Dead pressed explosive

Detonation, Dead Pressing in. See Dead-Pressed Explosives" in Vol 3 of Encyfcl, p D20... 

Other evidence indicates that the pre-compression need have no dynamic character, to cause quenching of the detonation. All that is required is the achievement of an initial density above a critical value. In general, this critical value depends on the charge dimensions the smaller the charge, the lower the critical density. For some explosives this density may be lower than the TMD at atmospheric pressure for instance, MF 8t LA,under certain conditions, will not support a high-velocity detonation at densities near crystal (See "Dead-Pressed Explosives in Vol 3 of Encycl, p D20)... 

See Dead-Pressed Explosives in Vol 3, p D20-L. Ficheroulle Kovache claim that this salt is not useful as an explosive primer (Ref 4)... 

Hypercompression of Explosives. See Vol 3, p D20-R under Dead-Pressed Explosives... 

Initiation by Flame. Various aspects of this process were described under Burning and Combustion, Vol 2, pp B343-346 Dead-Pressed Explosives, Vol 3, p D20 Ignition in this Vol Thermal Explosion in a future Vol... 

Dead-Pressed Explosives. Some expls, such as MF, LSt, TATNB, Tetracene or N4S4, lose their sensitivity to detonation (become insensitive) to flame, hot wire, spark or fuse if they are previously subjected to very high pressures, such as 25000-30000psi (Muraour, Ref 3 gives for MF 700kg/cm 2). These expls are then said to be dead-pressed (surcomprimee, in Fr). 

HMTD is an explosive of the initiating type it is more powerful and brisant than MF, rather being comparable to LA and Cyanuric Triazide. It does not become dead-pressed even at pressures of 11000 psi (an advantage over MF)... 

The brisance of tetracene, if it is used alone and is fired by a fuse, is greatest when the explosive is not compressed at all. Thus, 0.4 gram of tetracene, if uncompressed, crushed 13.1 grams of sand in the sand test if compressed under a pressure of 250 pounds per square inch, 9.2 grams if under 500 pounds per square inch, 7.5 grams and, if under 3000 pounds per square inch, 2.0 grams. The data show the behavior of tetracene as it approaches the condition of being dead-pressed. 

Tetracene is easily dead-pressed, its self-acceleration is low, and it is not suitable for use alone as an initiating explosive. 

Cohen and Price s model was applied to several HMX propint formulations with the results shown in Figs 6, 7 and 8. The model information is represented by the solid line plot 58) D. Price A.R. Clairmont, Jr, Explosive Behavior of Simplified Propellant Models , Comb Flame 29, 87-93 (1977) CA 87, 55269 (1977) [The objective of the study was to determine deton vel (D), detonability and shock sensy as functions of loading d (p0) and (critical) charge diameter (dc) for a model proplnt compn contg AP/Al/wax/HMX (50/15/ 15/20%). From the data the authors conclude that (1) D varies directly (or linearly) with po (2) dc increases with increasing p0, (3) deton is diffusion controlled, (4) the proplnt cannot be dead-pressed (it will always detonate), (5) the proplnt is a group 2 expl, and (6) addn of 20% HMX to a proplnt model without expin at 55% theoretical max d lowers the relative Eyring reaction time (to deton) from 1.0 to 0.45 units]... 

To manufacture this explosive, take AN which has been previously powdered to a very fine consistancy (see Powdered AN-AL explosive for methods of particle size reduction). To this is added the fuel oil or diesel in the proper amount. This is thoroughly mixed. If desired, the small amount of "Tide" is added to this mixture after it has been reduced to the consistancy of flour. This addition is highly recommended due to the enhancement of the detonation and sensitivity characteristics of the explosive and decreasing somewhat the sensitivity when packed or "dead pressed" with the subsequent loss of sensitivity. Of course this mixture should be kept from all moisture and stored in a waterproof container until ready for use. The explosive consists of the following ... 

Lead azide is a more efficient detonating agent than mercury fulminate. It requires a higher temperature for its spontaneous explosion, and it does not decompose on long continued storage at moderately elevated tem )cratures. It cannot be dead-pressed by any pressure which occurs in ordinary manufacturing operations. Lead azide pressed into place in a detonator capsule takes the fire less readily, or explodes from spark less readily, than... 

When higher pressures are used to achieve higher densities, a phenomenon called dead-pressing may occur, leading to a material which is hard to ignite and which, if ignited, only bums without detonation [1]. Pressing a primary explosive to a point where it loses its capability to detonate is therefore not desirable. 

The phenomenon of dead pressing is not common to aU primary explosives. Many azides, including lead azide, cannot be easily dead-pressed. On the other... 

---