Ignition / Sustain Issue

[AzoMittle]

Hey everyone,

 

So as some of you may know I'm currently experimenting with PTFE based formulas. Overall things have been going well but I have two major problems:

 

1) This stuff is damn nigh impossible to ignite, even with a thick layer of hot prime (tried BP, monocapa, and fencepost primes -- each with 10% flake titanium).

 

I want to avoid step priming because it not only gives a muddier star but also takes forever to weigh, mix, and roll each step. Plus, if I can have a pure star comp and a pure prime comp (rather than varying mixes of each) I can have more of the pure star comp.

 

2) When it does ignite it often either self-extinguishes or has a slow inconsistent strobing burn, usually in sporadic bursts. I believe the inconsistent burning is due to the dry components not being screened or mixed thoroughly enough.

The PTFE is a PITA to get through a mesh screen; it likes to clump and get stuck in the holes, anything over ~12-20 mesh flat out would clog up.

I have two ways to mix the components, either dry or shock-gel style. The dry method is exactly the same as you would handle flash. Shock-gel style is adding the PTFE to a slurry of solvent and the plastic, mixing, and then adding the metal/other ingredients and mixing again. I prefer the shock-gel as it is much safer and can work with larger quantities, it is hard to tell how homogeneously mixed everything is though.

--------------------------------------------

 

So, I have an idea on how to fix both issues: mix the formula with another one that will take fire easier. These PTFE based formulas give the brightest most incredible white I've ever seen and I don't want to muddy it or lose any intensity.

 

I've already tested my theory using BP and it worked, burned much better, but it destroyed the color and overall effect.

 

I'm figuring the best way to accomplish this would be to mix in another simpler white formula. Probably something based on nitrates/perchs with sulfur and antimony would be the cleanest. I'm guessing that charcoal/organic fuels will throw off the color (probably yellowing/orange it) and I want to avoid aluminum, magnesium, etc as I already have those balanced how I want them in the PTFE formula. I'm not sure what sulfur will do to the color.

 

The purpose is to make it take fire easier, and stay lit better with minimal impact on the color and intensity. Barium nitrate is probably my best bet for preserving the color but I'm not sure how well that takes fire in comparison to Potassium nitrate or perchlorate, or even Ammonium nitrate or perchlorate, I don't want to use chlorates for safety reasons.

 

---------------------------------

 

Thoughts? Alternate ideas? Suggestions for formulas to try? Can anyone give me a comparison of the oxidizers for this?

 

I was thinking something like this:

 

Example PTFE White

56....PTFE

27....Magnalium

12....ABS Plastic

06....Dibutyl Phthalate (DBP)

 

Faber's White Star

66......Potassium nitrate

16.5...Sulfur

16.5...Antimony sulphide

01......Meal powder

 

Mixed Formula (PTFE + Faber 4:1)

43.08....PTFE

20.77....MgAl

13.20....Potassium nitrate

11.54....ABS

04.62....DBP

03.30....Antimony Sulphide

03.30....Sulfur

00.20....Meal powder

 

Lancaster's White Fire

64....Potassium perchlorate

15....Potassium nitrate

13....Antimony

10....Copal Gum

 

Mixed Formula (PTFE + Lancaster 4:1)

43.08....PTFE

20.77....MgAl

12.55....Potassium perchlorate

11.54....ABS

04.62....DBP

02.94....Potassium nitrate

02.55....Antimony

01.92....Copal Gum

Edited April 19, 2016 by AzoMittle

[FlaMtnBkr]

Are you just making white stars? When I hear the word color I don't usually think white so just making sure.

 

It sounds like you need a fuel that burns better and has a lower ignition temperature. Especially with the strobe like burn.

 

I have read quite a few times to add a few percent of charcoal if something is hard to light. If you aren't using much and it's airfloat so it's a really small size it will likely burn up in the flame envelop without changing the color or adding sparks. But that's a guess and it might but could be worth a try.

 

Sulfur is also used because it's a good fuel and has a very low ignition temp. It burns a light blue by itself and I doubt it would add any color as it will be significantly over powered and washed out by the metal.

