Membrane Emulsification-assisted Suspension Assembly And Performance Study Of Energetic Composite Microspheres

Polymer-bonded explosive（PBX）is a compound composed of binder and main explosive with high-energy blunt characteristics,which has become the main charge type for weapon systems.As for pressurized PBX,the molding effect of the modeling powder directly affects the quality of the charge,and how to prepare modeling powder particles with uniform performance and good dispersibility is one of the key technologies to be solved at present.Therefore,this paper combines membrane emulsification technology with water suspension granulation technology to develop a universal membrane emulsification-assisted suspension assembly technique for the preparation of Energetic microspheres.RDX-based,HNS-based and HMX-based energetic microspheres with uniform particle size were prepared,and the influence law of process parameters on the morphology and particle size of Energetic microspheres was systematically investigated,and the performance of the samples obtained by the optimized process was tested and analyzed.The main studies are as follows:（1）RDX/GAP/EC composite microspheres were prepared by premixed membrane emulsification using glycidyl azide polyether（GAP）and ethyl cellulose（EC）as binders,and their properties were characterized by scanning electron microscopy（SEM）,X-ray diffractometry（XRD）,differential scanning calorimetry（DSC）,BAM impact sensitometry and BAM friction sensitometry.The results showed that the sphericity of the RDX/GAP/EC composite microspheres obtained from the template made with 200 m L emulsion increased by0.151 and 0.069,respectively,compared with those made from the remaining two emulsion templates,and the RDX/GAP/EC composite microspheres made from the template with 200m L emulsion were more homogeneous in the particle size range of 270-450μm compared with the raw RDX;In addition,the composite microspheres had unchanged crystalline shape,increased activation energy by 20 k J/mol,increased thermal explosion critical temperature by30°C,and increased impact susceptibility and friction susceptibility energies by 3.5 J and 48N,respectively.（2）HNS microspheres were prepared by the rapid membrane emulsification method using nitrocellulose（NC）as the binder,and the laws of NC solution concentration,stirring speed and polyvinyl alcohol（PVA）solution concentration on the particle size and morphology of the microspheres were investigated.They were characterized and analyzed by scanning electron microscope（SEM）,X-ray diffractometer（XRD）,differential thermal analyzer（DTA）and resting angle tester.The results showed that:the viscosity of the system increased with the increase of NC concentration in the oil phase,and the degree of emulsion droplet fragmentation decreased with the increase of viscosity;the stirring speed affected the stability of the emulsion and the volatilization rate of ethyl acetate,which in turn affected the homogeneity of the microspheres;the stabilizer in the external aqueous phase played an important role in the preparation of the microspheres to prevent the droplets from agglomerating during the emulsification and solvent removal process;at 5 wt%NC solution concentration,stirring speed of 100 r/min and 2 wt%PVA solution concentration,the prepared HNS microspheres had a more uniform particle size distribution compared to the refined HNS,and the sphericity was the highest compared to the microspheres obtained from other process parameters,with a sphericity of 0.985,no change in crystallinity,and an increase in activation energy of 114.95 k J/mol.The resting angles of raw HNS and microspheres were 42.2°and 25.2°,and the flow dispersion was significantly improved.（3）HMX-based composite microspheres were prepared by rapid membrane emulsifica-tion method,and the effects of different polymer types and suspension methods on the preparation of microspheres were investigated.Scanning electron microscopy（SEM）,X-ray diffractometer（XRD）,differential scanning calorimetry（DSC）and rest angle determination were used to characterize and analyze them.The results showed that the HMX-based composite microspheres with different particle sizes were prepared by two suspension methods:single emulsion（O/W）and composite emulsion（W₁/O/W₂）,and the microspheres had a regular morphology and unchanged crystalline shape compared with the refined HMX,The impact sensitivity energy of HMX-4,HMX-7 and HMX-8 increased by 6J,7J and 9J respectively,and the friction sensitivity energy increased by 60N,84N and 108N respectively,which greatly reduced the mechanical sensitivity of HMX.The fast membrane emulsification technique can provide a solution for the preparation of particle size controllable energy-containing composite microspheres.