Sciencemadness Discussion Board - Help find out what LZY is - paper on a potentially viable cryogenic solid propellants using H2O2

Help find out what LZY is - paper on a potentially viable cryogenic solid propellants using H2O2

DubaiAmateurRocketry - 2-11-2015 at 15:24

http://onlinelibrary.wiley.com/doi/10.1002/prep.201400219/ep...
This paper talks about a method of curing a solid propellant with H2O2 as their oxidizer and an unknown ( maybe the author did not want to tell ?) polymer called LZY.

The hint is in the paper -

when they said...

Unfortunately,almost all binder system used in conventional solid propellant can’t be com-patible with 98%H2O2,such as HTPB, CTPB, and PU et al.Liquid room temperature vulcanized silicon rubber is an ex-ception. It has a perfect compatibility with 98 %H2O2 and can cure at room temperature with the existence of 98 %H2O
.However,the main chain of silicon rubber contains many silicon¢oxygen bonds, which can be turned into sili-con dioxide during combustion process. This combustion product has a very negative effect on Isp performance. So we refer to the curing mechanism of liquid silicon rubber for reference and synthesize a hydrocarbon binder with the same functional group as liquid silicon rubber by ourselves,

...

I am not sure what this polymer look like..

Any guesses ?

Bert - 2-11-2015 at 16:56

I would like to see the rest of the paper before hazarding a guess-

DubaiAmateurRocketry - 2-11-2015 at 17:03

Did the link not work ?

if it does not, here is the paper.

Attachment: Zhang_et_al-2015-Propellants,_Explosives,_Pyrotechnics.pdf (891kB)
This file has been downloaded 734 times

Bert - 2-11-2015 at 18:14

Rest of the descriptive paragraph:

Quote:

Unfortunately,almost all binder system used in conventional solid propellant can’t be com-patible with 98%H2O2,such as HTPB, CTPB, and PU et al. Liquid room temperature vulcanized silicon rubber is an exception.

It has a perfect compatibility with 98 %H2O2 and can cure at room temperature with the existence of 98 %H2O

.However,the main chain of silicon rubber contains many silicon-oxygen bonds, which can be turned into sili-con dioxide during combustion process. This combustion product has a very negative effect on Isp performance. So we refer to the curing mechanism of liquid silicon rubber for reference and synthesize a hydrocarbon binder with the same functional group as liquid silicon rubber by ourselves,
named LZY, but its main chain is comprised of saturated carbon-carbon bonds with no silicon-oxygen bonds. Experimental results show that the LZY binder system is compatible with H2O2 and can ensure SPHP cure at room temperature successfully.

Silicon rubber

[Edited on 3-11-2015 by Bert]

DubaiAmateurRocketry - 2-11-2015 at 19:58

So a siloxane terminated rubber ? such as siloxane terminated polyurethane ? for example.. http://pubs.acs.org/doi/abs/10.1021/ja209328m this ?

Bert - 2-11-2015 at 20:39

After beating about the net, I suspect that either the author's descriptive English or my understanding of polymer chemistry may be less than perfect- Almost certainly the latter.

deltaH - 3-11-2015 at 11:56

It's probably polyisobutylene (PIB), the same stuff used as the binder for C4.

http://www.tpcgrp.com/tpc-group/products/polyisobutylene-150...

It cures to form butyl rubber:

https://en.wikipedia.org/wiki/Butyl_rubber

Now I want my prize

aga - 3-11-2015 at 12:00

All sounding familiar deltaH.

Time to make some S₂Cl₂ again ?

[Edited on 3-11-2015 by aga]

deltaH - 3-11-2015 at 12:05

ha ha, yes it did remind me of that! Anyway, in this case they wouldn't have vulcanised it, they would have cross-linked it with peroxide most likely, since it's there in abundance and it's done at RT.

For some reason polyisobutylene doesn't have a wiki, there's only the butyl rubber article about it (which is vulcanised PIB), but you can see the structure from that article, it's basically the hydrocarbon equivalent of polydimethylsiloxane for the most part with some residual double bonds available for cross-linking.

PIBs are transparent viscous liquids which fit the pictures in the paper posted.

[Edited on 3-11-2015 by deltaH]

DubaiAmateurRocketry - 3-11-2015 at 14:04

Quote: Originally posted by deltaH

It's probably polyisobutylene (PIB), the same stuff used as the binder for C4.

http://www.tpcgrp.com/tpc-group/products/polyisobutylene-150...

It cures to form butyl rubber:

https://en.wikipedia.org/wiki/Butyl_rubber

Now I want my prize

Ughh that could be the main chain of the polymer, paper says

...

'' Liquid room temperature vulcanized silicon rubber is an exception ''

... etc

synthesize a hydrocarbon binder with the same functional group as liquid silicon rubber by ourselves

and....