 

Phenolic resin and lactose are 2 more fuels that are used because they burn well and don't denature the color.

 

These are just guesses and what I would try first. Someone will likely be along with a better grasp of flame chemistry.

[AzoMittle]

Correct, I said color but I do mean white; there are a lot of different whites I've noticed, ranging from dull greys and silvers to blue-whites to varying shades of yellow-white and golden/amber tinged. I'm talking a pure white, brighter and as white as burning a ribbon of magnesium.

 

Not sure if I need a fuel or an oxidizer or both. I hadn't thought of lactose/sugars/resins, IIRC they are used in blues because they burn cooler; if it gets too cool though it may not ignite the PTFE/Mg mix so I was guessing that a medium heat would be best. Antimony as the only fuel would probably be too hard to ignite, you're right.

 

I don't know why but I have a suspicion that red gum and sulfur would work better than charcoal/lampblack or sugars/resins, although red gum is very similar to vinsol/phenolic/shellac. It also makes me wonder about things like hexamine, alum, salicylates and benzoates. Also, going to try cutting the thermoplastic binder with nitrocellulose; I've bound with only NC before and it was still too hard to ignite and had poor mechanical properties but did burn slightly more consistently.

 

I'm not willing to use cryolite due to the sodium but according to wikipedia a combination of cryolite and aluminum fluoride increases the conductivity of electrolysis solutions. I've also seen a handful of white compositions that use chlorine donors such as PVC, I'm not clear on their purpose but probably acting as fuels.

 

I'm completely open to trying anyone's suggestions, I just, well, need some suggestions because there are so many possibilities out there. A push in the right direction if you will.

Edited April 20, 2016 by AzoMittle

[schroedinger]

I would try to substitute some of your PTFE with AP (not sure about ptfe/ap safety, research that first) or perc to get a better burn. AP would be preferred since it is better at oxidizing organics.

[AzoMittle]

I would try to substitute some of your PTFE with AP (not sure about ptfe/ap safety, research that first) or perc to get a better burn. AP would be preferred since it is better at oxidizing organics.

 

 

PTFE and AP are fine together, in fact, PTFE is compatible with almost everything except a few specially designed commercial perfluorinated solvents. I even have a composition that uses AP:

40....Ammonium perchlorate

20....Poly(tetra-Fluoroethylene) (PTFE)

15....Aluminium

10....Silicon

10.....Manganese dioxide

 

Tianshu, W., Zhu, C., Wang, J., Xu, F., Chen, Z. and Luo, Y. (1995) Study on spectral characterization of infrared flare material combustion with remote high resolution Fourier transform infrared spectrometry. Anal. Chim. Acta, 306, 249–258.

 

The above--and below--are specifically designed for infrared tracking decoy flares in military applications so they won't work great for our purposes. It does raise the question of silicon as a fuel. I found the following while looking up the one above, it makes use of hexamine, AP, and potassium nitrate which may make for a good base. It does use boron though which is silly expensive.

 

42.075....AP

14.000....Viton

10.150....Magnesium

09.900....Aluminum

08.250....Hexamine

06.600....Potassium nitrate

04.950....PTFE

04.125....Boron

 

Herbage, D.W. and Salvesen, S.L. (1995) Spectrally balanced infrared flare pyrotechnic composition. US Patent 5,472,533, USA.

[schroedinger]

Take the first comp, and substitute the silicon von mg/al

[AzoMittle]

Why do you suggest subbing silicon for MgAl? Would you recommend doing the same for the Al?

 

The amount of burn enhancing comp I'll need will have to be tested by trial and error. Maintaining the overall binder content and aiming for 10% AP places it at a 2.452 : 1 ratio of origin formula to burn enhancer, this also maintains the PTFE:MgAl ratio. Formula looks like:

 

44.30....PTFE
21.45....MgAl
10.00....AP

03.75....Al
02.50....MnO2

12.00....ABS
06.00....DBP

 

I'm not sure about it, it still feels like it won't be enough. The manganese dioxide should help lower the activation temperature. I'm thinking sub the Al for airfloat and replace a third to half of the binder with nitrocellulose.

