Friction initiation/sensitivity

Highly friction sensitive, with considerable explosion hazard [1], Repeating a published method ([2], where explosion at the m.p., 180°C is noted), the product was dried in a desiccator. When the lid (ground glass flange) was slid olf, the friction initiated explosion of a little of the compound deposited on the flange, and a severe explosion resulted [3],... 

The dry material is readily ignited, bums very rapidly and is moderately sensitive to heat, shock, friction or contact with combustible materials. When heated above its m.p. (103-105°C), instantaneous and explosive decomposition occurs without flame, but the decomposition products are flammable. If under confinement (or in large bulk), decomposition may be violently explosive [1], An explosion which occurred when a screw-capped bottle of the peroxide was opened was attributed to friction initiating a mixture of peroxide and organic dust in the cap threads [2], Waxed paper tubs are recommended to store this and other sensitive solids [3], Crystallisation of the peroxide from hot chloroform solution involves a high risk of explosion. Precipitation from cold chloroform solution by methanol is safer [4], Water- or plasticiser-containing pastes of dibenzoyl peroxide are much safer for industrial use. 

A pyrotechnic mixture containing the powdered ingredients was found dangerously sensitive to frictional initiation and highly explosive. 

The azide is very explosive, even when moist. Loosening the solid from filter paper caused frictional initiation. Explosion initiated by impact is very violent, and spontaneous explosion has also been recorded [1], It is also an exceptionally powerful initiator [2]. Detonation of the azide when dry has been confirmed [3], Good crystals are considerably more sensitive to shock, friction and electric discharge than is powder [4],... 

The following props are given In Blatt (Ref 3) Friction Sensitivity vety. insensitive Impact Sensitivity — less sensitive than PA Initiation Sensitivity — very insensitive when cast Power, by Trauzl Test — 146% PA Power, by Ballistic Mortar — 91% of Blasting Gelatin... 

Friction Sensitivity. LA is more sensitive than MF (Refs 73,79 110). Bowden Gurtcn (Ref 112) detd the effect of grit particles for frictional initiation of LA... 

Crazier, T. H. et al., 52nd Ann. Rept. HM Insp. Explos., London, Home Office, 1928 A pyrotechnic mixture containing the powdered ingredients was found dangerously sensitive to frictional initiation and highly explosive. 

The lack of understanding of the mechanism of frictional initiation of azides limits the operational usefulness of the data obtained. There is little intrinsic merit in the isolated data for any explosive taken alone, but when the data are compared with those for other explosives for which there is also laboratory or industrial handling experience, friction sensitivity data can serve as guides to potential hazards. 

Frictional initiation has been established as an important initiation mechanism, and the sizes of hot spots required for initiation of some explosives are now well known. However, many of the frictional tests used in practice involve shearing of a layer under load between two rapidly moving surfaces. It seems very likely that other processes, in addition to the frictional ones, are present. These tests, although practically very useful, could be improved if the true frictional sensitivity of the explosive is to be investigated. 

Explosives are commonly categorized as primary, secondary, or high explosives. Primary or initiator explosives are the most sensitive to heat, friction, impact, shock, and electrostatic energy. These have been studied in considerable detail because of the almost unique capabiUty, even when present in small quantities, to rapidly transform a low energy stimulus into a high intensity shock wave. 

Molex no s 2 3 are physical mixts of AN 52—84, K perchlorate 0—20, DNT oil 7—12, baked cork 1—10, A1 powd 5—7 Ca carbonate 1%. They exhibited satisfactory sensitivity to impact, friction, flame initiation, and had excellent stability. Philips (Ref 4) reported on tests of Molex B and BB , manufd by the National Explosives Co. They are described as physical mixts of AN 80.77—85.06, flake A1 6.02—6.10, DNT oil 4.32—5.84, activated cork 2.55—4.47, Ca stearate 1.10—1.99 and Ca carbonate 0.83-0.95%. They were shown to be stable, to have fairly high brisance, but to be sufficiently sensitive to expl in the rifle bullet impact test. Byers (Refs 1 3) describes blasting expls similar in compn... 

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