Crystal orientations of 1,3,5-triamino-2,4,6-trinitrobenzene-based polymer bonded explosives during the pressing process by neutron diffraction

Hot-pressed 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)-based polymer bonded explosives (PBX) will show significant anisotropic and irreversible expansion properties, resulting in both the deterioration of their performance and weapon reliability issues. The anisotropic mechanical and irreversible expansion characteristics of TATB-based PBX have shown to be closely related to the crystal orientation. In this work, the orientations of TATB crystals in PBX under different thermal–mechanical coupling loading conditions were studied by neutron diffraction measurement technology. The microstructures were observed by computed tomography (CT) and scanning electron microscopy (SEM), and the effects of hot pressing parameters (temperature and pressure) on the TATB crystal orientation were systematically analyzed. Combining the density and compression strength of the formed samples, the optimal hot pressing parameters were determined. The results showed that during the in-situ compression process, the TATB crystals would be reoriented. The rotation angle of the (002) plane was mainly concentrated within a 35° angle from the perpendicular pressing direction. After hot compaction, the rotation angle moved from 35° to 52°, and the orientation of the TATB crystals had obvious rebound phenomenon. The (002) plane orientation degree was related to the deformation, fragmentation, and reorientation of the TATB crystals, as well as the phase transition, thermal softening, and gap filling of the binder, and the interfacial interactions. In order to obtain higher detonation energy, better mechanical properties and better shape stability of the formed samples, (120 °C, 140 MPa) was selected as the optimal hot pressing parameters for TATB-based PBX.