DUAN Yilong, XU Yuxuan, JI Wei, SHEN Jinpeng

Abstract

Objective In order to address challenges associated with irregular morphology, easy formation of hot spots and high sensitivity of benzotrioxafurazan (BTF), it is necessary to reduce the sensitivity of BTF, which is crucial for improving the safety performance of BTF.

Methods BTF-NC composite explosive was prepared by electrostatic spray method employing BTF as the main explosive and nitrocellulose (NC) as the binder. The micro-morphology and structure of BTF-NC composite explosive were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The thermal decomposition performance and mechanical sensitivity of BTF-NC composite explosive were tested by synchronous thermal analysis and mechanical sensitivity instrument.

Results and Discussion The raw material BTF exhibits a particle size ranging from 5 um to15 um, characterized by long prismatic and rough surface. The particles of BTF-NC composite explosive are spheroidal or quasi-spherical, with a particle size ranging from 500 nm to 2 000 nm. Compared with the two raw materials, the infrared spectrum of BTF-NC composite explosive reveals a certain offset in characteristic peaks, indicating the bonding of NC to BTF. At the temperature ranging from 190 ℃ to 200 ℃ ,the Differential Scanning Calorimetry (DSC) curve for the BTF-NC composite explosive exhibits a endothermic peak indicative of melting. Moreover, the thermal decomposition peak temperature increases with the increase of heating rate. At the heating rate is 5, 10, 20 K/ min, BTF-NC composite explosives show the maximum decomposition peak temperature of 261. 4, 268. 3, 282. 2 ℃, respectively. Notably, these temperatures are slightly lower than those observed in the raw material BTF. The thermal decomposition process of BTF-NC composite explosive shows the same trend as that of raw material BTF, indicating that the thermal decomposition mechanism of the raw material BTF is not changed by the composite process. Compared with the raw material BTF, the apparent activation energy of BTF-NC composite explosive is reduced by 29. 06 kJ/ mol, and the pre-exponential factor is also substantially diminished. The self-accelerating decomposition temperatures for BTF and BTF-NC are 525. 05 K and 526. 35 K,respectively. Moreover, the critical thermal explosion temperatures are recorded as 538. 18 K for BTF and 542. 39 K for BTF-NC, respectively. The self-accelerating decomposition temperature and thermal explosion critical temperature of BTF-NC composite explosive are increased by 1. 3 K and 4. 21 K respectively, compared with raw material BTF. The observation indicates that the addition of NC improves the thermal stability of raw material BTF. The entropy change in the BTF-NC composite explosive is significantly reduced, indicating that the coated BTF possesses reduced susceptibility to decomposition into gas during thermal decomposition. The positive value of enthalpy change , closely related to activation energy, suggests that the thermal decomposition reaction is a non-spontaneous process. According to the thermal analysis, the shift of the exothermic peak temperature of the raw material BTF and BTF-NC composite explosive is 1. 3 ℃ , accompanied by a 15. 8% alteration in activation energy. The raw material BTF has good compatibility with NC, and the compatibility grade is 1. Compared with the raw material BTF, the characteristic drop height of BTF-NC composite explosive increases from 23 cm to 68. 12 cm. Simultaneously, the explosive percentage decreases from 72% to 24%.

Conclusion The thermal stability, impact sensitivity and friction sensitivity of BTF-NC composite explosive prepared by electrostatic spray method have been significantly improved.

Keywords: benzotrioxafurazan; nitrocellulose; composite explosive; electrostatic spray method; thermal decomposition performance; mechanical sensitivity