Sciencemadness Discussion Board - PETN vs. RDX

PETN vs. RDX

Frontier9 - 4-7-2006 at 09:14

After inquiring for quite a while about the power and brisance of PETN & RDX, I have yet to get a definitive answer. Certain so-called experts will state that PETN is slightly more powerful but slightly less brisant than RDX; while certain other so-called experts will claim that the opposite is true, that is, RDX is slightly more powerful but slightly less brisant than PETN. Can anyone shed some light on this matter? :cool:

Rosco Bodine - 4-7-2006 at 09:53

It depends on the quantity and I'm not sure where the
" critical mass " is ....perhaps ten or fifteen grams ,
beyond which RDX rules in terms of brisance and power ,
and below that PETN is always superior to RDX .

PETN performs better in small charges ,
RDX performs better in larger charges .

nitro-genes - 4-7-2006 at 14:51

For PETN:

Detonation pressure at crystal density (1,77 g/cc) = 332 kilobar

Brisance:

Sand test: 129-141% TNT
Plate dent test: 127% TNT
Leadblock compression test: 130-137% TNT

Total power:

Ballistic mortar: 137-145% TNT
Trauzl test: 161-189% TNT

For RDX:

Detonation pressure at crystal density (1.806 g/cc) = 340 kilobar

Sand test: 125-145% TNT
Plate dent test: 135-141% TNT
Plate cutting test: 125% TNT

Total power:

Ballistic mortar test: 150-161% TNT
Trauzl test: 151-170% TNT

It's difficult to draw any decisive conclusions from all these test since they are all different and have a substantial margin of error. I thought that it was generally agreed that RDX was slightly more brisant (mainly because of it's higher density/VoD), with PETN having a slightly larger total energy release. This because of its higher heat of explosion. (6311 kJ/kg for PETN vs 5625 kJ/kg for RDX)

But like Rosco mentioned, the critical diameter for highorder detonation is extremely low for PETN.
only 0.9 mm for PETN at a density of one gram per cubic centimeter, getting even smaller at increasing packing density. For RDX this is in the 3 mm plus range IIRC. Then again, the crystal shape of PETN (needles) make high density, high PETN percentage compositions more difficult to realise than with RDX...

[Edited on 4-7-2006 by nitro-genes]

Rosco Bodine - 4-7-2006 at 16:06

What I have seen pretty consistently reported is that for small charges like a blasting cap base charge that PETN performs better , and then for booster size charges there is reached a point where PETN and RDX are about equal , and then as the charge size increases further the RDX takes the lead . This is not uncommon that it depends on the particular charge and firing train which one is going to perform better . Many different explosives have desirable characteristics which all come together well in one particular size and type of charge fired in a specific way .

Actually a composite of the two would likely have nice properties for intermediate sized charges , something like an EGDN plasticized PETN binder for crystalline RDX could be interesting .

BTW , my PETN from acetone appears cubical about like table sugar , and my RDX is the same way , but I haven't really looked closely at it under a microscope so it could be monoclinic or rhombic .....but definitely not needles . And the RDX will crystallize very coarse like rock salt from a slow evaporation of acetone .

[Edited on 5-7-2006 by Rosco Bodine]

nitro-genes - 4-7-2006 at 16:52

The difference in performance depending on the charge proportions is probably the result of the higher critical diameter of RDX compared to PETN...

Quote:

Originally posted by Rosco Bodine
BTW , my PETN from acetone appears cubical about like table sugar , and my RDX is the same way , but I haven't really looked closely at it under a microscope so it could be monoclinic or rhombic .....but definitely not needles.

Great!

What is your method of recrystallization? I was planning to look into this a bit more as I read from PATR that slow cooling of ethylacetate yields cubic crystals of PETN. But If this is also possible with acetone somehow...

My standard method of recrystallization of PETN is heating the acetone to it's boiling point in a water bath, adding as much PETN as possible with the solution remaining clear, then slowly adding 2 times the volume of water with a little ammonia or ureum added as stabilizer. This method however defenitely produces visible needle like crystals, and gives a powder thats is absolutely not free flowing and "hardens" as it is compacted.

Not very good properties for usage in plastiques...

Rosco Bodine - 4-7-2006 at 17:30

I would have to dig through a pile of paperwork to find the exact proportions , but the method is similar to yours only the hot acetone solution is only about 75% saturated with PETN , the acetone solution neutralized
with small amount of solid sodium bicarbonate which doesn't dissolve , and urea which does dissolve , along with dropwise addition of a few ml of strong ammonia water till a very slight yellow tint appears . IIRC a bit
of denatured alcohol is added to the hot solution also ,
and then a slow dropwise addition of * warm * water containing dissolved urea and bicarbonate is added to the well stirred mixture which clouds as it cools and is diluted , and then an ice cube is dropped on the surface
to hasten the preciptiation temporarily , and the slow drip continued . When most of the warm water has been added , then ice is added as liberally as it melts
to get the final mixture very well diluted and ice cold .
It is allowed to stand for a few minutes and filtered
to give a product which looks very much like table sugar .

This method was adapted from a patent process and
the same method works as well for ETN only more
alcohol and less acetone must be used because the
acetone is actually too good a solvent for ETN and produces a solution too heavily loaded from which the ETN doesn't drop out in a controlled fashion , unless a
cosolvent system heavy on alcohol is used . One thing
I can report is that I have had zero stability issues with
the purified and urea stabilized ETN gotten by this method , even on long storage at tropical outdoor temperatures .....so I attribute others reported problems
with stability for ETN to an inadeqaute technique or materials . I have samples stable for several years
by this method .....and the samples of PETN look like
they will easily go a hundred years also , showing
no color or weight change or odor , but retaining the
clean crystalline appearance as if they were made
yesterday , years later .

nitro-genes - 5-7-2006 at 08:38

Thanks for the information.

I always saturate my acetone completely with PETN, this because the acetone is quit expensive here to buy....

It would be great if you had some more detailed information, like the temperature of the warm water, the amount added and especially over what period of time the warm water is added. I usually make the addition of water over a period of several minutes, still to fast probably for controlled crystal formation.
The addition of the denatured alcohol is another thing. I guess it acts as a crystal modulator somehow? Do you have any idea how much approximately was added, I mean was it like a few percentages or parts?

[Edited on 5-7-2006 by nitro-genes]

Rosco Bodine - 5-7-2006 at 12:20

General rule for crystallizations to go better is to form a saturated solution at or very near boiling and then to
dilute with ~1/10 to 1/5 the volume additional solvent with reheating to drop the system well below saturation .
This gets you away from that saturation region where
an avalanche precipitation tends to occur suddenly and
defeat the purpose of a more gradual crystallization allowing for good crystal growth . The alternative is
to insulate the container to slow the cooling particularly for small batches . If you aren't working with a hundred grams of dissolved solids then the thermal conditions aren't favorable for good crystal growth unless you compensate for the evaporative and radiational cooling to slow it down for good crystal formation . So the process isn't directly scalable downwards to smaller batches unless you control the conditions for the smaller batch .

I'll look this up later concerning the alcohol with PETN ,
thinking more about it I may not have used any alcohol at all except with the ETN . It should work for either one ,
but it would have been a minor amount 10% or less if
it was added to the acetone solution of PETN , and probably 3 or 4 times that amount ( or more ) for the acetone solution of ETN .

The idea of the alcohol was to drop the solubility a bit more gradually for the solvent system before introducing water , and the vessel in which this was being done was partly covered to reduce the evaporative cooling which
would otherwise induce too rapid crystallization , the
same idea for using warm water to help hold heat in the
system and let the initial precipitation be driven by
decreasing the solubility by water addition more than by
evaporative cooling of the mass . The water solution was about the same temperature or slightly warmer than the solvent to which it was being added . The cloudiness is actually microscopic seed crystals forming and then their growth is driven slowly by the dropwise addition of more and more water ......the longer you can stretch out the precipitation the larger the crystals will grow until they are too heavy for the stirrer to keep suspended , and they sink to or near the bottom . The occasional addition of an ice cube would stimulate more
crystal nuclei in the local area near the melting cube while the water from its melting would add to the growth
of the main crop of crystals already developing in suspension , ice cubes acting as kickers for the process
while the system was still warm but not yet fully diluted .

