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Advice on potassium perchlorate based (visco) fuse formulation


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#1 markx

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Posted 11 July 2019 - 01:36 PM

So I've run myself into a curious situation and perhaps the more knowledgeable folk here can share some of their wisdom with me.

I have not really worked much with K perchlorate based applications in practice (although I've done quite a bit of work on producing perchlorates by electrosynthesis). Lately I have tried to devise a visco fuse formulation based on KClO4 (preferably a simple one) and to my amazement I have found the potassium salt to be so stable that it simply does not want to produce a decent fuse that burns reliably. 

I've tried several combinations with carbon as the fuel (70/30, 80/20, 75/25 KCLO4/C), I've tried to add iron oxides as catalyst, I've tried adding a portion of Al powder and using erythritol as an experimental fuel.

The components were milled separately in electric grinder and then thoroughly mixed together. Ethyl alcohol was added and the damp powder granulated through a fine sieve several times. Then let dry until the granules flowed freely. 

All of the combinations, although when burned as powder seem to work reasonably well, but produce a very feeble fuse that burns just barely and tends to go out on it's own.  In contrast a 70/30 combination of KClO3/C turned into fuse by the very same process and visco machine produces profoundly excellent results. But for obvious reasons I would not like to use chlorates as the main component in a fuse formulation. 

 

Are there any tested and true KClO4 based fuse formulations that anyone has had success with? Any tricks or tips for preparing the mix (apart from the obvious "get as well mixed as possible")? 

 

I know that benzoates and terephtalates are supposed to work well in combination with K perchlorate as an agressive fuse formulation, but then again according to some expermentation reports that was supposed to be true also for carbon. 

 

I was hoping to produce a more agressive fuse than the regular BP based formulations and also aimed to possibly use an excess of oxidiser to burn away the threads, but so far it seems quite hopeless. Even getting a consistent burn seems to be a real challenge. 

 



#2 Mumbles

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Posted 11 July 2019 - 06:44 PM

Perchlorate and carbon does burn quite well, but generally requires pressure to reach its full potential. I'd suggest a mix of benzoate/salicylate and charcoal as the fuel if you'd like to spice it up a bit. This is effectively what the perchlorate Blackmatch and quickmatch out of China is made from. It may be terephthalate and have some other additives but it's all the same concept.
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#3 markx

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Posted 12 July 2019 - 09:09 AM

Thanks Mumbles! Ill try to get ahold of them organic salts and test it out. Also the problem might be that the mixture needs more intimate contact between the ingredients. The sort of contact that is achievable only by milling them together as is done for BP? But I would be very hesitant to try it with perchlorates. Wetting the mixture and warming with a water bath might also do the trick. Also I have the possibility to apply vaccuum to the wet mix....that may also enhance the penetration of perchlorate rich solution into the pores of carbon.

#4 davidh

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Posted 13 July 2019 - 11:38 AM

BP can be milled because of its extreme insensitivity to friction and impact. To the best of my knowledge, no chlorate or perchlorate composition shares that insensitivity. So unless a composition is made out of KNO3, charcoal, and sulfur (in some combination), do not mill it.


Edited by davidh, 13 July 2019 - 11:38 AM.


#5 Arthur

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Posted 14 July 2019 - 04:25 AM

For compositions that should not be milled together, the size of the individual components can be important, Try milling the ingredients separately.



#6 markx

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Posted 16 July 2019 - 12:59 PM

I made a small 2g sample of 75/25 KClO4/C, but this time I changed the preparation process to try out the vaccum idea:

 

Ingredients were weighed into a small glass dish and 0,5ml of azeotropic EtOH +1ml water was added. The alcohol serves the purpose of lowering surface tension to yield better wetting effect of carbon. 

The ingredients were mixed with a spoon until uniform (a few minutes) and compacted into a solid cake. The consistency of the mix was like damp dirt so it stuck together nicely. 

After that the sample was placed into a vaccum chamber and evacuated for 30 minutes at room temperature (20C). Then the sample was taken out, the cake broken up into loose rubble and put back into the chamber. Another session of 30 minutes under reduced pressure and slight warming at 40C yielded a semi dry granulated product. It was still damp, but good enough to test for burning speed.

