Novel Melt-cast Carrier Explosive Based On Flexible Side Chain Modification

Trinitrotoluene(TNT)is currently a widely used melt-cast carrier explosive,but it also has shortcomings such as low energy,easy oil penetration,high sensitivity,and high toxicity.In addition,2,4-dinitroanisole(DNAN),a low-sensitivity melt-cast carrier explosive that has been widely used in recent years,also has the problems of low energy and poor manufacturability.For these reasons,the design and synthesis of a new type of melt-cast carrier explosive has always been a research hotspot and an important direction in the field of energetic materials.In this paper,a series of new energetic compounds were synthesized and prepared by the design strategy of combining energetic framework and flexible side chains.Among them,the energetic compounds represented by ANQ-3 and MSR-5 have a suitable melting point range(90?100?),better energy level than TNT(detonation velocity>7500m·s^-1)and other characteristics,showing certain application potential in melt-cast carrier explosives.The main research content and results are as follows:(1)Using 3-nitro-2-methylisothiourea as a raw material,it was substituted with three-carbon alkylamines(n-propylamine,propargylamine and isopropylamine)to prepare propyl nitroguanidine(Pr NQ),propargyl nitroguanidine(Pra NQ),isopropyl nitroguanidine(IPr NQ)three nitroguanidine derivatives.The influence of different alkyl chains on the physical and chemical properties of nitroguanidine derivatives was studied in detail.Among the three compounds,Pra NQ has the highest oxygen balance(-101.4%)and the strongest hydrogen bond interaction in the crystal structure.It exhibits high density(1.53 g?cm^-3)and high melting point(179.1?).The highly active alkynyl moiety allows Pra NQ to exhibit the lowest decomposition temperature(198.1?).As isomers,Pr NQ and IPr NQ have the same oxygen balance(-120.6%),close density(1.35 g?cm^-3 and 1.34 g?cm^-3,respectively),decomposition temperature(242.6?and 250.6?,respectively)and detonation velocity(7164 m·s^-1 and 7063 m·s^-1,respectively),but their melting points are significantly different(101.5? and 156.1?,respectively),which is closely related to the different dimer con Fig.urations in their crystal structures.(2)Using 3-nitro-2-methylisothiourea as the raw material,the substitution reaction with alkylamines with energetic groups(nitrate ester,azide)was carried out to obtain four kinds of energetic alkyl chains modified nitroguanidine derivatives ANQ-1 to ANQ-4.Compared with Pr NQ,the introduction of energetic groups significantly increased the density(>1.45 g?cm^-3)and energy(detonation velocity>7700 m·s^-1)levels of the compound.Among them,ANQ-1has the highest density(1.67 g?cm^-3),and its detonation velocity is 8214 m·s^-1.However,the nitrate and azide groups also have an adverse effect on the thermal stability of the molecule,especially the nitrate substituted compounds ANQ-1 and ANQ-2,which have lower thermal decomposition temperatures(168.5?and 176.9?,respectively).The decomposition temperatures of azide-substituted ANQ-3 and ANQ-4 are 199.6?and 216.1?,respectively,and have suitable melting point ranges(97.6?and 111.7?,respectively),and can be candidates for melt-cast carrier explosives.Although the friction sensitivity of the four compounds is higher than 108?120 N,the impact sensitivity of ANQ-3 and ANQ-4 is lower,both greater than 20 J.(3)Using dinitropyrazine,dinitrobenzene,trinitrobenzene as the energetic parent structure,and aminoethyl nitrate as the energetic flexible side chain,synthesized six new energetic compounds MSR-1 to MSR-6.Among them,MSR-1 has the highest density of 1.80g?cm^-3due to the highest oxygen balance(-20.51%).The density of the other five compounds is not much different(1.66?1.71 g?cm^-3),which is related to the synergistic effect of its crystal stacking efficiency and oxygen balance.The melting points of MSR-5 and MSR-6 with 1-chloro-2,4,6-trinitrobenzene as the energetic skeleton are 90.5?and 104.8?,respectively,and the decomposition temperatures are 172.8?and 177.3?,respectively.The melting point is relatively low and there is a sufficient difference with the decomposition temperature(about 80?).The performance meets the requirements of melt-cast carrier explosives.The six compounds all have good detonation performance(detonation velocity>7400 m·s^-1),low impact sensitivity(all greater than 20 J),but the high friction sensitivity is 84?160 N.