Sciencemadness Discussion Board

Plastic Energetic Materials

quicksilver - 22-3-2007 at 05:26

It took a bit of searching but I found some of the original patents dealing with both plastiques and the utilization of flexible, moldable energetic materex.
Here is one of the more comprehensive patents from 1967. Illustrating the design for a granulated crystalline plastic bonded explosive material. The "flow chart" design of how the items are incorporated in to the product is quite interesting.

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quicksilver - 22-3-2007 at 05:31

Flexible explosive compositions containing block co-polymers. Again; a difficult patent to find as it illustrates the answers to balancing plasticity and tackifier.

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quicksilver - 22-3-2007 at 15:42

There are a heck of a lot of interesting things that go along with this subject. For instance, it seems that nitrated solid alcohols (PETN) allow for more than 1/3rd inerts in a plastique. Could ETN or MHN be used as a sensitizer to further that percentage?
Could nitrated phenols be used as a base energetic material in a plastque? Could primaries be developed in a plastic design to enhance detonation via alternative shapes? Could shaped charges be designed from a simple cone shape within a plastic mass? The ideas that occur from the free-form of plastic energetics are many!
I would love to hear from those with either learned study or experiences on this subject.

This is another patent using the binder / tackifier concept that is standard now.

Anyone know an OTC source for Di (2-ethylhexyl) Sebacate????

[Edited on 23-3-2007 by quicksilver]

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quicksilver - 28-3-2007 at 07:09

I have found a very safe & effective method of crystal shaving:
When in process of re-crystalization, material is dissolved in boiling hot acetone, etc. in Erlenmeyer flask, material is left to completely go into solution. Hot acetone or ethanol (if ETN is used) is then placed into refrigeration and crystals (needles) are forming. At the point ( approx 2 hr) that all has formed into needles, flask is stoppered and sealed. The flask is shaken vigorously. Water drowning is applied to acetone and sealed flask is shaken vigorously to complete. This shaking rubs crystals together (shaving) and if continued will drop out needles that are smaller and smaller. This then is a safe shaving mechanism: within water when drowning the acetone ladened solution! The water must be above 50 C in the initial drowning and then the crystals will shave with some intensity due to the combined action of the hot water softening the needles just enough to break them down when they rub against one another. As size comparison via microscopic examination indicates this may just reduce the needles to a 4 micron powder if continued. Some larger needles will exists but most will reduced to a very surprising degree. Decant without swirling and larger needles will exist on top, separation being made easier...

Deceitful_Frank - 28-3-2007 at 10:00

Quote:
Originally posted by quicksilver
There are a heck of a lot of interesting things that go along with this subject. For instance, it seems that nitrated solid alcohols (PETN) allow for more than 1/3rd inerts in a plastique. Could ETN or MHN be used as a sensitizer to further that percentage?
Could nitrated phenols be used as a base energetic material in a plastque? Could primaries be developed in a plastic design to enhance detonation via alternative shapes? Could shaped charges be designed from a simple cone shape within a plastic mass? The ideas that occur from the free-form of plastic energetics are many!
I would love to hear from those with either learned study or experiences on this subject.

This is another patent using the binder / tackifier concept that is standard now.

Anyone know an OTC source for Di (2-ethylhexyl) Sebacate????


[Edited on 23-3-2007 by quicksilver]


I once inadvertantly stumbled across an OTC source of dioctyl ADIPATE . I was searching model making supplies looking for nitromethane and found a 500ml bottle of this plastisizing ester for sale. It was meant for softening putty or incorparating into resins used and model aircraft making. I dismissed it as useless and carried on browsing...

You can imagine my frustration at not being able to find it again when I learned of its usefulness!


[Edited on by Deceitful_Frank]

pinky - 28-3-2007 at 12:15

Here you have a complete(method with solution of the binder in solvent and water/slurry process) patent for manufacture of C-4 composition...the water slurry process provides better coating of crystals with binder...
But in practice,it is not so simple as it looks...
I've been trying plasticizie PETN with dioctyl sebaceate...
The most important thing in plastic bonded explosive is shape and size of explosive crystals,it is a feature that has a main effect on denisty,performance and consistency of final composition...



