Theoretical Study On The Stabilization Mechanisms Of Aromatic Amines In The Decomposition Of Nitrate Esters

Propellants are substances that can rapidly generate large amounts of high-temperature gases.they are widely used in the launch of missiles and rockets.Nitrate esters are important components of double-base propellant,The mechanism of their decomposition has become popular and systems consist of mononitrate esters or trinitrate esters have thus received extensive attention.However,aromatic amines as stabilizers can delay the decomposition of nitrate esters and increase their storage time,due to the instability of nitrate esters.In particular,the addition of an electron-donating group can enhance the stabilizing effect of the stabilizers.Based on the quantum chemical method,the alkyl dinitrate(DNP/EGDN)and alkoxy dinitrate esters(Di-EGDN/Tri-EGDN/Tetra-EGDN)were studied at the level of B3LYP/6-31G**.And the decomposition mechanisms of polyfluoro-substituted alkyl dinitrate system(TFDT),contain: nitrogen dioxide catalyzed self-decomposition reaction and hydrogen abstraction reaction of nitrate esters,and then the stabilizing effect of aromatic amine stabilizers on nitrate esters is studied.These stabilizers mainly include: aniline(PA),diphenylamine(DPA),aminophenol(p-HPA)methylaminophenol(p-MAP)o-methylhydroxyphenol(o-MAP),m-methylhydroxyphenol(m-MAP),4-nitrodiphenylamine(4-NDPA),4-hydroxydiphenylamine(p-HDPA),o-nitromethylaminophenol(o-HMN),m-nitromethylaminophenol(m-HMN),o-nitrosomethylaminophenol(o-HAN)and m-nitrosomethylaminophenol(m-HAN).Based on the above two aspects of work,related kinetic studies are carried out.The research results show that:For alkyl dinitrate esters and alkoxyl dinitrate esters,hydrogen abstraction reaction prefers to occur,which is consistent with the decomposition method of trinitrate esters(BTTN,NG).However,for poly-fluoride nitrate esters,NO2 catalyzed self-decomposition is preferred,which is contrary to the decomposition method of trinitrate esters.For mononitrate esters,dinitrate esters and trinitrate esters,the order of their stability is consistent under the two decomposition methods.Namely,mononitrate esters are the most stable,dinitrate esters are the next,and trinitrate esters are the most unstable.Although polyfluorinated nitrate esters have excellent thermodynamic properties,they tend to decompose during storage and are slightly less stable than non-fluorinated nitrate esters.The stability of polyfluorinated oxygen-containing nitrate esters designed by adding oxygen atoms to polyfluorinated nitrate esters was slightly improved compared with that of fluorinated nitrate esters.The reaction rate constants of nitrate esters' decomposition and the reaction between stabilizers and nitrogen dioxide were calculated by using traditional transition state theory(Eyring equation).At the same temperature,the reaction rate constants of O-attacking reaction are always larger than those of N-attacking reaction.