Nearly all of the precipitation occurs over the course of
only a small addition of the total water , while the system is still warm . Good crystal growth is favored by
warm temperatures . It can be a bit tricky to finesse
such crystallizations , but the difference is evident compared with a rapid precipitation type of crystallization
which produces amorphous granules or fines or an aggregated mixed product .

nitro-genes - 6-7-2006 at 03:35

Many thanks for the detailled description.

I had been experimenting a little with longer precipitation times and hot water allready, but they gave only larger needle like crystals. So I was afraid that I would be making huge, unusable needle like crystals from acetone this way...
Now that I know this isn't the case I will give the dropwise method a try next time, (with and without ethanol) and make sure that those little crystals can grow into nice and densely packed cubic crystals.

The icecube for proving crystal nuclei is a nice thought indeed...

[Edited on 6-7-2006 by nitro-genes]

Rosco Bodine - 6-7-2006 at 06:59

The PETN which was the source of my work was already quite pure from the
nitration by the d 1.5 nitric acid only method which provides ~98% yield of pure product directly from nitration and dilution . Crystal form can be greatly affected by even trace impurity , and the method of synthesis for some compounds has a bearing in this regard .
I got no needles even in the nitration mixture , but only a finer form of what I got from the solvent recrystallization . I have rarely seen any needle formation for anything in a stirred mixture for any compound except as a transient form , because the stirrer simply mills the needles to granules or a powder by abrasion on long stirring . Only in standing solutions have I observed any intact needle form crystals , and what I say here is general because I haven't seen this for PETN , but just the form which I have gotten . I am busy with something else right now , but I will look later and dig out my old notes and try to shed more light on this .

[Edited on 6-7-2006 by Rosco Bodine]

nitro-genes - 6-7-2006 at 07:41

From PATR I understood that the usual synthesis and recrystallization methods of PETN result in tetragonal crystals (density 1.77 g/cc) that form elongated structures (needles). Only one other crystal modification that is mentioned for PETN is the orthorhombic modification with slightly lower density (1.72)...

Further they state that: "Nearly equi-dimensional PETN crystals rather than the usual needle-like crystals can be obtained by slow cooling of a 40% soln of PETN in boiling EtOAc. (J. Tranchant, Ibid 117 & CA Ibid)"
So therefore I assumed that there was no easy way to produce free flowing crystals from PETN rather then from ethyl actetate.

It could be a impurity problem though, since I use slightly less concentrated NA (~90%) and also tend to rush the reaction a bit, (at the edge of the temperature limit) sometimes with substantial bubbles formed in the reaction mix due to oxidation of the PE. It is reflected in my yields that are usually no more than 90% max and could well lead to higher impurity levels in the final product...

Not that I use reagent grade stuff anyway, my PE is from acros organics and only technical purity, 98%. It keeps this hobby somewhat affordable...

Rosco Bodine - 6-7-2006 at 15:10

Okay as promised I looked through my lab notes for another one of Rosco's good old country recipes

....this time for PETN . This method is basically the old DuPont process with a bit of added detail of my own , knowing that DuPont probably didn't spell out every particular in the patents .
The relevant patents are attached . I should clarify the matter about the usage of warm water as I have now remembered the specifics of how and why I used the water and it is different from what I said earlier before looking at my notes . The slow drip of dilution water containing urea was secondary to the principal mechanism of dilution which
follows the patent process exactly , and the water drip
was only serving to add a small amount of urea as solution
to the major dilution water which was being produced by the melting ice . The water drip was simply a little extra which
I added to get some additional dissolved urea into the system where crystallization was occuring , think of it as
a minor modification relating to stabilization , more than
being involved as a driver of the crystallization , only serving to add the stabilizer as a slight impurity and maintain a
slight percentage of it in the solution as it was being diluted by the melting ice . I hope that makes sense .

EXPERIMENTAL :

A tall form 600 ml beaker was secured in a three jaw extension clamp attached to a vertical support rod and
clamp holder and lowered into the center of a clear plastic
bowl of about 3 liters capacity sitting atop a magnetic stirrer .
A stirbar was placed in the beaker , and a thermometer
was held in a thermometer clamp was lowered vertically
until its tip nearly touched the bottom near the inner wall
of the beaker where it would not interfere with the spinning stirbar . The plastic bowl was filled about a third full with ice cubes and a fume intake and exhaust hose was held in a ring
near the opening of the beaker . To the beaker was added
100 ml of d 1.5 ( 97% ) pale yellow HNO3 which had been
pre-measured in a 100 ml glass stoppered volumetric flask and prechilled in a freezer to -10C . The stirrer was started
at a low speed and 1 gram of urea nitrate was added . Additions in small portions of 33 grams total pentaerythritol by sprinkles from a teaspoon were begun , observing the temperature and maintaining the reaction in the range of
18-23C by regulating the rate of addition and adding ice to the bath as needed , siphoning off excess of melt water IIRC was at least once required as it takes a surprising amount of ice for even this small batch nitration . It is a very exothermic
nitration and should be carefully watched . The total reaction time was 1 hour from the beginning of the addition to the completion of the nitration . The pentaerythritol appears to first dissolve in the strong acid and then in seconds precipitates as the end product insoluble in the mixture as fine crystals which accumulate steadily , making the mixture thicken more and more as the process continues until towards the end the slurry of PETN is so thick as to be barely stirrable . The temperature range is critical , for at 25C red fumes will appear , but the reaction seems well behaved in the 18-23C range . At the end of the hour the mixture is quickly drowned with ice water , plunging the beaker sideways into its own icewater bath is fine for this , and the PETN filtered , suspended in warm water and neutralized with sodium bicarbonate and a little ammonia and then filtered and dried .

The crude PETN was placed in a sealed 1 liter jar with a
magnetic stirbar and 375 ml acetone . The loosely capped
jar was placed in a hot water bath on the stirrer and heated
just to the boiling point of the acetone , cooled slightly below
and then unsealed . To the solution of PETN in acetone was
added 1 gram of urea and 1 gram of sodium bicarbonate and the mixture capped lightly and stirred for a couple of minutes
and then 2 ml of strong ammonia water was added . To
the rapidly stirred hot acetone solution was then added in portions small pieces of ice allowing each portion to melt before more was added , total ice about 200 grams , simultaneously with a slow drip 1 drop per second of warm water 250 ml containing about 1% urea as a stabilizer .
When all was added the stirrer was stopped and the mixture
allowed to stand for a few minutes and filtered . The dried
crystals of PETN weighed 73.6 grams , yield 96% of theory
based upon pentaerythritol used . The product is a snow white , colorless and odorless , reflective free flowing crystalline material which very much resembles table sugar and is very temperature and storage stable , and has desirable handling and loading properties . The product
was dust free and appeared very consistent in particle size
although it was not screened . It was good for use and lumpfree straight from the drying on the filter , the sort
of material where one simply folds the filter and pours the dried material directly into the storage bottle , and there is little to no residue left sticking to the paper . Ah yes , the good stuff

Attached here is the DuPont PETN nitration patent
In the next post will be attached the crystallization patent

[Edited on 6-7-2006 by Rosco Bodine]

Attachment: US2370437 Nitration Process for PETN.pdf (154kB)
This file has been downloaded 2285 times

Rosco Bodine - 6-7-2006 at 15:11

Attached here is the DuPont PETN crystallization patent

Attachment: US2204059 Crystallizing PETN.pdf (260kB)
This file has been downloaded 1635 times

nitro-genes - 7-7-2006 at 05:18

Quote:

Originally posted by Rosco Bodine
The water drip was simply a little extra which I added to get some additional dissolved urea into the system where crystallization was occuring , think of it as a minor modification relating to stabilization , more than being involved as a driver of the crystallization , only serving to add the stabilizer as a slight impurity and maintain a slight percentage of it in the solution as it was being diluted by the melting ice . I hope that makes sense.

I understand, although I wonder if the urea solution as a stabilizer is even necessary. Only well neutralized should the PETN be stable enough to go for several decades anyway. The slight yellow tint upon addition of ammonia is a good indication for the completion of the neutralization indeed. With 25% ammonia it is quickly overdone though. I've wondered if it doesn't comprimise stability to a great extend...

