Sensitivity to electric discharge

CoUoidaV lead azide. This is a pure fomi of lead azide (over 99% purity) in fine particles of 3-4 m. It is non-hygroscopic but not readily pourable and hence less adaptable for mass production. It is particularly sensitive to electric discharge and hence used for electric detonators. For tliis purpose colloidaf lead azide is often mixed wdth a concentrated nitrocellulose solution in ethyl ether-ethanol or oilier solvents. 

Silver fulminate is considered as an extremely dangerous primary explosive to handle due to its high sensitivity, particularly to electric discharge and friction. It is more sensitive than MF with respect to both of these initiation stimuli. The sensitivity to electric discharge is extreme, particularly when it is dry [92]. The sensitivity of silver fulminate depends on its crystal form the amorphous form is less sensitive to impact than the crystalline form. However, since it is practically impossible to produce purely amorphous material without any crystals the whole mass might be nearly as sensitive as the crystalline form itself [29]. Taylor and Buxton published preparation of SF in form of fine crystals with an impact sensitivity significantly lower than MF (no explosion from 32.7 cm for 1/2 kg hammer vs. only 12.7 cm for MF) approaching values typical for lead azide [93]. Comparison of impact sensitivity of SF with other common primary explosives is shown in Fig. 2.15. 

The sensitivity of cyanuric triazide to friction and electrostatic discharge has recently been measured by Mehta et al. [140]. They observed that sensitivity to friction of a recrystallized sample is lower than that of a nonrecrystallized one contrary to sensitivity to electrical discharge. The photographs of both samples are presented in Fig. 4.16. The values observed for these two types of cyanuric triazide are compared with lead azide in Tables 4.15 and 4.16 [140]. 

Table 4.16 Sensitivity to electric discharge of cyanuric triazide compared with LA (in mJ) [140]...

Heavy metal salts of 5,5 -azotetrazole are highly sensitive to impact and friction [2, 14]. The lead salt of 5,5 -azotetrazole coated with dextrine showed reduced sensitivity [90]. The values of impact and friction sensitivity, ignition temperature, and sensitivity to electric discharge given by various authors are summarized in Tables 8.14 and 8.15. 

As can be seen in Table 8.14, the mercury salt of 5,5 -azotetrazole is more sensitive to electric discharge than lead styphnate [90]. 

Table 8.14 Initiation temperature, sensitivity to friction (weight used 4 kg), and sensitivity to electric discharge (gap between the needle and vial 2 mm) of metallic salts of 5,5 -azotetrazole...

Compound Impact sensitivity—hso. Ball Disc test (cm) Friction sensitivity (m s- ) Sensitivity to electric discharge Test for sensitive Standard test (J) expl. (No.7) (pJ) ... 

Comparison of sensitivity to electric discharge with other primary explosives is presented in Fig. 2.21. Yeager tested pure TATP and found that 50 is 160 mJ (325 mJ for PETN). When calculating the probability of initiation at lower energies he found that it is statistically possible to initiate TATP at an energy level that can be generated by the human body in approximately 1-2 % of cases. Further, he found that unpurified samples are more sensitive than pure recrystallized ones [62]. 

Electric Spark Sensitivity to. MF is capable of being ignited by a spark from a person charged to less than 5000 volts, a condition that is possible in plant operations. Brown et al (Ref 27) give for Sensitivity to Electrostatic Discharge 0.025 joules (Ref 34)... 

Rate of Detonation. See Detonation Race Rifle Bullet Impact Test — not found Sand Test. See under Brisance Sensitivity to Electric Spark or to Electrostatic Discharge. See under Electric Spark Sensitivity to Initiation — not found Sensitivity to Pressure. When pressed at pressures in excess of 25000psi,. MF will... 

High ignitability by direct action of a flame or electric spark is a characteristic feature of lead styphnate. The salts enormous sensitiveness to the discharge of static electricity was first disclosed in 1938 by Barcikowski, Dobrzynski and Kielczewski [541. 

The sensitiveness of nitrocellulose or nitroglycerine and similar esters to thermal or mechanical factors or to electric discharge. 

TNT, like RDX and Composition B, is not classified as dangerous with respect to hazard from electric sparks. Sensitivity to electrostatic discharge of TNT (thru 100 mesh) is 0,06 Joules (unconfined) and 4.4 Joules (confined) TNT can be detonated by electric discharge (Ref 108)... 

The only nearly pure (99+%) form of lead azide used today in the United States is the so-called colloidal lead azide made by quickly mixing dilute solutions of lead and azide salts. Despite the information in reference [5], colloidal lead azide is neither colloidal in particle size (the specification [6] calls for an average of particle size of 5 pm) nor safer to handle, as this form of lead azide is particularly sensitive to electrostatic discharge. It is used in contact with bridge wires in electric detonators (sometimes applied by mixing with a lacquer binder). The process as developed commercially is a proprietary product, and only small amounts are made as needed. 

Static electric discharge is a serious problem in the electronics industry. Electronic devices are extremely sensitive to static electric discharges. Examples of the sensitivity to electrostatic discharge (ESD) are given in Table 2 (26). 

For the power distribution cable industries, insulatirMi compoimds are selected primarily to obtain required electrical properties for their intended service and anticipated conditions of use. PE insulation is very sensitive to partial discharges. 

MF is highly sensitive to electrostatic discharge— ESD. The published values show a significant spread, and range from 0.51 to 0.62 mJ (Majzlik and Stmad tmpublished work) [70] to 25 mJ [30]. The comparison of sensitivity to BSD with other primary explosives is shown in Fig. 2.21. MF can be initiated by discharge of static electricity generated from the human body [29]. 

Silver azide is generally considered to be highly sensitive to friction and much more than other common primary explosives including LA [21, 84] and, just as with impact, friction sensitivity depends considerably on its crystalline form [65]. The values reported by Millar [81] for two specific kinds of LA (RD 1343) and SA (RD 1374) are presented in Table 4.6. It follows from the results that the sensitivity of at least some commercially produced SA is lower than that of LA. Sensitivity of SA to electrical discharge is higher than that of LA (Table 4.6), while sensitivity to flame is about the same as that of mercury fulminate [6, 21]. 

Sensitivity of HMTD to electric discharge is about the same as that of lead azide, according to our measurements (see Fig. 2.21). 

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