The Response Law And Safety Designs Of Primary Explosives To Static Electricity

Electrostatic phenomenon frequently appears in our daily life and works. When theaccumulated potential is high enough to breakdown the surrounding medium, electrostaticspark discharge occurred, and that may arouse the blasts of energetic materials. Primaryexplosive is the initial energetic materials of initiator, and is easy to accumulate charges asthey are insulating materials, and are sensitive to electrostatic spark discharge. Hence, it isvery important to solve the safety problem of primary explosive and initiator caused bystatic electricity, which requires the studies on the response law and safety design ofprimary explosive to static electricity, and obtain the anti-static products. This paper isfocused on these issues theoretically and experimentally, and the main works andachivements as followings:(1) A new static electricity accumulation tester was developed in this work, which cancontinuous measure the static charges and mass of samples flowed into the Faraday cage inreal time. The static electricity accumulations of LS, LA, LP, BS, GTM, GTN, GTX andGTG were measured under various conditions. The influences of instrument conditions,particle size of sample and environmental temperature and humidity on static electricityaccumulations were investigated comprehensively, and the response laws and mechanismsof the electrostatic electrification and accumulation of primary explosives were obtained.The static electricity accumulations between primary explosives and different flumesdiffer a lot. After friction with nonconducting shellac painted kraft and fabroil flumes,primary explosive generated a great amount of static charges, follow which is theconductive rubber flume, and then are the conducting stainless steel and aluminum flumes.The static electricity accumulation increases with the increased length of flume linearly.Along with the increasing of the tilt angle of flume, the static electricity accumulationincreases firstly, and then decreases, the optimal angles of LS, LA and GTX to accumulatecharges are50o,45o,45o, respectively. In the process of electrostatic electrification ofprimary explosive, the static electricity accumulation increases with the increased frictionand speed of flow, and a binary linear regression model was obtained between them. The model of LS can be described as: Q=105.1125-22.4894f-27.9744v. Along with thedecreasing of the particle size of primary explosive, the static electricity accumulationincreases exponentially, and the equation of GTX can be described as Q=4.7580+966.7923exp (-d/22.9172). The static electricity accumulation increases with thedecreased environmental temperature and humidity. The linear equations for the staticelectricity accumulation of LS on temperature and humidity are obtained as: Q=-19.1110+0.3690T, Q=-26.3080+0.5052H.(2) A set of±50kV electrostatic spark sensitivity tester was established, that employs adigital high voltage generator and a vacuum switch to improve its’ accuracy. Thecapacitance of the capacitors is up to0.22μF. By the electrostatic spark sensitivities ofeight primary explosives tested under various conditions, the influences of instrumentconditions, particle size of sample and environmental temperature and humidity onelectrostatic spark sensitivity were investigated comprehensively, and the response laws andmechanisms of primary explosive to electrostatic spark were obtained. Furthermore, theDSC thermal decomposition parameters,5s delay explosion temperature and flamesensitivity of the8primary explosives were tested, and the prediction models ofelectrostatic spark sensitivity of primary explosive were established based on them.Primary explosives are easier to be ignited by electronegative discharge. After ancurrent-limiting resistor presented in the discharge circuit, the time of discharge lengthen alot, the E50of LS, LA, GTN and GTG increased, but which of LP, GTM and GTXdecreased. As the increase of the value of capacitance, the E50of primary explosivedecreased first and then increased, and the relationship of GTX between them can bedescribed as: E50=1.5130-12.2697C+27.7419C2, an optimum ignition capacitancevalue existed, that of GTX is0.22μF. A bigger electrode gap needs higher electrostaticspark energy to ignite primary explosives. The E50of GTX decreases with the decreasedelectrode gap linearly as E50=0.0956+0.9516gap. The smaller primary explosive particlesare more sensitive to electrostatic spark, the exponential equations between E50and particlesize are found, which of GTX is E50=0.2530+0.0030exp (d/67.2791). The binary linearregression equation between the electrostatic spark sensitivity of LS and temperature andhumidity can be described as: E50=0.4012-0.0097T+0.0031H. E50increases with the decreased temperature and the increased humidity.