Quote:

Originally posted by Rosco Bodine
It was good for use and lumpfree straight from the drying on the filter , the sort of material where one simply folds the filter and pours the dried material directly into the storage bottle , and there is little to no residue left sticking to the paper . Ah yes , the good stuff

That sounds really good. Can't wait to experiment a little with this

(Which will be after my two week vacation that is)

[Edited on 7-7-2006 by nitro-genes]

Rosco Bodine - 7-7-2006 at 08:34

The urea may not be necessary for PETN but I use it anyway , and it is necessary
for ETN or other nitroesters which have less stability than PETN . Basically I use it because it likely provides an extra margin of stability for high temperatures which could be encountered in storage , even though PETN is perfectly stable at ordinary temperatures even with no added stabilizers .

Yeah the ammonia is something not to get excessive .
A small amount of ammonia is something which I use as an
" olfactory indicator " and penetrant sort of neutralizer which will be volatile after it has served its purpose . The idea is that if free ammonia can be detected by smell , then the other neutralizers have done their job because there is no residual acidity to tie up the ammonia indicator , and any trace amount of ammonia will evaporate off the drying crystals . It requires very little ammonia for this as it is quite easy to smell its presence for a few seconds as it is leaving a warm solution . There is not enough of it used to cause any problems with decomposition of the product .

[Edited on 7-7-2006 by Rosco Bodine]

franklyn - 25-7-2006 at 15:27

Take this with a grain of salt as my experience with these two
materials is somewhat limited, but having handled and observed
their use in practice I can see no difference between the two,
and they can be used interchangeably. As evidence for this I
submit the example of the czech product called Semtex which is
a blend of nearly equal amounts of both. There is no practical
reason that I know of for doing this and neither do those who
should know. So go figure ?
See -> http://en.wikipedia.org/wiki/Semtex

.

nitro-genes - 11-10-2006 at 05:05

After numerous attempts to modify the crystal shape of PETN I have only been able to produce needle like structures. Different solvents, temperatures and concentrations to alter nucleation/growth ratio were tried, but this simply doesn't seem to help...

The process described by "US2370437 Nitration Process for PETN" was attempted many times with PETN directly from nitration and recrystallized PETN, but only yielded needles or almost plate like structures from completely saturated solutions...

Purity is not the issue I think, the crystals in the picture below were very slowly crystallized from acetone two times before crystallized from ethylacetate. The result after slow cooling of a near saturated solution were perfect needle shaped crystals of which some were over 3 cm long...

GB1184292 suggest that the it is especially high purity PETN that behaves like this and a small percentage of di-PETN added produces free flowing crystals of PETN that look like the picture below...

Does anyone know a how to produce more di-PEHN during nitration? The PE that I use is 98% purity from acro organics. IIRC the impurities would be mainly di-pentaerythritol and tri-pentaerythritol, so I can't see why di-PEHN shouldn't be present already after nitration...

According to the patent, the bulk density increases from 0.70 to 0.96 g/cc. This indicates that when crystallized this way, plastiques of 1.6 g/cc instead of the usual 1.4 are feasible. Providing CJ pressures of 250+ kilobars instead of the miserable 160 kilobar semtex 1A produces...

[Edited on 11-10-2006 by nitro-genes]

Attachment: GB1184292 Free Flowing PETN.pdf (103kB)
This file has been downloaded 1274 times

quicksilver - 11-10-2006 at 06:53

Needles do not nessesarily inhibit flow charactoristics if the needles are fine enough and shave on one another until they are uniform powder. however the REVERSE re-crystalization method -=will=- give you some granular, course crystals. See US2204059 - Roscoe have it posted. It works! In a nutshell it's dropping ice to form seed crystals into the hot acetone and building from there instead of drowning the acetone INTO ice and water. However I have also seen a unique technique wherein the hot saturated acetone is immediatly placed into a cold (O C) environment and left for a considerable period and the needles are HUGE - left to simply evaporate on there own in cold from the saturated acetone. These then are washed with etoh and broken via shaving becoming quite powdery. But US2204059 points to granular crystals as the focus of the patent and may be quite funtional.
There is a method for altering flow charactoristics using the simple addition of anti-caking agents commony used in technical grade chemicals, etc.

[Edited on 11-10-2006 by quicksilver]

nitro-genes - 11-10-2006 at 07:33

The di-PEHN acts as some sort of a crystal modifier, which gives the crystals a hexagonal shape with superior properties. It is also mentioned in:

"Stability Studies on Pentaerythritol Tetranitrate"
Propellants, Explosives, Pyrotechnics
Volume 17, Issue 6 , Pages 307 - 312

I don't know why US2204059 doesn't work for me, I can get coarser crystals, but they still are rather elongated. What shape and size do the crystals have when you recrystallize from acetone using the process described in the patent and what is your batch size? They need to be hexagonal or cubic shaped for good performance...

Rosco Bodine - 11-10-2006 at 21:42

The DuPont patent method works for me .

The density of the PETN crystals via the DuPont patented crystallization method is high and the shape is cubical I think ...I didn't look at it under a microscope . The mesh size is about like table salt or sugar , granular consistent and free flowing , shiny hard glittering crystals , with no fines or rocks . When the crystals so obtained are wetted with molten ETN , in a 2/5 ETN/PETN , a eutectic melt of ETN/PETN forms and wets the undissolved portion
of PETN crystals which results in a PETN solids filled slurry
in a melt liquid phase of ETN/PETN eutectic . The composition solidifies to a density of 1.69 with a very
slight shrinkage which can be managed by gently pressing the charge as it is solidifying but still
slightly plastic ....before it has cooled and completely set up rock hard . The composition is much harder to initiate in a way that it detonates at its highest velocity , than is compressed particulate or crystalline PETN alone , with
its microscopic airspaces trapped between the compressed crystals . This characteristic probably
follows for plastiques and gelatins also , where the density of the charge is high . You can get higher performance from increased density charges , by exclusion of airspaces , and crystal modification , but you also can get decreased sensitivity , low/high velocity detonation schemes , increased critical diameter as the
price paid for the increased brisance and velocity .

quicksilver - 12-10-2006 at 06:48

I have seen it work with no problem. : Work with HOT acetone saturated solution (don't let it cool to a great extent). Place a single small ice cube in first and let seed crystals start around it's circumfrence then start the addition of more - timing becomes an issue here. Use a reaction vessel with a lot of surface area...sounds ridiculous but I believe that the greater the surface area has an influencing factor in that the shallow spread of acetone saturate is subjected to temp changes quickly and that needles need more time and depth to grow hence the granular formation.

nitro-genes - 12-10-2006 at 06:57

Hehe, ok, I think there is a bit of miscommunication from my side...

The point is that not only need the crystals to be cubical or hexaganal shaped, but in order to obtain a moldable high density plastique they have to be very small too. Larger, coarse crystals aren't the problem, but making a moldable plastique of this is not possible of course. Try plasticizing table sugar and see what properties the plastique will have!

GB1184292 describes free flowing PETN that has particle size much smaller than the flow tube they use of 0.2 mm. There is something about using di-PEHN and tri-PEON that can act as a crystal modulator in certain quantaties to abtain small, hexagonal crytals. I got some reference to a los alamos technical report about this, but it doesn't seem to be available...

"LA-4486-MS PETN-DiPEHN-TriPEON system"

HMTD - 12-10-2006 at 10:02

IMO, there is no difference between cubic and needle crystal shape for certain applications. I use PETN mostly for PBX, and it’s crystals is always needle-shaped, which are produced from hot acetone and water. These crystals are not convenient for using in PBX directly, so I crush them with mortar/pestle in presence of water and antistatic agent (commercially available static strain remover spray) . Time of procedure determines the resulting crystal size. After drying the PETN looks like slightly yellowish(depends on color of antistatic agent) fine powder with more or less observable no-more-needle-like crystals, which no more electrifies. Of course, I made for one time not more than 50 grams, but there is no problem to make more. The greater part of this PETN I use for producing PBX, the rest for hand-pressed boosters to this PBX. Using 14% - 5 % of polybutylene as binder, the resulting measured density varies from 1.56 to 1.65. When I need PBX with small critical diameter ( less than mm), I use raw PETN after above mentioned procedure, 86/14 has about 1.51 and quite stable, it detonates in 0.5 mm sheets.

