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Author: Subject: RDX synthesis
Dany
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[*] posted on 19-4-2014 at 09:19


Quote: Originally posted by NeonPulse  
So i did finally get around to attempting a synthesis of RDX. it was a fairly sucessful attempt yeilding 19.3g dry RDX from 95ml HNO3 and 40g hexamine dinitrate. ithe acid was incorrectly measured though as i used the wrong measuring beaker (doh!) so i doubt it was the full 100ml. but anyway i did recrystallize it from acetone and got two nice clean crisp white crops sparkling RDX crystals. leaving the acetone to evaporate, the next night after work i was surprized to see these rather large crystals in the bottom of the beaker somewhat like broken glass, these were many, many times bigger than the first crops i got and hardly any of the acetone had evaporated. my question is: firstly are these crystals dangerous? like being prone to detonate due to internal stresses like some energetics?
i2: is it normal to grow rdx crystalls this size?
how big can they actually get if left to grow?



There is nothing to fear about single crystal RDX. Single crystal explosive have the highest possible Theoretical Maximum Density (TMD) thus the highest detonation velocity compared to other RDX form (e.g., RDX powder). The sensitivity of single crystal RDX is far low then the powdery form of the same explosive for a simple reason: single crystal RDX are voidless and contain no structural defects while powdery RDX contain many voids and possibly other solid impurities. When subject to a shock wave, the voids (and other impurities) in powdery RDX will act as hot spot, concentrating the shock energy around their structure via adiabatic compression or other hot spot formation mechanism (e.g, internal shear, jetting, friction [1], etc...). The reaction start at these hot spot and shock wave from each hot spot coalesce to form the detonation wave. Since single crystal explosive are lacking hot spot site, it is more difficult to initiate these explosive, so you need a more powerful shock wave to be able to initiate detonation. Another beautiful example is the one given in paragraph entitled :"Hot Spots and Transverse Waves" which can be found in [1]. The author is talking about powdery PETN and single crystal PETN. Experimental shows that powdery PETN (pressed to almost TMD) can detonate when subjet to a shock wave of 2.5 GPa (or 25 kbar) while a single crystal PETN need a 11 GPa (110 kbar) to detonate the reasons are the same for the example of RDX given above.

For the case of lead azide were spontaneous explosion have been seen in single crystal, the reason of this is not entirely an internal stress of crystal. Other reason exist but poorly understood.

Reference:

[1] William C. DAVIS, High explosives-the interaction of chemistry and mechanics (LOS ALAMOS SCIENCE).

Dany.

[Edited on 19-4-2014 by Dany]
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VladimirLem
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[*] posted on 21-4-2014 at 01:37


Hi guys...

could it be possible to "grow" explsoives crystals into special shapes?

exmple: dissolving ETN into warm-hot (below meltingpoint of the explosive) ethanol/aceton and then filling the sollution into some shaped charge container and letting the crystals gorw when putting that into a freezer?

when making ammoniumnitrate and "recystalize" it at a cold place it has exactly the shape of the container and a really high density, so could that work at other HEs? (ETN, PETN, RDX...)
if that would work, there where no need for phlegmatised/plastic/cast explosives anymore and the possiblity for getting the max density seems pretty good (only some percents [how many?] of solvent left)

Vlad
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[*] posted on 21-4-2014 at 02:54


Quote: Originally posted by VladimirLem  
Hi guys...

could it be possible to "grow" explsoives crystals into special shapes?

exmple: dissolving ETN into warm-hot (below meltingpoint of the explosive) ethanol/aceton and then filling the sollution into some shaped charge container and letting the crystals gorw when putting that into a freezer?

when making ammoniumnitrate and "recystalize" it at a cold place it has exactly the shape of the container and a really high density, so could that work at other HEs? (ETN, PETN, RDX...)
if that would work, there where no need for phlegmatised/plastic/cast explosives anymore and the possiblity for getting the max density seems pretty good (only some percents [how many?] of solvent left)

Vlad


yes it is possible to grow explosive crystals in special shape. This is done by recrystallizing the explosive using different solvents. This will led to different shape/polymorphs being produced. See this effect for the production of different HMX polymorphs

What is not possible is to grow single crystal explosive to a dimension suitable for shaped charge. Although you mentioned that NH4NO3 has the shape of the container and seems like it is homogenous, this is not true. At macroscopic scale the materials will look as if it was homogenous, but at the microscopic scale the material is non-homogenous but heterogeneous (polycrystalline) in nature. This is due to the method of precipitation/recrystallization and to the temperature gradient encountered in the layer of explosive during cooling which led to polycrystalline material. The best method in shaped charge to achieve the highest density materials is by casting the explosive (e.g., Octol) into the shape charge body or by making the explosive into a Plastic Bonded Explosive (PBX). PBX are known to achieve high density approaching 99% Theoretical Maximum Density (TMD).

