Molecular Dynamics Simulations for Pure ε-CL-20 and ε-CL-20-Based PBXs

Abstract

Molecular dynamics has been employed to simulate the well-known high energy density compound epsilon-CL-20 (hexanitrohexaazaisowurtzitane) crystal and 12 epsilon-CL-20-based PBXs (polymer bonded explosives) with four kinds of typical fluorine polymers, i.e., polyvinylidenedifluoride, polychlorotrifluoroethylene, fluorine rubber (F(2311)), and fluorine resin (F(2314)) individually. The elastic coefficients, isotropic mechanical properties (tensile moduli, bulk moduli, shear moduli, and poission's ratios), and bonding energy are first reported for epsilon-CL-20 crystal and epsilon-CL-20-based polymer bonded explosives (PBXs). The mechanical properties of epsilon-CL-20 can be effectively improved by blending with a small amount of fluorine polymers, and the whole effect of the adding fluorine polymers to improve mechanical properties of PBXs along the three crystalline surfaces of epsilon-CL-20 is found to be (100) approximately (001) > (010). The interaction between each of the crystalline surfaces and each of the fluorine polymers is different, and the ordering of binding energy for the three surfaces is (001) > (100) > (010); F(2314) always has the strongest binding ability with the three different surfaces. F(2314) can best improve the ductibility and tenacity of PBX when it is positioned on epsilon-CL-20 (001) crystal surface. The calculations on detonation performances for pure epsilon-CL-20 crystal and the four epsilon-CL-20-based PBXs show that adding a small amount of fluorine polymer into pure epsilon-CL-20 will lower detonation performance, but each detonation parameter of the obtained PBXs is still excellent.

Efficient Preparation and Performance Characterization of the HMX/F2602 Microspheres by One-Step Granulation Process

“…Currently, fluorine polymer is frequently used as the binder of PBX [4][5][6], given its specific advantages, such as higher burning rates, lower impact sensitivity, and better thermal stability. There are many preparation methods for mixed explosives.…”

Molecular dynamics simulations on the structures and properties of ε-CL-20-based PBXs

“…On the other hand, the optimized molecular structure of ε-CL-20 from Compass agrees well with that from quantum mechanics method [23] , and the predicted cell parameters of ε-CL-20 using Compass force field is well consistent with experiment values. Besides, Compass force field has been successfully used to study some related properties of ε-CL-20-based PBXs with different fluorine binders [10] .…”

“…The (2×2×3) model of crystal cells was constructed using MS program. Molecules on (001) surface of ε-CL-20 crystal have been predicted to be very compact and can strongly interact with binders [10] . In this paper, the "cutting" model was chosen, in which ε-CL-20 crystal was cut along the crystalline surface (001) and put in the periodic boxes with 20 Å vacuum layer along the c direction.…”

“…HEDMs consist of high energy density compounds (HEDCs) as the main body and other additives, and its performances depend on good formulation. CL-20 (hexanitrohexaazaisowurtzitane) is the most well-known HEDC [6] , and CL-20-based polymer bonded explosives (PBXs) with a small amount of polymer binders have attracted much attention [7][8][9][10] . For example, the Lawrence Livermore National Laboratory (LLNL) in U.S.A. has prepared four kinds of CL-20-based PBXs with polymers, Estane5703 (polyurethane) and EVA (ethylene-vinylacetate copolymer) [7,9] .…”

“…It is helpful for theoretically guiding the formulation design by molecular dynamics (MD) simulations on the structures and properties of explosives [11][12][13][14][15] , polymers [16] and PBXs [10,[17][18][19] .…”