Detonation rate lead azide

The rate of detonation of a thin film of lead azide (0.1-0.5 mm thick) is 2100 m/sec (Bowden and Williams [101]). Lead azide is less sensitive to impact than mercury fulminate, but drop test figures quoted by various authors differ widely. Some of them report a negligible difference between the two, while others state it is considerable (e.g. that azide requires 2-3 times the height of drop necessary to explode fulminate). On the other hand, when mixed with pulverized sand lead azide is more... 

Brisance by Sand Test Q.4g sample initiated by Lead Azide in 200g sand bomb crushed 57.4g sand vs 62.7g crushed by PETN(Ref 24) Detonation Rate 7410m/sec at sp gr 1.59 vs 8340m/sec at sp gr 1.71 far PETN (Ref 5, P175 and Ref 12)... 

Chaudri et al (Ref 21) claim to have observed an unexpectedly high detonation velocity of about 8km/sec for single crystals of cr-lead azide of 2 x 2mm cross-section. They used a framing camera at a framing rate of 5 x 106 sec 1 for their measurements. Frequently it is difficult to obtain reliable quantitative data by this method... 

Chaudhri and co-workers [190] determined the rate of detonation of single crystals of a-lead azide. Crystals of cross section 2 mm X 2 mm and above detonated at 8000 m/s, and smaller size (od. 1 mm) exploded at 3000 m/s. 

According to Bowden and Singh [201] it is not decomposed by a and y-radiation. It shows the rate of detonation 4200 m/s.. According to Wohler and Martin [202] it is less sensitive to impact than lead azide, but more sensitive than silver azide. 

Normally, the rate of production of lead azide is geared to the rate at which it can be incorporated in explosive trains. In this manner the total quantity on hand is minimized and is broken down into small lots and packaged so that the accidental detonation of one component will be less likely to result in the sympathetic detonation of large stores. However, during the South East Asia conflict a substantial overproduction of lead azide occurred, and bulk quantities were produced far in excess of normal rates. This situation required a special awareness of three problems which, although always of concern, do not normally assume such proportions. These were the problems associated with bulk storage and handling of the finished product with the accumulation of hazardous waste... 

Under the conditions found in detonators, a transition to detonation is not necessarily instantaneous. As discussed in Volume 1, Chapters 8 and 9, the extent to which deflagrations or different orders of detonation occur in the azides is not clear. But there is considerable evidence that both unconfined and small confined samples of lead azide will sustain, at least transiently, propagation rates less than those of full detonation. Table III summarizes some of the data, which are dis-... 

The data are consistent with the observations of Chaudhri and Field [12] on single crystals of lead azide (see Chapter 8, Volume 1) they concluded that the maximum propagation rate prior to detonation is the longitudinal wave speed. The data are also consistent with the fracture velocity obtained by Fox [47] (Chapter 9, Volume 1). 

It appears that insofar as growth to stable detonation is concerned lead azide displays characteristics similar to those of heterogeneous secondary explosives. The delayed stress excursions evident in measured stress profiles were interpreted as reactions behind the shock front. Reactions produce pressure waves which travel through the explosive at a velocity at least equal to its velocity of sound and interact with the undecomposed explosive ahead of the reaction front, causing a nonuniform rate of growth. 

Sukhushin and Zakharov [16] investigated the shock sensitivity and detonation rates for lead azide-silver azide, lead azide-copper azide, and silver azide-copper azide mixed-crystal systems. The most striking effect occurred when the minor constituent was less than 10% of the composition. Such systems are perhaps better viewed as being heavily doped than as mixed crystals. 

C min (LA type RD 1333) [35] 357-384 C at a heating rate of 40 °C min [43]. The 5-s explosion temperature of LA is 340 °C [49]. LA has been found not to have changed after being stored for 4 years at 80 °C. The thermal stability threshold is, according to Danilov, 200 °C at which temperature it keeps its explosive properties for 6 h. It is therefore used in thermostable detonators TED-200 with maximum application temperature 200 °C [3]. We have tested various types of lead azides at our laboratory and found that standard industrial dextrinated LA (product of Austin Detonator) is surprisingly even more thermally stable than pure crystalline product. The decomposition of both types (pure and dextrinated) of LA under the same conditions is shown in Fig. 4.2. 

Lead azide is used in many applications accompanied by other substances that compensate for its drawbacks, particularly its low sensitivity to flame and stab. The most common additive in detonators is lead styphnate which improves the inflammability of resulting mixture. A typical composition of this binary mixture is 30 % LS and 70 % LA. It is sometimes presented that lead st3q)hnate can serve as a protective layer against access of water and carbon dioxide to LA surface [3, 4]. However, lead styphnate increases the level of acidity and accelerates the rate of hydrolysis of LA in presence of moisture [35, 49]. Regardless of this fact a combination of LA/LS is still used in detonators. 

When a 0.5 gram sample of tetryl is heated at a rate of 20°C per minute, ignition occurs between 190°C and 194°C. If the temperature of a sample is held at 180°C ignition occurs in 40 seconds. The minimum primary charges necessary for reliable detonation of tetryl with mercury fulminate is 0.20 to 0.29 grams and with lead azide is 0.025 to 0.10 grams. Tetryl containing 60 percent water cannot be detonated by a commercial detonator. Shock sensitivity as measured by the gap tests are summarized in table 8-30. 

The crystalline product appears less stable than the diazide, spontaneously decomposing, sometimes explosively [1], It was rated as too unstable for use as a practical detonator or explosive [2], Lead(IV) acetate azide (probably the triacetate azide) is also rather unstable, evolving nitrogen above 0°C with precipitation of lead(II) azide [3], Lead(IV) azide will be considerably more endothermic than the lead(II) salt. 

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