Study On Thermal Risk Of Three Nitro Compounds

Energetic materials as special energy material with an important strategic position,are widely used in defense and civil industries.However,the thermal decomposition of such materials often has autocatalytic properties,which are easily triggered during storage and transportation and cause thermal runaway.Therefore,it is of great significance to study their thermal hazards in constrained condition and provide references for the safe operation.This paper selects three commonly used nitro compounds:Modified Nitroguanidine（M-NQ）,Triaminotrinitrobenzene（TATB）,and Diaminodinitroethylene（FOX-7）as research objects.Study thermal decomposition kinetics to obtain the corresponding thermal hazard reference index in constrained condition.Firstly,perform DSC test to obtain thermal decomposition characteristic and decomposition reaction types.Based on DSC data,use Friedman method and model fitting method to build kinetic models and solve parameters,respectively.Then carry out ARC test to obtain exothermic characteristics,and compare ARC data with model-based adiabatic prediction data.Finally,the thermal safety parameters are predicted based on the obtained kinetic model.DSC test shows that compared with raw material NQ,M-NQ has lower initial decomposition temperature and higher specific exotherm.The thermal decomposition of M-NQ,TATB,FOX-7 is mainly divided into two stages,of which both of the two-step thermal decomposition of M-NQ and FOX-7 have autocatalytic properties,while TATB has autocatalytic properties only in the second step.The activation energy of the M-NQ,TATB,and FOX-7 calculated from Friedman method fluctuated were in the ranges of 40k J/mol～109k J/mol,90k J/mol～208k J/mol,and203k J/mol～433k J/mol,respectively,indicating that the decomposition mechanism is complex.Based on model fitting method,the results shows that thermal decomposition of M-NQ and FOX-7 both conform to a two-step continuous autocatalytic reaction model,and the thermal decomposition of TATB can be descriped by a two-step parallel reaction kinetic model of"N order and autocatalysis".ARC test shows that their thermal decomposition processes under adiabatic conditions all generate a large amount of non-condensable gases and exhibit autocatalytic decomposition characteristics.Based on the comparison between the actual measured data of ARC and the adiabatic prediction data based on the kinetic model,it is found that the curves of the two are closer.The Thermal safety parameter prediction results show that under the same loading and packaging conditions:SADT_（M-NQ）<SADT_（FOX-7）<SADT_（TATB）.Their adiabatic induction periods under ideal adiabatic conditions by the effect of initial temperature,and T_{D24（M-NQ）}<T_{D24（FOX-7）}<T_{D24（TATB）}.Under the isothermal conditions that reach the same specified conversion rate:TCL_（M-NQ）<TCL_（TATB）<TCL_（FOX-7）.Overall,the thermal stability of TATB is best,while the thermal stability of modified NQ is worst.In summary,it should be protected from sunlight during storage and transportation,strictly control the storage and transportation temperature,also stored separately from flammable and flammable dangerous materials.