Sciencemadness Discussion Board

PETN?

believer - 13-12-2011 at 18:52

Yesterday, I synthesized PETN. I used Powerlabs method of synthesizing PETN (I did not follow it exactly). The result was 18.5g of fine powder. I put 40mg of petn on a concrete block and then I struck it 2-3 times with a hammer, Nothing happened. I tried this about 15 times more and I got a loud crack two times (Im sure it was not the hammer, lol). Why did my PETN come out so insensitive? Did I mess up? I have not tried to detonate it with HMTD.

reactants used:
32ml of 70% HNO3 (instead of 34ml of 65% HNO3)
24.8ml of 98% H2SO4
10g of 98% Pentaerythritol (instead of 99.8%)
about 240ml of Acetone
41g sodium bicarbonate
distilled water

Bot0nist - 13-12-2011 at 21:44

Concrete block is not suitable for impact test. Try hammer on steel anvil or dock plate. You need a smooth hard surface. In the past I have even failed to get pops on polished granite. Metal on metal is the only way to go.

VladimirLem - 14-12-2011 at 03:07

By the way...it seems to be the TRI nitrate, not the TETRA nitrate of Pentaerythrol...

But its a strong compound too ! :)

Some small improvised shaped charge initiated with HMTD had made some nice results...

Bot0nist - 14-12-2011 at 04:44

You should post your results in the unconventional shaped charge thread. Some good work going on in that thread.

believer - 14-12-2011 at 10:30

Quote: Originally posted by Bot0nist  
Concrete block is not suitable for impact test. Try hammer on steel anvil or dock plate. You need a smooth hard surface. In the past I have even failed to get pops on polished granite. Metal on metal is the only way to go.


Thanks, It did work a lot better on a thick steel plate.
Quote: Originally posted by VladimirLem  
By the way...it seems to be the TRI nitrate, not the TETRA nitrate of Pentaerythrol


Why do you think that?

killswitch - 14-12-2011 at 10:42

Quote: Originally posted by believer  
Quote: Originally posted by Bot0nist  
Concrete block is not suitable for impact test. Try hammer on steel anvil or dock plate. You need a smooth hard surface. In the past I have even failed to get pops on polished granite. Metal on metal is the only way to go.


Thanks, It did work a lot better on a thick steel plate.
Quote: Originally posted by VladimirLem  
By the way...it seems to be the TRI nitrate, not the TETRA nitrate of Pentaerythrol


Why do you think that?


Because the presence of water in the azeotropic nitric acid (as opposed to fuming nitric) pushed the equilibrium too far to the left. The equation looks something like Keq = [PETN]*[H2O]^4 / ([pentaerythritol][HNO3]^4). Keq is the equilibrium constant. The presence of water drastically lowers yields, as it is raised to the fourth power.

P.S. Does anyone happen to know the equilibrium constant for the nitration of glycerin? The equation is something like K = [nitroglycerin]*([OH-]^3)/([glycerin][HNO3+]), where K is somewhere around 50, but I can't find the exact number. Equations for the other esters would also be helpful.

[Edited on 14-12-2011 by killswitch]

hissingnoise - 14-12-2011 at 12:27

The presence of di-pentaerythritol hexanitrate could certainly reduce sensitivity in PETN!
It is less powerful than PETN but quantities would likely be quite small.
The lower nitrates are all soluble in water, to some extent, and even the trinitrated compound can be removed by washing in warm water.


VladimirLem - 14-12-2011 at 12:50

Quote: Originally posted by believer  

Why do you think that?


absolutly other kind of crystals...
and that, the other posters above said...

Tetra:
crystals like normal sugar -
dry, extreamly hard to compress


Tri:
fine, long crystals -
dry easy to press up to ~1.3g/cm3

quicksilver - 14-12-2011 at 15:42

Like to take a moment and point out some material (from "The Pentaerythritols by Barlow); I am paraphrasing here from ch13:
There are basically two types of pentaerythritols, one is a high reagent grade used by military and industrial mfg known as Penta.- "M" and the other is a "paint or vinyl grade" materials that is commonly used in the paint and vinyl industry.
Basically the lower standard is not a "technical-grade: material buy (perhaps) even lower in standards. This is often found in large (20-30lbs) sealed cans and is diverted to make some fast money. It may even have some extraneous material (dirt debris) within it as well as foreign matter that may be microscopic. It will not produce PETN with any real ease even with 1.51 HNO3.
Unfortunately there is no simple way to determine at simple eyesight the difference. However PRICE may be a substantial "red-flag". The paint and vinyl industry uses this in great abundance and as for crystal shape, this is many times a product of the re0crystalization procedure and needles could exist in both. One is a HIGHLY refined product that is certainly a reagent grade product; the other is a very rough materials, yet superficially they could look similar to the naked eye.
This was a basic reason why PETN had assumed a higher price than RDX in military and industrial energetics. Aside one is a nitric ester, the other a nitroamine and available via a very simple precursor using formaldehyde / ammonia. RDX and PETN have another idiosyncrasy. aside from their similarity in performance, RDX appears to be more suited for larger levels of weight / volume usage while PETN works well in small designed (Deta-cord, caps, etc).

