Sciencemadness Discussion Board

How to create the most sensitive PETN or ETN crystals

Gargamel - 16-10-2021 at 13:17

This is about caps, where one wants to use a minimum of primary (or an NPED stage) to get things going.
Not the booster itself, but the transition between primary and output booster

What is your procedure for our typical favourites, ETN or PETN, to get a minimum particle size?
There are patents out there that mention milling, but I'm either not comfortable doing this or simply lacking the equipment.

So recristalisation alone should do the trick.
What are your methods?
A hard icewater crash cristallisation is the first thing that comes to ones mind - is there anything else, any other trick?

aromaticfanatic - 16-10-2021 at 16:23

To get the finest crystals you want to use a hot organic solvent and slowly drip that into water that is as cold as possible with strong stirring. You can get -20C from salt water as well.

Even without dripping and just pouring the hot solvent into ice water gets crystals that are so fine they pass through the filter paper. Fine tune from there for whatever densities you are attempting to reach.

However, larger crystals will be more sensitive.

A big thing to note is that density also has a lot to do with sensitivity. Generally, the higher density, the less sensitive it is. So keep the pressing/packing to a minimum and that should help.

Your best bet is to have a high density, heavily packed into high density, layer, and then a less dense lightly packed layer. That is a typical set up.

[Edited on 17-10-2021 by aromaticfanatic]

Gargamel - 17-10-2021 at 02:17

I'm aware of the density, but lets ignore that for now.

My feeling is that crystal size has an effect on sensitivity apart from the density the stuff has been pressed to.


However, larger crystals will be more sensitive.

Are you sure?
Smaller crystals seem to ease DDT. Is that because they burn better or because they are more susceptible to get shocked by their neighboring colleagues?


You can get -20C from salt water as well

That would induce chloride contamination...

[Edited on 17-10-2021 by Gargamel]

XeonTheMGPony - 17-10-2021 at 05:33

forget crystal size for now!

Base, high pressing
mid moderate pressing
Primary interface layer hand pressed then some lose powder dusted on to form the final primary to main charge seal

I use 150mg average of PVA - Pb Azide to Pb Styphnate 80/20 (Better tooling could use even less but better to use a bit more and have 0 doubts)

If you want to play with crystal size the answer is above, you can try different solvents different drip rates and such.

Gargamel - 17-10-2021 at 12:01

I agree with everything. But I'm especially interested in crystal size and it's effects.

aromaticfanatic - 17-10-2021 at 18:43

Larger crystal size causes higher internal strain in the crystal. This in turn supposedly increases the sensitivity of crystals as the extra strain causes a bit of a kick to any other outside stimuli.

And yes the salt water will contaminate the sample but I question to what extent if the resulting crystals are washed. It may be worth playing around with it. The contamination might be so small that it is favorable to use freezing salt water due to the extra fine crystals you would theoretically create.

I have nothing official at the moment to back this all up but it seems that the general consensus is that smaller crystals are less sensitive.

In the case of heat shock, smaller crystals will be more sensitive as it is much easier to quickly heat up a small amount of mass than it is a large amount of mass.
But generally, in terms of shock and friction, I am fairly certain that smaller crystals display lower sensitivity.

Herr Haber - 18-10-2021 at 07:02

6 devices were tested:

3 had 1000mg melt cast ETN
3 had 700mg melt cast ETN + 300mg pressed with a wooden dowel.
All had 100mg DLA pressed on top.

After sieving the sand and retrieving the remains it was absolutely clear that melt cast ETN performed better.
Since then I've seen other papers confirming that information.