Advice on potassium perchlorate based (visco) fuse formulation

[markx]

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.

 

[Mumbles]

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.

[markx]

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.

[davidh]

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 July 13, 2019 by davidh

[Arthur]

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

[markx]

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

[Mumbles]

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.

[markx]

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

[markx]

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:

 

 

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.

 

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 July 20, 2019 by markx

[Fliyud]

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

[Mumbles]

English only please.

[markx]

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 July 22, 2019 by markx

[Fliyud]

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.

[markx]

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.

 

There are different additives suggested for catalytic effect regarding KClO4 in available patent literature: mostly mixes of common carbonates, sulfates and nitrates in about 5-10% mass ratio to KClO4. E.g. CaCO3, CaSO4, KNO3. It should yield a lower decomposition temperature of the perchlorate, but when mixed dry I have not found these additives to be effective in the mix at any point. Perhaps a wet preparation process that I used may produce some positive results, but I've not tried it yet....

[FlipperFuego]

thanks for the pics, super helpful http://freeimagehost.info/i/bWB78LtRcv.png

[WillowPineAndBoom]

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:

 

 

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.

 

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.

 

how you make this fuse , actualy this stracture! with what ? can you upload a video to share with us?

[markx]

how you make this fuse , actualy this stracture! with what ? can you upload a video to share with us?

 

The fuse is made by the abovepictured "contraption". It is just a garden variety visco machine, but I've been tinkering around settings and adjustments/improvements for years. Now it makes a pretty decent quality product

[markx]

So I've been tinkering around the topic in the meanwhile and came to the conclusion that a ball milling step is unavoidable if one wishes to get the most out of "simple" perchlorate based fuse formulations. For that purpose I went forth and built a small ball mill type of contraption:

Fabrication of the drive shaft (304 stainless steel):

The frame, power supply and support rollers:

The rollers are adjustable, so one can accommodate and balance different sized mill jars in the frame. Starting from small ones with a capacity of a few hundred ml up to several litres if needed.

Milling a relief into the motor support to be able to assemble the system. I managed to weld the motor support into place in such a way that it made it impossible to assemble the drive shaft into the bearing seats:

In operation with a 300ml jar, 10mm glass marbles as milling media, strictly wet milling in alcohol for perc formulations:

 

The dc motor came from an old cordless drill and is more than capable of handling the job. There is a pwm module and a timer module to be able to set the suitable rpm and milling time for consistent results. Works like a charm....

 

 

As for the results.....I've settled at a combination of

80% KClO4

20% C (charcoal)

 

30g batch milled for 3 hours in alcohol, grained once through a 0,5mm stainless sieve and let dry at ambient temperature. Produces very simple yet agressive and hot fuse that burns evenly at moderate speed (about 1cm/sec).

If one adds red iron oxide into the ball milling step (0,3g on top of a 10g 80/20 mix), then the agressiveness of the burn is further increased, but not really the speed of the flame propagation. The iron doped fuse starts to fly if a lit piece is let go unrestrained.

80/20 seems to be a sweet spot for the simple base formulations based on carbon fuel. If I stray into 70/30 or the other way into 85/15, the burn rates and overall "joy" of the flame jet drop off quickly.

The simple 80/20 works really good for practical purposes now and I could deem it done, but where's the fun in that I'll try out different accelerators to study if there are ones with a sharper effect than iron oxide. I'll also try to get some flame color effect....red(ish) should be achievable with strontium and lithium compounds. I would really love to get a good green one, but I fear the extra fuel from the fuse coating and threads is going to wash it out. Boron compounds might have a chance though.....

 

[dave321]

 

The fuse is made by the abovepictured "contraption". It is just a garden variety visco machine, but I've been tinkering around settings and adjustments/improvements for years. Now it makes a pretty decent quality product

that's a nice looking visco / fuse machine

[markx]

Some shots of the fuse cross section under mild magnification....80/20 KP/C composition in 2mm and 3mm versions:

 

The 3mm version burns like an angry worker bee! I'm quite pleased with this simple yet effective formulation approach

 

 

[markx]

The following formulation makes a pretty decent red burning fuse....

 

Parts by mass:

8 KClO4

2 C (charcoal)

1 SrCO3

 

Ball milled for 3 hours in ethyl alcohol, filtered, granulated through 0,5mm sieve and dried. Even without an external organic chlorine donor the granulated formulation burns with an outstanding bright red flame. Perhaps a bit pinkish, but still quite impressive.