Dany.
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[*] posted on 21-4-2014 at 10:26


If one really wants to use a single crystal ..... Grow one that is oversize using a seed crystal. And machine it to your needs with the proper safety precautions.
All that work just seems unnecessary when you can achieve 99% ... As Dany mentioned, using PBX.




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[*] posted on 21-4-2014 at 11:06


It is not bad to be mentioned that the vast majority of manufactured shaped charges are made by using pressed explosives like 95% RDX/HMH 5% wax, thermoplastic polymer, etc. Plastic bonded explosives are almost never seen, except in improvised devices. Casting (by melting or using polymers) is also increasingly rarely encountered, except in high caliber devices.

Pressed explosives provide very high percentage nitramine load that is impossible to achieve in any other way.

[Edited on 21-4-2014 by simply RED]




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[*] posted on 21-4-2014 at 11:40


Quote: Originally posted by simply RED  
It is not bad to be mentioned that the vast majority of manufactured shaped charges are made by using pressed explosives like 95% RDX/HMH 5% wax, thermoplastic polymer, etc. Plastic bonded explosives are almost never seen, except in improvised devices. Casting (by melting or using polymers) is also increasingly rarely encountered, except in high caliber devices.

Pressed explosives provide very high percentage nitramine load that is impossible to achieve in any other way.

[Edited on 21-4-2014 by simply RED]


What do you mean by improvised device??? PBX are special type of composite explosive which requires a high level of knowledge in manufacture. PBX are used in high performance shaped charge or Explosively Formed Projectile. One example is the PBX called LX-19. LX-19 is composed of 95.8 wt. % CL-20 (Hexanitrohexaazaisowurtzitane) and 4.2 wt. % Estane binder [1]. It is one of the best PBX known for shaped charge design.

I should also mention that plastic explosive (e.g., C-4) is also desirable in shaped charge because it is easy to load and to shape the explosive into the shaped charge body. However, plastic explosive do not offer the highest density of an explosive materials so their use may be limited where high performance are required. Liquid explosive, have also been used because they offer a homogenous medium, so a non-disturbed detonation wave can be expected from liquid explosive. It is well known that the symmetry of the detonation wave is critical when the latter interact with the liner. this can be achieved via liquid explosives. It is difficult to make perfectly homogenous solid explosive inside a shaped charge body. Any air cavity or density gradient in the explosive body will affect the detonation wave and the collapsing of the metal liner which may degrade the overall performance of the shaped charge

Reference:
[1] Murphy, M.J.; Baum, D.; Simpson, R.L.; Monoto, J.; Montesi, L.; Newman, K.; Tuerpe, D.; Osborn, J., Demonstration of enhanced warhead performance with more powerful explosives-UCRL-JC--127575.

Dany.


[Edited on 21-4-2014 by Dany]
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[*] posted on 22-4-2014 at 00:57


Dany, exactly! LX-19 is exactly "a PRESSED solid explosive formulation containing 95.2% by weight
epsilon phase 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW) and 4.8% Estane binder".

http://www.osti.gov/scitech/servlets/purl/105039

Of course it is plastic bonded but it is formed by pressing and not by casting. This is completely different class of explosives than cast-polymer bonded or "plastic" ones. Plastic explosives are never going to be found in anything other than improvised devices because of their poor mechanical properties and high sensitivity in case of extreme acceleration (and often rotation) that munitions endure!!!! 100% of all "eastern" made shaped charges munitions are press loaded and speaking from the literature, a very high percentage of the western ones are press loaded too.

""""It is not bad to be mentioned that the vast majority of manufactured shaped charges are made by using pressed explosives like 95% RDX/HMX 5% wax, thermoplastic polymer, etc."""" in this case 95% Cl-20 and 5% thermoplastic polymer.


[Edited on 22-4-2014 by simply RED]




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[*] posted on 22-4-2014 at 01:25


The debate here is not about pressed or not. Of course LX-19 can be used as a pressed explosive but it's defenition is a PBX, not a plastic explosive ( PBX explosives can be made by pressing, casting or by injection moulding. Plastic explosive are made to be soft and moldable like C-4 or PE-4 explosive. I'm clarifying the situation because you said that PBX are used in improvised shaped charge which in my knowledge is not possible because pressing a PBX to almost 99% TMD require special techniques that are beyond the capability of an average pyroman (a good review on techniques used in PBX pressing can be found in the book of Paul COOPER, Explosives Engineering). PBX explosive is used in almost all high performance shaped charge and warheads. The Tomahawk missile for example uses the the PBXN-107 explosive (the N in PBXN is for Navy).

beautiful pictures and informations on tomahawk missile can be found here.

Dany.

