the rate of decomposition is very fast.（4）Based on the DTG curve,the apparent activation energies obtained by the two methods are 306.8kJ/mol and 301.8kJ/mol,respectively,and the lgA measured by the Kissinger method is 28.9;based on the DSC curve,the apparent activation energy are 265.2kJ/mol and 261.1kJ/mol by the two methods respectively.The lgA measured by the Kissinger method is 24.8;based on the TG curve,the apparent activation energy and lgA values at different conversion rates are calculated with the Kissinger method,and the relationship graph of conversion rate is completed.The calculation results are consistent with the graph.（5）The breakage of the C-N bond is dominant in the early stage of decomposition of HMX predominates,and the final gas products of decomposition include CH2O,N2O,CO,CO2,H2O,and NO.Then,the MITTA minimum ignition temperature tester is used to test the lowest ignition temperature of the dust cloud,and the effect of dust particle size and dust concentration on the minimum ignition temperature is studied.The research achievements indicate that:（1）The dust particle size of HMX has a certain effect on the minimum ignition temperature.When the diffusion pressure is 0.3bar and the dust concentration of HMX is750g/m3,the minimum ignition temperatures for dust particles with D50 of 15μm,35μm,and 60μm are 310°C,330°C,and 360°C,respectively.Thus it is concluded when the diffusion pressure and the dust concentration of HMX are constant,the lowest ignition temperature increases with the increase of the dust particle size.（2）When the diffusion pressure is 0.3bar,the current dust particle size D50 of HMX is35μm,and the concentrations are 450g/m3,600g/m3,750g/m3,900g/m3,1050g/m3,1200g/m3,1350g/m3,the minimum ignition temperatures of the dust cloud are 370°C,340°C,330°C,320°C,315°C,310°C,310°C,respectively.When the diffusion pressure and the particle size of HMX are constant,the minimum ignition temperature decreases with the increase of the concentration,and the rate of change decreases.。Finally,the 20L spherical device is used to study the lower explosion limit of the HMX dust cloud with a particle size of 35μm,the research achievements indicate the lower explosion limit of HMX is 60g/m370g/m3. |
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