Preparation And Performance Study Of Membrane Emulsification-assisted Preparation Of Energetic Composite Microspheres With Narrow Particle Size

2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20),1,3,5,7-Tetranitro-1,3,5,7-tetrazocane(HMX)and 1,3,5-Trinitroperhydro-1,3,5-triazine(RDX)are widely used in various weapon energy such as mixed explosives and propellants due to their high energy level.However,the mechanical sensitivity of these explosives is high,and in many occasions they need to be passivated to improve their safety in use.It is a feasible way to improve safety performance to compound explosive particles with binder.in this paper,three kinds of energetic composite microspheres with high sphericity and narrow particle size distribution were prepared by combining Premix Membrane emulsification technology with water suspension assembly technology,and their properties were tested and analyzed.The main contents are as follows:(1)Oil-in-water(O/W)pre-emulsion was prepared by using CL-20 and CAB(cellulose acetate butyrate)ethyl acetate solutions as the dispersed phase and water as the continuous phase,and the homogeneous oil-in-water emulsion was prepared by Premix Membrane emulsification.Then making the emulsion as template,the binder and the CL-20 explosive were co-precipitated and the assembly was realized in suspension through the getting rid of the solvent,the energetic composites microspheres with different proportions(the content of CAB are 3%,5%,10%,15%,20%respectively)were prepared.The morphology of the prepared samples was analyzed by scanning electron microscope(SEM),the results showed that with the increase of CAB content,the particles tend to be spherical,and when the content was 20%,the particle size distribution of the sample was narrow,and the particle size distribution span(SPAN)was 0.87;the results of X-ray diffraction(XRD)and Fourier infrared spectroscopy(FT-IR)showed that the crystal form of the energetic composite has changed to?-CL-20,and the XRD pattern with a CAB content of 20%showed an amorphous state,indicated that the CAB film had been coated on the CL-20;The thermal analysis of different samples by differential scanning calorimeter(DSC),when the CAB content exceeded 10%,the thermal stability of the sample decreases,but the impact sensitivity test results showed that the safety of energetic composite improved with the CAB content increased.(2)The GAP(polyglycidyl azide)and NC(nitrocellulose)ethyl acetate solution as the dispersed phase,water as the continuous phase,and then the oil-in-water emulsion was prepared by Premix Membrane emulsification,the refined HMX powders were suspended in the emulsion template,the particles and the binder were suspension assembled through volatilizing the solvent,three kinds of energetic composites microspheres with different ratios of binder content were prepared.The results of SEM,image particle analysis and laser particle size measurement showed that the composites had a high circularity and a narrow particle size distribution,when the binder content were 80%and 3%,the SPAN values of the composites were 0.51 and 0.45,respectively;XRD,FT-IR,XPS(X-ray photoelectron spectroscopy)results showed that there was no chemical bond reaction between the binder and HMX particles,and the crystal form of HMX had not changed;When the binder content was 80%,the core-shell structure of the composite particles can be seen from the SEM image,and the composite with GAP/NC as the shell has no exposed crystals,indicating that the binder has been completely coated on the surface of the refined particles,which can also explained the reason why the characteristic height(95.2cm)of the composite was higher;The DSC test showed that the composite has two decomposition peak temperatures(200.16°C and 244.91°C),under the exothermic condition of the binder,the activity of HMX was enhanced and the thermal decomposition was advanced.When the binder content is 3%,the structure of the composite was characterized by TEM(transmission electron microscope),and the structural composition between the particles can be seen clearly,the binder was coated on the surface of the particles and the particles were bonded into a ball;By comparing the thermal decomposition performance of the samples,it was found that the apparent activation energy(E_a)of the composite was 33.61k J?mol^-1 higher than that of the refined HMX,while the critical explosion temperature(T_b)was slightly lower(0.28K),which was almost unchanged,indicating that the thermal stability of the composite was better;The impact sensitivity test results showed that the safety of the composite microspheres was higher than that of the raw HMX,but the sensitivity was slightly than that of the refined HMX,although the safety was worse than the refined particles,the static compression test can be seen that the compressive performance of the composite microsphere was better.(3)Using the ethyl acetate solution of GAP and NC as the dispersed phase,the oil-in-water binder emulsion template was prepared by Premix membrane emulsification technology,then the refined RDX particles were suspended in the emulsion system,the explosive and binder were assembled by driving solvent.The SEM results showed that the composite structure was that the explosive particles were coated with a binder and then bonded into a sphere;The image particle analysis and laser particle size distribution test showed that the circularity of the composite microspheres was 0.875,and the particle size distribution span was 0.47,which had the characteristics of high circularity and narrow particle size distribution;It can be seen from the XRD and FT-IR spectra that the crystal form has not changed and there is no chemical bond reaction between the molecules,which makes there was a complementarity relationship between the binder and explosive particles;The thermal performance of the samples was analyzed with the data obtained from the DSC test,and the results showed that the composite had a higher E_a,but a slightly lower T_b,and the binder promoted the decomposition of explosive particles;Impact sensitivity experiment showed that the composite microsphere had a higher special height than the raw RDX,indicating that the safety performance had been improved to a certain extent.