Sciencemadness Discussion Board - PETN recrystallisation procedure for LOW density

PETN recrystallisation procedure for LOW density

Gargamel - 5-8-2015 at 07:06

Hi guys,

in most professional recrystallisation procedures people want to grow high density stuff.

In this case I want something as DDT friendly as possible. To my knowledge this means a very small crystal size.

My strategy is to create a warm Acetone solution and let it drip into ice water to give the crystals the shortest possible time to form.

How would you grow your crystals in this case? Are there any other tricks?

I've read about ball milling, but I'd rather feel uncomfortable about that

greenlight - 5-8-2015 at 07:24

I have been mucking around with recrystallizing PETN for a couple of months now for making plastic explosive after getting some advice from others on the forum.

The method I have stuck to using is dissolving the PETN in minimal near boiling acetone and letting it cool to about room temperature before pouring very slowly (you could try dripping) into about the same volume of ice cold water.
This gives a large amount of small crystals and some powder which I think works well to fill in the gaps.
The last batch I added 5 grams of RDX to the 75 grams PETN as well during the recrystallization.
I have some decent plastic explosive I just made using this technique with 15% Polybutene and 1% motor oil @ about 1.43 density.
10 grams easily punches a clean hole through a steel plate just over 3 mm thick which isn't really a tough target but the size of the lump of plastic look very small due to the density.

VladimirLem - 5-8-2015 at 11:47

Quote: Originally posted by Gargamel

Hi guys,

in most professional recrystallisation procedures people want to grow high density stuff.

In this case I want something as DDT friendly as possible. To my knowledge this means a very small crystal size.

sounds like your real problem is the detonator cap, not the high explosive itself...PETN normaly is pretty easy to ignite...

and i would try big crsytals instead of fine powdered material...just crash the whole solution into water, without any delay...this will make a "powder" like dry sand at a beach, with a low density, when not compressing (0.8-1.0g/cm3)
With fine material, you will fill the gaps between the crystals (even when not compressing) and making is a bit more "difficult"

to ignite, i guess...

NeonPulse - 5-8-2015 at 15:35

Just crash the acetone solution into iced water with heavy agitation or mechanical stirring and that should do it for you

nux vomica - 5-8-2015 at 19:42

Quote: Originally posted by NeonPulse

Just crash the acetone solution into iced water with heavy agitation or mechanical stirring and that should do it for you

I agree with Neon I use petn made this way in my ebw dets and it is fine enough to detonate every time .
Nuxy.

greenlight - 5-8-2015 at 20:11

Does fast addition of the PETN/acetone solution to the ice water with rapid stirring give crystals that would still be good to plasticize?

[Edited on 6-8-2015 by greenlight]

nux vomica - 5-8-2015 at 22:39

Quote: Originally posted by greenlight

Does fast addition of the PETN/acetone solution to the ice water with rapid stirring give crystals that would still be good to plasticize?

[Edited on 6-8-2015 by greenlight]

Sorry Greenlite I cant help you there someone should have a answer, ive only just found some PB to make some plastic up I have always used it straight nuxy

[Edited on 6-8-2015 by nux vomica]

greenlight - 6-8-2015 at 02:38

What are you using for the PB?
Is it bird repellant?
Are you plasticizing PETN or ETN?

nux vomica - 6-8-2015 at 02:57

Quote: Originally posted by greenlight

What are you using for the PB?
Is it bird repellant?
Are you plasticizing PETN or ETN?

Cant get bird repellant or rat boards , animal lovers have pushed government to ban it ,I am hopeing a sticky bug trap from major hardware chain here is pb
I am going to plasticize etn as I have 500grms of sweetener and only 50 grms of penta. Cheers Nuxy.

[Edited on 6-8-2015 by nux vomica]

greenlight - 6-8-2015 at 03:39

I can't get the bird repellent here either i searched many hardware and garden stores after Neonpulse told me to use it.
Its easy to ontain on ebay which was my source.

Heres one: http://m.ebay.com.au/itm/Bird-Proof-gel-apply-to-roosting-ne...

[Edited on 6-8-2015 by greenlight]

nux vomica - 6-8-2015 at 04:15

I actually need to put some spikes on my pergola to keep the birds out might try and sneak a tube in the order ,I will tell the wife its to keep the birds away luv.

