Sciencemadness Discussion Board - Effects of Various Binders on PBX Composition Performance

Effects of Various Binders on PBX Composition Performance

Marsh - 12-11-2021 at 01:01

To clarify the title;

When producing a PBX of PETN+binder, there are many forms of binders I have seen used, though the end effects they have on the final PBX performance is of obvious concern. As far as binder forms I am referring to, there are: rubbers in cross-linked or non cross-linked form, then resins of polymers which can be cured with isocyanates, such as HTLO/HTPB (hydroxyl-terminated polybutadiene).

My particular interest is in the performance capabilities of PBX using the resin types of polymer binders, and this is for a few following reasons;

1. To blend/distribute PETN into a rubber binder, the rubber needs to be softened using a solvent, and therefore the solvent used must be found that only reacts with the binder and not the energetic compound (to preserve energetic crystalline structure size and prevent recrystallization).

2. The solvent must then be dried away, adding further drying procedures, as well as a slowly changing PBX shape while it is drying, as the solvent leaves and the rubber stiffens up again.

3. It would seem highest density loading into a container or shaped-liner assembly would be easiest achieved using the low-viscosity form the resin takes on before being cured. (It will cure into the same shape as first cast.)

After thinking about those reasons, it would seem a PBX made with polybutadiene resin would actually be the preferred method of binding, though I don't find it discussed here. For the record, it would be plasticized for a more rubbery ending state, using IDP (isodecyl pelargonate), which has anti-cure properties.

My question at this point would be, would this actually create a desirable PBX composition, vs the more textbook rubber binders used such as SBR (styrene-butadiene rubber) or PBR (polybutadiene rubber)?

I'll leave it at that before speaking on the topic of crosslinking within the rubbers, which may only further complicate things at this point--though it is binder subject of another concern, once moving forward.

Thanks

P.S. I have pure polybutdiene rubber (clear and not from vulcanizing tape, which I've always considered to be rather impure form, as it contains dies and unknown modifiers). The clear PBR I have is not workable into PBX without solvent, it's fairly stiff high molecular weight. It is CAS #9003-17-2. I don't often see molecular weights of rubbers ever used in PBX formulas, normally just weight of rubber, weight of energetic, and any other compounds like oil by weight. These polymer compositions seem to have more variables than I ever see addressed in the details creating the PBX mixture.

[Edited on 12-11-2021 by Marsh]

Brightthermite - 12-11-2021 at 14:53

I believe you have to add some kind of oil to the dissolved rubber to keep it from fully hardening. If you do any testing I would love to hear your results, binders are a niche I just started exploring.

Marsh - 13-11-2021 at 03:35

There's some evidence throughout various publishings suggesting HTPB-based binders are of many benefits in PBX compositions vs traditional rubber dissolving methods to create binders, and the reasons are seemingly similar to what I suggested above in numbered order. Primary reasons are for obtaining maximum solids loadings and easily casting without heat or nasty solvents. It is surprising to me that more discussions about this method for PBX compositions has not surfaced more prevalently around here; we seem to still be embracing self-vulcanizing tape recipes with oils added to assist what is potentially a strenuous mixing task. There's no need to extract a rubber, try to turn it liquid to mix the PBX and then go back to solid again over long drying period. Simply use HTPB, start with the liquid form for mixing/casting and go right to the solid rubber form within hours later, have a stable casting ready to use fully hardened within 24hrs. I abandoned those old methods a long time ago, because I had troubles utilizing any good solvent towards PBR that wasn't also a good solvent of the energetic compound (which is not desirable). Hexane will turn dense PBR to corn-syrup consistency, but also dissolves PETN. Petrol they say is a good solvent for PBR, yet in my experience it is a very tough solvent to dry and remove from the PBR without displacing it out using yet again another solvent that dissolves the energetic, such as acetone. Well enough on that anyways, as it looks like isocyanate cured polymers are here to stay for PBX compositions.

I'll get back on topic.

A publishing from Jan 3 2018 by Beijing Institute of Technology, titled "Thermal and mechanical reinforcement of a novel paraffin-based hydroxyl-terminated polybutadiene (HTPB) binder containing a three-dimension (3D) diurea–paraffin wax (DU–PW) for prevention of PW leakage", goes on to state:

"Hydroxyl-terminated polybutadiene (HTPB) binders significantly contribute desirable polymer features to PBX."

And:

"In the past few decades, hydroxyl-terminated polybutadiene (HTPB) has been widely used as a binder in military engineering due to its superior mechanical and ballistic properties. In addition, HTPB-derived polyurethane can provide a matrix of networks to impart dimensional stability and structural integrity to PBX."

In that article they talk about the role paraffin wax plays as a desensitizing agent in such PBXs. However the structure they show in the study of PW+HTPB shows a porous structure containing many holes throughout (structure witnessed from SEM photos), and as such, also due to low melting point of PW, it tends to leak out in warm environments. They use diurea+PW to form a very phase stable ending product PBX which does not suffer from such leaking effects. That paper is published here: https://pubs.rsc.org/en/content/articlehtml/2018/ra/c7ra1057...

