Polyvinyl azide

They also found that by adding small amounts of dextrin, polyvinyl alcohol or other hydrophilic polymers explosion could be prevented. It is known that these compounds are able to alter the crystal habit of several substances, including lead azide. 

USP 2421778 (1947), p 5 8t CA41, 5724 (1947) [El ectrostatic charges were detd by means of an electroscope for pure LA (Lead Azide), DLA (dextrinated LA), and PVA-LA (polyvinyl.alcbhoI LA), before and after tumbling. Before starting the experiment each sample was allowed to stand for 16 hours before its electrostatic charge, prior to tumbling, was measured. 

The use of polyvinyl ale or gelatin for the desensitization of cupric azide, its decompn in moist air or high temp and its use in detonators were described recently (Ref 20a)... 

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)... 

As a binder system polymers are utilized. If the binders contain energy or gas-producing molecular groups (-N02, -N3), one classifies the binders as Active Binders (e.g. polynitropolyphenylene, glycidyl azide polymer, polyvinyl nitrate and nitrocellulose). If these substances are not present, then the binders are classified as inert binders. Depending on available processing methods, binder types such as thermoset material, thermoplast or gelatinizers can be used. They can then be formed and cured by chemical or physical means. 

D.E.Seeger, PicArsn EDS Rept No 60 (1959) "Investigation of Polyvinyl Alcohol Lead Azide for Use in Detonators 24)R.L. Wagner, PATR 2662(1960), "Lead Azide,... 

Polyvinyl Alcohol Lead Azide (PVA Lead Azidej. Polyvinyl alcohol was used instead of dextrin in Germany [2]. In the U.S.A. it is in use in OUn Mathson Corporation [1311. The addition of 3% PVA makes lead azide of better initiating properties, higher density and an easier inflammability than dextrinated lead azide [1],... 

The first cousin of British Service lead azide is the crystal form precipitated in the presence of polyvinyl alcohol PVA lead azide. At the present time, little (if any) PVA lead azide is produced in the United States, although it is believed... 

In this procedure [3, 12, 13] a known excess of standard ceric ammonium nitrate solution is added to an azide solution or slurry. The excess ceric ammonium nitrate is titrated with standard ferrous ammonium sulfate or sodium oxalate, using ferroin as indicator. The method is extremely simple and flee from hazard once the reagents have been mixed. A serious drawback is that dextrin and polyvinyl alcohol are oxidized by ceric ion. Blay [1] reports gelatin and carboxymethyl cellulose are not oxidized. The method is as follows. 

Of the many types of lead azide—pure or basic, dextrinated, colloidal. Service, polyvinyl alcohol. Special Purpose, RD1333, RD1343, RD1352, and dextrinated colloidal—the types which have been used for military or commercial... 

In another study, Sukhushin and coworkers [35] studied the impulse breakdown strength of lead azide pellets of different thicknesses and densities. The effect of changing electrode polarity was also investigated. The specimen was a wafer pressed on a polished, hardened steel cylinder into a polyvinyl chloride sheath. The outer spherical electrode was of 10 mm diam and positioned against the outer surface of the specimen. Square-wave pulses, 1.5-40 //sec, were used to determine the breakdown voltages. 

Table Vll shows how the process used to manufacture lead azide, or the consequent product, significantly affects the quantity required to initiate a standard secondary explosive, RDX, in the stab-sensitive detonator (Figure la). Dextrinated lead azide has a lower output because it is less compressible and has more diluent namely, 8.5% dextrin compared to the 3.5% carboxymethyl cellulose (CMC) [34] in RD 1333, 2% polyvinyl alcohol in PVA lead azide, and no binder in Service lead azide (see Chapters 1 and 2). This situation is shown quantitatively in Table VII, which shows the minimum charge weights of each...

In the case of lead azide, Andreev [42] and Bowden and Yoffe [43] suggest that lead azide detonates immediately after being ignited and that a burning regime is absent. The theory of fracture that was subsequently developed to explain the initiation of fast reaction [44,45], and the previous observations lead to the conclusion that the shock initiation mechanism of this primary explosive is not likely to exhibit the same characteristics as those exhibited by the secondary explosives. However, examination of the shock sensitivity of dextrinated and polyvinyl lead azide to pulse durations vaiying from 0.1 to 4.0 psec shows that the initiation characteristics are indeed similar to those observed for heterogeneous explosives. 

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