Powerful FP variant

[MadMax]

I just tested a new flash powder comp which is quite powerful. Here's what I did...

 

I took 1 gram of guncotton (nitrocellulose) and completely dissolved it in acetone. Then I used that liquid to wet about 10 grams of standard 70/30 (KClO4/AL) flash powder. It was about the consistency of clay. As it was drying, I repeatedly passed it through a 100 mesh sieve so to evenly distribute the NC. Eventually it completely returned to it's powered form but coated evenly with NC. This powder is quite powerful in deed. It not only super-heats the air around it to produce a report when confined but it has the dual property of generating lots of gas which is super heated by the flash to produce an even more powerful report.

 

The NC in this case can also act as a binder so that had I wished to corn the FP for use in aerial salutes it could have easily been done while still wet with acetone.

 

Note: The FP I used was based on really pure and fine KClO4 and Eckart dark Al and included 0.5% sodium bicarbonate to prevent potential acidity buildup.

 

A modest 5mg of it reported under the confinement of 1 layer of electrical tape with surprising power!

 

If you decide to make this comp please be safe with it.

[dagabu]

Are you adding water to the mix? If not, then the sodium bicarbonate will only slow the burn and is not necessary. A note to others, screening metals at any time is risky if not dangerous.

[MadMax]

The KClO4 I used had been ball milled with 0.5% sodium bicarb before mixing into flash. The addition of half a percent of bicarb did not appear to in any way hinder the speed of the FP. I added it as a safety measure to prevent acid buildup. Even though it is probably not necessary for this mix it is more for my own peace of mind. I had read somewhere that over time NC can degrade becoming slightly acidic leading to it being more sensitive but from what I read that can take years or even decades for that to happen - probably longer then one would save FP for anyways so it's probably not even an issue. Still it's better to err on the side of caution.

 

Some background on this composition... (apologizing in advance for writing a book - )

 

Here's originally what gave me the idea. From what I understand explosive material can fall into 2 categories. The first category being ones that generate a large volume of gas very rapidly. NC for example as I recall decomposes rapidly under confinement to produce a gas that occupies roughly 400 times it's original volume. (correct me if I'm wrong) The other category being compositions that burn rapidly at high temperatures but don't actually generate any gas (such as 70/30 flash). All the byproducts of this reaction are solids - (KCl, Al2O3). In this case the explosion comes from the air being rapidly super-heated resulting in a sharp rise in pressure inside a container causing it to burst.

 

NC also has a low ignition temp so adding it to flash would significantly lower the ignition temp of the flash thus increasing the burn rate. People often add sulfur to flash for this very reason. Sulfur has it's own set of problems such as acid production over time making it incompatible with other materials such as chlorate stars. So in this case the NC acts as an ignition temp reducer, a reaction rate increaser, a gas volume increaser, and potentially a binding agent.

 

On the other side of it, it is known that a small percentage of aluminum can be added to conventional explosives such as TNT, NG/NC to increase their power by adding to their thermal pressure effect. (I know this is not the forum for HE but wanted to briefly touch on it only for reference)

 

My idea originally came from wanting the best of both worlds and in that it appears to have been a success.

 

Another interesting piece of information is that NC is monomolecular and provides itself with both the fuel and oxidizer all in the same molecule so it should not interfere with the flash reaction. It is however slightly oxygen defecient having an oxygen balance (OB%) of roughly 30% so it's combustion byproducts could make use of the unused oxygen in the 70/30 flash. 30% of the 1 gram added is would mean 0.3 grams of oxygen is needed to balance it out. 7 grams of KClO4 was added but the stoichiometric ratio is 2:1 so really only 6 grams is needed. KClO4 is ~46% by weight oxygen and during decomposition all of the oxygen is liberated leaving behind KCl. So 0.46 grams of oxygen is present so the mixture would still be slightly oxygen rich by 0.16 grams.

 

I do feel it fair to warn anyone wanting to make this that it's a low ignition temperature mixture and should be treated with respect.

