Primary explosives impact/friction sensitivity

Silver azide is generally considered to be highly sensitive to friction and much more than other common primary explosives including LA [21, 84] and, just as with impact, friction sensitivity depends considerably on its crystalline form [65]. The values reported by Millar [81] for two specific kinds of LA (RD 1343) and SA (RD 1374) are presented in Table 4.6. It follows from the results that the sensitivity of at least some commercially produced SA is lower than that of LA. Sensitivity of SA to electrical discharge is higher than that of LA (Table 4.6), while sensitivity to flame is about the same as that of mercury fulminate [6, 21]. 

This primary explosive is created by adding lead acetate to a solution of sodium or ammonium azide. Lead azide has a good shelf life in dry conditions but is unstable in the presence of moisture, oxidizing agents, and ammonia. It is less sensitive to impact than mercury fulminate, but more sensitive to friction. Since lead azide is a nonconductor, it may be mixed with flaked graphite to form a conductive mixture for use in low-energy electronic detonators. 

Tetrazene (C2H8N10O) is a pale yellow crystalline explosive generally used in ignition caps, where a small amount is added to the explosive composition to improve its sensitivity to percussion and friction. Tetrazene is not suitable for filling detonators because its compaction properties make the transition from burning to detonation very difficult. This primary explosive is stable in ambient temperatures. Its ignition temperature is lower and it is slightly more sensitive to impact than mercury fulminate. 

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... 

Diazodinitrophenol (CgH Oj) has been used as an initiator in industrial blasting caps. It is less sensitive to impact, friction, and electrostatic energy than other primary explosives. It is orange-yellow in color and is sparingly soluble in water.11... 

Pentaerythritol tetranitrate (PETN) is a colorless crystalline solid that is very sensitive to initiation by a primary explosive. It is a powerful secondary explosive that has a great shattering effect. It is used in commercial blasting caps, detonation cords, and boosters. PETN is not used in its pure form because it is too sensitive to friction and impact. It is usually mixed with plasticized nitrocellulose or with synthetic rubbers to form PBXs. The most common form of explosive composition containing PETN is Pentolite, a mixture of 20 to 50% PETN and TNT. PETN can be incorporated into gelatinous industrial explosives. The military has in most cases replaced PETN with RDX because RDX is more thermally stable and has a longer shelf life. PETN is insoluble in water, sparingly soluble in alcohol, ether, and benzene, and soluble in acetone and methyl acetate. 

There seems to be a noticeable difference in the Ball Drop Impact results and this could be attributed to the inherent error associated with this relatively crude test for instance, the manner and precise location, at which the steel ball impacts the explosive particles can vary and lead to inconsistent results. Friction and electrostatic sensitivity was consistent across all of our batches of DBX-1 as well as PSEMC DBX-1 (Table 3) In terms of determining the effectiveness of a primary explosive, sensitivity tests results are generally only predictive in how to safely handle the material in order to determine if the explosive is practical or not, performance tests need to be done to see how well the material behaves in actual items, such as detonators. 

Although C.v. Girsewald patented the use of HMDT as a primary explosive for detonators, its sensitivity to heat, friction and impact, its incompatibility with metals and its poor storage qualities make it unsuitable for practical use (Ref 16)... 

Priming (or Primary) Explosive Compounds or Mixtures (such as Lead D in icro re sore inace and Lead Styphnat )are sufficiently sensitive to impact or friction to explode (or deflagrate), developing a high temperature and producing... 

Some pyrotechnic formulations Ti/KDN/NC and Ti/CsDN/NC were formulated and tested for combustion velocity, sensitivity to impact, friction and electrostatic discharge etc. The data show that both formulations are extremely sensitive to impact (the sensitivity being in the range of pure HMX and PETN ). Further, it is also seen that the Ti/KDN/NC formulation is less sensitive [145] than Ti/ CsDN/NC. On the contrary, the formulations show a moderate sensitivity to friction and electrostatic discharge. The evaluation of such systems as components in ignition formulations appear to be very promising as this may allow replacement of the heavy metal primary explosives which are toxic in nature. 

According to Ficheroulle and Kovache [137] barium azide has a low sensitiveness to impact (a 2 kg weight falling from 100 cm causes 14% of explosions) but it is very sensitive to friction. It does not possess the properties of a primary explosive,... 