(3) The density functional theory was used to study the crystal structure, molecularstructure and electronic structure of LS, LA and GTX under external electric field for thefirst time. And the active centres of decomposition of primary explosive in electric field andbreakdown field strength were obtained.In the electric field, the changes of crystal structure are anisotropic, and cellparameters alters non-monotonously, that may be caused by the phase transition of thecrystal of primary explosive. Investigation on molecular structures and partial density ofstates of LS, LA and GTX under external electric field show that: notro group is the activecentre of LS, the activity of whole LA molecule was heightened, in the molecule of GTX,carbohydrazide and perchloric anion are both active site. Along with the increasing ofelectric field intensity, the characteristic peaks of DOS curves were separated, the energyband curves became flatter and the band gap became smaller. At last, the primary explosivewas break down. The band gap of LS under the electric field of4.626V·nm-1is0.299eV,LS became semi-conductor, that is to say, the breakdown field strength of LS is above4.626V·nm-1. Under the electric field of2.570V·nm-1, the band gap of LA is0eV, LA wasbreakdown. GTX was breakdown under the field of4.626V·nm-1.(4) New criterions of the electrostatic spark sensitivity of primary explosive weredescribed as: volume density of average electrostatic potential, band gap and molecularparameters. The prediction models for electrostatic spark sensitivity of primary explosiveon structural parameters were established by linear regression and neural network. Thestatic electricity accumulation of primary explosive was explained by frontier orbital energylevel for the first time.The quantify potential of primary explosives were calculated for the first time. Therelation between E50and volume density of average electrostatic potential can be describedas: lnE50=1.3033-4.3599×ESPave/V. The volume density of average electrostatic potentialof LS is2.125kJ·mol-1·eV-1·-3, is much higher than other primary explosives, that is whyLS is so sensitive to electrostatic discharge. The relation between E50and band gap is: E50=-0.1428+0.9430×ΔEg. Higher energy level of highest occupied molecular orbital (EHOMO)of primary explosive is easier to loss electrons, and to accumulate positive charges. Lower energy level of lowest unoccupied molecular orbital (ELUMO) of primary explosive is easierto accept electrons, and to accumulat negative charges. The relationship between staticelectricity accumulation of primary explosive and ELUMOcan be described as: Q=4.9199+2.2382×ELUMO.(5) The anti-electrostatic design of primary explosive was put forward as: addinggraphene nanoplatelets to modify primary explosive, adding antistatic agents into thereaction solution to modify primary explosive, design and exploitation new primaryexplosive molecules. GNP modified LS and LA were obtained as the replacement of normalLS and LA applied in the priming system with depressed electrostatic hazards.GNP modified LS and LA were obtained by adding GNP to the reaction solution or bycoating normal primary explosives with GNP. SEM, Raman spectroscopy and XRDcharacterization reveal that GNP is well composited with primary explosive crystals. GNPmodified LS and LA exhibit excellent anti-electrostatic performance, as well as thermalstability and sensitivities. Products obtained in industrial scale are uniform and with goodfree-running property. The stab detonator, flame detonator and electric detonator fillingwith the modified samples can detonating reliably, and meet the requests of application.Conclusively, GNP modified LS and LA by adding GNP to the reaction solution with thecontent of GNP is1%can replace the normal LS and LA applied in the priming system.Antistatic agents can improve the anti-electrostatic performance selectivity. CMC canreduce the electrostatic spark sensitivity effectively, and BS12can reduce the staticelectricity accumulation of LS and LA substantially. Nine anti-electrostatic primaryexplosives were designed as the K, Rb and Cs salts of picric acid, styphnate and its’ acidicsalt. The optimized synthetic routes and processes of these compounds were obtained. Thecrystal structures of RbPA、Rb2TNR and CsHTNR were reported for the first time, and allthe nine crystal structures of the compounds were investigated contrastively. The obtainedexperimental electrostatic spark sensitivity of KPA and K2TNR are well according to thepredicted values, which confirmed the dependability of the prediction model.