[Edited on 22-4-2014 by Dany]
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[*] posted on 22-4-2014 at 01:29


Quote: Originally posted by VladimirLem  
Hi guys...

could it be possible to "grow" explsoives crystals into special shapes?

exmple: dissolving ETN into warm-hot (below meltingpoint of the explosive) ethanol/aceton and then filling the sollution into some shaped charge container and letting the crystals gorw when putting that into a freezer?

when making ammoniumnitrate and "recystalize" it at a cold place it has exactly the shape of the container and a really high density, so could that work at other HEs? (ETN, PETN, RDX...)
if that would work, there where no need for phlegmatised/plastic/cast explosives anymore and the possiblity for getting the max density seems pretty good (only some percents [how many?] of solvent left)

Vlad

With the very low mp of ETN, it would be more easy to melt it externallly with hot water and allow it to harden slowly. Most of the time there is some contraction of the media while cooling so an open cylindrical recipient filled with a molten stuff usually will have an incurved U or V surface shape at the upper side in contact with the air.

The idea with the solvents is less good because in a recipient you have walls and this will prevent the evaporation of the solvents...what could only escape via the open side...this side will by the way harden faster and the rest below will remain "wet" much longer following a gradient of "wetness".The unevaporated solvent will have to travel the all material to be able to escape by the open side which upon time becomes harder to travel through owing to increased viscosity/hardening.

In the case of sensitive explosive; the bigger the cristals, the higher the risk of inner cristaline stress and sensitivity to shock and friction...if the cristals are growing in a closed recipient the walls will restrict their grow and favourise breaking/anomaly in the cristal partern...what means stress. The cristals will also be limited by other cristals and interpenetrate increasing friction sensitivity. Last but not least, the cristals will usually make voids between them so density might be less than finer powder filling and pressing.




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[*] posted on 22-4-2014 at 02:02


Quote: Originally posted by Dany  
PBX explosive is used in almost all high performance shaped charge and warheads.

Dany.

[Edited on 22-4-2014 by Dany]


Quite a bold statement.
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[*] posted on 22-4-2014 at 02:52


Improvised shaped charges are often made with plastic and not "polymer bonded" explosives, type mistake.

Manufactured (low caliber <130 mm) shaped charges are pressed because the cast formulations require (too much) at least 12% polymer. AFAIK no russian shaped charge design uses polymers! They use A-9-1, okfol etc. mostly (95-5) - that substitute the polymers with parafines and ceresine. But parafine is also a polymer, it is low molecular mass, low melting point polyethylene! So things can get confused in some point...
Being all PBX, pressed and cast formulations are completely different and are manufactured using completely different machines in the factories. I do not see a reason why amateurs can't make cast formulations! I've done it numerous times! Pressed formulations on the other hand are not available for the amateurs as special machinery is needed for them to be manufactured.




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[*] posted on 22-4-2014 at 02:56


Quote: Originally posted by Jimbo Jones  
Quite a bold statement.


The Truth, The Whole Truth, and Nothing But The Truth

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[*] posted on 22-4-2014 at 03:04


Quote: Originally posted by Dany  
Quote: Originally posted by Jimbo Jones  
Quite a bold statement.


The Truth, The Whole Truth, and Nothing But The Truth

Dany.


OK Dany. OK.
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[*] posted on 22-4-2014 at 03:33


Here's a quote that prove that PBX are widely used in army's weapons were high performance is required, from [1]:

"Polymer bonded explosives based on hexogene or octogene, aluminium and polymer binder (PBX) fall into castable secondary explosives. Besides decreased detonation wave parameters, they are characterised by relatively slower delivery of energy in the detonation process and longer positive impulse phase. These explosives are used for the laboration of warheads with strong blast effect, such as main charge explosives for Navy underwater weapons (mines, torpedoes, bombs) and missile warheads"

Reference:

[1]Gordana Antić, Vesna Džingalašević, Milena Stanković, Zoran Borković, Explosive Characteristics of Cast PBX Based on HMX, AmmoniumPerchlorate and Aluminium, Scientific Technical Review,Vol.LIV,No.3-4,2004.

Dany.

[Edited on 22-4-2014 by Dany]
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[*] posted on 22-4-2014 at 09:29


Quote: Originally posted by Motherload  
If one really wants to use a single crystal .....


no not exactly one crystal...when cooling down ammoniumnitarte, then you can see large needles [Picture1] (around 1.5cm*0.4cm*10cm<;) filling the container up to the sollution is completely filled with crastyls and become a hard crystal block [Picture2]

so im talking about a high dense HE-crystalblock ;)


@ the other guy with the -ETN melting idea-
ETN was just an example and im not gonna melt that shit

@the guys saying PBX:
well how can i know that the explosive is pressed enough? and HOW can i see that i should stop pressing :o
cause some HEs tend to get "dead-pressed" (extremely hard to ignite) and others may detonate when pressed to hard :D lol
i dont know if pressing an HE is the way i should go since i dont habe professional equipment for that :-/


Vlad

p1.jpg - 154kBp2.jpg - 159kB
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[*] posted on 22-4-2014 at 09:58


You can not do pressed, but you can do cast. Just cast it with HTPB binder for amateur rocket engines and you know it is okay :) . RDX and PETN will not get dead pressed even if you cast under deep vacuum!

