Study On Thermal Stability And Safety Of Modified Double-base Propellant With High Solid Content

Solid propellant,as the power source for weapon system delivery,has been the main goal pursued by people in the process of research and development,and has become one of the main development directions of solid propellant today.Modified double base propellant,as a solid propellant with excellent performance,is an optimized system formed by adding corresponding high-energy explosives to the basic system of nitroglycerin and nitrocellulose to improve its energy,burning rate,safety,and other properties.It has been vigorously developed and widely used in various countries around the world.In order to explore the thermal stability and safety characteristics of modified double-base propellant,the thermal decomposition of modified double-base propellants with different solid contents（RDX,HMX）was studied by differential scanning calorimetry（DSC）.The thermal decomposition temperatures at the heating rates of 2,5,10℃·min^-1 and 20℃·min^-1 were obtained.The apparent activation energy,pre-exponential factor,reaction rate,Gibbs free energy,activation enthalpy and activation entropy were calculated by thermal reaction kinetics analysis.Combined with the chemical stability test of methyl violet,its thermal stability was further analyzed.Secondly,the response characteristics of modified double-base propellants with different solid content were obtained through slow cook-off and 5 s burst point tests to characterize the thermal safety of the propellants;Through flame sensitivity and mechanical sensitivity tests,the safety and desensitization performance of modified double-base propellant containing solid content components was further studied.The results showed The results showed that with the increase of solid content,the temperature of the first decomposition peak of DSC shifted back and the apparent activation energy decreased;When the content of RDX is 18%and the content of HMX is 21%,the apparent activation energy is the largest after adding solid components in the formula system;The discoloration time of methyl violet chemical stability test paper is prolonged,which indicates that the addition of solid content can effectively improve the thermal stability of modified double-base propellant.In the slow cook-off test,as the solid content increases,the sample response temperature moves towards a higher temperature direction compared to the sample without solid content components,which reduces the thermal sensitivity of the system to some extent;However,the increase of solid content increases the intensity of its reaction.When the content of RDX is 18%and the content of HMX is 21%,the intensity of slow cook-off response is the lowest.When the content of RDX reaches 46%and the content of HMX reaches 40%,the response level is determined as explosion and cannot pass the slow cook-off test;After adding solid content components in the sample,the temperature of its 5 s burst point moves to the high temperature direction,and the rising trend is obvious;With the increase of solid content,50%firing distance shows a downward trend,the flame sensitivity decreases significantly,and the mechanical sensitivity decreases first and then increases.When the content of RDX increases to 46%,and the content of HMX increases to 21%,the mechanical sensitivity of the formula system is the lowest.On the whole,it is very effective to replace the double-base components with low-sensitivity high energy density materials to reduce the sensitivity;To sum up,selecting an appropriate solid content can help improve the thermal stability and safety characteristics of the formula.