Preparation And Investigation Of Structured Microcellular Oblate Spherical Propellants

In order to achieve the progressive combustion performance of the propellants,the structured microcellular oblate spherical propellants,which possess pore layer with large number of miropores and compact skin,were prepared by modifying double-base propellant though supercritical carbon dioxide foaming technology.The foaming process and surface layer redissolve process were proposed to prepare this special structure and the relations between processing parameters,internal morphology and combustion performance were investigated.The effects of processing parameters in saturation,desorption and foaming on the the formation and thickness of skin were investigated by scanning electron microscope.The results show that this special structure is base on adequate dissolution of CO₂,more desorption time and lower foaming temperature lead to thicker unfoamed skin.Under certain conditions,the compact skin was not obtained.But the different morphology of the bubbles caused by gradient concentration of CO₂ result in the approximate skin.Longer foaming time may generate amalgamative bubbles and increase the diameter to 15μm～20μm.The combustion performance of microcellular oblate spherical propellants with special structure were investigated by analyzeing the datas baised on closed bomb tests.The results indicate that foamed samples possess less burnout time and higher dynamic combustion activity（L）.Reduceing desorption time or increasing foaming temperature lead to higher decrease amplitude of burnout time and higher increase amplitude of L.Different types of double-base propellant can realize progressive combustion performance in different processing parameters by delaying the peak of L-B curves.In surface layer redissolve process,more dissolve time and more dosage of ethyl acetate increase the burnout time and reduce L.The computational formulas about mass fraction of skin in three different shape propellants were deduced by design the geometrical model.Extraction phenomenons of plasticizer by supercritical carbon dioxide were discussed in different saturation times,saturation pressures,saturation volumes and grain sizes.