Polyvinyl Alcohol Lead Azide PVA

Wyatt [7] showed that the minimum energy value of PVA lead azide decreases from approximately 2.2 X 10 J to about 1 X 10 J when the polarity of the steel needle is changed from negative to positive (rubber-base electrode). The minimum capacitance for initiation is also lowered from about 400 pF to about 200 pF. This effect is not observed when the bottom (stationary) electrode is steel. 

Montcsi [10] reported a minimum energy value between 3.1 X 10 and 4 X 10 J for PVA lead azide. The value was obtained with a fixed-gap, needle-plane apparatus, using a 1.25-mm (0.050-in.) gap, 100-Q series resistance, and a 1000-pF storage capacitor. The apparatus is used primarily to provide relative sensitivity data for explosives. The high minimum energy value obtained may have been due to the use of the 100-Q series resistance and the large 1.25-mm gap. 

Montesi [21] reported a minimum initiation energy between 3.1 and 4.5 X 10 J when he used Wyatt s approaching-needle, metal-base electrode apparatus and procedure. Substituting a rubber base increased the minimum initiation energy to greater than 8 X 10 J. In a more recent report, Montesi [22], using Wyatt s apparatus and the interim test procedure described in the United States Joint Service Safety and Performance Manual [23], reported min- 

Two energy values are reported for dextrinated lead azide using a fixed- 

Flgure 14. Partially burned dextrinated lead azide (magnified 15X) [11]. 

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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],... 

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