Explosibility testing confinement sensitivity

The relative shock sensitivities of explosive compositions are commonly assessed by means of gap tests. In these tests, the shock from a standard donor explosive is transmitted to the test explosive through an inert barrier (the so called gap ). The shock sensitivity of the test explosive is characterized by the gap thickness for which the probability of detonation is 50%. In reference 26, the Los Alamos standard gap test and the Naval Ordnance Laboratory (NOL) large scale gap test were modeled using the 2DE code with Forest Fire burn rates. The Los Alamos gap test uses Dural for the inert barrier while the NOL gap test uses Plexiglas. The test explosive is unconflned in the Los Alamos gap test. In the NOL gap test the test explosive is confined with steel. The model showed good agreement between the calculated and experimental gap test values for PBX-9404, PBX-9502, Pentolite, Composition B, and an HMX based propellant, VTQ-2. 

The explosive decomposition of the solid has been studied in detail [6], The effect of moisture upon ignitibility and explosive behaviour under confinement was studied. A moisture content of 3% allowed slow burning only, and at 5% ignition did not occur [7], Thermal instability was studied using a pressure vessel test, ignition delay time, TGA and DSC, and decomposition products were identified [8], The presence of acyl chlorides renders dibenzoyl peroxide impact-sensitive [9], There is a further report of a violent explosion during purification of the peroxide by Soxhlet extraction with hot chloroform [10], Residual traces of the peroxide in a polythene feed pipe exploded when it was cut with a handsaw [11]. The heat of decomposition has been determined as 1.39 kJ/g. The recently calculated value of 69° C for critical ignition temperature coincides with that previously recorded. 

Fia 6 Effect of A on shock sensitivity of various explosives. NQ-f is low-bulk-density nitroguanidine with hollow-needle crystals of about 5 n diam X 60-65 it long. NQ-h is the high-bulk-density material made up of solid particles of about GO-65 n diam. DATB, TNT, and Tetryl are, respectively, dia-minotrinitrobenzene, trinitrotoluene and trinitro-phenylmethylnitramine. RDX is cyclotrimethyl-enetrinitramine which contains 2.5% lubricant. Measurements were carried out with a standardized test (Ref 16) in which a 3.65-cm-diam test explosive confined in 0.55-cm-thick steel is the acceptor and polymethyl methacrylate is the gap material MGl = NCro filt ro uasiM i ... 

The explosive was exhaustively characterized for thermal behavior, impact sensitivity and electrostatic discharge sensitivity etc. Based on this data, CP has been described as much less sensitive to accidental initiation than primary explosives such as LA but at the same time, initiation grows rapidly to detonation when properly confined. Its performance evaluation in a test detonator or hardware indicates that CP can replace primary explosives in many hot wire detonator applications especially if safety considerations are of prime importance [239]. 

Explosion temperature no ignition up to 340° Impact sensitivity - less sensitive than TNT Power by Trauzl test, 86% of TNT Sensitivity to initiation, requires a powerful detonator when confined... 

Sensitivity. 1) B.D. Pollock R.F. Gentner, Impact Sensitivity of Wetted Primary Explosives as Determined by the Ball Drop Test , PATR 4311 (1972) [Table 8 lists the impact sensy data found by these workers on unconfined dry and w-wet Pb Azide. Addnly, they found that w completely desensitized Pb Styphnate and Tetracene and that all fully-wetted unconfined primary expls were less sensitive to impact than when dry, but that partially wet (w-soaked but no excess of w present) confined initiating expls are more sensitive to impact than when fully dried... 

Sensitivity to Heat and Electric Charge The Ignition (or Explosion) Temperature Test measures thermal stability, which is discussed under Chemical Properties . The test is run with the sample either confined or unconfined (see Vol 1, XVI). Test results are quite sensitive to conditions and to sample purity, and as a result, ignition values for TNT reported in the literature differ by as much as 200° C (Ref 156 see discussion in Vol 4, D583-L ff). Careful studies using different procedures with confined samples have given ignition temps of 275° (Ref 156),... 

For impact sensitivity of confined explosive charges thrown against a steel target -> Susan Test. 

This hquid acetylenic endothermic compound j estimated as 230-270 kj/mol, 2 kJ/g) may be decomposed by mild shock, and when heated under confinement, it decomposes with explosive violence and may detonate. Addition of 20-30 wt% of toluene makes the bromide insensitive in laboratory impact and confinement tests [1] More recently, it was classed as extremely shock-sensitive [2]. It can be ignited by impact derived from the liquid-hammer elfect of accidental pressurisation of the aerated liquid, and will then undergo sustained (monopropellant) burning decomposition. Propargyl bromide, added dropwise to bromine, exploded as it neared the halogen [3]. The chloro analogue is similar, but less readily ignited [4]. 

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