[pyrogeorge]

why do you want to make powerful FP for Pyro uses?

[MadMax]

I was thinking it might produce stronger reports in shells having a higher energy per unit of mass as regular fp. Also I was thinking it might make crossets split and fly farther apart. Another aspect is granulating it would make it a lot easier to work with - less messy. I've tried granulating fp before with other binding agents only to find that it hurt performance. The granules tend to burn like fast white stars. When I granulated this stuff the granules still seemed to pop like a loose pile of the stuff.

[SB15]

I feel that adding sodium bicarbonate to a composition containing aluminum powder will do more harm than good. Even weak bases will attack active metals over time and lead to severe corrosion. I doubt this will cause stability issues or spontaneous ignition, but you'll probably find that the performance decreases as the composition sits in storage. If you want to stabilize the NC and prevent acid formation, employ a proper nitrogen oxide scavenging additive such as diphenylamine or carbamide (Urea).

 

As for mixing flash with nitrocellulose, you will increase the molar gas output per mass unit, while slightly reducing the energy density of the composition. The reaction rate will likely not be affected significantly, so I suspect that this will increase the explosion pressure and 'brisance' of your powder, while reducing the thermobaric effect flash powder creates as the high temperature Al₂O₃ produced by the oxidation of aluminum rapidly heats the surrounding atmosphere.

 

In the end, it's probably not worth the mixing effort, but it's always interesting to experiment. Any chance you could upload a video of a test?

 

NC for example as I recall decomposes rapidly under confinement to produce a gas that occupies roughly 400 times it's original volume. (correct me if I'm wrong)

 

I'm not in the mood to calculate an exact figure, but you're looking at deflagration pressures in the range of thousands of atmospheres for NC. Flash powder only produces approximately 4.8 moles of gas per kilogram, so the internal casing pressures are much lower. However, a large fraction of its blast effects can be attributed to secondary atmospheric heating, which is what gives the composition its large and seemingly counterintuitive blast radius.

[dagabu]

Also I was thinking it might make crossets split and fly farther apart.

 

Flash (70:30) does not work on crossettes, you need something with LESS power. The brisiance shatters them and blows them blind.... I have video

[MadMax]

Hmmm you might be right about the bicarb thing. I was reading and found something saying a solution of it will strip away the oxide layer of Al. The more I think about I am leaning more towards replacing the Na bicarb with with boric acid instead. It protects Al from reacting with potassium nitrate - so should in theory do the same for cellulose hexanitrate right?

 

You said "Flash powder only produces approximately 4.8 moles of gas per kilogram". I'm not quite sure I am following you. I didn't think that normal flash actually created any gas. It just superheated the surrounding gas causing a dramatic increase in pressure. When integrating the NC the flash should still do it's thing and superheat but in doing so release the gas that is stored in the NC superheating that gas as well in the process. So it's a dual effect. An increase in both the amount of gas and it's temperature.

 

As far as the actual results it did make quite a difference. I used regular indian blackhead with milled perc. After mixing the NC it behaved more like MgAl flash in my opinion.

 

As far as the video I will get some experiments and projects posted but I am having problems with my camera at the moment. It's about 4 years old so I am in the market for a new one anyway. I'll post a vid of this when I get it..

 

Btw thanks guys for the tips and critiques.

 

I feel that adding sodium bicarbonate to a composition containing aluminum powder will do more harm than good. Even weak bases will attack active metals over time and lead to severe corrosion. I doubt this will cause stability issues or spontaneous ignition, but you'll probably find that the performance decreases as the composition sits in storage. If you want to stabilize the NC and prevent acid formation, employ a proper nitrogen oxide scavenging additive such as diphenylamine or carbamide (Urea).

 

As for mixing flash with nitrocellulose, you will increase the molar gas output per mass unit, while slightly reducing the energy density of the composition. The reaction rate will likely not be affected significantly, so I suspect that this will increase the explosion pressure and 'brisance' of your powder, while reducing the thermobaric effect flash powder creates as the high temperature Al₂O₃ produced by the oxidation of aluminum rapidly heats the surrounding atmosphere.

