The Sensitivity to Impact and Friction

It should be bom in mind that the sensitiveness to impact and friction increases with temperature. Hence any handling of warm powder (e.g. immediately after drying) should be avoided. >... 

Hutchinson, "The Sensitivity to Impact and Friction in H.D. Fair R.F. Walker, Eds, Energetic Materials 2 — Technology of the Inorganic Azides , Plenum, NY (1977), 122... 

Norris Powder. A low-freezing mining expl invented in 1901 by an American, Norris. It was much less sensitive to impact and friction than contemporary Dynamites. It contained NG 70, mononitrobenzene 15, and Huile empyroma-tique 15%. The latter ingredient consisted of ail oily substance obtained on distn of wood tar. 

The endothermic nitride is susceptible to explosive decomposition on friction, shock or heating above 100°C [1], Explosion is violent if initiated by a detonator [2], Sensitivity toward heat and shock increases with purity. Preparative precautions have been detailed [3], and further improvements in safety procedures and handling described [4], An improved plasma pyrolysis procedure to produce poly (sulfur nitride) films has been described [5], Light crushing of a small sample of impure material (m.p. below 160°C, supposedly of relatively low sensitivity) prior to purification by sublimation led to a violent explosion [6] and a restatement of the need [4] for adequate precautions. Explosive sensitivity tests have shown it to be more sensitive to impact and friction than is lead azide, used in detonators. Spark-sensitivity is, however, relatively low [7],... 

The thermochemical evaluation of the reactants is the place to start, as discussed in Chapter 2. If the potential energy release is 250 cal/g of substance (1000 J/g) or more, it is necessary to determine initiation properties, such as a sensitivity to impact and friction. Thermochemical evaluation of reaction... 

Mercury fulminate (C2N202Hg) is one of the most important primary explosives. It is usually found in the form of a gray powder, is sensitive to impact and friction, and is easily detonated by sparks and flames. It is desensitized by the addition of water, but is very sensitive to sunlight. It reacts with metals in moist environments. It is created by treating a solution of mercuric nitrate with alcohol in nitric acid. Its most important explosive property is that it easily detonates after initiation.10... 

Oxidative nitration avoids the isolation of em-nitronitronate salts, which are often unstable explosives with a high sensitivity to impact and friction. 

The energetic nature of the N-NO2 group means that At-nitro-based explosives are some of the most powerful explosives available and these have largely superseded aromatic C-nitro compounds for military applications. Many nitramines exhibit high brisance and high chemical stability in combination with a favourable low sensitivity to impact and friction compared to nitrate ester explosives of similar power. 

This represents the ease with which an explosive can be set off by a blow friction and is expressed in terms of what occurs when a pendulum of known weight scrapes across an explosive (ignites or explodes or snaps or crackles). Sensitivity to friction is less well-defined than the sensitivity to impact and is expressed only by figures compared with a standard. Some explosives can be arranged as follows in terms of decreasing sensitivity. 

The data indicate that BTATNB is slightly more thermally stable (m.p. 320 °C as compared with 310°C for PATO) coupled with better insensitivity toward impact and friction. Similarly, 5-picrylamino-l,2,3,4-tetrazole [72] (PAT) [Structure (2.28)] and 5,5 -styphnylamino-l,2,3,4-tetrazole [73] (SAT) [Structure (2.29)] have been synthesized by condensing picryl chloride and styphnyl chloride respectively with 5-amino-l,2,3,4-tetrazole in methanol. A comparison of thermal and explosive properties of newly synthesized PAT (deflagration temperature 203 °C and calc. VOD 8126ms"1) and SAT (deflagration temperature 140 °C and calc. VOD 8602 ms"1) reveals that PAT is more thermally stable than SAT but more sensitive to impact and friction. 

The performance of the illuminating formulations is assessed by various parameters such as burning rate, luminosity and luminous efficiency. In addition to performance, some other important characteristics such as sensitivity to impact and friction, ignition temperature, mechanical properties and luminosity are also... 

Sodium azide (see above, p. 189 and Table 36) can be decomposed on heating but it is of low sensitiveness to impact or friction and is not listed as an explosive in transport regulations. According to Gunther et al. [138] rubidium azide is much more sensitive to impact and friction than sodium azide. Gunther believes this to be due to the fact that the radius of the orbit of nitrogen atoms in rubidium azide is much shorter than that in sodium azide. 

This substance is prepared by the action of a hot solution of lead nitrate on a solution of sodium dinitroresorcinate. The lead salt is precipitated as the solution cools. Lead dinitroresorcinate ignites from a direct flame readily and burns with great velocity. Its initiating action is weaker than that of lead styphnate and it is less sensitive to impact and friction than styphnate. It has therefore recently found application as a component of cap compositions. It is valuable because it is safer to handle than styphnate. The preparation of dinitroresorcinol is discussed in Vol. I, p. 536. 