'' but its main chain is comprised of saturated carbon-carbon bonds with no silicon-oxygen bonds ''

There is still silicon in the rubber though, but there is no S-O bonds !!! and that there is saturated carbon-carbon bonds, which is a characteristic PIB inhibits. So LZY is a rubber that has a main back bone similar to PIB, but also has functional groups of trimethylsilane in the polymer? for example (CH3)3-Si- R ?

Bert - 3-11-2015 at 14:08

I do not thnk the article states that their is still Si in the backbone, I read it to mean there is NOT. But English is no the author's first language.

Crap tons of copolymers are feasible. I got lost looking at the possibilities and trying to cross correlate with various lists of materials approved for contact with 100% H2O2.

deltaH - 3-11-2015 at 21:14

Oh crap, I wrote a long reply, posted it, then edited it with delete by accident :mad:

I don't have much time now, but I think we can safely say the backbone is PIB, the question is how they functionalised it to cure it at RT.

Here they state:

Quote:

However, the main chain of silicon rubber contains
many silicon¢oxygen bonds

Why use the word many specifically here? I think it was a slip hinting that they use some (as opposed to many). Also:

Quote:

So we refer to the curing mechanism of liquid silicon rubber for reference and synthesize a hydrocarbon binder with the same functional group as liquid silicon rubber by ourselves...

They may indeed have used the industrial silicone based cross-linker because it's cheap, readily available and would work quickly.

The amount of silicon dioxide thus produced would be small because the cross-linker is only used in small amounts.

Here's a document that describes the chemistry the silicon cross-linkers in fair detail:

http://www.gelest.com/goods/pdf/reactivesilicones.pdf

Now to figure out which one would react with PIB and still be compatible with the peroxide and aluminium later on... well there's a wide range given in that document, I'm sure you can find one to do the job.

[Edited on 4-11-2015 by deltaH]

Bert - 4-11-2015 at 05:55

Interesting read, I forgot to eat breakfast.

Characteristic we want:

Room temperature cure (apparently, the peroxide catalyzed silicon rubbers mentioned in the Gelest PDF are HEAT CURED)

-----------

Characteristics we DON'T want:

Off gassing/foaming/bubbles produced during cure. Voids from off gass provide irregular additional burning surface area in finished propellant are generally BAD.

Any marked reactivity towards H2O2, the stabilizer added to the peroxide, Aluminum, absorbent crystals used as the peroxide carrier.

---------

Additional questions:

Can we determine the exact stabilizer used- The non stabilized propellant had significant weight loss and was turning into "Swiss cheese" in storage, looked like a guaranteed CATO.

What happens when you FREEZE a propellant grain with large amounts of H2O2? How storable under non climate controlled conditions would this class of propellant be?

Repeated mention in paper of the cured binder being less STIFF than the common ammonium perchlorate composite rocket fuels- And a clear mention that only static testing had been done.

Under heavy acceleration, soft rubbery fuel grains can SLUMP. Potentially pulling away from bonding with case walls or even tearing, resulting in increased burning area, higher pressures and (usually) a CATO. I recall some hobbyist builders hitting a wall around "O"class motors with HTPB formulations that had worked beautifully for smaller motors, the rubber needed to be stiffened up for the high acceleration desired. Some very expensive KABOOMS before they figured that one out...

deltaH - 4-11-2015 at 10:29

About the functionalisation of PIB, from the Gelest documentation I see that Si-H can be coupled to CH2=CH- and that alkoxy silanes can cross link with each other by hydrolyzing first (eliminating an alcohol) and then condensing to form Si-O-Si (eliminating water) at RT.

So I would like to propose that PIB (there are specific types in the link I provided earlier that are rich in terminal olefins) is reacted with something like this:

Structure.JPG - 5kB

"trimethoxysilane"

That requires a platinum catalyst (Pt/C?) :mad:

, but on the bright side, you can filter it all out afterwards.

Now you have PIB terminated with alkoxy silanes which can cure in the 'normal' way by hydrolysis at RT.

Trimethoxysilane is pricey though, so this is probably not what they did, but one get's the idea, now to find the right low cost readily available silicon reagent to do something similar.

[Edited on 4-11-2015 by deltaH]

DubaiAmateurRocketry - 4-11-2015 at 14:21

Quote: Originally posted by deltaH

Oh crap, I wrote a long reply, posted it, then edited it with delete by accident :mad:

I don't have much time now, but I think we can safely say the backbone is PIB, the question is how they functionalised it to cure it at RT.

Here they state:

Quote:

However, the main chain of silicon rubber contains
many silicon¢oxygen bonds

Why use the word many specifically here? I think it was a slip hinting that they use some (as opposed to many). Also:

Quote:

So we refer to the curing mechanism of liquid silicon rubber for reference and synthesize a hydrocarbon binder with the same functional group as liquid silicon rubber by ourselves...

Delta H,

I think when the author said ..