 

edit: Still thinking some sulfur and antimony trisulphide would help but not sure how they would fit into the above formula, possibly subbing for a portion of the PTFE/MgAl.

Edited April 20, 2016 by AzoMittle

[FlaMtnBkr]

Just remember that AP and KNO3 could make some ammonium nitrate and potentially turn into a mushy wet mess.

 

I would probably make a sample of your formula and then take small increments and add a reasonable amount of different fuels and oxidizers and burn them to check burn characteristics and color. That way you can test a lot of things quickly. Then take the most promising and explore them further.

 

Just what I do sometimes when I'm trying to modify something but not sure which direction to take.

[Mumbles]

Most of the above formulas are not at risk of developing ammonium nitrate. The fluroelastomer binder, Viton, typically seals it up extremely well. Clearly well enough to prevent the much less desirable reaction between magnesium and ammonium perchlorate.

 

It would be a little easier to help if we knew what you were doing. Stars have a different set of issues than flares, which have a different set of issues from ground illumination. These type of formulas really work best for flares by the way. I really don't know anything about how they'd fare when factoring in flying through the air in a star.

 

I do hope you're taking proper precautions. Mixtures of Mg and teflon are quite sensitive to thermal ignition, static, and friction. It's basically an extremely sensitive, extremely energetic thermite type reaction. Industrially, they're never mixed dry. Most of the time the metal is slurried with the binder, sometimes with an external solvent, before the teflon is added. Really the only reason you mess with them is for incredibly high intensity flares.

 

I would think your issues are really a combination of both mixing and poor primes. I would not consider what you mentioned to be real "hot primes". Sure they do the job for firework applications, but this is more in the military application realm. Think thermitic primes or ones containing high percentages of silicon. There is one specifically mentioned in Shimizu called "red thermit". It's 80% Red Lead, 20% ferrosilicon, and actually produces relatively little light though quite a bit of liquid slag. Similar mixtures containing silicon would also work. Silicon tends to emit in the near IR. I suspect this is part of why it's included in the above formulas. Magnesium oxides and fluorides tend to emit strongly in the visible and ultraviolet regions.

 

I wouldn't worry about adding charcoal or lampblack or any of that. First and foremost, the white light will obliterate any semblance of incandescence from carbon particles. Think about it. What do you think the final products of a Mg/PTFE reaction are? About 90% of the products are comprised of MgF2 and C. At a couple thousand degrees, the carbon will then burn with atmospheric oxygen as available, which is about the least desirable scenario for pure colors. All that carbon produced is covered up already. Adding a little more isn't going to affect anything. I suspect that is what the oxidizers in the above formulas take care of anyway. The work is done by the magnesium and teflon. Everything else is a binder or burn modifier.

 

If I were trying to make these easier to ignite, I'd mix in barium nitrate. It will burn happily with the metal of choice to get the reaction going. It has the added benefit of also emitting some almost white light at high temperatures. It tends toward slightly lime green. You can "correct" it by adding in a little salt of some strontium complex. It doesn't change the emission wavelengths, but the red + green obliterate each other to a more pure white by appearance. It's a trick that works for AP/BaSO4/MgAl strobes as well.

 

A little unrelated, but zirconium makes one of the brightest and purest white flames I've seen.

[lloyd]

Azo,

If you want an example of a very low-temperature "pure white", look up "Mohr's white fire". It's basically a black powder formula, and it burns a very pretty (but 'soft') white. And it's slow.

 

But it's 'secret' is - after all - THE secret that reveals that whites don't need to burn really hot.

 

Lloyd

[AzoMittle]

Wow, thank you to everyone for that info. Everyone here is so helpful, I love the pyro community.

 

Mumbles, great question, I should have clarified that up front: these are for stars and comets, I got the idea of using it while flipping through old military research on IR decoy flares and thought I could adapt and try to push it away from the IR and military spectrums. I've spent time reading up metal-fluorocarbon reactions, I've gone through the DTIC papers, patents, and own/read E.C. Koch's (amazing) book and assorted papers on the topic; I'm aware of its safety and instabilities, I keep my batches tiny, and take the same precautions as flash. I'm not telling people 'go out and try this' because I know it's not straight forward but at the same time if I/we can crack a reliable method of using it in our pyro I think it would bring something really unique to the table.

