Sciencemadness Discussion Board

Smoke production from HE

gregxy - 22-2-2008 at 13:13

I was watching the Mythbusters the other night and they
did a segment from a James Bond movie where a pen filled
with high explosive is used to blow some one up. In the
segment they used 3g of "the most powerful explosive
available". They never did tell what the explosive was,
but quite a bit of black smoke was produced.

Now usually the most powerful explosives like NG, PETN or
RDX have a good oxygen balance and I would not expect
them to produce much smoke.

But then maybe oxygen balance does not corelate with
smoke. I have made picric acid and HMTD and while the
picric acid has the better oxygen balance, it also made more
smoke. Im guessing that the aromatic ring in picric acid
is more stable and some of the molecules convert to graphite
while others become CO2. In HMTD each carbon is already
bound to an oxygen so CO is the most likely result.

ScienceGeek - 22-2-2008 at 14:51

RDX is very commonly referred to as "the most powerful explosive available", and also produces a lot of black smoke when detonated.

Axt - 25-2-2008 at 15:27

RDX and PETN are not going to be available as is commercially, its likely plasticised whereby it will give black smoke even in "pen sized" quantities. This movie is plasticised PETN which alone gives little smoke, but black when plasticised

It could also be pentolite or simular TNT based comp which are commercial explosives.

contrived - 25-2-2008 at 15:56

Originally posted by gregxy
Im guessing that the aromatic ring in picric acid
is more stable and some of the molecules convert to graphite
while others become CO2.

Surely you mean carbon here, not graphite. Graphite has a specific structure and there's no reason to expect it in an organic reaction is there?

Axt - 25-2-2008 at 16:21

"The physical structure and chemical bonding of the carbon in solid detonation products (soot) are largely unknown. It is well established that diamond can be manufactured by the application of explosive shocks to graphite loaded into the explosive, or in a fixture external to the explosive1. Here we report the formation of diamonds as a chemical product of the detonation process itself. The diamonds we observe are 4–7 nm in diameter and make up 25wt% of the soot; in size and infrared spectrum they resemble diamonds similarly isolated from meteorites2." <i>Nature</i> 333, 440 - 442

While only an "unknown" and diamond are mentioned as products I dont think its unreasonable to expect graphite to form a good portion of the "unknown". The above is the abstract, the full paper may shed more light on the subject.

EDIT: US5482695 gives the following example, 650g of 40:60 TNT:RDX gave 86g of soot comprised of 26g diamond and 71g of graphite.

[Edited on 26-2-2008 by Axt]