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A dangerous mixture with ap and mgal


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#1 Sulphurstan

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Posted 28 April 2018 - 05:46 PM

I've been trying to modify a formula given by Seymour in 2011, by replacing Ti with uncoated MgAl:

Ammonium perchlorate 63
Copper benzoate 19
Titanium 10 (replaced here with MgAl)
Copper (II) oxide 4
Nitrocellulose 4

After adding a few ml of acetone, and 10 second stirring, the stuff began to boil, God thanks, there was no ignition...

Just as information for those who read this, that this mix is a bad mix. With Titanium, it is just fine and nice! With magnalium, just BAD.

Don't make the same mistake than I did.

Edited by Sulphurstan, 28 April 2018 - 05:54 PM.


#2 NeighborJ

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Posted 28 April 2018 - 07:23 PM

Just to clarify, the AP/MgAl reaction will still happen even if the MgAl is protected with dichromate.

The original formula used Ti which had very little effect to the oxidizer/fuel ratio due to the fact that most of the Ti is burnt away from the body of the star and consumes atmospheric oxygen. Simply omitting the Ti would be a better option, adding MgAl would washout the color and change the fuel/oxidizer ratio.
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#3 Sulphurstan

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Posted 30 April 2018 - 01:00 AM

Yes, this was just a try to increase the burn rate...

Nevertheless, I'm starting to use AP, and the incompatibilities seems quite numerous!!

Any idea, where we could find a good source, indicating ALL the incompatibilites of AP in pyro?

Nitrates are of course mentionned, Copper-metallic, and some others, but nothing really complete... The wiley guide of incompatibilites gives the list of non-pyro compatibilities, not really useful for us...

Chlorates, nitrates are well documented, but AP...



#4 NeighborJ

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Posted 30 April 2018 - 03:21 AM

You seemed to have found most of the incompatabilities. Pretty much any easily corroded metal will react with AP. The only other major safety concern with it relates to particle size. If it is milled to a extremely small size it can become more sensitive. This isn't a big deal for most oxidizers because it wouldn't have a fuel, but AP can burn even without a fuel. This can create an explosion hazard simply from overmilling. Dont be afraid to mill it, just dont forget about it in a running mill.

Potassium dichromate is what you want to speed up the burn rate it works as a catalyst but it's also extremely toxic and every precaution should be taken when handling it.

Just for the record, MgAl can be successfully added to the comp of the chems are all dried and a non aqueous binder is used. It still has a chance of some slight reaction but it's usually not much more than a slight warming of the comp. Strobe rocket fuel is made this way and various other strobes. Moisture is what facilitates the reaction.

Edited by NeighborJ, 30 April 2018 - 04:27 AM.


#5 rogeryermaw

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Posted 30 April 2018 - 02:13 PM

just my experience: i know copper metal is not considered compatible with ap but i have used it with limited storage times and no ill effect. i may be wrong here but it was my understanding that it was soluble copper salts, like copper sulfate or nitrate, that are the biggest danger and more so in humid environments as moisture helps the reaction.



#6 NeighborJ

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Posted 30 April 2018 - 07:30 PM

Cu benzo is almost completely insoluble in water so it is one of the only few suitable cu compounds which are compatible with AP.

#7 Sulphurstan

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Posted 03 May 2018 - 10:13 AM

Yep, Moisture could have been the issue.

BUT: I was using acetone! - but due to its age (bottle opened 6 months ago) - it might have already catched some moisture, that's why it reacted with the MgAl (mesh was 230)?

 

Regarding the CU Benzo, I agree that this salt is - IMO - quite safe with AP, because nearly insoluble.

 

A nother problem could have been, that my Cubenzo is "polluted" with Na2 SO4 (because I produce it from Na Benzo + CuSO4 -> Cu Benzo + Na2 SO4...). Na2 SO4 is soluble, but does it reacts with AP? that's the question...

 

NeighbourJ, thank you for the information on milling AP!! I ignored it, though the only ammonium compound that could decompose volently by itself was AN... Good that I just milled my AP maybe 4 hours...

 

 

Short story: I replaced the MgAl with Hexamine, and this was probably the good choice:

- burnrate is high

- flame is getting a better blue, lower temperature with the Hexamine

- no reaction, no warming of the mix, looks quite stable after 4-5 days drying.

 

Will test it as go getter tonight, and see if that work.



#8 NeighborJ

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Posted 03 May 2018 - 07:33 PM

I made cubenzo with Kbenzo and CuSO4. I didn't want any sodium contamination. I still washed the product twice a day for a week to ensure the most pure product I could make. I still believe some of the KSO4 was trapped inside the Cubenzo but not enough to cause issues, I can imagine how difficult it would have been to get a good color from the Nabenzo.
I guess what I'm saying is that color is a awesome one and if your color is washed out then I'd expect the problem to be the purity of the chems. Adding the bright metal didn't help,

I've also messed around with adding hexamine yo several types of rocket motors but have found it to cause interruptions of the smooth burn(chuffing),almost a strobe.

Edited by NeighborJ, 03 May 2018 - 07:42 PM.


#9 Mumbles

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Posted 03 May 2018 - 10:42 PM

Wet acetone will definitely cause an issue between AP and metals.  This was more prevalent when poured go-getters were more popular.  You basically had to store your acetone over molecular sieves or another dessicant when messing with AP and magnesium.  

 

Basically all the useful copper salts we use are largely insoluble for a reason.  They also react pretty violently with most metals.  


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#10 Sulphurstan

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Posted 04 May 2018 - 05:34 AM

Neighbour

 

The burn test I made yesterday evening looks promising. No Sodium fringes.

The thing looks whitisch, but video taken from 2 meters away. I'm pretty sure, once i a shell, the blue will be a GOOD one . i'm used to Veline Blue, and the burn test on the ground looks really better with this AP based star.



#11 NeighborJ

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Posted 04 May 2018 - 09:26 AM

Looks great,blue stars dont get much better than that.

#12 Sulphurstan

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Posted 05 May 2018 - 05:24 AM

Thanx! Now my concern will be to prime that properly, and see how finished stars behave in storage!
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#13 OldMarine

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Posted 05 May 2018 - 09:44 AM

Pinball prime ought to work on those.


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