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In order to elucidate why the inclusion of a nonpolar desensitizing agent in polymer-bonded explosives (PBXs) affects their sensitivity and safety, the intermolecular interactions between nitroguanidine (NQ: a high-energy-density compound used as a propellant and in explosive charges) and FC=CF were investigated theoretically at the B3LYP/6-311++G(2df,2p) and M06-2X/6-311++G(2df,2p) levels of theory, focusing especially on the influence of intermolecular interactions on the strength of the trigger bond in NQ. The binding energies and mechanical properties of various β-NQ/polytetrafluoroethylene PBXs were also studied via molecular dynamics simulation. The results indicated that the weak intermolecular interactions between NQ and FC=CF have almost no effect on the strength of the trigger bond or the energy barrier to the intramolecular hydrogen-transfer isomerization of NQ, as also confirmed by an AIM (atoms in molecules) analysis. However, the mechanical properties of the β-NQ/polytetrafluoroethylene PBXs were found to be significantly different from those of pure β-NQ: the PBXs showed reduced rigidity and brittleness, greater elasticity and plasticity, and-in particular-better ductility. Thus, β-NQ-based PBXs with polytetrafluoroethylene are predicted to be less sensitive to external mechanical stimuli, leading to reduced explosive sensitivity and increased safety. [ABSTRACT FROM AUTHOR]

The effects of Mg content on the mechanical properties, corrosion resistance and the microstructure of Al–Cu–Mg–Ag alloys were investigated by hardness tests, tensile tests, intergranular corrosion tests, electrochemical analysis, optical microscopy (OM) and transmission electron microscopy (TEM). With the increase of Mg content, the aging hardening process of Al–Cu–Mg–Ag alloy was accelerated, and the peak hardness and the tensile strength at room temperature both increased and then decreased slightly, due to the smaller dimension and larger fraction volume of Ω phases, whereas the high temperature tensile strength increased gradually. In addition, the increase of Mg content led to a larger corrosion current density and thus a higher corrosion rate of Al–Cu–Mg–Ag alloy. The poorest corrosion resistance of Al–Cu–Mg–Ag alloy with the highest Mg content (1.2%) may be due to the largest potential difference between the PFZ and the matrix in this alloy. The alloy with higher Mg content consumed more Cu solution atoms to form the precipitations on the grain boundaries, which results in lower potential of the PFZ correspondingly. [ABSTRACT FROM AUTHOR]