I spun the formulation into 3mm fuse and impregnated the product with a chloroprene based contact glue diluted in xylene hoping to further enhance the flame coloration.....and it is quite impressive at least at the moment of ignition. Once the flame jet propagates and gets shielded by unburnt fuse casing, the effect obviously becomes diminished, but that is no fault of the core formulation.

 

Also tried a green variation based on barium carbonate, but that was not nearly as impressive as the red one. Green always tends to be way more tricky, especially if barium carbonate is used as the sole colorant for the flame.

[SharkWhisperer]

What's the subjective burn speed of a pile of the dried, granulated powder, compared to, say BP?

 

Wonder what that'd do if you stuffed it into a rocket tube?

 

Maybe tinkered with a little sulfur in the wet-milling...hmm.

[markx]

What's the subjective burn speed of a pile of the dried, granulated powder, compared to, say BP?

 

Wonder what that'd do if you stuffed it into a rocket tube?

 

Maybe tinkered with a little sulfur in the wet-milling...hmm.

Burn speed in loose granulated pile is higher than BP (well that is based on a subjective visual assessment)....the milled 80/20 KP version with just carbon as fuel goes off with a "thump" when ignited. Sulfur shall likely increase the speed even more (also sensitivity towards mechanical manipulations), but for fuse formulations that is overkill and I do not like the smell it produces while burning in combination with the threads and coating.

Do not know about the rocket application, but perchlorate mixtures tend to have a "positive void coefficient" regarding pressure and burn speed. The higher the pressure becomes, the higher the burn speed....so it might be a good candidate for CATOs. Definitely the 80/20 ratio is way too hot for rocket application, but a leaner mixture might have good potential for testing.

[markx]

Went down a dangerous path (beacause of curiosity and stuff) and stirred up the following fuse composition:

 

7,2 parts KClO4

0,8 parts KClO3

2 parts C (carbon)

 

Ball milled in ethanol for 3 hours, graded through a 0,5mm sieve in a damp state as all other formulations and dried. Spun into a fuse and son of a gun, does this kick up the agressivness of the final product. Let go of a burning piece of the fuse and it flies around aiming for your remaining good eye

Impressive, impressive stuff, but the chlorate content is troublesome and worrying.....not a good approach for practical application.

[Piccaso]

 

So I've been tinkering around the topic in the meanwhile and came to the conclusion that a ball milling step is unavoidable if one wishes to get the most out of "simple" perchlorate based fuse formulations. For that purpose I went forth and built a small ball mill type of contraption:

Fabrication of the drive shaft (304 stainless steel):

The frame, power supply and support rollers:

The rollers are adjustable, so one can accommodate and balance different sized mill jars in the frame. Starting from small ones with a capacity of a few hundred ml up to several litres if needed.

Milling a relief into the motor support to be able to assemble the system. I managed to weld the motor support into place in such a way that it made it impossible to assemble the drive shaft into the bearing seats:

In operation with a 300ml jar, 10mm glass marbles as milling media, strictly wet milling in alcohol for perc formulations:

 

The dc motor came from an old cordless drill and is more than capable of handling the job. There is a pwm module and a timer module to be able to set the suitable rpm and milling time for consistent results. Works like a charm....

 

 

As for the results.....I've settled at a combination of

80% KClO4

20% C (charcoal)

 

30g batch milled for 3 hours in alcohol, grained once through a 0,5mm stainless sieve and let dry at ambient temperature. Produces very simple yet agressive and hot fuse that burns evenly at moderate speed (about 1cm/sec).

If one adds red iron oxide into the ball milling step (0,3g on top of a 10g 80/20 mix), then the agressiveness of the burn is further increased, but not really the speed of the flame propagation. The iron doped fuse starts to fly if a lit piece is let go unrestrained.

80/20 seems to be a sweet spot for the simple base formulations based on carbon fuel. If I stray into 70/30 or the other way into 85/15, the burn rates and overall "joy" of the flame jet drop off quickly.

The simple 80/20 works really good for practical purposes now and I could deem it done, but where's the fun in that I'll try out different accelerators to study if there are ones with a sharper effect than iron oxide. I'll also try to get some flame color effect....red(ish) should be achievable with strontium and lithium compounds. I would really love to get a good green one, but I fear the extra fuel from the fuse coating and threads is going to wash it out. Boron compounds might have a chance though.....

 

 

Go big or go home the man says.