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golfpro
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RDX vs. ETN
I have a few questions about the differences in the two. I have read somewhere that ETN is favorable over RDX for power in small amounts, but then in
larger amounts ETN is sluggish compared to RDX. Is this only for certain density or all densities possible and what amount is the intersecting point
when RDX performs equally with ETN using whatever test for this. I haven't been able to wrap my mind around why this happens if it does?
500g ETN vs. 500g RDX at pressed density, what would be the difference between the two? (Steel Plate test, Sound, etc.)
I've also heard of ETN detonating much slower than the standard velocity even at cast density, how could this possibly happen?
Anyway, I think it would be cool to have an ETN/RDX cast that's cap sensitive, or ETN/RDX plasticized together.
[Edited on 1-9-2013 by golfpro]
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Dany
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it is not important if the charge is small or big. what is important is the loading density at which each explosive is detonated given that no other
effect is interfering (e.g.,detonation is far from critical diameter). So comparing ETN and RDX at density= 1.77g/cm3 you will find for ETN
Dcj= 8.3 km/s and Pcj= 303 kbar while for RDX Dcj= 8.7 km/s and Pcj= 338 kbar. (the value for RDX are from
(PROPERTIES OF CHEMICAL EXPLOSIVES AND EXPLOSIVE SIMULANTS, B. Dobratz, 1972) while that of ETN (Thermochimica Acta 566 (2013) 137– 148, the
detonation pressure is estimated using the polytropic equation of state).
A recent paper by J.C.OXELY, demonstrate that RDX performe better than ETN and other nitrate ester in a test called Small-Scale Explosivity Testing
(SSET). also RDX has higher decomposition temperature than ETN. the critical temperature for thermal decomposition is 181.8°C (Thermochimica Acta 566
(2013) 137– 148) while that of RDX is 260°C.
yes you can make ETN performance better than RDX if you detonate the ETN at higher loading density than that of RDX. so based on the information
above, detonating 500 g of RDX and ETN at the same loading density, you will notice a deeper depression in steel plate test (we calle it plate dent
test and not steel plate test) for RDX than that of ETN.
i don't understand what you mean by " ETN detonating much slower than the standard velocity even at cast density", but anyway the denser the ETN the
better the performance because ETN is considered an ideal explosive, so Dcj will increase linearly with density. For some type of
explosive like ANFO or Ammonium perchlorate/aluminium, detonation velocity will increase with density and then will drop after a certain point (after
a given value of density). Ammonium and hydrazinium azide behave like this, also mercury fulminate is susceptible to this behavior because it will
become dead pressed at high loading density (for more information see "CRITICAL PARAMETERS FOR DETONATION PROPAGATION AND INITIATION OF HE" for donna
PRICE).
below i will upload the paper of Jimmy OXELY where she compare the power of RDX to ETN and other nitrate ester along other important properties and
synthesis procedures for nitrate esters.
Dany.
Attachment: Characterization and Analysis of Tetranitrate Esters.pdf (806kB)
This file has been downloaded 1185 times
[Edited on 1-9-2013 by Dany]
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Ral123
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Is it just me, but I can't imagine anything being dead pressed if the diameter and boosters are big enough?
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Dany
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Dead pressing a material don't have anything with critical diameter or a booster. some explosive like mercury fulminate don't burn or explode if they
are highly compressed (nearly to their theoretical maximum density).
a good study on initiation of primary explosive (including the dead pressing effect) is that of P. M. Dickson and J. E. Field "Initiation and
Propagation in Primary Explosives"
http://rspa.royalsocietypublishing.org/content/441/1912/359
Dany.
[Edited on 1-9-2013 by Dany]
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Ral123
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Let's say we have a small planet made out of cast AN. It's gravity is so high, the core is let's say at 1.8g/cm2. Now you are telling me that if there
was a booster in the centre, let's say 9000 metric thons of C(NO2)4/TNT mixture, the whole thing wont go off at maximum velocity?
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Dany
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Ral123,
when i reply on golfpro question i said that Dcj of ANFO (Not AN) will decrease as the density approach the TMD (theoretical maximum
density). i didn't say that ANFO or AN will dead press (although this can be true, but i didn't do a search). anyway what you are asking is
extreme and purely theoretical, but if a material is dead pressed it is not possible to detonate it, even with strong initiator, this what laboratory
test shows on primary explosive compressed to high pressure (e.g., 30000 psi). but talking in general, why you are surprised that a planet made of
explosive would not detonate under this conditions? it may be hard to believe, but powerful high explosive cylinder would not detonate if they are
under the critical diameter even if you use hundred of grams of booster explosive to initiate this charge.
Dany.
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Ral123
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From what I've read MF and ANFO are the only examples of dead pressable material I can think of. So you are telling me that a barrel of dead pressed
MF wont go off with a 2kg cast HMX/TNAZ booster? From what I've read, dead pressed MF only suffers kinda laggy DDT and is prefectly detonatable with a
blast cap.
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Dany
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Material that can be dead pressed:
1,3,5-Triazido-2,4,6-trinitrobenzene and mercury fulminate ("Explosive" for Meyer, R.; Kohler, Josef; Homburg, Axel, Sixth Edition).
Diazodinitrophenol (DDNP), tetrazene and peroxides ("Primary Explosives", chapter 2 for Matyáš, Robert, Pachman, Jiří, 2012)
http://www.springer.com/chemistry/physical+chemistry/book/97...
