Electrostatic Sensitivity Apparatus

Static Electricity and Sensitivity to Initiation by Electrostatic Discharge. See under Electrostatic Discharges and Sensitivity of Explosives to Initiation by Them in Vol 5, E38-L to E55-L Addnl Refs 1) M.S. Kirshenbaum, Response of Lead Azide to Spark Discharges Via a New Parallel-Plate Electrostatic Sensitivity Apparatus . PATR 4559 (1973) 2) Ibid, Functional... 

Response of Primary Explosives to Gaseous Discharges in an Improved Appro aching-EIec-trode Electrostatic Sensitivity Apparatus , PATR 4995 (1976) 4) Ibid, An Improved Electro-... 

Iowa (Ref 28) reported static electricity developed during LA handling. Monte si (Ref 31) described a fixed gap electrostatic discharge apparatus for characterizing expls. Perkins of PicArsn (Ref 32) gave a survey of methods of testing for electrostatic sensitivity of expls, while Gentner (Ref 33) described a test for Comp B. Satyavratan ... 

NJ. The following tests are described Impact Test with PicArsn Apparatus (pp 2 to 4 with Figs 1, 2, 3 4 on pp 32 to 35) Impact Test with USBurMines App (4 to 7 with Figs 5, 6 7 on pp 36 to 38) Modified Impact Tests for Liquid Explosive Made with BurMinesApp and with PicArsnApp (7) Explosion Temperature Test (7 to 8 with Fig 8 on p 39) Decomposition Temperature Test (8) Sensitivity to Initiation as Determined by Sand Test (9—II with Figs 9, 10, 11 12 oh pp 40—3) Modified Sand Test for Liquid Explosives (12—14) Electrostatic Sensitivity Test (14—15 and Figs 13 14 on pp 44 45) Brisance by Sand Tests (16—17) Initiation Efficiency by Sand Test (17) Stability Tests, which include 75°C International Test (18) 82.2°C KI Test (19) 100° Heat Test (19) 90°, 100° 120°C Vacuum Stability Tests (19—22 and Figs 15, 16 17 on pp 46—8) 65.5°C Surveillance Test (22—3 and Fig 18 on p 49) ... 

For a given apparatus, electrostatic sensitivity is reported as the electrical energy (in Joules) that results in ignition (for some specific percentage of trials). Because of differences in test methods, it is not unusual to find a range of values reported for the same pyrotechnic material. 

The surface forces apparatus (SEA) can measure the interaction forces between two surfaces through a liquid [10,11]. The SEA consists of two curved, molecularly smooth mica surfaces made from sheets with a thickness of a few micrometers. These sheets are glued to quartz cylindrical lenses ( 10-mm radius of curvature) and mounted with then-axes perpendicular to each other. The distance is measured by a Fabry-Perot optical technique using multiple beam interference fringes. The distance resolution is 1-2 A and the force sensitivity is about 10 nN. With the SEA many fundamental interactions between surfaces in aqueous solutions and nonaqueous liquids have been identified and quantified. These include the van der Waals and electrostatic double-layer forces, oscillatory forces, repulsive hydration forces, attractive hydrophobic forces, steric interactions involving polymeric systems, and capillary and adhesion forces. Although cleaved mica is the most commonly used substrate material in the SEA, it can also be coated with thin films of materials with different chemical and physical properties [12]. 

Coulomb charged the pith balls in the apparatus with electrostatic charges. The first charged ball was fixed in place the second was attached to a horizontal bar suspended by a fiber or wire. When the two balls had like charges, they repelled one another. The force of that repulsion was measured by the distance between the two balls, which was the point where the tension in the twisting fiber equaled the force of repulsion. Using this difficult, sensitive instrument, Coulomb came up with the law now named for him. 

The cell and oscillator circuit should oscillate stably in the range 1 to 3 MHz and should have a frequency drift of less than 1 ppm per minute. The cell temperature should be held constant to 0.1°C by submerging it in a bath of water (or acetone and Dry Ice for low temperatures) contained in a Dewar flask. If the frequency is sensitive to placement of nearby objects (including the experimenter s hands), look for defects in the electrostatic shielding all visible parts of the apparatus should be at ground potential. 

From the above data it can be seen that copper azides are not significantly more sensitive than LA to mechanical stresses with just one exception—cuprous azide. This, however, does not apply to sensitivity to electrostatic discharge where copper azides are shown to be in most cases below the lowest possible limit obtainable with standard apparatus. The estimations of initiation energies by Lamnevik are 1—10 pJ [107], Holloway obtained 0.1-0.2 pJ for both CuNa and Cu(N3)2 [108],... 

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