Preparation Of ANTA-Based Lowest Eutectic Mixture And Its Melting Crystallization Kinetics

Higher standards for the overall performance of melt-cast liquid-phase carrier explosives are set forth by modern weapon charges.However,the currently used 2,4,6-trinitrotoluene（TNT）liquid-phase carrier explosive has drawbacks including a low energy level,significant pollution during manufacture,poor mechanical qualities,and easy cracking and shrinking during the casting process.New high-performance low-melting-point explosives must be developed in order to enhance the overall performance of melt-cast liquid carrier explosives.Despite reports of a few novel melt-cast liquid-phase carrier explosives,their potential uses are now constrained by these flaws.As a result,developing energetic eutectics has grown in importance as a means of supplying melt-cast carrier explosives to future fighting vehicles.In this paper,3-amino-2,4,6-trinitroanisole（ANTA）,N-methyl-2,4,6-trinitroa-nisole（TNA）and3,4-dinitropyrazole（DNP）were prepared by nucleophilic substitution hydrogen（VNS）amination reaction and nitration reaction with p-methoxybenzoic acid,2,4-dinitrochlorobenzene and 3-nitropyrazole as starting materials,and their thermal stability,detonation performance and mechanical sensitivity were studied.The aromatic polynitro compound ANTA with good thermal stability and higher density was selected as the substrate to construct binary energetic eutectics with TNA,DNP and 3,4-dinitrofurazanfuroxan（DNTF）.The microstructure,mechanical sensitivity,and energy properties of the three groups of eutectics were studied by XRD,FT-IR,mechanical sensitivity test,and detonation performance calculation.The effects of HMX,RDX and aluminum powder on the melting crystallization kinetics and thermal stability of eutectics were further studied.The main research contents are as follows:（1）Preparation,characterization and properties of ANTA,TNA,and DNP.Three aromatic nitro compounds ANTA,TNA and DNP were prepared by nitration reaction and VNS amination reaction,and their thermal stability,mechanical sensitivity and detonation properties were studied.The results show that the difference between the melting point and the decomposition temperature of ANTA,TNA,and DNP is greater than 100°C,the friction sensitivity is greater than 360 N,and the impact sensitivity is greater than 40 J,which has good thermal stability and safety performance.Although the detonation velocity and detonation pressure of ANTA and TNA are slightly higher than those of TNT,the melting points of ANTA and TNA are higher（128.63°C and 110.50°C）,so they are not suitable to replace TNT as melt-cast liquid carrier explosives alone.（2）Preparation,characterization,performance test and melting crystallization kinetics of the lowest eutectic mixture of ANTA/TNA.The T-x phase diagram of ANTA/TNA mixed system was obtained by DSC-phase diagram method.When the mass ratio was 40/60,the lowest eutectic mixture was formed,and the eutectic temperature was 83.02°C.FT-IR and XRD tests showed that the lowest eutectic mixture of ANTA/TNA did not produce new chemical bonds,and there was intermolecular force between ANTA and TNA,and the compatibility was good.The results of the mechanical sensitivity test and the calculation of detonation performance show that the density(1.68 g·cm^-3)and the detonation velocity(7178 m·s^-1)of the lowest eutectic mixture of ANTA/TNA are between the two raw materials,which are better than TNT,and have good detonation performance and safety performance.The study of thermal decomposition performance showed that the thermal stability of the lowest eutectic mixture of ANTA/TNA was better.After adding HMX and RDX,the decomposition peak temperature decreased by 48.08°C and 32.45°C,respectively.The melting crystallization kinetics study shows that the kinetic parameters E_a and lg A of the lowest eutectic mixture decrease with the increase of the heating rate.The melting process of the lowest eutectic mixture of ANTA/TNA before and after the addition of HMX and RDX conforms to the first-order reaction kinetics.The addition of HMX and RDX significantly reduces the undercooling of the lowest eutectic mixture.Before and after the addition of HMX and RDX,the crystal growth process of the lowest eutectic mixture is heterogeneous nucleation,and the crystallization mechanism is close to three-dimensional’nucleation and nuclear growth’.The functional groups contained in the two raw materials are beneficial to improve the thermal stability and energy level of the mixed system,and the comprehensive performance of the formed the lowest eutectic mixture is better than that of TNT,which can be used as a potential substitute for TNT.（3）Preparation,characterization,performance test and melting crystallization kinetics of the lowest eutectic mixture of ANTA/DNP.The mass ratio of the lowest eutectic mixture of ANTA/DNP obtained by DSC-phase diagram method is 30/70,and the eutectic temperature is69.44°C.The results of XRD and FT-IR showed that there was a molecular interaction between ANTA and DNP.The results of mechanical sensitivity test and detonation performance calculation show that the density of the lowest eutectic mixture of ANTA/DNP is 1.82 g·cm^-3,the detonation velocity is 7836 m·s^-1,the impact sensitivity is greater than 40J,and the friction sensitivity is greater than 360 N,which has good detonation performance and safety performance.The study of thermal decomposition performance shows that the addition of HMX and RDX makes the decomposition process of the mixed system more concentrated.The melting kinetics study shows that the melting process of the lowest eutectic mixture of ANTA/DNP before and after mixing with HMX and RDX conforms to the zero-order reaction kinetics,and the melting kinetic parameters E_a and lg A decrease with the increase of heating rate.Crystallization kinetic studies show that RDX can greatly reduce the undercooling of the lowest eutectic mixture,and crystal growth is a three-dimensional spherulite mode of heterogeneous nucleation.The lowest eutectic mixture of ANTA/DNP has good thermal stability because of the two raw materials.At the same time,the high content of DNP can improve the density and energy level of the mixed system and the compatibility with other high-energy compounds,so that its usability is improved.However,the freezing point of the lowest eutectic mixture of ANTA/DNP is low,and it is necessary to find suitable additives to inhibit the self-heating of the crystallization process.（4）Preparation,characterization,performance test,and melting crystallization kinetics of the lowest eutectic mixture of ANTA/DNTF.The mass ratio of the lowest eutectic mixture of ANTA/DNTF was 35/65 and the eutectic temperature was 84.31°C.The results of XRD and FT-IR show that there are intermolecular interactions between the raw materials of the lowest eutectic mixture.The results of the mechanical sensitivity test and the calculation of the detonation performance show that the density of the lowest eutectic mixture of ANTA/DNTF is 1.85 g·cm^-3,the detonation velocity is 8497 m·s^-1,the impact sensitivity is greater than 40J,and the friction sensitivity is equal to 168 N,which has good detonation performance and safety performance.The results of thermal decomposition test show that HMX and RDX have great influence on the decomposition process of the lowest eutectic mixture.The melting kinetics study shows that the melting process of the lowest eutectic mixture of ANTA/DNTF conforms to the zero-order reaction kinetics.The melting kinetic parameters E_a and lg A decrease with an increase in the heating rate.After the addition of HMX and RDX,the values of E_a and lg A of the lowest eutectic mixture in the melting process of the eutectics increase.The study of crystallization kinetics shows that the relationship between the crystallization process parameters and the cooling rate of the lowest eutectic mixture of ANTA/DNTF and its mixed system with HMX is not obvious within the test range.In the medium RDX,the nucleation and growth modes of the lowest eutectic mixture gradually diversified with the increase of the heating rate.In the lowest eutectic mixture of ANTA/DNTF,there is a complementary relationship between the two raw materials in safety performance and energy level.ANTA reduces the mechanical sensitivity of DNTF,while the presence of DNTF significantly improves the energy level of the lowest eutectic mixture.Therefore,the lowest eutectic mixture of ANTA/DNTF can be used as a potential TNT substitute.