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Frontier9
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PETN vs. RDX
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?
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Rosco Bodine
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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 .
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nitro-genes
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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]
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Rosco Bodine
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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]
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nitro-genes
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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...
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Rosco Bodine
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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 .
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nitro-genes
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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]
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Rosco Bodine
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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 .
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nitro-genes
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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]
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Rosco Bodine
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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]
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nitro-genes
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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...
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Rosco Bodine
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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)
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Rosco Bodine
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Attached here is the DuPont PETN crystallization patent
Attachment: US2204059 Crystallizing PETN.pdf (260kB)
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nitro-genes
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| 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]
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Rosco Bodine
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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]
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franklyn
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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
.
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nitro-genes
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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)
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quicksilver
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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]
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nitro-genes
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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...
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Rosco Bodine
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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 .
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quicksilver
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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.
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nitro-genes
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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"
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HMTD
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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.
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Rosco Bodine
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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 .
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HMTD
Harmless
Posts: 12
Registered: 24-10-2005
Location: MSC,RF
Member Is Offline
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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.
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