I assume it is the same consistency as clear silicon. ?
The boards I have I am sure are pb but its quite thick and not like silicon at all so I was going to use more oil to soften it up when I use it nuxy.

greenlight - 6-8-2015 at 05:51

Yeah it is about the same consistency as clear silicon and very sticky and tacky and never dries.
Your boards may have something else added into them as well

Hennig Brand - 6-8-2015 at 08:56

Quote: Originally posted by nux vomica

Quote: Originally posted by NeonPulse

Just crash the acetone solution into iced water with heavy agitation or mechanical stirring and that should do it for you

I agree with Neon I use petn made this way in my ebw dets and it is fine enough to detonate every time .
Nuxy.

Yeah, same simple method I use with decent results.

Regarding PB repellents, I have found the bird repellant PB formulations works best without added oil or at least very, very, little. The resultant putty explosive gets very soft, oily and sticky when much oil is added and it also doesn't hold together nearly as well as when the repellant is used straight or with minimal oil/softener.

VladimirLem - 6-8-2015 at 09:53

Quote: Originally posted by greenlight

Does fast addition of the PETN/acetone solution to the ice water with rapid stirring give crystals that would still be good to plasticize?

[Edited on 6-8-2015 by greenlight]

from my experience definitivly not when using high concentrated HNO3

I read about a method, placing the hot aceton/petn solution in a polysterol container and then putting it into a freezer for 10+h, so the petn crystalizes extremely slow and you will get extremely fine crystals...

When making PETN from 65-70% HNO3 (+H2SO4 of course), i had with this method very fine powdered PETN (still not sure if Tri or Tetra nitrate) - like tiny needles, perfect to compress...should be pretty good for chewing gum

i really wonder how the acid concentration has such an influence to the crystal shape...the material was the same quality/batch

nux vomica - 6-8-2015 at 17:04

I had better get some etn plastic made soon to test the 60 degree copper cones I have been working on at the moment.
Nuxy .

[Edited on 7-8-2015 by nux vomica]

greenlight - 7-8-2015 at 02:29

That tooling looks awesome Nux, I have been looking for a former like that for conical shaped charge liners for a long time.
Where did you buy them, or did you make them yourself?

nux vomica - 7-8-2015 at 03:06

Quote: Originally posted by greenlight

That tooling looks awesome Nux, I have been looking for a former like that for conical shaped charge liners for a long time.
Where did you buy them, or did you make them yourself?

Homemade, I am lucky and have a lathe at home and I do all of the more simple turning and milling at work, so I can slip my home jobs in between work ones.
The first two cones are annealed between getting formed into a polyurethane rubber pad in the tube to the right then I anneal then press into the 60 degree plastic former, it is quiet a simple process when you have worked out the bugs nuxy.

[Edited on 7-8-2015 by nux vomica]

Gargamel - 7-8-2015 at 13:53

Thank you for your answers.

Somehow I messed this up, using the least possible amount of acetone at ~55°C (started to boil) and crashing it into ~8°C Water somehow produced a lot of larger crystals. I was stirring like crazy and poured very slowly.

The density is now much greater than the unrecrystalised stuff.
Not good for DTT, rather for most other applications.

I made PETN some time before, but I did not take detailed notes back then. That stuff was much more fluffy. More Acetone would be my guess.

So the perfect DDT PETN "recipe" is still to be developed...

Nux, I envy your equipment. Cool stuff.

greenlight - 8-8-2015 at 09:16

I always use that procedure and get a nice mix of fluffy powder/granules. Good to plasticize.
Maybe you could try dumping it in fast like others outlined above otherwise just keep trying by recrustallizing the same stuff until you get a desired result. I just re-read your post and realized that you are looking for PETN to attain deflag-det transition with only and not plasticization.
Are you trying to build explosive bridgewire detonators?
If so I may be wrong as I haven't attempted to make one but wouldn't ETN be easier to acheive DDT with than PETN due to it being more heat sensitive?