 

In the end, it's probably not worth the mixing effort, but it's always interesting to experiment. Any chance you could upload a video of a test?

 

 

 

I'm not in the mood to calculate an exact figure, but you're looking at deflagration pressures in the range of thousands of atmospheres for NC. Flash powder only produces approximately 4.8 moles of gas per kilogram, so the internal casing pressures are much lower. However, a large fraction of its blast effects can be attributed to secondary atmospheric heating, which is what gives the composition its large and seemingly counterintuitive blast radius.

[SB15]

It protects Al from reacting with potassium nitrate - so should in theory do the same for cellulose hexanitrate right?

 

I wouldn't make that assumption. Nitric esters share very few of the properties of ionic nitrate compounds. Adding an acid, even one as weak as boric acid will likely just speed up the hydrolysis of nitrocellulose, making the mixture increasingly acidic and thus unstable.

 

My advice is to do some chemistry research and understand what you're handling before mixing up random chemicals. Look into nitrogen oxide scavengers. This is what you want to stabilize NC and prevent it from decomposing.

 

You said "Flash powder only produces approximately 4.8 moles of gas per kilogram". I'm not quite sure I am following you. I didn't think that normal flash actually created any gas. It just superheated the surrounding gas causing a dramatic increase in pressure.

 

This is by far the most common misconception about flash powder (Aside from it's reputation for being incredibly sensitive), and I don't really understand how this continues to propagate.

 

3KClO₄ + 8Al --> 3KCl + 4Al₂O₃

 

KClO₄/Al reaction temperature, based on enthalpy and average product specific heat capacities: ~2500K

KCl boiling point: ~1700K

Al₂O₃ boiling point: ~3300K

 

All 3 moles of KCl will be gaseous, while most of the Al₂O₃ will exist as a very hot solid. 3mol KClO₄ + 8mol Al = 632g, 3molKCl/0.632kg = 4.8molKCl/kg. Assuming the density of flash powder is about 0.8g/cm³ (Pulled that number out o' my ass), 1kg will fill a container of volume 1.25L, and ignoring any shockwave effects, 4.8 moles of gas will generate an internal pressure of ~770atm, or about 11 300PSI. This is our primary reaction pressure source; superheating of air really only occurs as a secondary thermobaric effect once the casing has ruptured and the high temperature Al₂O₃ is released into the atmosphere.

 

Just for kicks, lets take a look at how much pressure is generated by superheating of the air WITHIN the casing. We have 300g of aluminum @ 2.70g/cm³, and 700g of KClO₄ at 2.52g/cm³. That gives about 0.86L of air in our 1.25L casing. Assuming the reaction heats this air to 2500K, the pressure of the air will rise to ~8.5atm, or about 125PSI. This is approximately 1% of the total gas pressure. Negligible. The whole 'superheating the air inside the casing' rumor needs to be squashed, as it is absolutely false.

 

When integrating the NC the flash should still do it's thing and superheat but in doing so release the gas that is stored in the NC superheating that gas as well in the process. So it's a dual effect. An increase in both the amount of gas and it's temperature.

 

You'll probably increase both the molar gas quantity and the temperature, as you'll be introducing products with low specific heat capacity values. However, by reducing the proportion of aluminum in the mix, you will be lowering the energy density very slightly.

 

The most significant question here is how much the NC component affects the reaction rate. Larger gas volumes and higher temperatures will mean precisely squat if the reaction is inhibited by the NC binder.

 

As far as the actual results it did make quite a difference. I used regular indian blackhead with milled perc. After mixing the NC it behaved more like MgAl flash in my opinion.

 

Interesting. Have you tested both samples against any targets to compare the relative reaction pressures? That should give a clear idea of what's going on here.

