Investigations On Compatibility Mechanism And Desensitization Between Coating Materials And Novel High Explosives

The research on the application of novel high explosives(cyclopentamethylenetetramine(HMX),3,4-dinitrofurazanfuroxan(DNTF)and 2,4,6,8,10,12-Hexanitrohexaazaisowurtzitane(CL-20))in mixed explosives has become a hotspot.However,their wide application is limited due to their relative high mechanical sensitivity and shock wave sensitivity.Therefore,it is necessary to carry out the work on the sensitivity reduction of the three novel high explosives.A specific method to lower the sensitivity of the high explosives is its combination with coating materals(insensitive explosives and inert materials).However,such information is still limietd although the compatibility between the coating materials and high explosives is the primary step before the former can be further applied.The compatibility study between coated materials and high explosives is not only beneficial to the formulation design and optimization of mixed explosives,but also can be used to evaluate the potential risk in the process of its production,storage and transportation.For the desensitization by surface coating,insensitive explosives and inert materials were selected for potential coating materials in the present paper.Where,insensitive explosives include nitroguanidine(NQ),2,4,6-trinitrotoluene(TNT),2,4,6-triamino-1,3,5-trinitrobenzene(TATB),2,6-diamino-3,5-dinitropyridine-l-oxide(ANPyO),3-nitro-1,2,4-triazol-5-one(NTO)and 2,6-diamino-3,5-dinitropyrazine-l-oxide(LLM-105).Selected inert materials include fluororubber(F26),hydroxyl-terminated polybutadiene(HTPB),dinoctylsebacate(DOS)and wax.In the present paper,the compatibility of those coating materials with the high explosives was studied by the combination of experimental and theoretical analysis.Firstly,differential scanning calorimetry(DSC)that based on calorimetry,the vacuum stability test(VST)that based on gas production,and X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FTIR)that based on the structure characteristics of the material were carried out to investiga experimentally the compatibility for new high explosive/coating material binary mixtures.Then,molecular mechanicsimulations was used for the theoretical analysis of compatibilit from the intermolecular interaction level.The ab initio molecular dynamics was applied to investigate the initial reaction mechanism of typical immiscible systems.Finally,based on the study of compatibility,the influence of typical insensitive explosives on mechanical sensitivity of three kinds of high explosives was investigated.The main contents of this paper are as follows:For DSC studies of high explosive/insensitive explosive binary systems,HMX/NQ and HMX/TNT had an incompatible result,and the thermal stabilities of the two mixtures were significantly lower than that of the single component.HMX/LLM-105 showed a slightly incompatibility result,and HMX/TATB and HMX/ANPyO were regarded as compatible.HMX/TATB,HMX/LLM-105 and HMX/ANPyO mixtures were more thermal stable than HMX.DNTF was incompatible with ANPyO,while DNTF/NQ and DNTF/LLM-105 had partial compatibility,and DNTF was compatible with TNT and TATB.All the selected insensitive explosives could reduce the thermal stability of DNTF.CL-20/NQ and CL-20/TNT were considered as incompatible,and NQ and TNT could significantly reduce the thermal stability of CL-20.CL-20/TATB,CL-20/ANPyO CL-20/LLM-105 binary mixtures were considered as compatible with each other.TATB can enhance the thermal stability of CL-20 while ANPyO and LLM-105 had no significant effect on the thermal stability of CL-20.VST further confirmed that HMX was incompatible with NQ,and moderately reactive with ANPyO,and compatible with TNT,TATB and LLM-105.DNTF/NQ and DNTF/LLM-105 were incompatible,and DNTF was compatible with TNT,TATB and ANPyO.CL-20 was compatible with all selected insensitive explosives.Possible interaction was suspected for HMX/TATB,DNTF/TATB and CL-20/TATB,and interactions were confirmed for noval high explosives/other selected insensitive explosives mixtures from the XRD results.For HMX/NQ,HMX/LLM-105,HMX/ANPyO and DNTF/LLM-105 binary systems,interactions were suspected from the FTIR analysis.With respect to high explosive/inert material mixtures,the results of DSC showed that HMX was incompatible with HTPB.HMX/DOS and HMX/Wax binary mixtures were slightly compatible with each other,and HMX/F26 was compatible.F26 and DOS could enhance the thermal stability of HMX.DOS and Wax had no significant effect on the thermal stability of HMX while HTPB can reduce the thermal stability of HMX to some extent.F26 was compatible with DNTF and could increase the thennal stability of the latter.DNTF/DOS and DNTF/Wax were incompatible.DNTF is slightly compatible with HTPB,and HTPB could make the DNTF thennal decomposition process in advance substantially.HTPB,DOS and Wax could significantly reduce the thennal stability of DNTF.CL-20 was incompatible with HTPB and DOS.CL-20/Wax was slightly compatible.F26 didn't have significant effect on the thermal stability of CL-20,while other inert materials would significantly decrease the thermal stability of CL-20.VST results demonstrated that except for DNTF/HTPB,DNTF/DOS and DNTF/Wax,other high explosive/inert material mixtures were regarded as compatible.The reason that H radicals generated during the ecomposition process of HTPB,DOS and Wax promote DNTF thermal decomposition was considered to be the main reason for incompatibility binary systems DNTF/HTPB,DNTF/DOS and DNTF/Wax.In theory,the compatibility of the noval high explosives with the typical insensitive explosives-TNT was firstly studied by molecular dynamics simulation(MD)from the perspective of intermolecular interaction(binding energy).The study indicated that the MD results were consistent with the DSC analysis.Subsequently,MD was used to study the compatibility of the high explosives with the binder HTPB,plasticizers DOS and Wax,respectively.It was found that the MD results were in agreement with the VST results.The initial reaction mechanism of typical incompatible binary system DNTF/LLM-105 was explored by ab initio molecular dynamics(AIMD)simulation.The simulation results revealed that H radicals in the-NH2 group of LLM-105 molecule has strong activity,which would lead to N-O bond breaking for DNTF molecule,and then accelerate the decomposition process of DNTF,and even change its decomposition path.Finally,insensitive explosives and inert materials that were confirmed compatible with the high explosives by compatibility exploration were selected,and their effects on the mechanical sensitivity of high explosives were investigated experimentally.The results showed that LLM-105 can significantly reduce the mechanical sensitivity of HMX.TATB and LLM-105 can improve the safety of DNTF and CL-20 to a great degree,respectively.