Rosco Bodine - 12-10-2006 at 11:45

IIRC . there are an aggregate of differing mesh sizes of fines required for plasticizing high density mixtures whether it is PETN or RDX or mixtures of each that
is the active component of the plastique , the idea being
that the smaller mesh fines fill in the spaces between
the larger mesh crystals so that the bulk density is
greatest and there is least empty space between the
aggregate to be occupied with whatever binder .

I think that is the idea with semtex , the crystal sizes are
complementary for the aggregate and the result is a
higher density plastique easier to manufacture than
obatining the optimum distribution of particle sizes
for RDX or PETN alone .

I have seen DOD literature and patents related to this
for C4 density optimization , sensitivity retention , and
it requires special techniques in manufacture and appeared more complicated than would readily adapt
to laboratory technique . IIRC every step of the process
for crystallization and addition of the plasticizer was
tedious and meticulously controlled and required
*milling operations* through rollers and extruders for
the finishing operations to end up with the desired
properties .....all strictly industrial processes which were
done on remotely operated equipment due to the hazardous nature of the process . Nothing I have ever seen described about the manufacture of commercial plastiques indicates that this is attainable except perhaps
for small samples exhaustively worked up manually .....
more trouble than it's worth to try to replicate on a lab scale .

HMTD - 12-10-2006 at 13:19

I think, all stuff with C-4 and Semtex ( crystal shapes and sizes, just as plasticizers and production cycle) stands for not only the best expl. properties ( density, VoD) but also mechanical properties. The milling operation in water is not so dangerous , I think. PETN is not a primary explosive, and its detonation from friction in water practically impossible. Even if imagine that thin PETN layer under the pestle detonates, the surrounding crystals retarded by water couldn’t set off from such a weak initiator. About the density - when crystals milled their volume decreases probably due to crushing needles and also forming of different crystals fractions. My PBX compositions in their resulting state (i.e. prepared to be molded in charge) have almost theoretical density. But also they have (depends on amount of plasticizer and crystals fractions) decreased mechanical properties( I’m sure that my home-made 90/10 plastique worse than C-4 in mechanical aspect.) But for my applications it is acceptable. It has high density and calculated critical diameter of 2,5-3 mm and perfect performance in shaped charges(mostly EFP). The small critical diameter of raw non-re-crystallized PETN and corresponding PBX permits to explore performance of small SC (and other) directly devices at home (explosive mass usually not exceed of 0.25 g ). The difference of my way of producing base of PBX and industrial way – I control manually crystal shape and sizes, they study what crystal mix better for product and later prepare it automatically from re-crystallized and meshed PETN(RDX). It is not worth to do so in home lab, IMO, if you want to produce quality PBX. The most important thing is plasticizer, if you have not a good one – crystal shape wouldn’t be important.

Rosco Bodine - 12-10-2006 at 14:03

Quote:

Originally posted by HMTD
IMO, there is no difference between cubic and needle crystal shape for certain applications. I use PETN mostly for PBX, and it’s crystals is always needle-shaped, which are produced from hot acetone and water. These crystals are not convenient for using in PBX directly, so I crush them with mortar/pestle in presence of water and antistatic agent (commercially available static strain remover spray) . Time of procedure determines the resulting crystal size. After drying the PETN looks like slightly yellowish(depends on color of antistatic agent) fine powder with more or less observable no-more-needle-like crystals, which no more electrifies. Of course, I made for one time not more than 50 grams, but there is no problem to make more. The greater part of this PETN I use for producing PBX, the rest for hand-pressed boosters to this PBX. Using 14% - 5 % of polybutylene as binder, the resulting measured density varies from 1.56 to 1.65. When I need PBX with small critical diameter ( less than mm), I use raw PETN after above mentioned procedure, 86/14 has about 1.51 and quite stable, it detonates in 0.5 mm sheets.

I don't say this very often because of preserving a certain decorum ....

but you are full of bullshit .

The critical diameter of fine mesh PETN compressed and heavily confined in a glass tube is more than 1 mm ,
so it would be miraculous for your .5mm sheet plastique
having a diluent of a soft inert plasticizer to detonate
as you describe .

If you have good data to share , then by all means share , but if you come here to this forum to tell kewl tales ......then just STFU and keep kewl in " Moscow , Russia "
LOL .....
as if I believe that load of bullshit either .

[Edited on 12-10-2006 by Rosco Bodine]

nitro-genes - 12-10-2006 at 15:07

I know about the production of C4. The increased density is mainly about crystal size control (has little to do with the plasticizer or binder used), screening of the two exact particle sizes, strict crystallization procedures, vacuum removal of solvent, after which the granules are sold as a loose powder which can be pressed directly, like a PBX or kneeded into a clay consistancy. The extra steps in it's manufacture make that semtex is much cheaper and commercially available, though on the other hand it doesn't produce the detonation pressures of the latter. Semtex is mostly used as a booster, so for this purpose the extra amount of pressure sqeezed out would not be worth the cost. Only metal accelarating purposes as EFP's, shaped charges, or hard target demolitions this is necessary, hence army usage...

But enough on the practical side, after seeing some examples of 90+% PETN plastiques at densities of more than 1.60, I was just curious if there was any info available about different crystallization procedures for PETN.

HMTD does have a point about manually "milling" the coarse crystals until they become a more free-flowing powder. It is difficult to judge when this exactly is, and it is a lot of work, but after a quick try I was able to get to a density of 1.51-1.53!

8 grams of coarse crystals of about 5 mm long and 0.5 mm thick were crushed gently under water until it was the consistancy of rather fine sand. To this was added about 4 grams of very fine, instantly precipitated PETN from acetone, and 12% of plasticizer. The coarser particles made the plastique much more sticky and to overcome this, another 2 grams of the fine PETN was added. (Actually, more PIB should have been added but this was more work

) The density was considerably higher, my scale can measure down to 10 milligrams and it was done three times to get an accurate reading. A density of 1.65 seems a bit of a stretch though! And the process is considerably more work. Moreover the coarse particles give it the feeling of plasticized sand and results in greatly reduced moulding properties. The finished product starts to tear at about 1-2 mm thickness and doesn't have a good density homogenity. With only PIB in a PBX formulation you should be able to go thinner though...

Since no one has heard about di-PEHN and tri-PEON as crystal modifiers to make life a little more easy, I will experiment a bit further with the milling method. Although I don't really like the milling procedure, the goal was to make a SAFE, non-toxic, high brisance and small critical diameter, storage stable, cheap, insensitive and versatile explosive!

Thanks for the all the repies!

[Edited on 12-10-2006 by nitro-genes]

Rosco Bodine - 12-10-2006 at 18:03

Realistically

.....if you can get a *homebrew* PETN plastique with an inactive binder with a fine enough consistency and good enough aggregation to have a critical diameter of 2.0-3mm , then you are probably doing damn good !

To get it smaller you will likely have to explore MHN
or HNI as additions to the mixture , and *sensitive* energetic plasticizers which leads to compositions which really depart the PBX designation and are gelatins or fillered gelatins .... maybe designate it GBX ?

Yepper when PBX just won't cut it .... upgrade to GBX .

