Characteristic Research On Explosive Materials Under Hygrothermal Environment

The effects of storage and aging on properties and structure of explosive material were investigated. Three typical initiating explosive material:tungsten type delay, lead azide and tetrazene were exposed to humid and thermal conditions. In the meantime, performance indicators were proposed to illustrate the property change and the aging mechanism of tungsten type delay was studied by structural characterization and theoretical simulation.An experimental system with humidity and temperature was designed and constructed. Parameters, such as moisture absorption rate, coefficient of thermal conductivity and delay time were used to describe the property varation of moisture absorption, thermal conductivity and combustion performance quantitatively. Weighing method, HotDisk thermal constant analyzer and photoelectric method were used to determine these parameters. Experiment showed that:(1) tungsten type delay was hygroscopic and moisture absorption rate increased with time;(2) moisture absorption rate decreased with the increase of inner temperature;(3) the thermal conductivity and moisture adsorption rate of tungsten type delay changed with consistency, indicating that the thermal conductivity reflected moisture absorption;(4) as the growth of time, delay time drifted and was higher than that in the initial state under hygrothermal environment; the delay time of tungsten type delay in the high temperature was reduced and accelerated with temperature.Hygrothermal environment test for tungsten type delay compositions:tungsten, barium chromate and potassium perchlorate showed that:tungsten was of strongest hygroscopicity and greatest thermal conductivity among three compositions, which ultimately affected the combustion performance of tungsten type delay. Simultaneously, by the method of X-ray photoelectron spectroscopy, chemical changes may occur under high temperature and high humidity environment of tungsten. We found that tungsten was easily oxidized to generate WOx, which leaded to the increase of delay time under hygrothermal condition. Considering single factor of high temperature, no obvious change was detected and corresponding delay time of tungsten type delay was the shortest. A simulative method with Material Studio software was implemented to depict the interaction of water with tungsten crystal surface, to illustrate the phenomenon of electron transfer between water and tungsten from molecular lever.DTA thermal analysis method was carried out to study thermal performance of tungsten type delay under three hygrothermal environment: high temperature and high humidity, room temperature and high temperature, high temperature. Results showed:high water content or high temperature in agents brought down the energy required to pre-ignition combustion reaction zone and exothermic reaction area. The corresponding delay time at room temperature, high humidity and high temperature was smaller.Long term storage characteristics of lead azide and tetrazene were discussed under high temperature and high humidity. Experimental results showed that:(1) lead azide decomposed, quality declined, coefficient of thermal conductivity reduced and the semiconductor bridge ignition sensitivity lowered;(2) moisture was absorbed by tetrazene, and moisture absorption rate increased with rising time, thermal conductivity increased, semiconductor bridge ignition sensitivity improved;(3) FT-IR spectroscopy depicted the basis for the change of sample property:water absorption and the subsequent chemical interaction due to the existence of water and high temperature.