Study On The Structure And Properties Of PYX-based Polymer Bonded Explosives

2,6-dipicrylamino-3,5-dinitropyridine(PYX)is a kind of explosive with the best comprehensive properties.After the addition of polymer binder,it have many remarkable characteristics such as good stability and detonation performance,heat resistance and easy processing and forming.In this thesis,the structure and properties of PYX and Polymer Bonded Explosives(PBX)base on PYX are studied by using density functional theory(DFT)and molecular dynamics(MD)method.First,the nature of the interaction between four polymer molecules and PYX is studied by using the density functional theory(DFT)method,and to explore the influence of the addition of binder on the sensitivity of the complex.Research shows that,the interaction between PYX and the four polymer molecules is dominated by van der Waals interaction,supplemented by weak hydrogen bond interaction and steric hindrance.By analyzing the molecular surface electrostatic potential(ESP)and related parameters of pure PYX and complex,it is found that the addition of polymer molecules disturbed the original electron configuration of PYX and changed the original electronic structure of PYX.Further analysis of the H₅₀of pure PYX and the composite show that the binder has some influence on the sensitivity of the composite.Then,the structure and properties of the PBX systems constructed by placing different polymer binders on different crystal planes of PYX are studied by molecular dynamics(MD)simulation method,and to explore the effects of adding different binders and different crystal planes on the properties of PYX based PBX systems.Research shows that,the interaction between the PYX(0 1 1)crystal plane and each binder molecule is relatively strong,and the interaction between EPDM and PYX(0 1 1)plane is the strongest.The analysis of the cohesive energy density in the system shows that the interaction between F2641 and PYX molecules is strong.The radial distribution function analysis shows that the main interactions of O₁-H₂and N₁-H₂are electrostatic interaction in different PBX systems.The addition of binder has some effect on the mechanical properties of PBX systems,but it has little effect on the molecular structure of PYX in the system,indicating that the dulling effect of polymer binder is not caused by the change of PYX molecular microstructure.With the addition of binder,the detonation velocity and pressure of PBX systems are reduced.Finally,the PBX model systems are constructed by adding polymer binder on the selected PYX(0 1 1)crystal plane,and their performance at five temperatures(258 K,278 K,298 K,318 K and 338 K)are studied by MD simulation method,to explore the effect of temperature on PBX systems.The results show that the binding energy and cohesive energy density of the system do not change monotonously with the change of temperature.However,comparing the binding energies of PBX systems with different binders at the same temperature,it is found that the interaction between EPDM molecules and PYX(0 1 1)crystal planes is the strongest;By analyzing the cohesive energy density of different PBX systems at the same temperature,it can be seen that the interaction between F2641 and PYX is the strongest.By analyzing the mechanical properties of the PBX systems,it is found that the elastic modulus of the systems first increased and then decreased with the increase of temperature,and the modulus are the largest at 298 K.EPDM is superior to the other three binders in improving the mechanical properties of PYX.With the increase of temperature,the maximum bond length of PYX molecules in the PBX systems tend to increase,which is consistent with the experimental fact that sensitivity increases with the increase of temperature.At the same time,the diffusion coefficient(D)also tend to increase with the increase of temperature.