HMTD - 13-10-2006 at 01:19

Rosco Bodine, I didn’t outrage you! 0.5 mm sheet (not “bullshit”) was with ULTRA fine PETN which wasn’t re-crystallized! And you probably know, that the critical diameter ( just as critical width of expl. sheet) depends on conditions of its detonation. In my case it was located in 0.5 mm steel sheet (which was damaged), so the critical width is twice less than in case of free sheet in air. And 0.3 mm sheet in contact with the previous one didn’t set off. In my way of production PETN ( Urbansky’s 96% H2SO4+70% HNO3, then filtering, neutralization, boiling for 1 hour in 1 % Na2CO3 ) gives flour-like crystals, then I mill them with antistatic agent to free them from the extra in-crystal acid, and it gives me even finer powder.It is known that critical diameter depends on crystal size. And I know industrial samples of PBX (ELAS-2) based on 85% of 5 – micron size PETN crystals with inert plasticizer that have cr.diam. of 0.5-0.7 mm. I am sure, that milling process can’t give such a fine powder, probably they use some sort of re-crystallization, I don’t know. With the better plasticizer ( polyisobutylene+heavy oil from some old putty ( like blu-tak I think but yellow) 88/12 PBX(density not known) detonated in elongated charge (section 0.6 mm * 1.2 mm rectangle) . With 0.9 mm * 1.2 mm section charge I had measured VoD about 7848 +-250 m/s ( was measured time between breaking two wires on the charge’s ends). It is to be told that this ultra-fine non-re-crystallized PETN powder based PBX surely to be less stable and dense then one produced from re-crystallized, so it can be used mostly in special purposes I mentioned and shouldn’t be kept long. I have number of videos of testing such small-critical-width plastique, maybe later I would share some of them.

quicksilver - 13-10-2006 at 06:31

I am always interested in crystal modifiers, so if you do find the info by all means please post it. I just looked at some LA stuff and couldn't find anything on di-PEHN and tri-PEON at all....
However the phenomenon of crystal shaving via mix manipulation is such that I would bet once the granularity is established one could refine such a thing to reduce the overall size (where a needle shape would be impossible to work with).
I was taken off track frankly; I just thought you wanted to posit differnt shapes per se' but then I post with my morning coffee and I'm mostly not awake.

Rosco Bodine - 13-10-2006 at 09:43

@HMTD

I simply don't believe you because the scenario you
describe is inconsistent with published limitations
concerning these type compositions .

I also doubt the veracity of your reported chronographic data . I feel like you are pulling my leg so hard that
my hip joint has been dislocated .

The numbers and scenario you are describing are
simply not believable .

Even if you got below a millimeter using microfine PETN
pressed in a capillary providing strong confinement and
an optimum density to achieve a sustainable detonation ,
the velocity would drop way off , and that situation would quickly be worsened by the presence of an inert binder diluent , and worsened further by the absence of confinement for a thin sheet or ribbon . What you describe simply doesn't ring true for a PIB bonded plastique . Hell it might not even go that low as a
viable section for NG plasticized PETN where the binder
is active . 0.5mm thickness is like a heavy coat of varnish
in thickness , the thickness of a paper matchbook cover .
Does it sound reasonable that even a sensitive secondary like PETN is going to sustain detonation in
an unconfined layer that thin , when not even all of
the primary explosives could match that performance ?

Even pure NG has its limiting diameter .

HMTD - 13-10-2006 at 12:47

“It is impossible because it can’t be true” – this is like your words, Rosco Bodine, sounds to me. Just try the things I’ve described – you’ll see. Or maybe nitro-genes could try, he seems to be more practical person. Here some data from official sources (I can give you the all article if you want in Russian).
“Russian chemical magazine”
The magazine of Russian Chemical Community named after D.I. Mendeleyev
Vol. XLI

“ High energy substances”
Part 2

4,1997

Article “ Elastic explosive materials” by A.A. Kotomin

“ A.A. Kotomin – Doctor of Technical Sciences, professor of department of Chemistry and Technology of organic nitrogen compounds of Saint-Petersburg State Technological Institute.”
“
Explosive composition ELAS ( developed in assistance with candidate of Technical Sciences S.A.Dushenok)

ELAS-1/ELAS-2 Contains ( % by mass )

PETN 85 / -
RDX - / 85
Butadiene-nitrile rubber 6.5 / 6.5
Butadiene-styrene rubber 6.5 / 6.5
Polytetrafluoroethylene(Teflon) 1.5 / 1.4
Antioxidant 0.5 / 0.5
Carbon(soot) - / 0.1

Properties

Density, g/cm^3 1.57 / 1.59
Critical diameter, mm 0.5-0.7 / 3.0-3.5
Temperature when intense decomposition starts, °C 170 / 210
Flash temperature ( after 5 sec delay) °C 230 / 280
VoD , km/s 7.5 / 7.6
Sensitiveness to impact, % of explosions 52 / 48
Sensitiveness to friction(low limit), MPa 168 / 217
Sensitiveness to initial blast wave, kBar 15 / 28
Lead block expansion, cm^3 400 / 380
Brisance ( 25 g) , mm 16 / 18
Detonation Pressure, kBar 210 / 225
Breaking strength , MPa 4.0 / 3.0
Chemical stability ( 110 °C for 14 hrs) ,mercury mm 10-25 / 10-25
Application interval , °C from -55 to +80 / from -55 to +160
”

And here is some data about the critical diameters ( measured and [calculated]) of different crystal fractions of RDX, PETN and HMX at the 98-99 % of crystal density from the same article :
“
RDX (high dispersed, 3-5 micron) 0.27 [0.27]
RDX (fraction 0-60 micron) 1.7 [1.5]
RDX (fraction 90-160 micron) 2.4 [2.35]
RDX (fraction 200-250 micron) 3.3 [3.45]
RDX (fraction 250-350 micron) 3.8 [4.1]

PETN (high dispersed, 5-7 micron) 0.2 [0.2]
PETN (fraction 0-90 micron) 0.86 [0.85]

HMX (fraction 0-90 micron) 1.5 [1.45]
HMX (fraction 90-160 micron) 2.1 [2.05]
HMX (fraction 200-250 micron) 3.1 [3.05]
HMX (fraction 400-500 micron) 4.8 [4.4]
”

This data can be used to determine cr.diam. of PBX composition based on mentioned explosives ( method of calculation described in article). Later I’ll try to share some movies/photos which should prove my words, I hope.

Rosco Bodine - 13-10-2006 at 15:02

Oh I'm a practical person , and detaflex and detasheet
have been around for forty years .

That's the DuPont comparison of your " ELAS-1" .

The stated minimums on these highly specialized PETN
based products is about 2 mm for the inactve bindered
product and about 1 mm for the active bindered material .

But the products as used are increased well away from those minimums .

So maybe the Russian manufactured detaflex and detasheet is better stuff ?

I still doubt it .

What is the KGB doing these days , trying to get a
roll of detonating cord miniaturized to the point it can
be concealed as a spool of sewing thread

No wait ....dental floss and toothpaste ! That must be it .

[Edited on 13-10-2006 by Rosco Bodine]

quicksilver - 14-10-2006 at 05:50

ahhemmm....just for the record I want to reiterate what you all are talking about here. I'm just waking up so I'm sort of fuzzy & I am not a trained scientist but we are talking about a non-energetic PBX, at a thickness of 1/2 a mm detonating at what speed? I also didn't know they had Blu-Tac in Russia. Damn; this board has some new stuff every time I turn around.....I was always under the impression that energetic materials needed to have a critical diamiter and that the binder in a PBX (if non-energetic) would further reduce the density of said material. If the material is reduced in particle size oil will not keep it binded; thats why butyl styrenes are used - so it seems logical that if one reduces the thickness, density will suffer.....no?
When I think about it - it occured to me that "6 grain" det cord (the yellow shit) would be thin as Hell BUT that is det cord and packed down via a machine and utilizing no binder. The objective being to simply transfer shock from point A to point B. Would a material's energetic responses be altered by volume as well as density? Certainly some would, others would not. But deta sheet's usage woud almost preclude the desire for super thin sectioning; it's area coverage material, to move a larger mass. Unlike a cylinder, the purpose is to shove (or smack, however you like) a larger area.....no? And IF one were to develop a super thin deta sheet how do you get the thing into a fine, small, thin area, if the purpose (the only one left) is to insert same into a tiny crack between large surfaces (like large scale building rubble)???? But that's not the point of the discussion, so I'll drop that. But I was under the impression that PETN and RDX had similar stats but that if one used LESS material PETN would be more appropriate, yet the above sited material includes both and HMX as well. Perhaps this is a "lab-only" scenerio wherein the conditions are controled to such a fine extent that they could almost never be reproduced in industry.
Now the only reason I even bring this up (which I possibly shouldn't) is that I have been reading Rocsoe's posts for well over two years now and have not remembered him calling something bullshit. I have followed his suggestions in many areas and all of them have been on the money. But I also know that shaving of crystaline particulate is possable and that the above sited patent makes it clear that the granular particles can be mesh sized up or down. The siting of published material is a well respected method of debate however I also know that journal material may be taken out of context or non-peer reviewed (such as the clinical reference to "sexual additiction" which has a journal but is not peer-reviewed, nor part of the clinical references in the DSM-IV). Thus angels dance on the head of a pin for many in this world and for many they just don't exist.
OK...I'm ready to be flamed now...