[Edited on 28-3-2007 by pinky]

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pinky - 28-3-2007 at 12:22

This is how C-4 looks before kneading it into a final plastic consistency.

C4BULK .JPG - 18kB

Bert - 28-3-2007 at 17:44

Quote:
Originally posted by Deceitful_Frank
I once inadvertantly stumbled across an OTC source of dioctyl ADIPATE . I was searching model making supplies looking for nitromethane and found a 500ml bottle of this plastisizing ester for sale. It was meant for softening putty or incorparating into resins used and model aircraft making. I dismissed it as useless and carried on browsing...

You can imagine my frustration at not being able to find it again


Try Firefox. It's used as a plasticizer in composite rocket propellants.

quicksilver - 29-3-2007 at 07:41

The terminology "plasticize" is interesting - I believe most powders can be made into a dough-like material but what it takes to make an energetic into a material that may be formed to play certain roles in industry is more complex. The actions of tackifying and adhering to a surface as well as forming into usable sheets or cones is what separates beneficial energetic plastiques from the kook-books "home made" stuff which serves little viable use in productive energetic materials usage.
When discussing the actions of shaped charges and densities of energetics the actions of plastics become very significant to the uses in industry that these materials are put to. Apparently a tackifier and a plasticizer are needed along with a base powder of a certain consistency to achieve the optimum result. It would be easy to add oil to most any powder to make a malable material but it would not preform the same as one that has the density and maintenance of form that a true plastique would have. (Illustrated by Pink's pic above) That same material can form shaped charges, sheets, links, etc for doing work that would be out of reach with something that could only be rolled into a ball, etc.
Typically what is used is some form of butyl rubber as a binder and some form of oil as a plasticizer. This is a whole subject unto itself as both materials don't (superficially) combine with ease. This then allows the material to be formed and KEEP it's shape as well as stick to surfaces. These qualities are very important as they allow the utility to be broadened to a wide scope. Therefore once that has been achieved, the material powder itself can play a deeper role in it's utility.
Dioctyl ADIPATE may just be available OTC in certain hardware stores.....all of the materials may just be available. I stumbled upon a source of Polybutene (97%) which when combined with castor oil/methanol (which forms ricinoleate esters) and fulfills the needed plasticizer-tackifier. This then is added to a fine powder to achieve the optimum material consistency. Another issue is to find these materials that will form the needed plastique at a level of 25% or well below in relation to the energetic. Some energetic materials just won't shoot at more that 30% plasticizer. However some will. PETN supposedly will shoot at a level of 33%+ binder-plasticizer, while RDX will need about 23% max. ETN however is very sensitive. About the same level as MHN and may form a sensitizer with a high percentage of plasticizer.....

nitro-genes - 30-3-2007 at 06:55

Thanks for looking up all the patents! There are so many patents related to PBX type compositions that it is hard to sort out the usefull ones. Moreover are most of the patents about pressed rigid or sheet type PBX compositions...:)

You can find adipates or sebacates in every specialized hardware stores as heat and oxidation resistant lubricants for usage in pumps that compress air or draw a vacuum. The package should mention "diester based lubricant". The rotary evaporator in our lab uses the same kind of lubricant, it's a very viscous, straw coloured oil, probably a sebacate ester like DOS/DEHS. Less viscous lubricants are usually adipateesters, which are just as good plasticizers btw. Of course making an OTC plasticizer was just much more fun than just buying some. :D I'm not making heaps of plastic explosive anyway. I didn't notice any large differences between ricinoleates or sebacates/adipates as the plasticizers concerning plasticity and storage stability btw, although the ricinoleate derived plasticizers are somewhat less viscous, what occured to me as an advantage...

