Supercritical Fluid Technology Refine CL-20

Energetic materials and its application in weapon system are the core of the national defense science and technology, are the important foundation of weapons and ammunition that have high performance. As the current battlefield changes, the requirements of the weapon system to the energetic materials' s comprehensive performance are higher and higher, such as more powerful function performance, lower sensitivity, and so on. This requires to modify the existing energetic materials, and improve the performance, to meet the needs of the current national defence.Traditional energetic materials refining methods have many shortcomings, the new development of supercritical fluid technology recrystallization method shows excellent properties and wide development prospects. So using the supercritical fluid technology to control the energetic materials' crystal quality has important significance. Based on the study of supercritical phase equilibrium and the crystal growth mechanism, used SAS process and GAS process to recrystallize and refine the CL-20, compared the effects of the two recrystallization processes on the CL-20 crystals quality. Details were as follows:(1)Organic solvent solubility in the supercritical carbon dioxide(SC-CO2) was the basis of supercritical refinement. Therefore, the solubility of the organic solvent that explosive commonly used ethyl acetate, acetone, imethyl formamide and ethanol in SC-CO2 were tested. Under the condition of 308.15 K ~ 318.15 K and 7MPa ~ 12 MPa, the regularities of the organic solvents' solubility are as follows: at the same pressure, the solubility increases with the rising of temperature; at the same temperature, below the transition pressure, when the pressure rises the solubility increases, above the transition pressure, the pressure rises the solubility decreases. In the four organic solvent, in the same condition, the ethyl acetate solubility in SC-CO2 is the biggest, the maximum is 0.9773.(2)SAS method refining CL-20. The effects of supercritical carbon dioxide pressure, temperature, CO2 injection rate and explosives solution injection rate, and the position of CL-20 crystals were collected on the morphology and size distribution of the CL-20 crystal grains were analyzed. The results show that, above the several factors due to ethyl acetate solubility in SC-CO2 is greatly affected by the pressure of supercritical carbon dioxide, with the increase of pressure, solvent ethyl acetate is quickly extracted, CL-20 solution reaches saturation quickly, CL-20 crystal particle size is small, the average particle size can be as small as 600 nm, its shape is spheroidal; besides, due to the inner crystallizer mass transfer is slow, the CL-20 crystal particles collect location also has great influence on the crystalline grain quality, when the distance from the nozzle to the collect location becomes longer, the CL-20 crystalline particles become bigger, particle size distribution is more uneven.(3)GAS method refining CL-20. The effects of the two crystal modifiers Span80 and Tween60 and solution position on the morphology and size distribution of CL-20 crystal grains were studied. The results show that, the crystal modifiers by changing the crystal growth rate to improve the CL-20 crystal shape and make it more smooth; the farther distance from CO2 inlet to solution position, CO2 flux into the reaction kettle cause the less disturbance to the solution, the refinement CL-20 edges and corners become more obvious.(4) After SAS process, the average particle size of CL-20 is 600 nm, the particle size distribution is uniform, most CL-20 is spherical, impact sensitivity reduced 57% compared with raw materials, crystal form is ? and ?. After GAS method, particle size of CL-20 is between 20~25?m, crystal morphology is spheroidal and the impact sensitivity is 35% lower than raw materials, crystal form is ? and ?.