I've been thinking about ETN, and how it detonates when heated in aluminium foil. Id quite like to know more about what is going on during the process
& if a temperature could be calculated for the detonation of ETN by heat.
Is the shock wave caused by the combustion gas itself? Or the trapped air around the particles act as hotspots? or both?
Is the detonation caused by the temperature of the ETN itself? Or is it how quickly it rises to a given temperature?
If anyone has any insight on this I would be very grateful
Ral123 - 20-10-2013 at 12:05
ETN melts before it deflagrates or whatever. From my tests melt cast ETN performs poorly unless at ideal conditions(booster and/or confinement). I
would trust this process with MHN more. At least it has a higher melting point.User64 - 20-10-2013 at 12:17
I'm not exactly sure if containment, partial or complete, is the only contributing factor to the transition. Granted aluminum foil isn't much
containment, however, containing a solid turning into a gas may allow different burn characteristics all together.
Complete burn of the fuel in containment versus partial burn in a non contained state might be a factor... ? Alster337 - 20-10-2013 at 12:20
I'm not interested in the foil technique for practical purposes. I tend to use nichrome as its far more reliable. I'm using the foil method as an
example as im curious as to what happens during the heating process that causes the ETN to detonate rather than just continue burning.
Its quite frustrating as DDT isnt covered in any of the explosives books ive looked at so far, perhaps because most fuse/nichrome initiated explosives
tend to be primaries, so people think it just detonates straight away, and it doesn't actually go though DDT?
@user64 I think confinement does play a factor, as the gases are contained within the container and thus contribute to the heating of the explosive as
they remain in contact with the explosive for longer than they would if the explosive was not contained?
[Edited on 20-10-2013 by Alster337]Dany - 20-10-2013 at 12:22
What is going up is that when you heat the ETN (or any other explosive) in aluminium foil, the sample will heat up to reach the explosion temperature
or critical temperature Tc. Tc is a function not only of the explosive materials but it depend also on size, shape, previous
history, and initial conditions of the sample. Many test are devoted to get the Tc (and time to explosion) of explosives such as Henkin
test and the LLNL One-Dimensional Time to Explosion(ODTX). Also the Tc and time to explosion can be predicted using the Frank-Kamenetskii
equation (for more information see LLNL Explosives Handbook Properties of Chemical Explosives and Explosive Simulants, Dobratz & Crawford, 1985)
Now if you apply a direct flame on the ETN or other explosive it will start to burn and probably undergoes a deflagration to detonation transition or
DDT (the DDT depend on the sample size, porosity, confinement, how sensitive is the materials...). Maybe ETN, since it is sensitive it will explode
readily (the DDT is very fast such that you eyes will see only the explosion). However, for 1,3,5-triamino-1,3,5-trinitrobenzene (TATB) which is a
very insensitive explosive no DDT occur even under heavy confinement.
The handbook of Dobratz & Crawford can be downlod it from here:
If anyone has any insight on this I would be very grateful
I'd guess that fairly minimal confinement coupled with contact with very hot Al is sufficient to detonate ETN . . .Alster337 - 20-10-2013 at 12:28
@Dany
Thanks for the explanation, i would love to read more into it but when I click your link it claims I do not have access... I'm guessing its in the
references section? Dany - 20-10-2013 at 12:30