As I said before, the plasticizers saponification value and linearity is pretty important and greatly determines the plastic properties and storage ability of the plastique. I noticed that PBX in which only motoroil was used as a plasticizer hardens after as little as a few hours/days. Only when you kneed it again for some time it becomes soft en pliable again. Moreover does it easily seperate from the binder and leaves large stains of motoroil on whatever you keep the PBX on.
The hydrophillic groups of the plasticizer act as a sort of detergent which prevents seperation and thus keeps the PBX perfectly pliable and homogenous even after months of storage. It also reduces stickyness when large plasticizer-to-binder ratios are used, which is necessary to maintain mouldability when small crystal sizes are used or PBX containing less than 10% of binder+plasticizer. The smaller the crystal fraction to be plasticized becomes, the more plasticizer+binder it needs to be able to attain a near theoretical density, probably due to the increased surface area. In general, 1-10 micron PETN needs about 15% of binder+plasticizer, while about 5% was enough for a 100-200 micron crystal fraction with about 10% of very fine PETN added. But basically you are trading critical diameter for pressure, which is not always advantagous, especially when using small amounts for curiosity purposes...

Still no luck with the recrystallization procedure to yield cubic crystals, I've tried every solvent combination there is though equidimensional PETN remains the main problem with PETN according to Urbanski in the review below.

http://handle.dtic.mil/100.2/ADA396646

[Edited on by nitro-genes]

quicksilver - 30-3-2007 at 07:18

Ahhh, cubic crystals.....this is what I have found; the nitrophenols are the only ones that respond to the use of additional materials to alter the crystal shapes.....and man, I have searched! So what can be done? Well, I think that needles are not a hopeless cause. Due to their ability to break down. The idiosyncrasy of their re-crystalization in acetone - if left alone (for a long time!) to re-crystalize from a boiling temp to a violent temp change (immersion in a freezer) they get VERY brittle. IF at that point they are subjected to a shaving manipulation they will break to a point that is single micron size (2-7um). See the above concept of shaking them in the water drown from their acetone solution - they are then dried and manipulated in a plastic bag to further their shaving. I believe that at that point they are so small that they start to "line up" against one another and become very close to cubic/rectangular. The concept in general is to get the needles to form up as brittle as possible so that by their shaving they crumble. now if one compares that to something like nitroguanadine which does NOT get brittle - the phenomenon is clear. The nitroguanidine is flexible in it's needle configuration so it stays in that shape- BUT the needles of , say PETN, can become so fragile that they crumble and thats when they get smaller and smaller. I am willing to go out on a limb and say that if they are formed in a very fragile state and are very dry they can be reduced to a point that even with microscopic examination they start to loose the needle shape and become in effect cubic. The percentage of those that reach that size to be frank would be about 50% but the remaining ould fill the voids and then the whole of the material becomes viable for compression beyond what would appear possible with fresh needles alone. The thrust of this concept is furthered by a long period in manipulation. In industry they have roller machines that do this. but it could be imitated with a glass plate and glass cylinder as discussed previously.

To directly alter the shape of nitrophenols to a cubic shape Aluminum powder is added to the forming crystals within the nitration drown. I have tried this (there's a patent for it) and it works. It was used for lead styphnate. The esters on the other hand don't seem to be controllable in their formation: it just seems like apples and oranges unfortunately. But the needles don't have to have strength to their shape and that may be where the key is hidden.

[Edited on 30-3-2007 by quicksilver]

nitro-genes - 30-3-2007 at 08:33

The ability of PETN crystals to break is mostly determined by the crystal morphology indeed. Under certain circumstances needles are produced that are much more fragile than others. Very fast cooling of acetone/PETN solutions may yield the "hollow needle" or hourglass like structure mentioned in the review, while slowly cooled generally yields solid and quite strong crystals.

The bulk density of the product after the processing of the crystals says a lot about the maximum density achievable for the resulting PBX. Bulk densities of 0.9 were mentioned for RDX in some of the patents you posted, which reminds me of the British patent related to detcord grade PETN that I posted, in which hexagonal PETN was produced with a bulk density of 0.96. The patent isn't very detailled unfortunately, but as I can understand it there is a narrow range of di-PEHN impurity % for which this hexagonal shape is produced. It wouldbe really interesting if something like that could be reproduced, though I have no idea how. Detailled information about the actual crystallization process is not present in the 2 pages of the patent that are available...

