Fabrication And Performances Of Energetic Microporous Composites

In this study,microporous combustible composites of NC/TEGN/RDX were fabricated by solvent method and supercritical carbon dioxide foaming process,while nitrocellulose?NC?,triethylene glycol dinitrate?TEGN?and cyclotrimethylenetrinitramine?RDX?were the energetic matrix,and the methyl methacrylate was the binder.The effects of foaming conditions on its solubility and cell structure were investigated by experiments.We also produced constrained foaming mechanical spline to study the effect of thermoplastic elastomer's content and various foaming conditions on its mechanical properties.Finally,the effects of RDX content and foaming conditions on its burning characteristics were studied.The results show that the dissolved amount of SC-CO₂ in the NC-based energetic composites increased rapidly and then increased slowly to the final equilibrium state with the rising of saturation time.Increasing the saturation pressure and decreasing the saturation temperature can increase the dissolved amount of SC-CO₂ in the polymer matrix effectively.In the process of desorption,the diffusion coefficient increased with the increase of saturation pressure and saturation temperature.Increasing the saturation pressure leads to reduce the pore size and increase the pore density.With the increasing of foaming temperature,the cell size of the composites gradually increases,and the cell density shows a trend of increasing firstly and then decreasing.Excessive foaming temperature and time will lead to the decrease of bonding force between RDX particles and polymer matrix,even the phenomenon of RDX particles falling off and cell coalescence will occur.When the content of thermoplastic elastomer increases from 5%to 15%,the impact strength can increase by 37.74%.The impact strength of the microporous combustible composites NC/TEGN/RDX increases from3.21kJ·m^-22 to 4.31kJ·m^-22 when the saturation pressure is in the range of 10MPa to 25MPa.However,the impact strength gradually decreases with the increase of foaming temperature,foaming time and saturation time.Finally,the burning characteristics of microporous NC/TEGN/RDX composites was analyzed by closed bomb tests.The results show that the burning time of the samples after foaming is significantly smaller than that of unfoamed samples.With the increase of RDX content,the combustion time decreases,the value of maximum pressure change rate dP/dt increases,the time that reach the maximum dP/dt value decreases gradually,and the value of maximum dynamic combustion activity value increases.Increasing the foaming time and foaming temperature can promote the severity of combustion and decrease the burning time effectively.