Synthesis Of DAAF And Design Of DAAF-based PBX Explosives

With the increasingly harsh battlefield conditions and high-technology widely application in war,one of the key manifestations of the insensitive weapon warhead is the emergence of high-energy insensitive explosives.3,3'-diamino-4,4'-oxidized azofurazan?DAAF?is a furazan-type high-nitrogen energetic compound with positive standard enthalpy of formation(+443 KJ·mol^-1),high energy(8300 m·s^-1),low sensitivity(H₅₀>320cm?2.5kg)and good thermal stability?Melting point is 248°C?.In recent years,it has received much attention in the energetic materials field.This paper focuses on the synthesis process of DAAF,the acquisition of DAAF particles with different particle size distribution by recrystallization refinement method,and the PBX assembly and preparation of DAAF(D₅₀=300 nm)by water suspension coating method,The details are as follows:1.Using glyoxal solution and hydroxylamine hydrochloride as raw materials,3,4-diaminoglyoxime?DAG?was synthesized as an intermediate,and aminofurazan?DAF?was then synthesized in high temperature,high pressure and alkaline environment by DAG closing loop.Finally,the target product DAAF was synthesized with the new oxidant OXONE^TM,and the product was characterized by infrared analysis,elemental analysis,liquid phase analysis and other methods.Some improvements have been made in the synthesis process:?1?The reaction time was extended to 7 h,and the yield of DAG was increased from 65.2%to 81.3%.?2?Improved high pressure synthesis of DAF:when the volume of the solution in the reactor was increased 60%,the reaction temperature was164°C and the reaction pressure was 6 MPa,the yield of DAF reached a maximum of58.6%.?3?Na₂CO₃ was used instead of NaHCO₃,and the optimum molar ratio of the reactant was determined,n?DAF?:n?Na2CO3?:n(OXONE^TM)was 1:3:4,the yield of DAAF was up to 76.3%.2.To obtain DAAF particles of different scales,the particle size of DAAF was refined by dripping and recrystallization refinement.The morphology,crystalline form and thermal decomposition properties of the samples were characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?and differential scanning calorimetry?DSC?.The results indicated that the submicron DAAF with average particle size of 3?m,1?m and300nm was obtained.The activation energy of 300 nm DAAF was 29.26 kJ·mol^-1,which was lower than that of the raw material DAAF,and the thermal explosion critical temperature was reduced by 2.04°C.3.In order to replace PBXN-7 and PBXN-14,the theory detonation velocity of formulation should be more than 8100 m·s^-1.The results showed that:?1?The design of DAAF-based PBX was determined to be 95/5.?2?The PBX explosives were prepared by300 nm DAAF and three high polymer binders(Viton A,EVA and F₂₃₁₁)respectively using water suspension coating technology.The SEM image indicated that DAAF surface-coated with F₂₃₁₁311 was spherical,with smooth surface,good dispersion and best coating effect.?3?From DSC thermal analysis of DAAF based PBXs,DAAF/F₂₃₁₁311 has the best thermal stability,its average activation energy was 33.11 kJ·mol^-11 higher than that of raw material DAAF,and the thermal explosion critical temperature was increased by 1.99°C.?4?The DAAF/F₂₃₁₁311 compound was tested for cook-off characteristics,and the results showed that both fast cook-off and slow cook-off were in a burning grade,which was consistent with the burning characteristics of insensitive ammunition.?5?The impact sensitivity test of the DAAF/F₂₃₁₁311 composite showed that under the 2.5 kg drop hammer,the H₅₀0 was higher than100 cm,which indicated the sample was very insensitive to external impact.The friction sensitivity test was carried out,and the results showed that the friction sensitivity of the DAAF/F₂₃₁₁311 composite was 0%.