 

EDIT: Sorry in advance Mumbles. A good deal of this post (And the thread) really should be in the HE section.

Edited March 12, 2011 by SB15

[Ralph]

The KClO4 I used had been ball milled with 0.5% sodium bicarb before mixing into flash. The addition of half a percent of bicarb did not appear to in any way hinder the speed of the FP. I added it as a safety measure to prevent acid buildup. Even though it is probably not necessary for this mix it is more for my own peace of mind. I had read somewhere that over time NC can degrade becoming slightly acidic leading to it being more sensitive but from what I read that can take years or even decades for that to happen - probably longer then one would save FP for anyways so it's probably not even an issue. Still it's better to err on the side of caution.

 

Some background on this composition... (apologizing in advance for writing a book - )

 

Here's originally what gave me the idea. From what I understand explosive material can fall into 2 categories. The first category being ones that generate a large volume of gas very rapidly. NC for example as I recall decomposes rapidly under confinement to produce a gas that occupies roughly 400 times it's original volume. (correct me if I'm wrong) The other category being compositions that burn rapidly at high temperatures but don't actually generate any gas (such as 70/30 flash). All the byproducts of this reaction are solids - (KCl, Al2O3). In this case the explosion comes from the air being rapidly super-heated resulting in a sharp rise in pressure inside a container causing it to burst.

 

you are completely wrong just beacuse the reaction products at STP are solids certainly dose not mean they are solids at the reaction temperature at reaction temp the reaction products are infact gasses. its like saying NC wont produce any gas if it is initiated after soaking in liquid nitrogen because at those temps nitrogen is a liquid and carbon dioxide is a solid

 

on a side note I think making more powerfull and sensitive flash is a somewhat pointless research project

 

 

 

[Mumbles]

A properly packed bottom shot has a density around 2g/mL. Only if you're making ground salutes or inferior inserts/breaks will it even come close to 0.8. I bet the NC coating would screw up the packing, leaving this development to fairly kewl applications, or at least overall reducing overall power.

 

Very few people use straight flash for breaking crossettes, and those that do never really granulate it for reasons already mentioned.

[MadMax]

I tested it and found the new powder to be the slightest bit louder but a little less bright. I'm not sure that the little bit of sound gained warrants the extra work needed. My only way of comparing them was having exact amounts going off within a short time and actual observation so it may be biased.

 

As far as it only having "kewl applications", I would be disappointed if that were the only real purpose it served.

 

But it was worth a trying out anyways - and fun to test. Thanks for all the input guys. It's been educational!

[pillyg]

I think a kewl would be to lazy to get the NC and do the whole acetone and screening step. They want big boom now and dont want to wait or do anything to complicated.

[Liftanddeafen]

There are dozens of flash powder compositions but really a few only stick out from the crowd. I use the usual air float kclo4 and al blue

Al blue is special because when mixed with kclo4 in the standard 7:3 ratio It won't go off unconfined like ordinary flash powder does. It only combusts when confined in a salute casing etc. and that gives off one hell of a bang. Needs a bit more activation energy though than regular flash powder. A simple cross match inside the shell does it p. if you're making a firecracker which are illegal and very dangerous then 3mm visco. But be careful!

[SilentPro]

Have you done any sensitivity experiments, like friction or hammer tests, with that composition? Perhaps also wit the granulated form??

[dynomike1]

Flash (70:30) does not work on crossettes, you need something with LESS power. The brisiance shatters them and blows them blind.... I have video

Do you think Bp is enough or maybe needs to have something like flash mixed with it?

[Mumbles]

The break used is very dependent upon the size of the crossette. Smaller crossettes need a stronger break if you're trying to avoid rolling shots.

[rogeryermaw]

if this comp is able to produce a "pop" while granulated but unconfined, perhaps it could be used as a easier and cheaper way to make a dragon egg effect as star cores. i wouldn't want to put these in a roller but perhaps they could be dipped in a slurry or wetted and dusted?

Edited August 23, 2014 by rogeryermaw