Molecular Dynamics Simulation Of Diffusion Properties Of Deterrents In Propellants

As the diffusion and migration of the deterrents affect the service life of gun propellants during the storage period,molecular dynamics simulation(MD simulation)was applied to compare the diffusion coefficient of dibutyl phthalate(DBP),Butyl oxynitro,exyl ammonium nitrate(Bu-NENA),triethylene glycol dinitrate(TEGDN)and polyneopentyl glycol adipate(NA)in gun propellants.At the same time,the effects of temperature,nitrocellulose(NC)nitrogen content,deterrent concentration and nitroglycerin(NG)content on the diffusion of deterrents in propellant were explored.The diffusion mechanism of deterrents in gun propellants was studied from two aspects: the intermolecular interaction between the deterrents and nitrocellulose(NC)and the free volume fraction of the system.The research conclusions are as follows:The order of the diffusion coefficient of TEGDN,Bu-NENA,DBP and NA in the NC system is TEGDN>Bu-NENA>DBP>NA,at 25?.The research results show that the relative molecular weight of the deterrents,the interaction between the deterrents and NC,and the free volume of the deterrents/NC system all affect the diffusion of the deterrents.The diffusion coefficients of DBP and NA increase as the temperature rises.With increase of temperature,the hydrogen bonding between NC and DBP,NA has a tendency to weaken,and the effective space in the system also increases,resulting in the easier diffusion of DBP and NA.At 25?,the diffusion coefficients of DBP and NA increase with the increase of the NG content.The order of the diffusion coefficients of the deterrents in the NC system is: DBP(15%NG)> DBP(10%NG)>DBP(0%NG),NA(15%NG)>NA(10%NG)>NA(0%NG).The research results show that the addition of the plasticizer NG weakens the force between NC and DBP,NC and NA,resulting in more active movement of DBP and NA,enhancing diffusion ability.The diffusion coefficient of DBP decreases as the nitrogen content of NC increases.The order of the diffusion coefficient of DBP in the NC system is: DBP(11.43%)>DBP(12.3%)>DBP(13.16%).The higher the nitrogen content of NC,the higher the-NO2 content and the lower the-OH content,the intramolecular force of NC and the force between DBP and NC molecules are influenced;The diffusion coefficient of DBP increases with the increase of concentration.The order of the diffusion coefficient of 80%,75%,60%,30% concentration of DBP in the NC system is: DBP(80%)>DBP(75%)> DBP(60%)> DBP(30%).The research results show that the free volume of DBP / NC system increases with the increase of DBP concentration,and the larger the relative space for DBP motion is,which is conducive to the diffusion of DBP in the NC system.In summary,the molecular dynamics simulation method is used to study the diffusion properties of the deterrents in gun propellants,which provides important theoretical guidance for predicting the life of gun propellants.