 

I'll admit, I'm well aware of how dangerous dry mixing it is but I did try it twice to see if it mixed better (it didn't). I know the de facto is to slurry it (especially when using viton or a soluble polymer to coat the particles, much akin to dichromating the magnalium) but oddly I have come across at least one or two patents that mention screening separately and diapering together. Strangely enough, I haven't found anyone that sells viton to individuals, only bulk commercial supply and as sheets for gaskets which already have other plasticizers and polymers mixed in.

 

Most of the IR flare comps come with primer comps alongside them, so I should be able to dig some up. Problem with most of them is they usually contain boron or zirconium which are too expensive. I'll post two or three below that don't use either. The red thermit is a good lead, I'm guessing that will need its own layer of 'hot prime'?

 

"What do you think the final products of a Mg/PTFE reaction are?" I have to slap myself, I should have caught that. Reminds me of when I asked where the 1600 came from in oxygen balance formula, it was an 'oh, duh' moment.

 

I like the idea of barium nitrate, I know whites that use it and that I can look to. I doubt it will be enough to green it, if it does though I'm figuring you mean balance it with strontium nitrate similar to the non-sodium yellows? Or would the sulphate / oxalate be better? Oh, and by the way, don't bother with polystyrene as a binder, stars are like foam and crumble (though that may work for granulated flash).

 

Oh and I agree about the zirconium being nicer, it's just too expensive. Here's a good video of it by the by: https://www.youtube.com/watch?v=Vdkda0ZClbA

 

-----------------------

 

Lloyd, I'm not totally clear on what you're suggesting. I found Mohr's white fire, and I'll probably end up making a small batch for the next shoot. It's a bengal fire but I bet it would work as a star too.

 

I'm not trying to make it hot for hot's sake. When I mentioned looking for a medium heat instead of low heat earlier I was basing that off of the guess that I would need a higher heat to get the metal-fluorocarbon reaction going while keeping it cool enough to take fire from the priming.

 

I'm very interested in introducing unused/unusual components and methods into the average pyro's repertoire. I personally feel, literature and development on fireworks has been slowing down the past few decades, that most pyro's stick with what they know (it seems everyone and their grandmother have their own variations of Veline or KP+Parlon/PVC+Red Gum+Various nitrates style systems right now), that is entirely just my opinion though. Seeing new things, like copper benzoate blues for example, is great.

 

----------------------

 

Here are some slightly hotter prime comps I had written down with easily obtained components. I can go digging for ones specifically designed for IR flares but I wanted to put something up. The following were all designed to be bound with either laminac or NC lacquer.

 

Prime A
25....Silicon
25....Titanium
25....Fe2O3
25....Fe3O4

Prime B
75....BaN
25....Mg

Prime C
35....Pb3O4
26....Silicon
22....Iron Oxide (Scale)
13....Al
04....Charcoal

Edited April 21, 2016 by AzoMittle

[Carbon796]

 

" I'm very interested in introducing unused/unusual components and methods into the average pyro's repertoire. "

 

What is the advantage, to "average" pyro's, that this white formula is supposed to provide ?

 

 

" Seeing new things, like copper benzoate blues for example, is great. "

 

Formulas using Copper Benzoate for blues have been around for well over a decade . . .

[AzoMittle]

I'm trying to give back to a community that has helped me. I try a lot of different things, most of them are laughable failures but this one is rather promising. Maybe it will work, maybe it won't, I'm playing around and finding out. If I can give something back, even as minor as one white formula, then yay. Or do you believe that no one should ever try to contribute anything?

 

I thought the CuBenz blue was from the past couple of years, my mistake. It was just the first thing to pop into my head to use as an example of a recent advance in recreational pyro. If you want to give a more recent example I'd be happy to learn, I'm all for discussion. I'm the first one in line to admit that I make mistakes, and often, if I say something wrong then I invite anyone and everyone to correct me. My approach to pyro is much like food or music, I see it as a communal thing, a sharing thing, a thing to make people smile.