Preparation Of DAAF-based Microspheres By Droplet Microfluidics And Its Performance Study

3,3′-Diamino-4,4′-azafurazan（DAAF）,as one of the representatives of the furozan group of energetic compounds,has the properties of high energy,low sensitivity,good thermal stability and environmental friendly synthesis process.In this paper,DAAF-based microspheres with regular shape and narrow particle size distribution were prepared using droplet microfluidics.And the performance of the samples was analyzed and characterized.The main contents are as follows:1.Preparation of DAAF/F2602 energetic microspheres by droplet microfluidics.Using droplet microfluidics,DAAF/F2602 energetic microspheres were successfully prepared by a fluid-focused microchannel device using an aqueous solution with an active agent concentration of 0.5%as the continuous phase and an ethyl acetate solution of DAAF as the dispersed phase.The effects of the flow rate ratio of continuous phase to dispersed phase,the concentration of dispersed phase and the active agent on the morphology,particle size and roundness of DAAF microspheres were investigated,and the optimal process conditions were derived.The particle size of DAAF/F2602 microspheres was reduced from 121～356μm to20.22～53.85μm and the particle size distribution was more uniform compared with the samples prepared by water suspension process.The results of X-ray diffraction analysis showed that the crystalline shape of DAAF was not changed after the cladding was performed in two ways.The DSC data showed that the peak temperature of the sample prepared by droplet microfluidics was delayed by 6.45°C and the activation energy increased by 6.12k J·mol^-1than that of the sample prepared by water suspension method,indicating that the fluoroelastomer could uniformly coat the surface of DAAF explosives to form a good coating by droplet microfluidics.The mechanical susceptibility test results show that the impact susceptibility of both samples is greater than 100J,and the friction susceptibility Greater than360N,indicating that their safety performance is good.Meanwhile,the resting angle of the samples prepared by droplet microfluidics was reduced by 10°and 6°compared with those prepared by submicron DAAF and water suspension processes,respectively,indicating that the microspheres prepared by droplet microfluidics have better flow dispersion.This study demonstrates the feasibility of liquid droplet microfluidics for the preparation of explosive microspheres with narrow particle size distribution.2.The DAAF/composite binder energetic microspheres were prepared by droplet microfluidics.To improve the disadvantages of poorly formed microspheres and agglomeration caused by single binder NC and GAP.The effects of different ratios of composite binders on the morphology and particle size distribution of DAAF microspheres were investigated.DAAF microspheres with uniform particle size were prepared using droplet microfluidics.The optimum composite binder ratio was selected by combining the morphology,particle size distribution,particle size,and thermal properties of the microspheres,and the microspheres prepared under this ratio were characterized and analyzed.The results showed that the activation energy of DAAF was effectively improved by the use of composite binder for coating.And the activation energy was increased from 168.87 to225.36 k J·mol^-1.The crystalline shape did not change after the coating,The average bulk density was increased by 0.079 g·cm^-3compared to the submicron DAAF.And the impact sensitivity was increased by 5 J over the submicron DAAF.3.Preparation of DAAF/HMX-based high-energy insensitive microspheres by droplet microfluidics.Mixing DAAF and HMX in the ratio of 60:35 reduces the overall mechanical feel while maintaining a high energy output.The morphology,particle size distribution,structure,thermal properties,detonation properties and mechanical susceptibility of the prepared explosive microspheres were characterized and analyzed.The test results show that the components and structure of the prepared composite energetic particles remain unchanged,HMX promoted the thermal decomposition of DAAF.Compared with submicron DAAF,the burst velocities of DAAF/HMX/F2602 composite energetic microspheres and DAAF/HMX/NC/GAP composite energetic microspheres were increased by 380m/s and417m/s,respectively;the impact susceptibility values were increased by 45.4 J and 40.4 J,respectively.And the overall burst performance is improved while the mechanical susceptibility is significantly reduced,greatly improving the overall safety.4.Preparation of DAAF/HNS-based high-energy insensitive microspheres by droplet microfluidics.DAAF/HNS/F2602 composite microspheres were successfully prepared by mixing DAAF and HNS in a certain 60:35 ratio using droplet microfluidic technology.The morphology,roundness,particle size,particle size distribution,structure,thermal properties,bursting properties,and mechanical susceptibility of the microspheres were characterized and analyzed.The particle size analysis and EDS test results showed that the size range of the composite energetic microspheres was 21.09～40.46μm with narrow particle size distribution and uniform distribution of F elements on the surface,indicating that the fluoroelastomer was uniformly distributed on the surface of the microspheres;DSC test results show that the reaction rate of composite energetic microspheres is significantly lower and less prone to explosion,and their average apparent activation energy is increased by 11.66 k J·mol^-1;Explo5calculation results show that the composite energetic microspheres maintain a high burst velocity burst pressure.Mechanical susceptibility test results show that the composite energetic microspheres can improve the overall mechanical safety.