[Edited on 14-10-2006 by quicksilver]

Boomer - 14-10-2006 at 09:26

Rosco, have a look at the Los Alamos handbook, a PBX called XTX8003 (from memory) has a critical dia of under a mm, IIRC around 0.5mm *unconfined*. It is PETN based, with an inactice binder. XTX8004 is identical but RDX based and needs over a mm.
These two are also mentioned in Cooper.

Sheet explosive comes in 1mm thickness too, and they would not sell something that's on the edge of not working. Again, the mil version with RDX starts at 2mm.

He may well be right, even though I doubt his 'measured' VoD (ionization probes are better than breaking wires, I once got 20 km/s for BP because the hot gas conducts as well, fooling the timer)!

EDIT: His material was confined: "it was located in 0.5 mm steel sheet, so the critical width is twice less than in free air"

[Edited on 14-10-2006 by Boomer]

Rosco Bodine - 14-10-2006 at 10:48

I get it that the lower limits of propogation can be explored , but I would be doubtful about the consistency
of any high velocity performance on this material unconfined , particularly an improvised material not
made in an industrial setting .

When you are out a distance of about 100 times
the thickness or diameter of a charge that is close to
critical , the propagation reliability isn't there anymore ,
and the detonation can drop to a low velocity figure or
drop out completely . At a thickness of 0.5mm , that
would give you a couple of inches of reliable propagation
and then a big question mark as to what happens further out .

Anyway , I am highly skeptical about these microscale
microfine structured materials . I do not trust the reliability or practicality of these things that operating near to minimums , and I sure don't have confidence in any improvised compositions . We could go on forever
arguing about it , but I doubt the credibility of confirmatory claims for an improvised composition which
parallels work done at DuPont or Los Alamos to produce
something so specialized .....it just seems far fetched .

But by all means , anyone drag out their ball mill and screens , their blu-tak and solvents , stir sticks and
tell me all about it .......

I still don't believe it .
I would have to see it to believe it ,
and then see it replicated a few times just to be sure .

nitro-genes - 17-10-2006 at 18:28

After a few tries I got to 1.69 g/cm3, using 7-8% plasticizer, and estimated avarage PETN particle size of about 20 micron. A little more oil was required to make it soft and pliable. Like HMTD said also, using finer material will result in lower densities, but better sheet material properties. Supposedly, this ultra fine PETN can be made by spraying an acetone/PETN mixture under high pressure in icecold water. Partilce size was something in the nanometer range...

It is mentioned in some article that I am unable to find again.

Probably the figures given by HMTD are not that unbelievable. Regular semtex at a density of 1.40 g/cm3 is said to have a critical diameter of 3 mm. Though I have reliably fired it at 1.5-2 mm, and this was with fairly coarse PETN recrystallized from acetone! The failure diameters given are likely to be the "worst case senario" limits. Though an alternative explaination may be that there is a certain run up distance. I have seen it before with tubes filled with NG...

[Edited on 18-10-2006 by nitro-genes]

Boomer - 18-10-2006 at 07:43

I took the time to look up several plastic bounded (PBX...) and extrudable (XTX...) formulations using PETN in Los Alamos and LLNL files: *Many* are under 1mm either in critical diameter of in wedge test failure thickness. Only RDX comps are above 1mm. And Rosco, those peaple *do* replicate their test before publishing results.

BTW semtex has some 30% plasticiser, the kreml crooks probably sold the cheapest shit to terrorists that barely went bang. I once read there's two kinds, semtex 'H' for 'hardly detonable', and semtex 'A' for 'adultered'.

franklyn - 21-10-2006 at 15:35

The mesh size of crystal formation is a function of time.
The comparatively slow precipitation from a chilled solvent
can be avoided by spray aeration, as from a paint gun.

On page 382 of COPAE _
"extremely fine powder may be procured by the rapid cooling of
a mist or spray of hot nitroguanidine solution, either by spraying
it against a cooled surface from which the material is removed
continuously, or by allowing the spray to drop through
a tower up which a counter current of cold air is passing"

It would be easy to rig a vacuum cleaner with a spray nozzle
inside of a fine wire mesh cylinder ( of the type used for coffee
filters ) introduced inside the vacuum's bag, fitted to seal the
opening where the hose normally attaches. The partial vacuum
created will draw mist inside from the differential with
atmospheric pressure, flash volatilizing a high vapor pressure
organic solvent to produce the desired fine dust of the solute.

The solvent can be reclaimed from a condensor fixed to the vacuum's
exhaust. This entire arrangemnt works best if there is very minimal
air present so initial venting of fumes to purge the space is
advisable.

Of course then the greater insensitivity of the resulting product
would have to be addressed for a given application.

_______________________________________________

This is just an after thought. To explore the practicle limit for
thickness of sheet explosive. One may obtain good quality " rag "
writing paper of the type used for personalized stationary. Treat
this with mixed acids to produce "flash paper" ( nitrocellulose )
neutralize residual acidity, then place onto a piece of window glass
to dry without crinkles. Now using the spray gun approach one can
spray paint an explosive onto this substrate in the desired
thickness, although a combined one milimeter thickness would be
something of a reach.

.

[Edited on 22-10-2006 by franklyn]

quicksilver - 22-10-2006 at 09:44

{Not that I doubt it} but 30% binder is unique to my limited knowlege in a commercial PBX. That would certainly explain the "A" & "H"

- I can hardly imagine a material going bang at that level. And this brings to mind questions that I have had for awhile now....What is "Gulf Crown" oil - it's viscosity or equivilant ? And from what I have seen Silicon Oil is extremely expensive; does the value of it's use as a binder comes from it's viscoity or some other characterisic?

Boomer - 23-10-2006 at 07:42

Quote from a 1995 post on a.e.e.
Source is:
"Analysis of Semtex Explosives" J.R.Hobbs.
Chapter 39. p.409-428 in " Advances in Analysis and
Detection of Explosives" edited by Jehuda Yinon
Kluwer Academic Publishers ISBN 0-7923-2138-3 (1993)

Name Semtex H Semtex A
% PETN 49.8 94.3
% RDX 50.2 5.7
Dye Sudan I Sudan IV
Antioxidant N-phenyl-2- N--phenyl-2-
naphthalamine naphthalamine
Plasticizer n-octyl phthalate n-octyl phthalate
butyl citrate butyl citrate
Binder styrene-butadiene styrene-butadiene
rubber rubber

Table 2. Gravimentric Analysis
Sample size 1.0194 1.1061
Weight oil 0.0811 0.0994
% oil by weight 7.9 9.0
weight rubber 0.0920 0.1036
% rubber by weight 9.0 9.4
weight explosives 0.7029 0.7029
[ rest of table omitted ] (end quote)

See that last line. It is not % but grams out of 1.0194 and 1.1061 grams. I go on quoting (Jerry btw. alias Gerald L. Hurst - should ring a bell, think Astrolite/Kinepack):

"If comrade Vladimir
gets Col Khadaffi's order for a few tons of plastique, and
Vlad finds he is out of PETN from the Chernobyl plant, does
he apologize and not fill the order because he doesn't have
the "minimum" 21 percent PETN? Or does he simply manufacture
"Semtex U," short for USA, a material remarkably like C-4?

As long as these guys can get their hands on either PETN or
RDX individually or in a mixed ordnance scrap pile, they will
continue to manufacture "Semtex" and people will continue
to ask "What is the composition of Semtex?" I would be
willing to bet that there is plastique "Semtex" out there
adulterated with TNT, HMX (They should be so lucky) and tetryl
as well and probably a good bit of it cut with inerts to the
cap-sensitivity limit.

