Study On Preparation And Properties Of High Quality And Ultrafine CL-20 Based PBXs

Hexanitrohexaazaisowurtzitane(hereinafter refers to HNIW or CL-20)is one of the most representative new High-Energy-Density Materials(HEDM).As soon as synthesized by AT Nielsen at the US Naval Weapons Research Center in 1987,it has been popular all over the world because of its remarkable properties of high explosive energy.Although the CL-20 is known as “explosives for tomorrow”,it cannot be used directly for weapons equipment because it is sensitive to impact,friction,and static sparks,and has poor safety and mechanical properties.Refining and coating can reduce its sensitivity,improve safety and mechanical properties.In this paper,CL-20 was used as the main explosive,and ultrafine CL-20 was prepared by ultrasonic assisted spray recrystallization.On the basis of this,the CL-20/AR-71 complex was prepared by water slurry method and emulsion-demulsification method.The two methods were compared.Finally,several CL-20-based PBXs were prepared by emulsion-demulsification method and characterized.The main contents of this paper are as follows:(1)Based on the theory of quantum chemistry,molecular dynamics software(Materials Studio 7.0)was used to simulate the bond length distribution,binding energy and Mechanical properties between ε-CL-20 and binders of AR-71,Estane 5703,EVA.The simulation results show that the interaction between binder and ε-CL-20 does not change the micro-molecular structure of ε-CL-20;the order of binding energy of PBXs is: ε-CL-20/ Estane5703>ε-CL-20/ AR-71>ε-CL-20/EVA;the binder weakens the rigidity of the CL-20-based PBX,enhances flexibility,and improves mechanical properties.Among them,Estane5703 has the best improv-ement effect.(2)Ultrafine CL-20 particles were prepared by ultrasonic assisted spray recrystallization with ethyl acetate as solvent and 1,2-dichloroethane as non-solvent.With the single factor control variable method,the optimal technique of Ultrafine CL-20 indicates that the CL-20 crystal form remains ε-type stably under the optimum process condition.The ultrafine ε-CL-20 particles have regular morphology,the size of particle is between 400 and 600 nm,and the purity is increased from 99.45% of the raw CL-20 to 99.82%.The activation energy and special height H50 of ultrafine ε-CL-20 is 180.14 KJ/mol and 31.91 cm,which is12.89 KJ/mol and 18.78 cm higher than the raw CL-20,respectively.The ultrafine ε-CL-20 has better thermal stability and Lower mechanical impact sensitivity.(3)The CL-20/AR-71(98/2)compound was prepared by water slurry method and emulsion-demulsification one respectively.SEM,EDS,XRD,DSC and mechanical sensitivity tests show that both methods lower the sensitivity of the CL-20,and the emulsion-demulsification method is superior to water slurry method.Compared with the PBX prepared by water slurry method,the coating degree,activation energy,thermal explosion critical temperature and H50 of PBX prepared by emulsion-demulsification method was increased from 0.33 to 0.54,194.88KJ/mol to199.02KJ/mol,508.96 K to 509.22 K and 39.07 cm to 42.25 cm respectively.The friction sensitivity P decreased from 92% to 84%.The thermal stability and mechanical impact sensitivity of sample prepared by emulsion-demulsification method are superior to the sample prepared by water slurry ones.(4)The CL-20/AR-71,CL-20/ Estane5703 and CL-20/EVA composites were prepared by emulsion-demulsification method with binder’s content of 3%.The performance test results show that all binders can coat on surface of CL-20 and reduce the sensitivity of CL-20,but the effect is different.In summary,CL-20/ Estane5703 performed best,followed by CL-20/AR-71 and CL-20/EVA.This result is consistent with the MD simulation prediction.