Sciencemadness Discussion Board

PTFE near miss – split from Life after detonation

MineMan - 28-1-2019 at 19:20

[mod note]
This thread was split from yamoto71's thread https://www.sciencemadness.org/whisper/viewthread.php?tid=22...
Yamato's thread is a sobering read for anyone not acquainted with it. It is a very important thread on this board.
Mineman's anecdote below is related but discussion is becoming tangential to the original thread – a split will allow discussion to diverge as appropriate.
[/mod note]



I was melting PTFE with MgAl powder in a tempature PID controlled Lee Hot Pot.

I was 7 feet away. There was an airblast, it did not burn like PTFE mixtures are suppose to...200 grams, burn marks on the patio roof. Luckily I am unharmed. I had just turned the temp up to 300C, and was going to stand above it and mix it, yet I decided to work on another piece of equipment nearby, it went off 30 seconds later.

I would have been under intensive care surgery removing the crisp of skin LEFT on my face, this would be happening currently if I was stirring it. By the blast I was sure the hot pot was turned into shrapnel. No. But it did pull it apart.

I don’t know what else to say, I saw it smoking the day before, I knew it heated to hot even with the PID I installed. But I needed my research to continue, I couldn’t think of an alternative.....

So. Here I am. Luckily lucky.

[Edited on 29-1-2019 by MineMan]



[Edited on 1-2-2019 by j_sum1]

Deathunter88 - 28-1-2019 at 19:59

Quote: Originally posted by MineMan  
I was melting PTFE with MgAl powder in a tempature PID controlled Lee Hot Pot.

I was 7 feet away. There was an airblast, it did not burn like PTFE mixtures are suppose to...200 grams, burn marks on the patio roof. Luckily I am unharmed. I had just turned the temp up to 300C, and was going to stand above it and mix it, yet I decided to work on another piece of equipment nearby, it went off 30 seconds later.

I not sure I would have been dead, but I would have been under intensive care surgery removing the crisp of skin LEFT on my face, this would be happening currently if I was stirring it. By the blast I was sure the hot pot was turned into shrapnel. No. But it did pull it apart. Luckily I am not under ketamine anastesia right now, luckily I didn’t half the products of flourene combustion forced down my lungs.

I don’t know what else to say, I saw it smoking the day before, I knew it heated to hot even with the PID I installed. But I needed my research to continue, I couldn’t think of an alternative.....

So. Here I am. Luckily lucky.


If you had done even a 30 second test lighting PTFE plumbers tape and magnesium powder you would never have thought it was a good idea to heat together 200 grams of the mixture.

MineMan - 28-1-2019 at 20:38

Like I said it was not a great idea, but I could not think of another way to make a solid shape of the said two. I have burned it... it’s impressive. This did not burn though. It deflagrated.

[Edited on 29-1-2019 by MineMan]

markx - 29-1-2019 at 12:13

Quote: Originally posted by MineMan  
I was melting PTFE with MgAl powder in a tempature PID controlled Lee Hot Pot.

I was 7 feet away. There was an airblast, it did not burn like PTFE mixtures are suppose to...200 grams, burn marks on the patio roof. Luckily I am unharmed. I had just turned the temp up to 300C, and was going to stand above it and mix it, yet I decided to work on another piece of equipment nearby, it went off 30 seconds later.

I would have been under intensive care surgery removing the crisp of skin LEFT on my face, this would be happening currently if I was stirring it. By the blast I was sure the hot pot was turned into shrapnel. No. But it did pull it apart.

I don’t know what else to say, I saw it smoking the day before, I knew it heated to hot even with the PID I installed. But I needed my research to continue, I couldn’t think of an alternative.....

So. Here I am. Luckily lucky.

[Edited on 29-1-2019 by MineMan]


A fortunate mishap and perhaps an omen....I am very glad that you are ok and nothing irreversible happened.

I have long ever since come to the conclusion that the most dangerous element in any experiment is usually the person conducting it.

It's thyself that one should fear and mind above all! :)

Vomaturge - 29-1-2019 at 21:55

Quote: Originally posted by MineMan  
I was melting PTFE with MgAl powder in a tempature PID controlled Lee Hot Pot.

I was 7 feet away. There was an airblast, it did not burn like PTFE mixtures are suppose to... I had just turned the temp up to 300C, and was going to stand above it and mix it, yet I decided to work on another piece of equipment nearby, it went off 30 seconds later.

By the blast I was sure the hot pot was turned into shrapnel. No. But it did pull it apart...

I don’t know what else to say, I saw it smoking the day before, I knew it heated to hot even with the PID I installed. But I needed my research to continue, I couldn’t think of an alternative.....
[Edited on 29-1-2019 by MineMan]


Wow. Who would have thought that walking away from the stove would prevent disaster, rather than cause it. Well, really being a few meters away from something like that lets you keep an eye on it, while still keeping your eyes in place.

You suggested that it could be getting too hot in spite of the PID. I wonder if the PID was faulty, or if the mix just has a low ignition point. Something to explore further, I suppose, with the right safeguards in place.

The hotpot was pulled apart? Did it have a lid, or did the stuff self confine like a fine flash powder?

Why did it burn so aggressively? Here is a post from wg48
Quote:
From my camping days: If you wrap a strike anywhere match head in Al foil then throw it in to a camp fire it does not go pop. If you place it near the edge of the fire in just the right position such that it heats up slowly, it will frequently make a bang. Occasionally matches thrown in to a camp fire that land near the fire or on the cooler side of wood such that they heat up slowly can ignite so quickly that they are propelled out of the fire.


In this pdf it states on PG 2 (pg. 3 of the file):
" It should be noted that in the case of a fast cookoff event, the lower
flux levels and longer thermal soak times may represent the most violent reactions, due to the involvement of a
larger amount of energetic material in the cookoff event."