[Edited on 8-8-2015 by greenlight]

Gargamel - 10-8-2015 at 01:32

Quote:

Are you trying to build explosive bridgewire detonators? If so I may be wrong as I haven't attempted to make one but wouldn't ETN be easier to acheive DDT with than PETN due to it being more heat sensitive?

Yes and yes. But I have personal reasons to prefer PETN.

Strictly speaking it's not about DDT but shock sensitiveness.
ETN would be slightly superiour, no doubt.

nux vomica - 10-8-2015 at 02:51

Quote: Originally posted by Gargamel

Quote:

Yes and yes. But I have personal reasons to prefer PETN.

Strictly speaking it's not about DDT but shock sensitiveness.
ETN would be slightly superiour, no doubt.

Your petn will be fine just go for it my petn is not to the recomended standards I am sure, but I still can set it off just as easy as etn with my ebw setup.

I would be more worried about my fireing set eg capacitors ,spark switch ebw head, fireing voltage, get those right and the petn shouldn't be a issue nuxy.

pjig - 2-6-2024 at 18:42

Sorry to resurrect an old thread , but felt it could be expanded upon and relevant to recrystallizing petn. There are several methods to obtain a clean serviceable material.
I’m sure depending on the final products usage one could tailor its crystal structure to suite the need .
Using low concentration hno3 (70%) for example it seems that a crash method of hot acetone/petn+urea ,instantly into ice cold water bath creates a sandy fine particulate that reduces to super fine powder with minimal effort . Low density I’m sure is the outcome ,v.s. Growing Slow large crystal formations, then Shaved to achieve max density of crystal for pbx charges. But for use in caps it( low density petn) can be desired I imagine. Only with a couple noted drawbacks on pressing it reaches pretty high density, making it hard to det. For some primary’s . Is it possible using the super fine materials comes with its own problems in this manner?

[Edited on 3-6-2024 by pjig]

Etanol - 2-6-2024 at 19:37

Quote: Originally posted by pjig

Using low concentration hno3 (70%) for example it seems that a crash method of hot acetone/petn+urea ,instantly into ice cold water bath

The hot acetone/petn+urea method does not decompose mixed sulfo-nitro esters. It is necessary to add ammonia or ammonium carbonate, filter ammonium sulfate, then crystallize the PETN.

pjig - 2-6-2024 at 20:01

I should note this is not the crash from the nitration, but the crash from the recrystallization of the crude dried petn.

pjig - 5-6-2024 at 19:04

Purification and crystal modification are both important for the end result of a stable and longevity EM material. End result / use of the material can be tailored via crystal density’s. I think for “simple detonators etc” a low density material would be sufficient to kick off other materials. One could simply press the material higher pressure to achieve higher density in a cap body, even a two stage press , dense base , simi dense layer and a primary to complete.

Is there a point where too fine of particulate presses to densities where normal primary’s are sufficient to ddt the train? Where a more coarse material of higher density /sensitivity is required so optimal loading pressures that can increase reliability of a detonator.
Again depending on the” End use” of the material, SC’s or plasticize for moldable use. Is there an industry standard that one size or type fits all?

Purity question:
The Re crystallization process of the hot acetone + Petn and a pinch of urea, taken and crashed into cold water created a wet sand like low density material that reduces into a very fine material. Even dry acts like it wants to cake up like wet due to the fine particles.

First, in this form of avalanche Re crystallization is this process enough to remove unwanted byproducts, and acids? Second is it stable for long term storage ?

Etanol - 5-6-2024 at 22:58

Quote: Originally posted by pjig

I think for “simple detonators etc” a low density material would be sufficient to kick off other materials.

PETN is quite sensitive to detonation. If you are not planning to make a non-primary detonator, then I see no reason to strive for low density. The higher the density, the higher the brisance and efficiency of the detonator.

Quote: Originally posted by pjig

a two stage press , dense base , simi dense layer and a primary to complete.

Yes

Quote: Originally posted by pjig

The Re crystallization process of the hot acetone + Petn and a pinch of urea, taken and crashed into cold water created a wet sand like low density material that reduces into a very fine material.

If this is recrystallization of pure PETN, then I see no reason to add urea. Urea is too weak a base. Ammonia is much better.

Quote: Originally posted by pjig

Even dry acts like it wants to cake up like wet due to the fine particles.