Dany.
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Microtek
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I think Golfpro was referring to the critical diameter phenomenon. Some explosives are more effective than others when considering the steady state
detonation of very large charges (so no edge effects, and no consideration of the acceleration phase), but when small charges are considered the
relationship may be reversed. I don't know the exact parameters of ETN and RDX, but RDX has a reputation for not performing so well in very small
charges.
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Dany
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You're right Microtek, at very small critical diameter, one should expect problem with reducing detonation velocity. I think that at very small
diameter nitrate ester will behave better (support a steady detonation state) than nitramine, for example it is known that PETN can support steady
detonation in micrometer charge diameter. however, i dont think that this is a very big problem for an amateur. this problem is more important to the
field of microdetonics where very small charge diameter are needed.
Dany.
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Microtek
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I think Golfpro was referring to the critical diameter phenomenon. Some explosives are more effective than others when considering the steady state
detonation of very large charges (so no edge effects, and no consideration of the acceleration phase), but when small charges are considered the
relationship may be reversed. I don't know the exact parameters of ETN and RDX, but RDX has a reputation for not performing so well in very small
charges.
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Ral123
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I think the enthusiasts are just the most interested in small diameter performance, so micro tests can be done. For now I have the feeling MHN may the
best small diameter material, with it's high melting point and high sensitivity.
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Ral123
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RDX vs ETN
I was very curious how would those two pressed only compare. I had the feeling that the sound was different and the flash was different, but the
recordings don't think so. I can't explain myself what particles pierced the cans, glass from the tubes or aluminium fragments. So far 3 years old
washed only RDX sample seems better then 1 year old recrystalised ETN btw.
https://www.youtube.com/watch?v=52WAQ5r3yV8&feature=yout...
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markx
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Looking at the distortion of the metal I see that the picture corellates nicely with my own results....RDX seems to leave a more uniform deformation
along the whole length of the charge whereas ETN and PETN seem to concentrate the pressure at about mid length of the charge, leaving a greater
deformation there. Curious to why that happens to be so? The effect is more apparent with smaller charges and when the witness plate is not penetrated
by the blast.
Exact science is a figment of imagination.......
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Manifest
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Yes, RDX seems marginally better but is much harder to make, how on earth do I get Acetic Anhydride?
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Zyklon-A
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I don't remember if Elemental Scientific ships to the UK, but if they do:
http://www.elementalscientific.net/store/scripts/prodView.as...
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Ral123
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@Manifest
Not if you have distillation setup. I've done WFNA with aluminium pipe and old flasks.
@Zyklonb
There may be fake sales put there to lure you and bring you police investigation. I know two such cases.
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plante1999
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I can provide some Ac2O if someone really needs it, contact via U2U or email, please.
I never asked for this.
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hissingnoise
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| Quote: | | how on earth do I get Acetic Anhydride? |
On ebay?
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Manifest
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When I search ebay Ireland I don't see any other listings for it.
Ebay UK has none either, ETN seems a better option to me and it might look suspicious if I buy Ac2O.
Hissingnoise, assuming you're irish, where abouts are you if you don't mind me asking?
I'm in Derry.
[Edited on 7-5-2014 by Manifest]
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NeonPulse
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These results Ral123 and markx are pretty consistent with the results I achieved testing the same. Two small charges of 3.5 grams each were placed
against a 5 millimetre thick steel plate. I don't know the exact density but I used a vise and a Dowell rod with a marking to press them identically
and initiated them electrically using 300mg of lead azide. ETN dented the plate around the center of the charge while the RDX seemed to deform it much
more there as well as the dent there was a large crack along the length of the area where the charge was placed along with spalling on the back
side.Also I noted a flash difference and the sound of RDXwas more like a crack. As RDX is more brisant than the ETN this didn't surprise me at all but
it was a good test or the two.
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Napolean Dynamite
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As far as sound I think ETN is louder than RDX. Once I detonated a 20g RDX charge on a cast iron metal sewer and from 300 yards away it sounded like
nothing more than an aerial firework with low pitched sound, but the metal was dented pretty good.
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Ral123
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The ETN ripped the can more. I have the feeling it flashed a bit more and was a little louder. I'm not sure why they are so similar on the camera.
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markx
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| Quote: |
The ETN ripped the can more. I have the feeling it flashed a bit more and was a little louder. I'm not sure why they are so similar on the camera.
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The framerate of the camera is not high enough to capture the flash of the blast...it just takes a single frame to miss it. If you use a high speed
camera then the chances are better to get all the interesting bits on tape. It may also happen with a regular camera, but purely out of coincidence.
It is also my observation that ETN has a very distinctive bright flash upon exploding. At first I thought it might be the aluminium foil around the
charge that ignites in the extra oxygen, but it is just the same without incorporating any Al metal around the charge.
Exact science is a figment of imagination.......
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Dornier 335A
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ETN does have a rather high explosion temperature and higher energy content than RDX, which could explain the brighter flash.
My equilibrium program calculated ETN's CJ temperature to 4478 K compared to 4238 K calculated for RDX (at 1.72 g/cm3 and 1.78
g/cm3 respectively).
The energies of detonation were calculated to 5.942 MJ/kg and 5.695 MJ/kg respectively, at the same densities as above.
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