From: ahahma@polaris.utu.fi (Arno Hahma)
Newsgroups: rec.pyrotechnics
Subject: Re: Grinding of sensitive materials
Message-ID: <1991Jul2.140848.14426@polaris.utu.fi>
Date: 2 Jul 91 14:08:48 GMT

In article <1991Jul1.024213.19092@minyos.xx.rmit.oz.au>
s884764@otto.bf.rmit.oz.au (Gran
t Waldram [Atom Smash]) writes:

>the one material is undergoing size reduction. Are either NaClO3 or
>NH4ClO4 sufficiently impact-sensitive to make this kind of equipment

Na-chlorate is NOT explosive, unless mixed with a combustible agent.
You can grind it with whatever suitable mill, just make sure the mill
is clean before you start. AP can be detonated with a very powerful
shock, so a ball or a hammer mill is not recommended for that.

>totally unsuitable, and if so, what method _should_ be used to achieve
>size reduction of materials in the 2000um range down to the <300um range.

I`d recrystallize them. You can get down to 100 um just by mixing the
solution vigorously while cooling it down. If you have a mill, then
using a hammer mill with a 300 um sieve might be the most efficient
way. For the AP, use more gentle methods, like the crystallization.

ArNO
    2

From: ahahma@polaris.utu.fi (Arno Hahma)
Newsgroups: rec.pyrotechnics
Subject: Re: AP milling
Message-ID: <1991Oct31.185129.8403@polaris.utu.fi>
Date: 31 Oct 91 18:51:29 GMT

In article <6159@hplabsb.hplabs.hpl.hp.com> schediwy@hplabsb.UUCP (Bic Schediwy) writes:

>p.s. Did anyone even see my post asking about ball milling ammonium
>perchlorate? I'm thinking the post may have been lost. Would someone
>please send me Email (schediwy@hplabs.hp.com) if they saw the post.

Yes. It is not completely safe. It is known, that AP is more sensitive
to impact than ammonium nitrate. There is a theoretical possibility of
an explosion. However, even black powder can be ball milled. AP is
definitely less sensitive.

In the industry they also have this problem with mechanical mills.
They have solved it by adding an inert solvent to cool the AP. Ultra
fine AP is made with a colloid mill (one of the processes only) using
carbon tetrachloride, tetrachloroethylene, trichloroethylene or other
polychlorinated solvents as lubricants/coolants. With a ball mill you
could also add some of these solvents to make the milling safer.

For coarsed than a few micron AP you don't have to mill it. Why not
recrystallize the AP? The crystal size is quite easy to control and
get it down to 20..50 microns.

ArNO
    2
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