Effects of Micro-Capsule Coating Materials on the Energy Output and Thermal Safety of Aluminized Emulsion Explosives
G.-D. Chen1, Y. Gong1,2,3, Q. Wang1,2, H. Su1,2,3, Y.-F. Cheng1,2
1School of Chemical and Blasting Engineering, Anhui University of Science and Technology, Huainan, China
2State Key Laboratory of Safe Mining of Deep Coal and Environmental Protection, Huainan, China
3Key Laboratory of Safety Intelligent Mining in Non-coal Open-pit Mines, National Mine Safety Administration, Guangzhou, China
Keywords: emulsion explosive, coating layer, high explosive, shock wave, thermal stability
Abstract
Traditional emulsion explosives (HE) are characterized by a contradiction between high energy release and operational safety. To address this issue, the use of a coating layer for aluminum particles was investigated in this study. Microcapsules with a core-shell structure, in which aluminum powder is encapsulated in polymethyl methacrylate (PMMA), were synthesized using suspension polymerization. Paraffin and stearic acid coatings were also formed on the surface of the aluminum particles using solvent evaporation. This allowed a systematic study of the effect of various shell materials on the detonation characteristics of aluminized emulsion explosives. Three groups of emulsion explosive samples were prepared with the addition of the indicated types of coated aluminum powders as an energy additive. The microstructure and coating quality of the aluminum particles were studied using scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The effect of coating structure on the shock wave parameters and thermal stability of aluminized emulsion explosives was studied using a pneumatic testing system and a DSC-TG synchronous thermal analyzer. Experimental results show that the PMMA coating forms a continuous, dense shell, while paraffin and stearic acid coatings exhibit localized defects. All three types of coated aluminum powders enhance the shock wave parameters of the emulsion explosive, with the best effect achieved for PMMA and aluminum microcapsules: the peak shock wave pressure increases by 25.1% compared to the control sample. The PMMA shell increases the activation energy of the aluminized emulsion explosive, thereby improving its thermal stability. Paraffin and stearic acid coatings reduce the activation energy due to the presence of defects at the interface. Microencapsulation technology in PMMA, by forming a dense core-shell structure, simultaneously increases the energy density and thermal stability of emulsion explosives, making it promising for the production of high-energy, insensitive emulsion formulations.
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