Attempt to plasticize PETN

[stanfield]

I tried to plasticize 50g of my PETN with lecithin and mineral oil. This method is usually used with RDX but PETN and RDX are very similar so, I substitued RDX with PETN
So, I mixed 50g of PETN, 0,3g of lecithin and 7,3mL of mineral oil in a plastic bag and I DIDN'T obtained a "modelable" material, it's still powder !!! Why ?

==&gt; <a href="http://stanfield.150m.com/plastic.htm" target="_blank">Photograpy of the experiment</a>
EDIT : HEAVY pictures ! ADSL or Cable recommanded...

see ya !

<small>[ February 21, 2003, 03:34 PM: Message edited by: stanfield ]</small>

[rikkitikkitavi]

just a thought, but the PETN didnt look so very fine? Shouldnt the powder be very very fine to make a good emulsion?

/rickard

[Mr Cool]

A very fine powder is needed to get a mouldable product, also I theorise that more rounded HE grains would be better than sharp/angular HE grains.
I personally find RDX to be much easier to plasticise than PETN, because it's much finer after recrystalisation from acetone. PETN forms quite coarse "sugary" crystals, RDX is much finer, more like flour.
A tip which 10fingers suggested to me a while ago is to add some detergent, just a drop of washing-up liquid, to the water into which the PETN soln in acetone is dumped. This seems to help keep the particle size small.
I've never had very good luck with oil-based mixtures though. I've made ones which work, but they were never as good as ones based on blu-tack binder with a bit of oil/parrafin to keep it soft. Such polymer-based plastiques are much more resiliant, and do not fall apart as easily.

[stanfield]

I ordered some SBR rubber but I didn't received it yet ! Then I'll try to make some Semtex...

How can I "grind" my PETN into fine powder ? is a mixer recommanded ?
Furthermore, this PETN on picture didn't dissolved totally in acetone (not enough solvent), maybe it's a problem...

see ya !

[rikkitikkitavi]

dissolve it in acetone(saturation) , dump into water so the PETN preciptates again instantly.

Doing so doesnt give the PETN time to slowly grow crystals, but instead a maximum amount of fine crystals can be formed, since this process is faster than crystal growth due to a high supersaturation.

I m not sure if it still small enough crystals though. But you wont loose any PETN, since it is almost insoluble in water.

/rickard

[Microtek]

I think you should look to the mineral oil rather than crystal size of the PETN. I have experimented quite a bit with plasticizing PETN myself and while the Blu-tack binder is unmatched, I did manage to make some good formulations with oil, wax and grease even though the crystals were more coarse than yours. I suggest you use the most viscous oil you can find, preferably that used for lubricating the chain on a chainsaw; it is designed to be able to cling to the chain even as it spins. I can't see what kind of oil you are using because I can't open the fourth picture.

[stanfield]

this is "standard" mineral oil, nothing more. Density = 0.8/0.9
I have 15W40 motor oil, maybe it's better ?

[Microtek]

It should be as thick as syrup or thin honey.

[bonnsgeo]

to obtain a very fine petn i think its maybe better to do it in hot acetone and add slowly some water (hot too).
and after let it cool in a fridge.
i think if u "precipitate" it slowly, u will obtain very small crystals.

Microtek, i remember (not very well) your way to plasticize petn with blu-tack.
u dissolve blu-tack, extract the binder and replace it with petn ? am i right ?
do u have pictures to show how u do that ?
bye

[Mr Cool]

That's right. Just leave blu-tack sitting in unleaded petrol until all that remains is a layer of sediment on the bottom. Pour the petrol off the top, and dump it into acetone. Stir it around for a while, and the precipitated binder will collect together in a sticky lump. Take it out of the petrol/acetone mixture, and allow it to dry.
To make a plastique, add a few mL of petrol to 1 part of the binder, and mix in 8 or 9 parts of a very fine HE. Spread it out thinly to allow the petrol to evapourate.
I found that very slowly the plastique will harden and go more rubbery. Adding a small amount of oil, such as paraffin, will help to prevent this. It should be used instead of a portion of the binder, not additionally.

[kingspaz]

bonnsgeo, small crystals are obtained by FAST cooling not slow cooling. slow cooling causes big crystals.

[Microtek]

I do a variation of Mr Cool's method:
I add about 10 g Blu-tack or a similar product to about 60 mL unleaded gasoline and heat/boil the mix to dissolve all except the filler. This is done with stirring and once only the powdery filler remains, the beaker is allowed to sit until the supernatant liquid has become clear. The liquid is then filtered, taking care to get most of the gasoline through the filter before any of the filler is poured into it; otherwise it will clog up the filter and make the process excruciatingly slow.
Most of the gasoline is then evaporated and the remaining viscous solution of plasticizer in gasoline is poured out onto a dish. A suitable amount of finely crystalline HE is added and the slurry is mixed thoroughly with a spoon while blowing air over the mass. When the mix is almost dry, it is spread out in a thin sheet and left to dry until no gasoline smell remains. It can then be pressed to increase density and cut into shape.
How much HE is needed per gram Tack depends on the actual product and the efficiency of your extraction procedure. Experimentation will be needed.

[Observer]

That way you don't know how many % binder you are using.
When I made PBHMTD I used a process similar to that of Mr Cool's. Only I didn't precipate the binder, but left the gasoline to evaporate. I would recomend using sufficient gasoline to get the whole mass of crystals damp, that way you ensure that all of them are coated with a thin layer of binder. The smaller crystals you use, the better it will stick together. Using the minimum amount of hot acetone to dissolve your PETN and large amounts of almost freezing water should give you very fine PETN.

<small>[ February 23, 2003, 09:29 AM: Message edited by: Observer ]</small>

[Microtek]

That was my point in saying that experimentation would be needed; once it has been established ( by experiment ) how much binder/plasticizer is extracted by a given amount of boiling acetone ( edit: gasoline, not acetone ), the entire isolation step can be skipped and thus save both time and solvent.

<small>[ March 09, 2003, 07:05 AM: Message edited by: Microtek ]</small>

[Observer]

I noted one thing today when I tried the method of precipating the binder in acetone. When the rubber had dried, it was harder than normal, it used to be sticky.
I checked the bottom of the container of the acetone/gasoline mixture, and small dropletts was lying on the bottom(might be residual rubber and it may in be in or partly in solution).
The softner(sp?) agent?
Sorry Microtek.

<small>[ March 08, 2003, 05:24 PM: Message edited by: Observer ]</small>

[andreas]

<a href="http://www.straightshooters.com/target/btputty.html" target="_blank">http://www.straightshooters.com/target/btputty.html</a>

Maybe this is a rather cheap source for PIB.
Worthwhile to check out.

[Mr Cool]

The trouble with the blu-tack binder is you can't stretch it well, it ends up going fluffy and falling apart in my experience. The same is true if you press a ball of it hard, the edges of the formed disc can split and go fluffy. For most applications it works well if you take care when handling it, but it would be nice to have a more plastic plastique.
Microtek, was it you who was using liquid latex a while back? Does this have the same flaw?

If you're using a plastique just to keep the HE in place, I personally prefer simple PBX-like compositions, formed from HE and two-part epoxy. You may need a simple mould while the epoxy cures, and it takes longer since you can't just squish the HE into place and fire it, but it's generally a lot less messy and the charge is more resistant to handling before firing.