It seems logical to me that heating the entire sample could make it burn faster, because it would require less heat transfer to reach ignition temperature deeper in the mixture. Say the mix does react at 300C. If you light a pile of it at 20C, that initial flare up has to heat the surrounding material by 280C before the reaction can propagate. If most of the pile is already 250C when the bottom reaches its ignition point, a temperature increase of only 50C is needed to spread to the surrounding matter. It also doesn't help that the heat is coming from the surface the mix was laying on; The flash had only one direction to go, up and through the rest of your composition.

It is my uneducated opinion that preheating also made less than a gram of ETN detonate in an open test tube, causing this accident.

On the bright side (in a good way, not a bad one) we know now that you can get some real energy output from a combination of ptfe and magnalium under the right conditions.

As far as how to safely mix this, is there any way to powder Teflon and press it into shape? Probably not, but something to think about.

Anyhow, I'm very glad you're okay. This is a good reminder to everyone that the unexpected happens... when we're least expecting it.

[Edited on 30-1-2019 by Vomaturge]

Herr Haber - 30-1-2019 at 04:57

MineMan,

I have a fairly good idea what you planned to do with that composition.
Maybe you can find some data (and avoid a fiery death!) looking for details on IR decoy flares ?

MTV compositions are interesting in that regard.

nitro-genes - 30-1-2019 at 06:14

Holy shit, sounds like a nasty experience! Good that you were not in the direct vicinity when it decided to blow. Had a couple of these experiences myself, what I found intriguing is that in every case were something went wrong, there was this unexplainable almost subconscious feeling of unease.

Next to no experience with teflon/metal powder mixtures...still on my things to try one day though :)

Is teflon soluble in anything but itself? Seems easier to lower the melting point of the teflon somewhat using lower molecular weight teflon f.e.. Is the high melting point of the teflon/metal composite needed for the flare to work properly? Maybe a sort of other polymer or silica matrix could be included for stability in this case, using (partly fluorinated) copolymers and crosslinking (maybe difficult with the metal present). Are there no other high weight % fluorinated polymers that are easier to dissolve/melt as teflon?

[Edited on 30-1-2019 by nitro-genes]

markx - 30-1-2019 at 10:19

There are teflon dispersions available:

https://www.sigmaaldrich.com/catalog/product/aldrich/665800?...

These are interesting stuff....mixed with solids and kneading the resultant mass, the ptfe particles strech out into a fine binder network of ptfe fibres that hold the solids together quite firmly.
We used to make carbon sheet electrodes with the 60% ptfe dispersion by adding together fine carbon dust, a small amount of the dispersion and ethanol. The mass was mixed gently and then kneaded to form a solid clump of carbon dust bound into the ptfe fiber matrix.
The clumps could be rolled into thin sheets of carbon under half a millimeter in thickness.
Perhaps a similar approach can be taken if a finely divided mix of ptfe and a metal particulate is desired....

Herr Haber - 31-1-2019 at 03:54

Or use Viton since it's soluble.

(Maybe a mod can prune this thread to keep it relevant. This conversation is very similar to another one)

j_sum1 - 31-1-2019 at 16:07

Quote: Originally posted by Herr Haber  
(Maybe a mod can prune this thread to keep it relevant. This conversation is very similar to another one)

I was thinking much the same thing. Done.

j_sum1 - 31-1-2019 at 17:17

Quote: Originally posted by fusso  
What is pruning?

It's when I delete your post, fusso. Watch this!

MineMan - 2-2-2019 at 23:59

Yes. I am thinking Viton is the best best. The incident was scary. I bought Viton with this in mind! Only problem is I wonder how the solvent will dissolve from large grains? If it will???

Herr Haber - 3-2-2019 at 05:04

Lucky you if you got powdered Viton. I have been looking at my Viton tubes for a while and wondering if I should make some tests to extract some. Once one gets damaged maybe :)

A bit more on MTV composition though. I think there's more in Conklin, he loves chatting about military compostions though the book is about fireworks.
If memory serves, Viton is the binder so it could really help you in making the cones you make by adjusting ratios with more and different metals.
Maybe less teflon. Viton has it's own Fl.

MineMan - 6-2-2019 at 11:23

Sorry. I have been taking a break since the incident. Clearing my mind of the excitement of my goal and project... so I can think more objectively when I come back.

It’s not powdered. I worded that wrong. It’s a sheet... I meant I am wondering when I use the solvent how it will evaporate from the interior of large grains that I create??

How did you know I wanted to make cones??? :)
Yes. But my question is if I put it in a mold of a couple of inches how will the solvent evaporate. I am more naive in some areas of this then I would like to admit.

I will respond to all others who have posted before... I just need some time.

MineMan - 22-2-2019 at 23:44

Vomaturge Thank you for your detailed response!

All. I really don’t know why I did this.... previous to this accident I had seen YouTube’s of PTFE flash powder... yet I thought it would be ok to mix molten PTFE with a 325 magnesium mesh alloy (300 grams of it)I truly deserve the Darwin Award. The day before I saw it was smoking too...when I had tried it with aluminum powder. But with aluminum powder it would not ignite... even up to 360 C.

The hot pot is used to melt lead, so even with the PID controller it would reach tempatures 150C higher than the PID read. This is because it was a 15cm tall by 10cm wide pot with a one wrap 6mm heating coil that only wrapped around the bottom.

I just don’t get my I thought it was a good idea. WTH mineman!

Nitro and Markx. Yes. I thought about dissolving in a solvent but I want to make complex shapes....and pour into molds and try to make rocket propellant with it. Can you give me more details Markx?