I am not after further desensitization, as HTPB based PBX by nature should be very stable and insensitive. HTPB causes endothermic reaction shift, so I have been thinking about improving the heat of explosion capabilities to benefit the effects of the PBX. I noted in a study titled, "Influence of Aluminium on Performance of HTPB-based Aluminised PBXs", published October 2004 in Defense Journal 54(4), they go on to state:

"It is observed that about 15 per cent aluminium content in the aluminised PBXs shows the optimum VOD."

I find this particularly interesting because the possibility may exist to further enhance heat and VoD effects in a PETN-based PBX particularly, by introducing an oxidizer that works well with aluminum into the PBX, such as CuO. Though I hypothesize good effects will come from maintaining higher loadings of PETN and not displacing it with so much metal fuel weight. I will have to begin to setup the experiment to see if and where this could become possible to realize among compound loading weights. Hopefully this gets more interesting soon. Will report back with further progress.

[Edited on 13-11-2021 by Marsh]

MineMan - 13-11-2021 at 04:44

What chemicals are needed to make that binder? I have no knowledge of binders.

Furthermore. Know aluminum will decrease VOD, but 15 percent is best valence for energy and VOD. In fact. Aluminum is kind of pointless if PBX… unless you want thermobaric.

Marsh - 13-11-2021 at 05:18

Quote: Originally posted by MineMan

What chemicals are needed to make that binder? I have no knowledge of binders.

Furthermore. Know aluminum will decrease VOD, but 15 percent is best valence for energy and VOD. In fact. Aluminum is kind of pointless if PBX… unless you want thermobaric.

Sounds like I will need to look for more data; I find it strange that they specifically state 15% Al produced highest VoDs in their aluminized PBX. I wonder, did they start at 15% and try 15/20/25 % etc.? If they started at 5% Al, I wouldn't expect to hear them say they achieved highest VoD at 15%. So maybe a little confusing at that source. Edit: Nevermind, I understand what you are saying now. "Optimum VoD" not maximum VoD, I misread my own reading material, yikes. Optimum VoD when trading some for enhanced blast effects and increased underwater bubble energy, makes sense now, I concur.

Surely there is a way to bump the heat of explosion up while improving stoichiometric balance and energize the binder a little more without losing VoD though, possibly. PETN+HTPB can't be the fastest det speed it's ever going to obtain, that's my hypothesis at least. Maybe PETN+GAP+HTPB, where GAP means glycidyl azide polymer. Any thoughts on a combination like that, where the ending composition maintains PETN loading seen for typical max VoDs in PBX but the binder is the component boosted with energy?

I'll post a formula up for HTPB when I return, right now my eyes are closing unexpectedly.

[Edited on 13-11-2021 by Marsh]

Nitrosio - 13-11-2021 at 06:48

Attachment: Buta.pdf (10kB)
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ManyInterests - 13-11-2021 at 14:46

While this is not directly related to exact type of binder OP is talking about. Binders and plasticizing energetics is something that I didn't really start to understand until recently (and I have yet to make a plasticized anything). I will be primarily using rubber cement and bar and chain oil to plasticize ETN and RDX. Also I want to plasticize potassium chlorate as well (with and without sugar).

But one of the first things I read when starting out on energetics is the Improvised Munitions Handbook, which has among its first entries making plastic explosives out of potassium chlorate with 9 parts chlorate to 1 part vaseline/petroleum jelly. I've seen others that substituted wax for the petroleum jelly or a combination thereof. Others had them try to dissolve the jelly or wax first, or dissolve it and add it to lighter fluid/camp oil (almost the same thing) but that did absolutely nothing. The result was a very grainy, sand-like texture and wasn't plastic at all.

Is there any way of actually using petroleum jelly/Vaseline as a plasticizer? I'd really like to know.

MineMan - 14-11-2021 at 09:35

Quote: Originally posted by Marsh

Quote: Originally posted by MineMan

Yah there is only one way I know of. You replace the oxide layer with aluminum iodate layer. That will boost VOD 30 percent.

Active binder is needed. Aluminum with non active binder is a joke.

MineMan - 14-11-2021 at 09:37

Quote: Originally posted by ManyInterests

While this is not directly related to exact type of binder OP is talking about. Binders and plasticizing energetics is something that I didn't really start to understand until recently (and I have yet to make a plasticized anything). I will be primarily using rubber cement and bar and chain oil to plasticize ETN and RDX. Also I want to plasticize potassium chlorate as well (with and without sugar).