[Edited on 22-4-2014 by simply RED]




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[*] posted on 23-4-2014 at 07:19


Quote: Originally posted by simply RED  
You can not do pressed, but you can do cast. Just cast it with HTPB binder for amateur rocket engines and you know it is okay :) . RDX and PETN will not get dead pressed even if you cast under deep vacuum!

[Edited on 22-4-2014 by simply RED]


yeah, of course i could...i just wonder if this way i said could work

would be very easy to get high dense without much work

biggest doubts i have are if the detonation wave could be infuluenced by the different cristallayers in those HE-Block so that the detonatiopnwave would act different than cast/pressed (some uniform det.-wave is very important for shaped charges, you know)
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[*] posted on 29-4-2014 at 08:22


Am I the only one here who wonders why the 95/5 material/phlegmatizer compositions aren't using TNAZ or TNT instead of wax? It would allow HMX based composition to reach similar performance and stability to CL-20 composition. I've read CL-20 is significantly more sensitive then RDX/HMX.
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[*] posted on 29-4-2014 at 08:42
Dirty RDX synthesis


In my observation non recrystallized, washed only RDX is many times more stable then ETN, NG, Tetryl- again washed only. I suppose the acidic components in the crude RDX evaporate easily and allow washed only RDX to be quite stable.
Is it a myth that heavily NOx contaminated WFNA is unsutable for straight hexamine nitrolysis? The clear WFNA gives off NOx during the process anyway so why bother clearing the acid from NOx?
Here's the average Joe's possible plan:
Use whatever fuming nitric acid available. Well after the synth, carefully heat the batch to 50C, to purge the unstable non RDX nitration products(IIRC). Dry in warm dark place. Recrystallization is optional under certain conditions. I believe RDX is a great way to learn about high R.E. materials with not as much hazard as other materials. The only bothering RDX hazard compared to nitric esters and organic peroxides is it's annoying flammability.
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[*] posted on 29-4-2014 at 12:12


use hexamine dinitrate instead of hexamine- in this case reaction is not very sensitive to NOx, presenting usually in conc. HNO3. I used yellow nitric acid and failed, trying to use hexamine. But reaction with hexamine dinitrate was successful.



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[*] posted on 29-4-2014 at 13:31


I can't imagine that the hexamine will completely fail where the dinitrate will work. Was everything else the same? I'm more worried of forming unstable products that would rot the storage stability.
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[*] posted on 29-4-2014 at 17:30


i cant understand why anyone would want to use the straight hexamine route given to the fact that the yeilds are greater and the synthesis proceeds more smoothly with using the dinitrate. it does seem less picky about dissolved NOx in it. The acid i have used in the handful of times i have made it was a light yellow and i dont believe it had any influence on the end result. i would think that if you are going to go to the trouble of preparing RDX then the small amount of time and acid used to make the hexamine dinitrate is worth the extra effort IMO. Also if you do go to the effort in the first place, then why not take the extra time to recrystallize the product. but then i could say the same on the effort of purging the NOx from the acid....



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[*] posted on 30-4-2014 at 05:11


Quote: Originally posted by Ral123  
I can't imagine that the hexamine will completely fail where the dinitrate will work. Was everything else the same? I'm more worried of forming unstable products that would rot the storage stability.


I can. I made such experiments. One problem with hexamine is that reaction with nitric acid is exothermic (base + acid), but reaction of didnitrate is the mild one. According to russian book, written by Orlova, there is a special method for performing oxidization of unstable linear nitramines. One have to mix solution of RDX in nitric acid with simple water- drop by drop. This mixture will boil and produce NOx, but simultaneously all unstable nitramines will be destroyed (and BTW one will get large crystals of RDX). Final concentration of nitric acid must be something like 50% (or 60, i do not remember now). This diluted nitric acid later can be used to make hexamine dinitrate.




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[*] posted on 30-4-2014 at 09:34


As I know RDX can be stored for 20 years. What stabilising additives do you think are appropriate? Urea would form water with the decomposition products. Sodium carbonate is quite a base. Magnesium bicarbonate, diphenilamine?
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[*] posted on 30-4-2014 at 12:04


As I know, RDX can be stored for infinity and does not require stabilizing addictive at all. Do not worry about it- RDX is not NG.



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