Study On Thermal Safety Of RDX Based Composite Explosive Based On Thermal Analysis Kinetics

Hexogen（RDX）is commonly used in mixed explosives,which is an important part of gun propellants and solid propellants.HMX is often doped with RDX to change its performances,but the interaction between RDX and HMX often changes the decomposition law of RDX,thus affecting the combustion performance of propellant.However,the complexity of the thermal decomposition process of RDX and RDX based composite explosive,and the coupling of heat absorption and exothermic of RDX and overlapping of two heat exothermic peaks of RDX based composite explosive.If the thermal decomposition curve is not decoupled,then the thermal analysis dynamics be made,which is not conducive to the prediction of the thermal stability of RDX based composite explosive.Therefore,it is necessary to decouple the thermal decomposition curve of these coupling substances,and accurately obtain the thermal behavior characteristics of these coupling substances in different thermal environments and the safety parameters such as the induction period of decomposition reaction,which is great significance to reveal the thermal decomposition mechanism and safety prediction of RDX based composite explosive.In this paper,the thermal decomposition characteristics of RDX and HMX were taken as the main line.Firstly,the linear temperature rise experiment of RDX was carried out by the microcalorimeter（C600）,and the thermal decomposition curve of RDX was obtained.The endothermic and exothermic curve was coupled.The kinetic calculation of the thermal decomposition curves of RDX were carried out by Kissinger,Ozawa and Friedman,and the kinetic parameters of thermal analysis in the coupled state were obtained.Under different heating rates,thermal decomposition tests were performed on RDX based composite explosive with different proportions（9:1,8:2,7:3,6:4,5:5）.The results showed that the thermal stability of RDX and HMX was good after mixing.The apparent activation energy,pre–exponential and other parameters were calculated by the above three kinetic methods.The thermal decomposition curves of RDX and RDX based composite explosive were decoupled by mathematical method,and the endothermic and exothermic peaks were obtained respectively.The results showed that with the increased of heating rate,the coupling degree of RDX thermal decomposition became smaller and smaller,which indicates that RDX is a melting decomposition material.As the proportion of HMX increased,the apparent activation energy of RDX in mixed samples gradually decreased.The correctness of decoupling was verified by dynamics,which showed that the decoupling result was correct.Through the kinetic parameters,to simulate the thermal decomposition reaction rate at different conversion rates,and the time to maximum rate under adiabatic conditions(TMR_ad)of RDX was solved by combining with the thermodynamic equilibrium equation,and the T_D2,T_D8,T_D24 and other parameters were calculated.At the same time,the self–accelerating decomposition temperature（SADT）was calculated.When the packaging quality was 5.0,15.0,25.0,50.0,100.0 kg respectively,the self–accelerating decomposition temperature was 115.0,109.0,107.0,104.0,100.0°C respectiely.With the increased of initial decomposition temperature,the reaction time of thermal runaway decreases rapidly and the risk increases further.Therefore,during the storage of the sample,it should be avoided to keep it in adiabatic environment or to accumulate large mass in order to prevent the formation of adiabatic environment and thermal accumulation in the interior.The self–accelerating decomposition temperature after decoupling should be taken as the key parameter to measure the thermal protection measures.With the increased of packaging quality,the self–accelerating decomposition temperature of sample was gradually reduced,and the risk was further increased.Therefore,to prevent accidents,it is necessary to control the initial temperature of sample and use small packaging as far as possible.