In large scale plant procedures where near anhydrous acid is inexpensively mfg,RDX can cut cost substantially. RDX is also easily both de-milled and re-cycled. Crystalline structures also vary in RDX as well. Frequently it may yield a consistent hexagonal crystal, yet 4-8x larger clear well formed crystals are present even when re-crystallization procedures are maintained consistently. This is one reason why TNT is often mixed with RDX (in addition to stretching supply and desensitization). Often times issues with PETN trace back to the precursor

Naoum had stated that PETN was not an ideal candidate for a mixed acid nitric ester due to difficulties in bringing the material to a neutral seven. This has been disputed, yet often acids & lower nitrated material was found in quality precursor mfg material even after two or more re-crystallization. According to mfg statistics published by DoD (via Scandia Corp), RDX had frequently been the front-runner in plant production. In many areas it does appear to be a simpler and less expensive material which has many properties so similar to PETN, that it seems the wiser choice (certainly financially).

_________________________
Hissingnoise: the only place that had some pointers toward equilibrium constant via NG / glycerin was :

http://webbook.nist.gov/cgi/cbook.cgi?ID=C56815&Units=SI...


Check out Jerry Hurst's material via google. -- was the best I could come up with. You'll get a lot of hits with:" equilibrium constant , nitro or glycerin", but it's not easy to find.



[Edited on 14-12-2011 by quicksilver]

believer - 14-12-2011 at 16:10

How did I get Pentaerythritol trinitrate instead of tetranitrate? Is it because I used 70% HNO3 instead of white fuming nitric acid? or maybe my pentaerythritol wasn't pure enough? Is powerlabs petn (http://www.powerlabs.org/chemlabs/petn.htm) actually trinitrate and not tetranitrate? I can't really tell by the picture, but the end product looks like the consistency of table salt/sugar. (my petn turned out finer)

VladimirLem - 15-12-2011 at 07:36

Quote: Originally posted by believer  
How did I get Pentaerythritol trinitrate instead of tetranitrate? Is it because I used 70% HNO3 instead of white fuming nitric acid? or maybe my pentaerythritol wasn't pure enough? Is powerlabs petn (http://www.powerlabs.org/chemlabs/petn.htm) actually trinitrate and not tetranitrate? I can't really tell by the picture, but the end product looks like the consistency of table salt/sugar. (my petn turned out finer)


im pretty sure you only got traces of Terta-nitrate when using 70% HNO3

btw, did you recrsytalised the product ?
Without that, you are not able to see that fine, long crystals of the TRI Nitrate, cause of the impurities (low- or not nitrated material)

[Edited on 15-12-2011 by VladimirLem]

nitro-genes - 16-12-2011 at 13:48

Quote:

"im pretty sure you only got traces of Terta-nitrate when using 70% HNO3

btw, did you recrsytalised the product ?
Without that, you are not able to see that fine, long crystals of the TRI Nitrate, cause of the impurities (low- or not nitrated material"

Definitely not true:

Even under the best conditions for formation of the trinitrate, only
1:1 ratios of tri-tetra can be produced, with decreasing acid strenght both yield of the tri and tetra drop.

IIRC, the solubility of the trinitrate in hot water is high enough to eliminate it with a few washes. When recrystalized slowly from acetone pure PETN will crystalize in needles btw...

[Edited on 16-12-2011 by nitro-genes]

VladimirLem - 16-12-2011 at 13:50

Quote: Originally posted by nitro-genes  
Quote:

"im pretty sure you only got traces of Terta-nitrate when using 70% HNO3

btw, did you recrsytalised the product ?
Without that, you are not able to see that fine, long crystals of the TRI Nitrate, cause of the impurities (low- or not nitrated material"

Definitely not true:

Even under the best conditions for formation of the trinitrate, only
1:1 ratios of tri-tetra can be produced, with decreasing acid strenght both yield of the tri and tetra drop.

IIRC, the solubility of the trinitrate in hot water is high enough to eliminate it with a few washes. When recrystalized slowly from acetone pure PETN will crystalize in needles btw...

[Edited on 16-12-2011 by nitro-genes]


hm...interesting stuff u said...going to check this out

nitro-genes - 17-12-2011 at 01:30

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA396646&Locati...