According to your gravimetric analysis table II, the total
explosive contents of Semtex "A1" and "H" respectively
are 64 and 69%. The corresponding oil/rubber contents are
17 and 18% for totals of about 81 and 87%. Based on the ratios
in table 1, the RDX would be 5.7*.64 = 3.6 percent which is
far less than the material not accounted for."...

"So, Mr. Entrepeneur formulates his plastique in the cheapest
way possible using PETN and all the passive materials he can
put in without losing cap sensitivity. He is not at all
concerned about the strength of his product as long as it
shoots.

Time passes and our businessman gets his hands on some price
competitive RDX. His first new batch of "Semtex" is a dud, it
won't shoot. He could raise the concentration of RDX up to 91
percent to make "Semtex C-4", but that would raise his costs
significantly. Then he finds a happy compromise. He blends in
enough PETN to allow the retention of cap-sensitivity at
higher inert dilutions.

Batches containing about 50/50 PETN/RDX can tolerate a hefty
30 percent or so of inerts while material with 95 percent
PETN handle a whopping 35 percent.

Without a rather sophisticated laboratory, your average
terrorist is unlikely to be able to tell 50/50 from 95/10, but
he can estimate the total explosive content by noting a couple
of solubilities (acetone and ligroin), so our vendor puts
labels on the material: "H" for "hardly detonable" and "A" for
"Awfully adulterated." This act of honesty helps assure the
manufacturer that he won't receive any "returns" from his
customers...." (end quote)

Good old times when there was intelligent discussion on a.e.e.
Discussion between professional blasters, veteran EODs, and people from the explosives industry like said Jerry. Now it's overrun by kewls and the pros keep silent/have given up. Sad world...

quicksilver - 24-10-2006 at 06:18

Yes indeed.
Thanks for digging that up; I do remember some interesting interaction back many years ago on UseNet A>E>E. It's now getting to be MANY years ago....
RE: butadiene styrene: it seems like a pretty damn good binder (toluene is the solvent as I remember). Seems it's sold in nearly pure form as an adhesive in the US.

Boomer - 25-10-2006 at 03:37

I am not that familiar with the old english names, but should a polymerized ...-dien not be named ...-tylen? That would close the link between poly(iso)butylene (PIB in C-4) and (poly-(styrene-))butadien in semtex.

These may be OTC via self-amalgamating tape or bubble gum, or rubber glue or whatever. But where does John Doe get WTF-phthalate/citrate and OMG-(ethyl-hexyl)sebacate OTC?
I have seen a barrel of IIRC octyl phthalate half a mile from my door in the backyard of a factory. Never went for a late-night-sample though.

The most surprising thing about C-4, apart from how they cram in 91% RDX without loosing coherency (hint: bimodal crystal size), is the high content of softener compared to rubber binder (1/50th part!):

Polyisobutylene 2.1
Motor oil 1.6
Di(2-ethylhexyl) sebacate 5.3

nitro-genes - 25-10-2006 at 04:27

You certainly don't want to use triethylcitrate!

God knows why this is used, since TEC is pretty water soluble, eliminating the possibility of underwater usage. There is nothing really special about sebacates IMHO. The hydrophyllic moment (detergent action) of the ester groups and the linearity of the molecule as a whole give it slightly better plasticizer properties, the resulting advantage is mainly that sebacates show no exudation whereas using motoroil alone does exudate at high rates from plastiques. Nowadays they often use low molecular weight polymers to plasticize, these are very long and linear molecules virtually eliminating exudation. The affinity of the sebacate ester groups towards the nitramine groups from RDX could also reduce exudation...

Ricinoates share the same properties as sebacate plasticizers (linearity and hydrophillic moment) and both are derived from castor oil (92% ricinic acid). The caustic oxidation process of castor oil to yield sebacate is rather difficult, needing high temperatures and pressures and Raney nickel as a catalyst. An attempt to do so produced an IMMENSLY strong "fungus like odour" throughout the entire building!

Probably due to octanols and other high C esters produced... (Their low volatility ensured days of pleasure...

)

Never seen my girlfriend that mad before, I wonder why?!

Ricinoate esters on the other hand are much easier produced. I tried the methyl and ethyl esters by transesterification reaction (Vogel) of castor oil and methanol/ethanol under reflux. the methyl/ethylricinoate seperates as an oily layer at the top. These plasticizers are somewhat less good solvents for PIB and need some 20% of motoroil added for better properties. Seeping of plasticizer is much reduced, but there is no other real advantage that I noticed... (Although I never tried with very low % of plasticizer)

[Edited on 25-10-2006 by nitro-genes]

quicksilver - 25-10-2006 at 06:17

Quote:

Originally posted by Boomer
These may be OTC via self-amalgamating tape or bubble gum, or rubber glue or whatever. But where does John Doe get WTF-phthalate/citrate and OMG-(ethyl-hexyl)sebacate OTC?
I have seen a barrel of IIRC octyl phthalate half a mile from my door in the backyard of a factory. Never went for a late-night-sample though.

I didn't want to create a run on the place or give it a bad rep but the hardware store chain that begins the letter A (I feel a little foolish saying that but I really would like to keep it available). The MSDS for a specific bulk adhesive reveiled amazing results. Look for related posts on Rogue Sci; I think I even posted the SKU number as well. It's not that big of a deal but it seemed to fall out of the sky....a canned bulk adhesive that could be used as is. Indoor floor adhesive.

nitro-genes - 26-10-2006 at 04:41

Wow! The increase in brisance is amazing with increasing density!

Following HMTD's advice, very fine PETN was produced by pestling wet recrystallized PETN in a mortar. To 4.50 grams of this was added 0.50 grams of plasticizer/binder to give a density of 1.59.

A spun formed 0.5mm thick, 60 degree coppercone with rounded apex of 17 mm in diameter was glued to a 25 mm long piece of 17 mm innerdiameter PVC tubing. The 5 grams of plastique was loaded into the container by hand. Headheight was about 0.5 times conediameter, but I figured the rest of the headheight would be provided by the detonator...

Whereas the usual plastique penetrated only about 3.5-4.0 cm with the same setup, this one penetrated the entire 5 cm block of steel and about 6 cm of soil!!! The much smaller critical diameter of this plastique must have helped too. I Made some really nice pictures of them that I will upload as soon as I figure out how the ftp of sciencemadness works...

Just to set the standard: 4.5 grams of HE --> over 6 cm penetration in steel!

Moehahahaha Beat that!

[Edited on 26-10-2006 by nitro-genes]

Rosco Bodine - 26-10-2006 at 06:24

Pentaerythritol and other polyols also form other esters
than the nitric acid esters , and some of the organic acid
esters may be useful as modifiers / plasticizers when added to the energetic nitric ester . There is a patent
concerning the use of the tetralactate IIRC in this regard ,
as a densifier and modifier for the tetranitrate .

There are a series of organic acid esters of the polyols
which are synthetic lubricants , synthetic " ester oils "
blends of which are used as refrigeration compressor oils and as synthetic engine oils . Some of these may have
a sufficient solvent or colloiding effect upon PETN to be useful in small quantity as a component of any binder
system . Of course the non-energetic esters will not
contribute to the power of the composition except by
physical improvements as a blending agent which exceeds their negative effect as a diluent . But it may be the case that even a small addition of such esters can
have significant effect on increasing the percentage of
the other energetic materials which may be " packed " at higher density into a composition , so that the net effect
is increased performance .

Anyway , when I see these compositions which use a small amount of motor oil as a component , it just may be that a particular oil is superior to others , depending upon how
it interacts with both the binders and with the PETN .

Also , certain of the silicone oils can may have superior properties in the same regard , so these should be looked at
as possibly better than just ordinary " motor oil " ..... as this particular " minor ingredient " may be more significant than
some would think in defining the physical properties of
the final composition . The component called " motor oil "
may be a proprietary ingredient which is highly specific in
its effect on the finished composition .

[Edited on 26-10-2006 by Rosco Bodine]

nitro-genes - 20-12-2006 at 04:58

Quote:

Originally posted by Rosco Bodine
The component called " motor oil "may be a proprietary ingredient which is highly specific in its effect on the finished composition.