[Edited on by nitro-genes]

Put more wood in your wax

franklyn - 30-3-2007 at 19:17

Energetic Polymers and Plasticisers for Explosive Formulations

http://www.dsto.defence.gov.au/publications/2210/DSTO-TR-096...

.

quicksilver - 31-3-2007 at 07:11

~-=Differing Nitrations of Pentaerythritol=-~
It had occurred to me that during the nitration of Pentaerythritol a lower nitration (PEN) may also be formed. It is more than POSSIBLE that this may form a differing crystal that PETN just as ETN forms differing shapes. PEN (7200mps) is a trinitrate and is nearly as powerful as PETN (about the same as ETN) but is claimed to be more sensitive. It is formed in the presence of urea during the nitration of PETN. I have heard of the use of urea as a stabilizer for PETN and have seen the procedure. The urea is brought to saturated solution in water which is miserable in acetone. Two procedures are listed in Ledgard's book and appear similar to the preparation of Quebrachitol nitrate. These are hexagonal granules and have the same impact sensitivity as ETN (high).
The major influences are a high nitric acid suspended in methylene chloride (or a mixed acid using solid nitrates!) The same technique could be used for Sorbitol, Inositol, or Gluconamide. As a matter of observation, when urea is used as an early stabilizer in the production of PETN the claim that PEN is formed in large percentages is seen as a layer of crystals differing from the needles as a bottom layer of higher density. The ratio is 1:24 grams of urea to penta during nitration. The claim is 2/3 PEN to 1/3 PETN. Overall VoD will be much higher than pure PEN but needle crystal shapes will not predominate!
Sources sighted are Rhom & Hass Company; Huntsviille AL. to the Hercules {Powder company} pp231-234 PMoE

~-=How To Alter Crystal Shapes In PETN=-~

I thought I would add this this as an addendum to the alteration of the needle crystal in PETN.
When the nitrated PETN is to be re-crystallized via acetone the addition of Double Based Smokeless Powder to the acetone will inhibit the growth of needles and the resultant will be ultra fine irregular crystals of a mixed shape that will also contain a variety of stabilizers! The following method had proved satisfactory:
To every 200ml of acetone used for re-crystallization the addition of 0.4 grams of DBSP is mixed completely into the saturated solution of PETN. If less than this weight is utilized the needles will resume growth. Weight of DBSP had been attempted from 1-.0,1 gram with 0.4 being the most satisfactory per 200ml acetone. This will also provide for stabilization in the re-crystallization of ETN as well. The material formed is powdery. When under microscopic examination it will prove to be somewhat crystalline but will be so small that it will resemble chalk. Remember to make sure that all material has gone into solution and the acetone is at a boil. This hot solution is drowned after it reaches room temp. If simply left alone some very light gray material will fall out of solution (no needles however) and they will mostly be of an irregular shape with some hexagonal crystals being seen at 100x. This then when mixed with a binder & tackifier will form a plastic substantially easier then needle crystals, no matter how well shaved, etc. The result is excellent and stabilized ! :D

-=Single Micron Size PETN Crystals=-
If crystals are needed at the 2-19 um level there IS a technique without crystal shaving to reduce size to such a level that the crystals feel like corn flour!
During re-crystallization, bring the acetone to a boil with a saturated solution of PETN. The drown should be at at least 3:1 in HOT water. That's hot acetone and a hot water drown. Let no crystals form (the acetone cool down) during the secondary purification process. This is from a WWII "patent" in Japan that the Allies used after the war. And it works VERY well. The hot saturated acetone with PETN forms what looks like "curds" in the hot water (water approx -70C, acetone at boil -50C) which are actually lumps of VERY tiny crystals that are visible as VERY bright reflections once they dry & break down. They look like microscopic glittering bit's they are so small they hide inside of the finger print. This technique WORKS for reducing the size of PETN crystals for plastique.

[Edited on 26-4-2007 by quicksilver]