In this book the term sensitiveness is used to describe the response of an explosive to accidental initiation, i.e. friction, impact, etc., whereas sensitivity is used when the explosive is initiated by non-accidental methods, i.e. shock from a primary explosive. 

Primary explosives have low values for the activation energy and collision factor compared with secondary explosives. Therefore, it takes less energy to initiate primary explosives and makes them more sensitive to an external stimulus, i.e. impact, friction, etc., whereas secondary explosives have higher values for the activation energy and collision factor, and are therefore more difficult to initiate and less sensitive to external stimulus. 

Triacetone triperoxide (TATP, Fig. 1.14) is formed from acetone in sulfuric acid solution when acted upon by 45 % (or lower concentration) hydrogen peroxide (the acid acts as a catalyst). Like most other organic peroxides TATP has a very high impact (0.3 J), friction (0.1 N) and thermal sensitivity. TATP has the characteristics of a primary explosive. For this reason and because of its tendency to sublime (high volatility) it is not used in practice (apart from terrorist and suicide bomber activities). 

The sensitivity of K2DNABT was tested and was found to be very sensitive to impact, friction and ESD, as all primary explosives are. K2DNABT is more sensitive compared to lead azide, lead styphnate and DBX-1 (as shown in Tab. 1.3a). 

Primary explosives are substances which unlike secondary explosives show a very rapid transition from combustion (or deflagration) to detonation and are considerably more sensitive towards heat, impact or friction than secondary explosives. Primary explosives generate either a large amount of heat or a shockwave which makes the transfer of the detonation to a less sensitive secondary explosive possible. They are therefore used as initiators for secondary booster charges (e.g. in detonators), main charges or propellants. Although primary explosives (e.g. Pb(N3)2) are considerably more sensitive than secondary explosives (e.g. RDX), their detonation velocities, detonation pressures and heat of explosions are as a rule, generally lower than those of secondary explosives (Tab. 2.1). 

Table 6.1 shows a summary of typical values for the impact, friction and electrostatic sensitivities of some primary and secondary explosives. 

Primary explosives. Primary or initiator explosives are most sensitive to heat, friction, impact, and shock. This class of explosives has been studied in detail and they are very reactive even when present in small quantities. Primary explosives are capable of transforming a low-energy into a high-intensity shock wave. 

Both impact and friction were considered by Bowden and Yoffe [8, 83] to be stimuli which lead to initiation via the formation of hot spots. Insofar as no existing test is entirely free of both impulsive loads and the movement of explosive particles with respect to contiguous surfaces, both adhesion and shear may be suspected to play a role in determining sensitivity, and it is not uncommon to consider the brittleness and hardness of azides and other primary explosives when comparing their sensitivities to those of secondary explosives. 

High explosives are further divided into primary, secondary, and tertiary explosives. Primary explosives can be made to detonate by the application of a spark or flame. They also tend to be rather sensitive to impact and friction. Primary explosives are not usually used as demolition or weapon charges instead, they are normally used to make blasting caps. 

There is little information readily available on lead picrate. However, it is a workable primary explosive. This material is not very powerful and should always be used with a booster charge of an easily detonated secondary explosive. Like all primary explosives, this material is very sensitive to impact, friction, and sparks. 

The most sensitive of the military explosives classed as primary explosives. In a finely divided state, it is as sensitive as mercury fulminate. Veiy sensitive to heat, shock, and friction. Sharp blows or metal-on-metal friction is sufficient to cause detonation. Readily detonated by bullet impact and may be ignited by sparks. Not normally ignited or detonated by static electricity generated on the body or in routine handling. Extremely sensitive to ignition by lead azide but not from the spit of a fuze. Very insensitive to flame, shock, and friction in primacord so must be detonated by cap. Does not detonate under long, slow pressure. 

Explosive, primary Explosive substance manufactured with a view to producing a practical effect by explosion which is very sensitive to heat, impact or friction and which, even in very small quantities, either detonates or bums very rapidly. It is able to transmit detonation (in the case of initiating explosive) or deflagration to secondary explosives close to it. The main primary explosives are mercury fulminate, lead azide and lead styphnate. UN App. B, ICAO A2, lATA App. A... 

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