After experimenting a bit with some fresly made methylricinoate I come to believe that the hydrophillic moment of the plasticizer is very import in determining the "stickyness" and "stiffness" of the plastique, especially with low % plasticizer, high density plastique...

Whereas using motoroil alone as plasticizer gives an almost rocksolid plastique at 5-10% plasticizer, replacing 60-70% of the oil by methylricinoate makes it perfectly kneedable while not sticky, even at very small particle sizes.
It is no coincidence that all plasticizers contain some hyrophillic groups. My theory is that the reppellant action of these groups towards the hydrophobic environment allows for a much better separation of the long chain molecules of the polymer to be plasticized, giving them far better mechanical properties. I noticed though that above a certain percent of methylricioate the plasticizer mix seems to become cloudy, probably due to some precipitation, or emulsification, of the PIB. Adding some oil, analogous to the C4 composition can overcome this and makes the plastique stiffer...

Anayway, I'm quite pleased to have made 12% plasticizer plastique at 1.60-1.62 g/cc which has better mechanical properties than plah-doh. You can press it with your fingers to 0.5 mm thick without any cracking or tearing!

[Edited on 20-12-2006 by nitro-genes]

quicksilver - 20-12-2006 at 06:18

Quote:

Originally posted by nitro-genes
]
After experimenting a bit with some fresly made methylricinoate I come to believe that the hydrophillic moment of the plasticizer is very import in determining the "stickyness" and "stiffness" of the plastique, especially with low % plasticizer, high density plastique...

Whereas using motoroil alone as plasticizer gives an almost rocksolid plastique at 5-10% plasticizer, replacing 60-70% of the oil by methylricinoate makes it perfectly kneedable while not sticky, even at very small particle sizes.
It is no coincidence that all plasticizers contain some hyrophillic groups. My theory is that the reppellant action of these groups towards the hydrophobic environment allows for a much better separation of the long chain molecules of the polymer to be plasticized, giving them far better mechanical properties. I noticed though that above a certain percent of methylricioate the plasticizer mix seems to become cloudy, probably due to some precipitation, or emulsification, of the PIB. Adding some oil, analogous to the C4 composition can overcome this and makes the plastique stiffer...

Anayway, I'm quite pleased to have made 12% plasticizer plastique at 1.60-1.62 g/cc which has better mechanical properties than plah-doh. You can press it with your fingers to 0.5 mm thick without any cracking or tearing!

[Edited on 20-12-2006 by nitro-genes]

I have been VERY interested in this issue for as long time as well. Could you please post your "nuts & bolts" methodology in regards to what materials you used and the methods of mixtrure?

THANKS!

nitro-genes - 20-12-2006 at 09:45

First I recrystallize the PETN slowly from acetone, to give needle shaped crystals of about 5 mm long. These are GENTLY crushed with at least 40% water in a strong bowl until there are no needle shaped crystals left. This is the tricky part, if you keep on milling too long, the crystals will become smaller and the density of the final product will go down, if you mill too short on the other hand, there will still be needle shaped crystals left, also reducing the final density.

I'm not happy about the milling step, and I advise everyone attempting this to use extreme caution, and only small amounts at the time! (few grams or so) I'd rather go with better recrystallization control of crystal shape, but no luck with that untill so far...

After drying the milled crystals, I add about 2.8% PIB and 6% plasticizer containing 60% methylricinoleate and 40% motoroil in gasoline as a solvent. The gasoline solvent must be completely evaporated before your start rolling the plastique. At this point the mixture deliberately contains too little plasticizer, because the stiffer the plastique is, the better is the crystal shaving you mentioned and erosion process upon rolling. Smooth surface to roll on is a must, I use a glass bottle filled with water for rolling on a glass cutting board.
The rolling has to be continued for a VERY long time, and this is really not the fun part. I reckon for industrial manufacture this is done by mechanical means, but since this is out of reach for most amateurs there is no other option than to roll by hand.

As you keep on rolling the plastiqye, you will see it becoming more brittle in the beginning. This is due too an excess of air that works as a plasticizer, that is removed from the plastiqe, but after prolonged rolling you will notice that very gradually the plastique will become more cohesive again, due to rouding of the crystals by abbrassing against eachother. The longer you roll, the more pliable it will become...

When all of that is done, (and you have probably put more energy in working on the plastique than is in the plastique itself

) You add another 3.5-4% of methylricinoleate, depending on the crystal size, to make it really pliable...
ps:

Methylricinoleate can be replaced by ethylricinoleate (or better, even higher alcohols) For transesterification I found the PDF attached very helpfull. (Tried to link to it, but didn't work

)

[EDIT]: For all clarity, ricinoate esters are derived from ricinoleic acid, which makes up 90% of the fatty acids from castor oil. The rapeseed oil PDF was just a guideline for the proper transesterification reaction conditions...

[Edited on 22-12-2006 by nitro-genes]

Attachment: EthylEsterofRapeOil.pdf (666kB)
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Microtek - 29-12-2006 at 01:50

@ Nitrojet:

When you do the transesterification of castor oil to obtain methyl- or ethyl ricinoleate, which set of reaction conditions do you follow ? In that pdf they used both high and low temps, both KOH and NaOMe as catalysts, etc.
When I attempted the reaction, I mixed castor oil and ethanol ( 100 % excess ) with ca. 1 % KOH dissolved.
I then capped the flask and shook it vigorously. It quickly became homogenous ( I had thought this would take quite a while ) so I added a magnetic stir bar and stirred it for 2 hours at room temp.
I then let it sit overnight, but no phase separation occured. If I add some of it to an equal amount of water, slight agitation causes an emulsion to form, which isn't the case with fresh castor oil so this is promising, I suppose. However, the product doesn't seem to be very soluble in gasoline.

Does this correspond to your experiences on the subject ?

quicksilver - 29-12-2006 at 06:35

I am pretty sure needle size / shape could be controled with temp and other specifics within the recrystalization process. And I'm also willing to bet that the actual moxing results in shaving of the material more than would be expected. but a source for industrial / pure PIB...that, I have not found. (If anyone knows, please U2U me, or post). - IF the process of re-crystalization is done in reverse using a single ice cude as a seed the length of the needle becomes much shorter and thicker, making them "fit together" in a denser format.

nitro-genes - 30-12-2006 at 14:18

I took 100 ml of methanol and 100 ml castor oil. A very large excess of methanol was used since this makes dissolving the NaOH/KOH easier and prevents this gelatin mass you describe. Then I warmed the methanol slightly to dissolve all of the catalyst, this is easier with KOH than with NaOH btw since the first is more soluble in alcohols than the latter. All of the catalyst, KOH or NaOH, should have dissolved in the alcohol before you add the castor oil! When using ethanol be sure though that it is as waterfree as it can possibly be, since using a large excess of water-containing-ethanol will result in a very bad yield or even no product at all...

After adding the castor oil, warm to near boiling point of the alcohol to reduce the reaction time to about 3 hours IIRC. (could have been 4 hours

) Unfortunately, phase separation will not occur. According to the article this is mostly determined by the catalyst used. IIRC, using sodium ethoxide does result in phase separation, whereas KOH or NaOH (like I used too) does not...

Not that it really matters, the oil is the only reactant that would be difficult to seperate from the isopropyl rincinoleate, but the conversion of the oil should be near 100% (when using absolute alcohol). The rest of the products, like potassium oleates, glycerine and the excess ethanol can all be removed by washing with water. The end product should be a very runny oil, slightly more viscous than water and completely non-volatile...

nitro-genes - 30-12-2006 at 14:19

I took 100 ml of methanol and 100 ml castor oil. A very large excess of methanol was used since this makes dissolving the NaOH/KOH easier and prevents this gelatin mass you describe. Then I warmed the methanol slightly to dissolve all of the catalyst, this is easier with KOH than with NaOH btw since the first is more soluble in alcohols than the latter. All of the catalyst, KOH or NaOH, should have dissolved in the alcohol before you add the castor oil! When using ethanol be sure though that it is as waterfree as it can possibly be, since using a large excess of water-containing-ethanol will result in a very bad yield or even no product at all...

After adding the castor oil, warm to near boiling point of the alcohol to reduce the reaction time to about 3 hours IIRC. (could have been 4 hours