"binary" reactive targets

[Swede]

A few years ago, I saw a demonstration of a pretty unique system. A bottle of white prilled chemical is mixed with what appeared to be pyro-grade aluminum flake. The mixture is casually mixed, about a tablespoon of Al powder to about 8 ounce volume of salts, then the bottle is capped, and becomes a target for rifle shooters. When hit, the blast was very impressive, not requiring any confinement. But interestingly, the material was NOT sensitive. On the contrary, it requires either a blasting cap, or a solid hit from a high-velocity rifle bullet. A pistol bullet will not set it off.

 

I snooped a bit more and found out that the bulk chemical was a mix of ammonium perch and ammonium nitrate, unknown proportions. The material was very coarse (prills), not a fine powder. I found out the metal powder was in fact Al.

 

These targets are still beig sold despite a few morons doing stupid things with them. My main question is on the chemistry of this material. The stability of it is impressive, and I wonder if the stability of the composition is due to the coarse nature of the ammonium salts, or perhaps the proportions. Ammonium nitrate is not a particularly sensitive salt.

 

I'm thinking it might be a useful composition for pyrotechnics, and by altering the proportions (and the mesh size) of the ammonium salts, one could engineer a sensitivity appropriate for pyro use, or better yet, it would almost be a case of engineering whatever sensitivity you might need for a particular application.

 

Summary: Prilled NH4CLO4 + NH4NO3 + Al powder = insensitive but potent explosive material.

[TheSidewinder]

I wonder if you're talking about Tannerite?

 

Some moron here in MN set off 100 pounds of the stuff in the back of a junked out dumptruck. He'll be cooling his heels in jail for some time as a result of this, I think. What a freaking idiot.

[Swede]

Yes that is what it is. I found out the proportions - 75% nitrate, 25% perchlorate, and the al powder has 5% zirconium hydride.

 

Could it become a useful pyro comp by altering the proportions at all? As it is now, it is too insensitive. I'm thinking it might be useful in some way as a safer alternative to traditional flash mixtures.

[TheSidewinder]

Well, I'm not the one to ask.

 

Mumbles might know, or one of the chem-heads here.

 

I think this has been covered before (here?) and the concensus was that it isn't suitable for pyro uses. Cost may have been a big factor, but I'm not sure.

[jacob]

That guys real downfall (as I understand it) is that he let it off to close to a Nuclear power plant, which was quickly powered down or put on alert or something, made alot of people pretty unhappy.

 

Swede, this link might be helpfull link

Turns out that Copper oxide/Al powder makes for quite a reactive mix.

[FrankRizzo]

As usual, the media blew that whole issue out of proportion. The power plant was simply put on alert, which means the gates were secured. There was no reduction in power or any other silliness.

[NightHawkInLight]

I don't think this could ever have pyro purposes, it is not flammable in any way. At least not without a significantly larger amount of fuel. You could not simply stick a fuse in it and use it as flash. The mixture detonates via decomposition (and a bit of combustion as the Al uses up the excess oxygen released) which is something you don't want any sort of firework doing. It does however preform its purpose as an entertaining rifle target

[Swede]

It does however preform its purpose as an entertaining rifle target

That it does, very well. At a thanksgiving shoot, a guy overcooked a turkey. It was inedible. Into the beast went a bottle of the binary, and the turkey carcass was hung on a stake. A guy from England was given the honors.

 

Deep-fried turkey parts rained.

 

Of course commonly there are idiots who put the stuff inside a metallic object like an oven or fridge, and there are plenty of videos of entire doors and panels flying 100+ yards directly back at the firing line.

 

Too bad that variations of this comp are not useful for pyrotechnics. It would certainly be nice to be able to replace flash powder with something significantly less sensitive, and that could be initiated not with a shock wave but via flame.

[qwezxc12]

Lot of info in this thread already:

Binary Impact Sensitive Explosives

[hst45]

I snooped a bit more and found out that the bulk chemical was a mix of ammonium perch and ammonium nitrate, unknown proportions.

I can't see ammonium nitrate bases comps having a good usage in pyrotechnics; it seems to me that it's too hygroscopic to store well. Tannerite is mixed and used on the same day so this isn't an issue.

[psyco_1322]

Yep and it isnt magically resistant to the hygroscopicity of NH4NO3 either.