Effects of Micro‐Encapsulation Treatment on the Thermal Safety of High Energy Emulsion Explosives with Boron Powders

Abstract

The effects of micro‐encapsulation technology on the thermal safety of boron‐containing emulsion explosives were experimentally studied. Micro‐structures of additives, demulsification states and thermal characteristics of boron‐containing emulsion explosives were characterized by the laser particle size analyzer, scanning electron microscope and thermal analysis equipment, respectively. The storage experiments showed that emulsion explosives with boron powders would be demulsified in a short time, while those with micro‐encapsulated boron powders were not demulsified and had good surface morphologies and structures. The results of TG‐DSC experiments showed that the thermal stability of emulsion explosive with polymethyl methacrylate (PMMA) micro‐encapsulated boron powders was higher than that of other samples with boron powders, and the order of thermal stability was as follows: PMMA/Boron sensitized emulsion explosive > Paraffin/Boron‐Glass microspheres (GMs) sensitized emulsion explosive > Boron‐GMs sensitized emulsion explosive. The experimental data of accelerating rate calorimeter (ARC) tests showed that the addition of boron powders would significantly increase the risk of thermal explosion of emulsion explosives under the adiabatic condition, and PMMA micro‐encapsulation for boron powders could largely reduce the thermal explosion risk of boron‐containing emulsion explosives compared with paraffin coating. The coating effect of micro‐encapsulation technology was much better than that of traditional paraffin coating method, and the compatibility and thermal safety of boron‐containing emulsion explosives were also improved.

Effects of Boron Powders on the Detonation Performance of Emulsion Explosives

“…Furthermore, when compared to the emulsion explosive with 16 mass % boron powders (Sample B3), the positive pressure duration and positive impulse of emulsion explosive with 24 mass % boron powder type of microcapsules (Sample B5) were increased by 9.0 % and 7.6 %, respectively, while the peak pressure of explosion shock wave had almost no change. The reasons of this phenomenon could be attributed as follows: compared with adding GMs and paraffin‐coated boron powders into emulsion explosives directly, the addition of boron powder type of microcapsules into emulsion explosives could make boron powders and sensitizing bubbles distribute more evenly, increase the charge density and stability of emulsion explosive, which would finally improve the detonation performance of emulsion explosives [13, 25]. The results of air blast experiments show that the change trends of shock wave parameters of emulsion explosive with boron powders and boron powders type of microcapsules were basically consistent with the change trends of explosion temperature fields.…”

“…The reasons for this phenomenon could be attributed as follows: compared with adding GMs and paraffin-coated boron powders into emulsion explosives directly, the addition of boron powder type of microcapsules into emulsion explosives could make the distribution of boron powders and sensitizing bubbles (there were combined together) more evenly and save more charge space to increase the charge density of emulsion explosives [25]. Meanwhile, the shell of boron powder type of microcapsules could effectively avoid the demulsification and crystallization phenom-ena of boron containing emulsion explosives when compared with the paraffin film, which would finally improve the detonation performance of emulsion explosives [13]. In addition, the boron powders in emulsion explosives were easy to be oxidized to form an oxide film, and then could not fully participate in the detonation and combustion reactions, which eventually limited their promotion to the explosion parameters.…”

“…[a] Y.-F. Cheng Previous studies showed that boron powders had many advantages in improving the explosion performance of solid explosives and propellants. However, when boron powders served as energetic materials were added to emulsion explosives, emulsion matrix would be demulsified, which would significantly reduce the safety of emulsion explosives [13]. In order to enhance the stability of energetic materials and their compatibility with explosives, some insensitive materials were usually used to coat them.…”

Effects of biodiesel on thermal safety and detonation characteristics of emulsion explosive**

“…The detonation velocity and brisance are the important parameters related to explosive characteristics [19][20][21].…”

Novel Sensitizing Agent Formulation for Bulk Emulsion Explosives with Improved Energetic Parameters

“…EEs are obtained by sensitizing an EE matrix—a water-in-oil emulsion of ammonium nitrate—either physically (e.g., with the use of glass microspheres) or chemically (e.g., through tractions, in which gas is released within the entire volume of the matrix), with the two types of processes being used to produce cartridged and bulk EEs, respectively. Regardless of their form of use, the development of EEs with continuously improving properties is a highly-active and multidisciplinary field that attracts significant scientific interest, focused on various aspects of those materials, be it their rheology [ 4 , 5 ], their energetic properties [ 6 , 7 ] or their safety features [ 8 ]. Most of the recent developments in the field focus on introducing a variety of additives into the EE formulations [ 9 , 10 ].…”