This is due to the needle-like shape of the particles.

Quote: Originally posted by pjig

First, in this form of avalanche Re crystallization is this process enough to remove unwanted byproducts, and acids? Second is it stable for long term storage ?

I do not understand you.
For the recrystallization of pure PETN for the purpose of crystal modification, urea is not required.
For recrystallizing dirty PETN to remove acids and other impurities, urea does not work. Such PETN will not be stable.

Microtek - 7-6-2024 at 07:53

The function of urea in this context is not to act as a base, but as a NOx scavenger. The same reaction can be employed to remove NOx from RFNA. During decomposition of PETN in storage, NOx is evolved which increases the rate of further decomposition. By incorporating small amounts of urea in the PETN crystals, this feedback loop can be broken.

pjig - 8-6-2024 at 08:52

Im speculating about crystal formation and its ability to release its waste acids , other slow crystal growth , or immediate upon a crash (avalanche method) . I believe the slow method is more effective in purifying and density. The trade is manipulation to reduce large crystals (shave) to desired size (for its function ).

Now the ease of the fast crash method is appealing, (fast results) but I’m not 100% sure it’s as effective at removing trace acids(hense the use of urea) , and it reduces to a very fine particulate. I assume that is low density. It takes on a unique caking problem due to crystal structure.

The fast crash material also presented another weird trait . It almost seems (under normal pressures ) to go max density when pressed and it’s need for more initiating power required. Making it less predictable with normal priming methods.

Any experiences or results other have to back this up or explain unique processes?

Microtek - 9-6-2024 at 01:41

You could do both. First a slow crystallization for obtaining a pure product, then redissolve in fresh solvent and crash precipitate for fine powder. From my perspective, the main advantage of fine powder is the smaller critical diameter and better performance at the microscale. I prefer crystallizing by addition of water to the neutralized acetone solution. Then I can adjust temperature, agitation and speed of addition to tune the crystal size and morphology to the application.

pjig - 9-6-2024 at 11:59

Excellent ideas.. ty

As per your crystallization process are you doing this at higher temps, rm temp , or cold to precipitate out your solution? Stirring will obviously aid in the shaving process ( how long are you continuing to stir after all water is added and precipitation is done ?

[Edited on 10-6-2024 by pjig]

Etanol - 9-6-2024 at 13:12

Quote: Originally posted by Microtek

First a slow crystallization for obtaining a pure product,

It is better not to dilute the acetone solution with water, but by a mixture of 40% alcohol and 60% of water. Then yellow resins and pentaeritritol trinitrate remain in the solution.

Microtek - 13-6-2024 at 01:37

@Etanol: My PETN does not contain the impurities you mention, possibly because I synthesize it from 100% HNO3 rather than mixed acid.

@pjig: I usually do the precipitation close to the boiling point of acetone, then maintain stirring until it has cooled most of the way to room temp.

pjig - 14-6-2024 at 20:54

Ty microtec
The hot PETN acetone solution instant crash may have some undesirable variants (less sensitive forms of the petn family . This Leaving the final product less sensitive to initiating, but in a way, safer for an industrial level where munitions may call for insensitivity . Unfortunately for sensitive initiators it is counter productive. Soi assume a slow process is more desirable for the precipitation being more sensitive . Never seen the oily yellow derivatives, but that may be from the heating after nitration process to max yield, and destroy impurities . Losses from the “cold only “ process is minimal in small scale production… not worth the risks and potential near ddt temps if residue resides on sides of reaction glass . Just my 2 cents

pjig - 6-11-2024 at 21:33

This is a good section to discuss some general questions on precipitation and the Crystal modification.

Couple methods suggested : (1) a hot acetone saturated solution crashed into cold water for a precipitate. (2nd) suggestion was cold water added too hot saturated solution acetone. (3rd) was cooling of the hot acetone solution not disturbed = large crystal formation, to be broken up by manual shaving.

Curious the performance, sensitivities, and Benefits of different Re- crystallization methods . Both RDX and Petn seem to be similar in there crystal formations from this process. So processes should result in similar results for either E.M. Utilized.

[Edited on 7-11-2024 by pjig]