| Emulsion explosive is mainly composed of emulsion matrix and sensitizers,and sensitizers form "hot spots" under the action of shock wave,triggering the detonation reaction of emulsion explosive.However,in deep hole or deep water blasting operation,emulsion explosives in the bore holes will be subjected to static pressures(static loading);while in the delayed blasting operation,shock waves generated by the earlier detonated explosives may put dynamic load on the emulsion explosives which has not been ignited yet.The phenomenon that the detonation performance of emulsion explosive affected by dynamic or static loading is called "pressure desensitization".Pressure desensitization will seriously affect the blasting effect and make the emulsion explosive half explosion or misfire,and it is easy to cause safety accident in the process of dealing with the misfired explosives.In order to solve the problem of pressure desensitization of emulsion explosive,a novel pressure resistant microcapsules with double layers was prepared by mixing cenospheres,blowing agent,blowing promoter and hydrophobic nano-silica through the high-speed shearing.In the study,the synthesis processes of the pressure resistant microcapsules were divided into five steps:screening of cenospheres,perforating of cenospheres with hydrofluoric acid(HF),loading blowing promoter into the perforated cenospheres,coating cenospheres with polymer and formation of pressure resistant microcapsules by high-speed shearing method.The results of laser particle size analysis showed that the particle size of cenospheres coated with polymer was about 3?m larger than that of the cenospheres.However,the average particle sizes of the pressure resistant microcapsules were concentrated at ca.200?m.The results of scanning electron microscopy(SEM)and optical microscopy(OM)showed that the pressure resistant microcapsules presented a translucent ellipsoid shape,and the shell of the pressure resistant microcapsule was composed of hydrophobic nano-silica,which was different from the appearance of cenospheres.The difference in brightness between the inside and outside of the microspheres indicated that the core and shell of the microspheres were composed of different materials.The gray opaque spheres inside the microsphere were cenospheres loaded with blowing promoter.Using a small hard iron spoon to crush the pressure resistant microcapsules on the glass slide,and when the microcapsules were crushed,many microbubbles will be created.Cenospheres is the main component of fly ash,and rational use of it can create good economic and environmental values.In this study,cenospheres were used as the core materials of the pressure resistant microcapsules.Firstly,the detonation performance of cenospheres sensitized emulsion explosive was studied to obtain an optimum formula.At the same time,the effects of content and particle size of cenospheres on the detonation characteristics of emulsion explosive were also investigated.The particle size distribution,micro structure and chemical composition of cenospheres were measured by the laser particle size analyzer,SEM and X-ray fluorescence spectrometer(XRF),respectively.The results showed that both cenospheres and glass microspheres were ellipsoid with an uniform particle size distribution.The specific surface area and bulk density of cenospheres and glass microspheres both decreased with the increasing mean particle size(Dso),while the particle size distribution span(D90-D10)increased with the increasing D50.The wall thickness of the cenosphere was ca.10?m,which was a high-strength aluminosilicate shell.The shell had a porous structure formed by bubbles and was covered by an amorphous nanoscale thin film,so that the cenospheres had high mechanical strength and were not easy to be crushed during the utilization.The components of cenospheres and glass microspheres were inert materials whose main functions in emulsion explosive were to provide"hot spots".The experimental results of brisance,detonation velocity and air explosion showed that the optimum content and particle size of cenosphere as a physical sensitizer of emulsion explosive were 12 mass%and 83?m,respectively.Cenospheres had good compatibility with emulsion matrix,and demulsification phenomenon was not found after being stored for three months.The experimental data of TG-DSC showed that cenospheres and glass microspheres sensitized emulsion explosives both had good thermal stabilities.The detonation performance of emulsion explosives with different content of pressure resistant microcapsules were studied by the brisance and detonation velocity experiments.The detonation performance of emulsion explosive gradually declined with the increasing pressure resistant microcapsules content compared with emulsion explosive sensitized by 4 mass%glass microspheres,and the major reason for that was the density of emulsion matrix decreased with the increasing content of pressure resistant microcapsules,because the main components of the pressure resistant microcapsules were silicon and water,which were inert materials in emulsion explosive.The addition of pressure resistant microcapsules was determined to be 2 mass%by the brisance and detonation velocity experiments.The underwater experimental results showed that the degree of pressure desensitization of emulsion explosive with 2 mass%pressure resistant microcapsules was much lower than that of emulsion explosive without the pressure resistant microcapsules at the same distance,indicating that the pressure resistant microcapsules could significantly alleviate the dynamic pressure desensitization of emulsion explosive.The pressure resistant agent of emulsion explosive not only provided hot spots in the detonation process but also solve the pressure desensitization problem,providing a new idea for the development of anti-pressure emulsion explosive.Figure[32]table[15]reference[77]... |
PDF Full Text Request