Computer Simulation Study On The Mechanism Of HTPB Curing Reaction And The High Explosive System

In this paper, the curing reaction mechanisms of HTPB and toluene diisocyanate （TDI） were researched by the quantum chemistry methods.By using Gaussian.03W software, HTPB、TDI （2,4-TDI and2,6-TDI） and their transition states were took geometric optimization frequency analysis、natural charge and Wiberg bond order analysis as well frontier molecular orbitals analysis at the B3LYP/6-311G**level. The stagnation point of the reaction potential energy and their mutual connection were confirmed by the vibration analysis and the IRC. The activation energy was calculated, and which was corrected by the zero-point energy. The results showed that, under the conditions of no heating、no catalysts and solvent-free, the bulk curing reaction of HTPB and2,4-TDI （or2,6-TDI） was completed only through an annular transition state without intermediate; their reaction are exothermic and the reaction of HTPB and2,4-TDI was easier the reaction of HTPB and2,6-TDI.By using Materials Studio software, molecular dynamics simulation were applied to method to study on the cyclotrimethylene trinitramine （RDX）、cyclotetramethylene-tetranitr-amine （HMX） and RDX-based PBX （polymer-bonded explosives） with COMPASS force field and using NPT ensemble. The detailed contents and conclusions are listed as follows:①MD simulation was employed to study the PBXs with RDX as a base explosive and PS as a polymer binder under the different temperature. The simulation results show that with the temperature increase, the maximum bond length (L_max) of N-N trigger bond increases, and the interaction energy (E_N-N) between two N atoms of the N-N trigger bond and the cohesive energy density （CED） decrease, we propose to use L_max and E_N-N as theoretical criteria to judge or predict the relative degree of heat and impact sensitivity for the energetic composites such as PBXs and solid propellants.②The study of the three different PS concentrations of RDX/PS system was done by the MD method, The results indicate that when PS is added to a base explosive of RDX, the rigidity and toughness weaken, the brittleness increases. The interactions between PS and RDX mainly comes from the hydrogen bonding and vdW force. With the increase of PS concentration, materials’hardness enhances, the ability of material deformation weakens, the brittleness increases; L_max changes small; the binding energy changes complexly; E_N-N increases; CED decreases.③Using the method of MD, HMX and RDX were simulated respectively in the five different temperature. The results show that with the rise of temperature, the rigidity of HMX and RDX lowers, L_max increases,E_N-N and CED decrease; At each temperature, compared to HMX, RDX has lower rigidity、longer L_max、smaller E_N-N and smaller CED. It was found that L_max and E_N-N relate with sensitivity, which can be considered as theoretical criteria to judge or predict the relative degree of heat and impact sensitivity for the energetic composites.④Using the MD method, PBX-9007system and its related multicomponent system were simulated. The results show that with DOP in the system the rigidity increases, brittleness enhances, ductility reduces, and with rosin the system goes soft and toughness is increased. And we also find that DOP and rosin can improve the binding energy between explosive components and non-explosive components.