Phlegmatization of energetic materials with polymer films in supercritical conditions

摘要

A simple and effective method of coating of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) particles with fine films of polymethylacrilate (PMA), polyurethane rubbers Desmocoll-400 and Surel-9 has been developed. The coating was conducted in the supercritical carbon dioxide medium using the gas anti-solvent method (GAS). This method was previously used to cover CL-20 particles with hydroxyl-terminated polybutadiene (HTPB), but for the first time we applied it for HMX phlegmatization. In this process, the supercritical fluid is used as an anti-solvent that causes precipitation of the polymer dissolved initially in a liquid solvent. Since PMA and polyurethane rubbers are components of most polymeric binders in energetic composites, the use of 1-3 % wt. of them will not significantly decrease energetic parameters of the final product. Along with this, a higher flowability and significantly lower sensitivity to impact (1.7-7.8 times) and friction (1.4-1.9 times) have been reached compared to the original compounds. The obtained powders exhibit the increased flowability which is beneficial for manufacturing. These advantages of the coated particles correspond to the quality of their surfaces analyzed with scanning electron microscopy, as well as probe atomic force and electric force microscopy. The achieved level of phlegmatization makes it possible to increase the proportion of energetic materials in the formulation without compromising the safety of production.