But one of the first things I read when starting out on energetics is the Improvised Munitions Handbook, which has among its first entries making plastic explosives out of potassium chlorate with 9 parts chlorate to 1 part vaseline/petroleum jelly. I've seen others that substituted wax for the petroleum jelly or a combination thereof. Others had them try to dissolve the jelly or wax first, or dissolve it and add it to lighter fluid/camp oil (almost the same thing) but that did absolutely nothing. The result was a very grainy, sand-like texture and wasn't plastic at all.

Is there any way of actually using petroleum jelly/Vaseline as a plasticizer? I'd really like to know.

Ahh. So you do want more then a few detonators. Knew it

ManyInterests - 14-11-2021 at 11:29

I do want to plasticize the leftovers, yes. :p

Microtek - 15-11-2021 at 08:43

The purpose of the vaseline jelly in the chlorate mixes is mainly to act as a fuel. The plasticity is secondary.

HTPB would be nice to work with, but is difficult to find in Europe (in my experience). Additionally, most of the efforts on this forum has been directed at making a moldable plastique, rather than a rigid PBX. For PBXs, I have been using non-crosslinked Viton dissolved in acetone.

Laboratory of Liptakov - 15-11-2021 at 09:55

Quote: Originally posted by ManyInterests

Is there any way of actually using petroleum jelly/Vaseline as a plasticizer? I'd really like to know.

Vaseline has weak bonding effect. You must use 40% for good bonding effect
with vaseline. With PIB /oil is 10% enoug. Maybe even 8% only for a same effect.
Also is possible use PIB / vaseline. But properties is necessary try on flour,
fine table salt and similarly. Answer not exist. Is necessary try it.

ManyInterests - 15-11-2021 at 16:33

Quote:

The purpose of the vaseline jelly in the chlorate mixes is mainly to act as a fuel. The plasticity is secondary.

Quote:

I see. So it isn't 9 parts chlorate 1 part Vaseline, it is 6 parts chlorate 4 parts Vaseline. I can try that out. It's interesting you mentioned that the vaseline is good for fuel, because when I did burn the sugar/chlorate mixture I tried to plasticize with vaseline (I use a generic brand) it burned quite viciously, more than just the sugar/chlorate alone.

Microtek - 16-11-2021 at 04:32

1:9 is correct for the cheddite you mentioned, it's just not very moldable. If you increase the vaseline content to 40%, it will be easier to mold, but almost impossible to detonate. Even if you do manage to set it off, performance will be very poor, due to the extremely rich (oxygen deficient) blend.

ManyInterests - 16-11-2021 at 19:43

I find it interesting that all instructions show 1:9 as a 'plastic' when that isn't accurate, but I have seen people make other energetics from the manual following the instructions as described, such as picric acid, DDNP, and others.

I think the PiB/motor oil or the rubber cement/bar and chain oil will make for a good plasticizer for chlorates.

At my local art supply store they sell pure liquid latex, would that work for a plasticizer, along with some 5W50 motor oil as a softener?

[Edited on 17-11-2021 by ManyInterests]

Laboratory of Liptakov - 16-11-2021 at 23:48

Basic ratio is PIB OB = - 342,2 motor oil has OB - 344, KClO3 has OB + 39,15. Next : 5% PIB + 5% Oil + 90% KClO3 = OB + 0.925.
Usually is better ratio slightly negative. Thus 5,5% PIB + 5,5% Oil + 89% KClO3. OB = - 2,898 counted on CO2. 6 + 6 + 88 will works also.
OB = - 7,720.

Microtek - 17-11-2021 at 06:43

Latex can work as a binder, but not as a plasticizer. From the context in which you use the term, I assume that was what you meant. Whether it works as a basis for a moldable plastique, I don't know. One problem is that the product called liquid latex is a dispersion of polyisoprene (natural rubber) particles in water. There is usually also some stabilizers (such as ammonia) to give it more shelf life. When the water/ammonia evaporates, the emulsion collapses and the particles adhere strongly to each other, forming a latex film. This limits the kind of charge you can prepare with liquid latex, since the water must be able to escape.
One possiblity is to make a granulated molding powder which is dried, and can then be pressed into whatever shape is required. The latex coating of the individual granules should then give you some cohesion, but it probably won't be moldable (which may or may not be an issue).

ManyInterests - 17-11-2021 at 16:12

I think with natural latex the type of explosive it would make is called a 'sheet' explosive instead of plastic explosive. They're preformed as a rubber-like sheet that can be cut and bent, but not molded in the same way plastic explosives can.

Microtek - 18-11-2021 at 23:51

Exactly. I still think it is possible to produce a more conventional charge geometry using the method I outlined above but, as you say, it won't be moldable. The question is if you really need moldability for the application you have in mind?

ManyInterests - 19-11-2021 at 11:51

I don't have anything specific in mind. I am just making them for the sake of making them. They're fun.

Brightthermite - 19-11-2021 at 17:28

Id like to see if that liquid tool dip would work to make a dense charge.
https://www.amazon.com/Performix-075815116048-Blue-Plasti-Di...

something like this