 

A small lump of the prepared mix was collected onto a stainless spoon and ignited with a butane torch: the sample burned with satisfactory violence and was energetic enough to flying the burning lump off the spoon. Definitely the uniformity and vigor of the burn has been improved by the vaccum assisted  preparation process.

I shall let it dry completely and then try how it performs as a fuse filling.....there seems to be hope :)



#7 Mumbles

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Posted 16 July 2019 - 09:38 PM

You might want to look into some of Dave Forster's experiments with ”super milling" charcoal. I'd think it might convey some benefits you're looking for.
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#8 markx

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Posted 17 July 2019 - 12:30 AM

You might want to look into some of Dave Forster's experiments with ”super milling" charcoal. I'd think it might convey some benefits you're looking for.

 

Yes, it seems that thorough mixing and intimate contact between the components of the mix are of utmost importance when trying to formulate KClO4 based compositions that need to perform in small diameter "charges". Much like BP based formulations. Figuring out the best preparation process for the mix and adhering to it shall likely be the key element to success. 

A bit of a setback actually....I was hoping to achieve the ferocity of chlorate based compositions coupled with the stability and reasonable insensitivity of the perchlorate, but without a lenghty preparation process. Seems that it does not work this way and one still needs to concentrate quite a bit of effort on preparative process for the mix. But it is an interesting challenge that offers a nice learning curve :)



#9 markx

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Posted 19 July 2019 - 12:32 PM

So here is the sample of fuse I spun from the 2g vaccum assisted mix of 75/25 KClO4/C after it had completely dried out:

 

DSCF2095

 

It was impregnated twice with alkane diluted rubber cement (rubber glue) to make it waterproof and create structural integrity. 

 

And wow what a difference.....it burns very hot with a nice consistent hiss and a sharp long flame jet. Almost comparable to chlorate based mix with carbon. The previous attempts with this composition tended to barely smolder along instead of burning violently. I'm quite pleased with it as is, but since the mixture was far from being completely homogenous, I think that it may be improved even further. 

 

2019 07 20T10 34 10 025Z
  2019 07 20T10 33 59 247Z
2019 07 20T10 33 26 452Z
 
 
 

Definitely the key is in the preparation of the mixture more than the composition and the incorporation of the perchlorate into and around the carbon particles at a molecular level. The dissolution in the added water and the vaccuum seem to have accomplished that quite effectively. I guess warming the wet cake on a water bath would accomplish about the same if not more.  


Edited by markx, 20 July 2019 - 04:40 AM.


#10 Fliyud

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Posted Yesterday, 09:09 AM

уменьши C на 2% и добавь 2% серы для стабильности горения.



#11 Mumbles

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Posted Yesterday, 10:20 AM

English only please.
Just so you guys quit asking, here is the link to the old forum. http://www.xsorbit2....forum/index.cgi

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#12 markx

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Posted Today, 06:05 AM

уменьши C на 2% и добавь 2% серы для стабильности горения.

Would not like to add sulfur to the mix if I can do without.....It is not very readily available in my neighborhood and I really do not like the stinkiness that comes with sulfur containing formulations.  It does burn very stable without it and has minimal smoke and smell.

 

I'll try to seal the wet cake into plastic vaccum packing (sous vide style thing) and simmer it in boiling water bath to further promote the intermixing of ingredients. See how that one works out. It should in theory produce a hotter mix than the 40C I applied in the chamber.

 

For further possible developments I could try to make a small batch of ammonium perchlorate from purified stock of sodium perchlorate solution that I have in unreasonable amounts from the development phase of the diy plantinum coated electrodes. This would in theory produce an even better fuse formulation with really minimal smoke (the absence of solid KCl that inevitably forms from KClO4). 


Edited by markx, Today, 06:11 AM.


#13 Fliyud

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Posted Today, 09:52 AM

Ammonium perchlorate works poorly at atmospheric pressure without the addition of metals. There is information that the addition of a few percent CaCO3 as a catalyst to improve combustion.






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