Study on the mechanism of TATB's effect on the thermal stability of HMX-based PBX

Thermal loads can induce thermal damage of varying degrees and subsequent performance degradation in energetic materials. In this study, thermal shock experiments were carried out on two types of polymer-bonded explosives (PBXs), namely the HMX-based PBX and the HMX/TATB-based PBX. The composition ratio of the composite energetic system was optimized via Materials Studio. By integrating scanning electron microscopy (SEM), industrial computed tomography (CT), thermal analysis, Brazilian splitting test and impact sensitivity test, a systematic investigation was carried out on the structural evolution and performance variation of PBXs with different components under thermal shock. The results demonstrate that the introduction of TATB can effectively mitigate the damage at the crystal/binder interface and improve the structural integrity of the material. Under identical thermal shock conditions, the porosity of the HMX-based PBX increased by 4.45%, while that of the HMX/TATB-based PBX only showed a 3.51% increment.Thermal analysis results demonstrate that the HMX/TATB-based PBX presents significantly better apparent thermal stability after thermal shock. This favorable performance is mainly ascribed to the partial melting of the binder under thermal loading, which fills the intergranular gaps, restrains the escape of pyrolysis products, and thus concentrates the subsequent decomposition reaction. Mechanical property tests further reveal that the tensile strength of the HMX-based PBX decreases by 17.5% after thermal shock, while the HMX/TATB-based PBX only shows a 5.8% reduction in tensile strength. The two PBXs presented typical brittle fracture and distinct tearing characteristics in their fracture morphologies respectively, which indicates that TATB can reduce the stiffness of the material and improve its fracture toughness. Subsequent impact sensitivity tests further show that the impact sensitivity of both PBXs decreases after thermal shock: the HMX-based PBX records an 11.54% reduction, while the HMX/TATB-based PBX only sees a 1.46% drop. This comparison confirms that TATB can effectively suppress the sensitivity variation induced by thermal shock. In general, the introduction of TATB can moderately sacrifice the material stiffness to a certain extent, while remarkably enhancing the toughness, thermal stability and structural stability of PBX under thermal shock conditions. It can effectively inhibit the overall performance degradation of the material, and provide a solid theoretical basis for the design of high-reliability PBX formulations and the optimization of their service performance in complex thermal environments.