Care should be taken that cuprous acetylide is not contaminated with cupric acetylide which may occur if the cuprous chloride used for the reaction contains cupric salt. This is of importance since cupric acetylide is unstable and explodes on heating even between 50 and 70°C. It is also more sensitive to impact and friction than cuprous acetylide. The pure cupric acetylide is black or brown. 

It must be borne in mind that generally aromatic nitro compounds are not highly sensitive to impact and friction, but become more sensitive at elevated temperatures as they melt (changes in the sensitiveness of TNT are discussed in Vol. I, p. 319). If, therefore, a mechanical device is used for the preparation of mixtures by melting, its construction should be such as to exclude any possibility of friction or impact. It is probably best to use a converter heated with steam or water jackets and fitted with a stirrer that can be lifted out by a special arrangement. After the stirrer has been removed, the contents are poured out by tilting the vessel. 

The first attempts to substitute potassium chlorate for potassium nitrate undertaken by Berthollet [32], who discovered potassium chlorate, were unsuccessful. It was immediately evident that a mixture of potassium chlorate, sulphur and charcoal was exceptionally sensitive to impact and friction, and was therefore too dangerous to manufacture. The removal of sulphur from the mixture did not increase safety and thus the powder has never found practical application. 

These mixtures, however, brought no new advantages and did not fully meet requirements with regard to safety in gassy and dusty mines, sensitiveness to impact and friction and mining efficiency. In addition, perchlorate explosives, like chlorate ones, have the defect that under certain conditions they do not detonate, but burn out in the shothole, which may lead to a catastrophic fire or explosion. Perchlorate explosives were then withdrawn from coal work after World War I and restricted exclusively to rock work. Japan seems to be the only country where some perchlorate explosives are accepted as permitted explosives (see p. 474). 

A disadvantage of mixtures of liquid oxygen with combustible substances lies in their high sensitiveness to impact and friction. This property depends largely on the composition of the combustible material used. Oxyliquits containing sawdust show the lowest sensitiveness, while those containing hydrocarbons (e.g. naphthalene) pitch or petrol are more sensitive. 

The operation in kneaders or disk mixers begins with the mixing of all the ingredients, except those which sensitize the mixture to impact and friction, e.g. potassium or ammonium perchlorates. Molten TNT or another nitro compound (DNT) is then poured in, the whole is carefully stirred and cooled while stirring. Only when the temperature has fallen to 40-50°C, are the perchlorates added. When the material is cooled down to a temperature of 25-30°C, it is stirred for a certain time, then unloaded and transported in sheet metal or wooden boxes to the storeroom. 

Smokeless powders have low sensitiveness to impact and friction. They do not ignite when hit by rifle bullets and are thus fairly safe to handle in war-time. Nevertheless there have been accidents caused by the sudden ignition of nitrocellulose powder brought about by the violent friction between the sharp edge of a heavy bin and powder scattered on the floor. 

Powder grains are sensitive to impact and friction. This is due to the sensitiveness of the main ingredients, nitrocellulose and nitroglycerine. The sensitiveness of these compounds was discussed in Vol. II. 

As a rule, a small quantity of DPEHN present in PETN improves its stability and sensitivity to impact and friction, while large quantities decrease the stability slightly (Ref 2)... 

Classification of substances by their sensitivity to impact and friction is particularly important for the handling of explosives. Some explosives are known to detonate on impact, whereas others will only deflagrate. Table 4.2 presents information on the sensitivity of explosive substances to impact and friction. The values shown describe the force required to initiate the explosive compositions. 

Although this compd is a powerful expi (1,3 x TNT in the ballistic mortar and 1,6 x TNT in the Trauzl block at d 0.8), it cannot be considered suitable for military purposes because of its low stability and high sensitivity to impact and friction(Ref 2)... 

According to Stettbacher, mercuric azide develops the same vol of gas on deton as MF but it is 20 times more brisant. Wohler Krupko (Ref 3) observed that its sensitivity depended on the cryst size of the azide. Mercuric azide is considered to be more sensitive to impact and friction than MF and is so unstable that it frequently undergoes spontaneous deton at the slightest touch even under w (Refs 5 7). Hitch (Ref 4) noted this sensitivity expecially when the azide was prepd from mercuric nitrate and Na or K azide solns but by careful thermal studies he decompd it quanty into its elements without expln below 300°. Miles (Ref 8) reported that in every case when /3-crysts of Hg(N3)2 were present the material was likely to expl, and in w or more rapidly in mercuric nitrate soln, the /3-type was unstable being transformed to the o-type, as in the parallel case of LA,... 

These tests showed that Hexanitrosorbitol is about as sensitive to impact and friction as NG and that it is less stable to heat. Its exp props, with the exception of power (as detd by... 

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