''However, the main chain of silicon rubber contains
many silicon oxygen bonds''

They were talking about the reasons why they did not use the industrial silicone rubber. They said because the SO2 would hurt the Isp, which is why they developed another rubber called LZY that produce lower SO2 so it would effect the Isp much less.

[Edited on 5-11-2015 by DubaiAmateurRocketry]

deltaH - 4-11-2015 at 20:49

So you think that the PIB is cross-linked a non-silicon way?

DubaiAmateurRocketry - 4-11-2015 at 23:28

Oh it definitely does, just using much less silicon.

They said they do it without having Si-O bonds (LZY rubber).

do they mean R-Si(CH3)3, instead of R-Si(OCH3)3

[Edited on 5-11-2015 by DubaiAmateurRocketry]

deltaH - 5-11-2015 at 10:01

I don't see how R-Si(CH3)3 could be crosslinked.

DubaiAmateurRocketry - 5-11-2015 at 18:04

Me too. hehe. I am not sure if the author had another method of curing ? So.. after all it might not have silicon at all as Bert said.

Bert - 5-11-2015 at 18:32

(Bert busily reads more on polymer chemistry and keeps his pie hole shut)

deltaH - 5-11-2015 at 20:38

Well, if the PIB had hydroxyl groups instead of double bonds, then you might have used the 'silly-putty' trick of adding boric acid to cross-link it. Even if it just turned into a gel, it would be (beeping) hard when frozen.

BTW Bert, the peroxide cure mentioned that cross-links double bond is only high temperature because the organic peroxide reagents used require high temperature to form the radicals required for the reaction. If you use other methods to form those radicals at RT, it should still work.

As an example, ferrous salts reacts with H2O2 to form radicals (Fenton chemistry), but unfortunately this is a catalytic process and will quickly decompose all the H2O2 as well... obviously not viable.

However, instead of Fe(II), you might use Ti(III) to do something similar. Ti(III)=>Ti(IV) with H2O2 might generate the required radicals, but if the end result is Ti(IV) peroxide complexes, then it's dead, no?

Here's something from the literature, though there's way more out there:
https://books.google.co.za/books?id=gr1hTponjtQC&pg=PA210&lpg=PA210&dq=ti(III)+fenton&source=bl&ots=F0lxe4vlJM&sig=YlPiKEIs2SR Gw-Wu1Yv_v83nnGw&hl=en&sa=X&ved=0CBwQ6AEwAWoVChMI-6XGiPz6yAIVCcMUCh0kdgIB#v=onepage&q=ti(III)%20fenton&f=false

Seems such a shame to not use the peroxide that is there already in such abundance!

[Edited on 6-11-2015 by deltaH]

Bert - 6-11-2015 at 04:07

Quote:

Even if it just turned into a gel, it would be (beeping) hard when frozen.

I read the paper to mean this procedure is intended to produce a solid fuel that can be manufactured, stored and used AT ROOM REMPERATURE. Why are others repeatedly referencing "frozen"?

Whole point of solidifying the liquid oxidizer by absorbing the H2O2 in poly sorb crystals and using a room temperature vulcanizing rubber!

deltaH - 6-11-2015 at 09:40

Oh... I was under the impression it was going to be frozen. If gels would work, then you might as well mix aluminium powder with agar gum and water and make propellant that way. I don't think the non-frozen versions work so well or do they?

DubaiAmateurRocketry - 7-11-2015 at 13:55

Does all polyacrylate salts have insane absorbent power ? Such as ammonium polyacrylate ?

deltaH - 8-11-2015 at 02:30

You mean swelling/thickening power? There are easier versions that are OTC, like xanthan gum (available in some supermarkets and health shops as thickeners). I think they would spontaneously react with HTP though, probably the same for acrylates

But good thinking, maybe not and worth a try.

BTW, hydrocolloids can be cross-linked simply by mixing in a small amount of calcium salts in solution. I used to do this as part of food chemistry experiments.

Sodium alginate (Gaviscon syrup for heart burn) also cross-links like mad with a little calcium, as would xantham gum powder.

Just dissolve a few percent of the gums to get a thick solution and then stir in your calcium salt solution, the downside is that gelation is very fast.

[Edited on 8-11-2015 by deltaH]

deltaH - 8-11-2015 at 02:50

I suggest if you go the hydrocolloid route, dissolve 1-5% of the hydrocolloid powder (e.g. xantham gum or sodium alginate) to make a thick solution, then when you're ready to cast, mix in a small amount of a calcium salt powder straight in with rapid stirring, not solution, this way it will form instantly a skin of gel around the particles and temporarily prevent the whole thing from setting into a jelly, this skin that forms around the particles would be permeable to calcium ions and after some time the whole mass will set. With the hydrocolloids, you might need to let the solution stand for quite long (before adding calcium salt) to let the bubbles escape that formed during dissolving the gums, this could be a problem when what you have in there is HTP. Then again, if you can pull a vacuum slowly, you will get rid of the bubbles in no time.

[Edited on 8-11-2015 by deltaH]