Explore New Methods To Improve The Anti-segregation And Anti-migration Properties Of Chemical Stabilizers MNA

Propellants are important energy sources in rocket engines.However,the nitrates in the propellants are easy to absorb water or decompose when heated during storage.The decomposition products,acids and NO₂,will cause the autocatalytic decomposition of the propellants,leading to the bad performance of the propellants,and even give rise to explosion,combustion and other dangerous accidents.Therefore,in order to keep the performance of the propellants and prevent the occurrence of a dangerous accident,chemical stabilizers are normally added in the propellants.The main function of the stabilizers is to absorb the acids and NO₂ released by the propellants and inhibit its autocatalytic decomposition.N-methyl-4-nitroaniline?MNA?is currently a common chemical stabilizer in rocket propellants.However,it has significant migration tepndency and aliquation in the nitrates and lead to the decline of the mechanical property of the propellant grain.Therefore,this thesis attempts to alter the migration and aliquation problems of MNA by theoretical estimation and synthesizing new MNA derivatives.In one hand,the possibility to form cocrystals between MNA and a few compounds was estimated by calculation;in another hand,some new MNA derivatives with p-nitroanilino group being mainted,were designed and synthesized using p-fluoronitrobenzene,alcohols,glycine and allylamine as raw materials.The detailed contents are as follows:?1?The binding energy of MNA and a series of amino acids or some typical energetic compounds were calculated using Gaussion 09 software to estimate the possibility to form cocrystals.It has been showed that the binding energies of MNA and amino acids are less than the binding energies themselves.Therefore,it is difficult for MNA and amino acids to form cocrystals;it was also found that the binding energy between MNA and NQ is slightly larger than those of themselves,it is possible to form cocrystal between them,but it is difficult to form cocrystals between MNA and other energetic compounds.?2?N-allyl-4-nitrobenzenamine?1?,methyl 2-?4-nitrophenylamino?acetate?2?,ethyl 2-?4-nitrophenylamino?acetate?3?,isopropyl 2-?4-nitrophenylamino?acetate?4?,butyl 2-?4-nitrophenylamino?acetate?5?,iso-butyl 2-?4-nitrophenylamino?acetate?6?,2-?4-nitrophenylamino?acetic acid?7?and 2-hydroxyethyl 2-?4-nitrophenylamino?-acetate?8?were synthesized by esterification and substitution with different alkyl alcohols,glycine and p-fluoronitrobenzene as raw materials.The synthesis processes are simple and the yields and purities are high.The structures of 1-8 were characterized by NMR,FT-IR,UV-Vis and MS.The cryatal structures of 1-3 were further characterized by single crystal X-ray diffraction.?3?The thermal stability of the new compounds was studied by TG technology.The results showed that the thermal stability of compounds 1-8 is high,with their decomposition peak temperatures being higher than 120 ?.The decomposition peak temperatures of 3 and 5 are higher than 160 ?,and those of 7 and 8 are higher than 180 ?.?4?The compatibility between compound 1-8 and main components of solid propellant?mass ratio 1:1?,such as AP,RDX,HMX,FOX-7 and NC,were evaluated by DSC technique and compared with MNA.The results showed that compounds 1-8 are good compatible and are better than MNA.?5?A two-month migration at 70 ? was performed on MNA,1 and 3-6,with their weight percentages being 1%,1.5%,and 2%.On comparison their migration distances,it can be seen that the migration distances of the novel MNA derivatives are shorter than that of MNA at a same content,indicating that 1 and 3-6 are better in anti-migration ability than MNA.?6?The modified double base?CMDB?propellants containing 1%C2,0.3%Res was compared in stability with the modified double base?CMDB?propellants containing 1%C2,0.3%Res and a novel MNA derivative?50:1 mass ratio?.Their stability was evaluated by Methyl Violet Test?MVT?and Vacuum Stability Test?VST?.The tested results displayed that 1 exhibits bad stability through MVT,due mainly to the existence of a chemically active double carbon-carbon bond in it,and its vacuum outgassing amount is also higher than those of the common chemical stabilizers.The discoloration time of 2-6 by the MVT was longer,and their vacuum outgassing amounts were lower,showing their better stability.?7?The NO₂ absorption experiments were carried out for 1-6 and 8.It was observed that they all display a certain degree of NO₂ absorption.Among them,the appearances of 1,2,4-6 and 8 are liquefied after the absorption process and each compound was characterized before and after NO₂ absorption by FT-IR spectroscopy.In summary,eight new MNA derivatives synthesized in this thesis have good compatibility with some main components of propellants and have high thermal stability.Additionally,they exhibit lower migration tendency and good stability,and most of them are better in the absorption of NO₂ than MNA.These new compounds are therefore potential chemical stabilizers as substituents of MNA.