Dextrinated lead azide

Lead azide is not readily dead-pressed, ie, pressed to a point where it can no longer be initiated. However, this condition is somewhat dependent on the output of the mixture used to ignite the lead azide and the degree of confinement of the system. Because lead azide is a nonconductor, it may be mixed with flaked graphite to form a conductive mix for use in low energy electric detonators. A number of different types of lead azide have been prepared to improve its handling characteristics and performance and to decrease sensitivity. In addition to the dextrinated lead azide commonly used in the United States, service lead azide, which contains a minimum of 97% lead azide and no protective colloid, is used in the United Kingdom. Other varieties include colloidal lead azide (3—4 pm), poly(vinyl alcohol)-coated lead azide, and British RE) 1333 and RE) 1343 lead azide which is precipitated in the presence of carboxymethyl cellulose (88—92). 

The original initiating explosive used by Nobel and all manufacturers for many years was mercury fulminate. This had the disadvantage of decomposing slowly in hot climates, particularly under moist conditions. For this reason mercury fulminate is no longer widely used. In most countries it has been replaced by a mixture of dextrinated lead azide and lead styphnate. In the U.S.A. some detonators are made containing diazodinitrophenol. 

Evans and Yuill [97] investigated the ignition of dextrinated lead azide by the adiabatic compression of air surrounding it, and estimated that the 50% explosion level corresponds to a temperature of 990°C. 

The presence of dextrin in the solution favours the precipitation of tiny, equal sized, rounded crystals. In Fig. 47 magnified crystals of dextrinated lead azide are shown and in Fig. 48 crystals of ordinary lead azide are shown for comparison. According to Sudo [96] gelatine exerts an influence similar to that of dextrin. In this author s opinion when precipitated from a solution containing gelatine lead azide is less sensitive to friction than that from solutions without added colloids. 

It has been applied in expls industry for coating various expls to render them less sensitive. An example is "Dextrinated Lead Azide (DLA), described in Vol 1 of this Encycl, pp A545 R to A548-R md A557-R to A563-L... 

DLA (dextrinated Lead Azide) has usually been used with PETN as a base chge... 

MLSt - Milled Normal Lead Styphnate mixed with NC lacquer DLA — Dextrinated Lead Azide l —Igniter 30/70-Boron/Lead Peroxide... 

A) Dextrinated Lead Azide (abbrd as DLA), known also as Type l LA((/S). Its prepn and props are described under Lead Azide... 

Miles, JCS 1931 2532-42 (Formation and characterization of crysts of LA and some other initiating expls) 5)K.S.Warren, PATR 1152 (1942), "Study of the Action of Lead Azide on Copper 6)J.Fleischer J.B. Burtle, USP 2,421,778 (1947) "Initiating Explosives 7)Wm.H.Rinkenbach A.J. Clear, PATR Rev 1(1950), "Standard Laboratory Procedures for Sensitivity, Brisance and Stability of Explosives 8)U.S.Military Specification MIL-L-3055, Amend 1(1952) (Requirements and tests for dextrinated lead azide) 9)J-Bernstein, GLR 51-HI-2332, Pic Arsn (1952) "Hygroscopicity of Dextrinated Lead Azide 10)J.W.Lavitt, PATR 1957 (1953), "An Improved Microscopic Method for the Determination of the Crystal Size Distribution of 2-Micron RDX" 11)F.P. Bowden K.Singh, Nature 172, 378(1953) (Size effects in the initiation and growth of explosives) 12)J.W.C.Taylor, A.T.Thomas... 

K.J.Holloway, ERDE (Explosives Research Development Establishment) Rept No 17/R/ 53(1953) (Manuf of RD-1333 LA) (Conf) 13) M.Falcione, GLR 54-HI-1354, PicArsn (1954) "Hygroscopicity of Dextrinated Lead Azide 14)D.E.Seeger, PATR 2198(1955), "Development of the M47 (T32E1) Detonator 15) Armour Research Foundation, Contract No DAI-ll-022-ORD-(P)-18, Rept No 6, 25 Apr 1956(CrystalIographic props of primary expls) l6)B. Furini, Jr, EPR (Eastern Process Rept)-220, No 10, Serial No 30, E.I. du Pont de Nemours Co (1956), "Special RD-1333 Lead... 

RDX, etc) are too sensitive to be used per se and must be desensitized. For example LA may be desensitized by coating its crysts either with dextrin (See Dextrinated Lead Azide in Vol 1, pp A 46 to A548) or with PVAlc (polyvinyl alcohol) (See Vol 1, p A558-R). It can also be desensitized by controlling the size and shape of its crysts [See Service Lead Azide (Brit) in Vol 1, p A557-R], or by pptg it in colloidal form (See Vol 1, p A558-L)... 

Lead azide is produced as a white precipitate by mixing a solution of sodium azide with a solution of lead acetate or lead nitrate. It is absolutely essential that the process should be carried out in such manner that the precipitate consists of very small particles. The sensitivity of lead azide to shock and to friction increases rapidly as the size of the particles increases. Crystals 1 mm. in length are liable to explode spontaneously because of the internal stresses within them. The U. S. Ordnance Department specifications require that the lead azide shall contain no needle-shaped crystals more than 0.1 mm. in length. Lead azide is about as sensitive to impact when it is wet as when it is dry. Dextrinated lead azide can apparently be stored safely under water for long periods of time. The belief exists, however, that crystalline service azide becomes more sensitive when stored under water because of an increase in the size of the crystals. 

Fig 10 Gas Evolution by Irradiated Dextrination Lead Azide at Different Temperatures (Ref 37)... 

M.Falcione, GLR 54-HI-1354, PicAtsn (1954) "Hygroscopicity of Dextrinated Lead Azide ... 

General Properties A545 to A550 Laboratory Preparation A546 Manufacture of Dextrinated Lead Azide A547... 

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