Poly-GLYN - Methods of solving the gassing problems of Poly-GLYN, a new theoretical approach?

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Abstract: This small thread discuss about a new theoretical possible, however not experimented low azide content GAP-GLYN co-polymer. This polymer could be cured with its azide groups to prevent the gassing problems with the original Poly-GLYN.
Note: My english is bad.
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Glycidyl azide polymer is energetic, however formulations for the high efficiency propellants today often contain energetic materials that are not very oxygen balanced. Take HMX and RDX for example, are only just enough to burn it self, therefore formulation is GAP and HMX/RDX can not achieve the best desired performce.

So we should turn our attention to Poly-GLYN(poly-glycidyl nitrate). Why Poly-GLYN? First, it can be uses cheap starting materials such as glycidol, and the only expensive chemical during nitration is acetic anhydride where Ac2O/HNO3 nitration is used. If produced on industrial scale, Poly-GLYN most likely will not be more expensive than GAP since GAP also need sodium azide, something not cheaper than Ac2O. However, Poly-GLYN have a handful of advantages and some deadly disadvantages.

Poly-GLYN Have a good stability, amazing density of 1.46 compared to GAP(1.3) [1], acceptable glass-transition temperature of -35, and it have a better OB than TNT (OB:-60.5%) Poly-GLYN has a structure of HO[2ONOCH2CH2CHO]n--R-- [OCHCH2CH2ONO2]nOH (Empirical formula :C3H5NO4) 2GLYN burn to give the product 5H2O, 3CO, N2, 3C. With most of it self burned and require only 3 more oxygen[1]. Therefore Poly-GLYN is more disired than GAP.

The deadly problem with Poly-GLYN is the stability of the polymer after curing with isocyanates. cured Poly-GLYN age very fast with gassing, which means it can not be used in propellants. This instability is the inherent problem with polyGLYN's structure and not dependending on the isocyanate used. The problem has been overcome by modification of the chain ends to give a diol terminated polyGLYN prepolymer.


Picture from reference [1]

However the diol terminated Poly-GLYN require many steps. First – nitration of glycidol to GLYN, then polymerization into Poly-GLYN, and the last step - changing hydroxyl-terimated-Poly-GLYN into diol-terimated-Poly-GLYN[2,3]. This production is expensive and unlikely to be scaled due to its cost. Further more, the diol terminated polymer is less energetic, it also require more isocyanates to cure, which give even less energetic properties. Here I present some theoretically possible method of manufacturing a low azide cotent GAP-GLYN-copolymer that could be synthesized in a single step.

First, Glycidol is mixed with epichlorohydrin in around 9:1 ratio respectively(more glycidol could be used, however it will negatively effect the curing process). After polymerizing with BF3-etherate compelex, the mixture is nitrated using Ac2O/HNO3, after the hydroxyl groups have reacted, sodium azide is added stoichiometrically to the mixture to turn the 10% epichlorohydrin into GAP.[4] The polymer will also be azido terminated because the hydroxyl terminated polymer will be nitrated, and be replaced by azido group in reaction with NaN3[5].



AT-GAP-GLYN-1/9 polymer (Azido-terminated poly-glycidyl azide and nitrate 1/9 polymer)

Density : 1.44 g/cm3(calc) (GAP = 1.3 g/cm3)
Tg: -50(guesstimate) (GAP= -45°C)
OB: -66%(calc) (each chain on GAP has an OB of -121.1, which require at least 4.5 oxygen to burn, while GLYN require 1.5O)

Elemental analysis :
14.35% Nitrogen
30.77% Carbon
4.31% Hydrogen
50.56% Oxygen

GAP1/9GLYN copolymer could then be cured with a range of liquid compounds containing have bis-propagyl or tris-propagyl group [6].


Picture from reference [7]

This curing method not only allow you control the amount of linkages present, but also produce strong tough polymer similar to isocyanate cured polymers[7]. After curing on the azido groups, this polymer will not age fast nor produce gassing properties.

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References

[1] Arthur Provatas - Energetic Polymers and Plasticisers for Explosive Formulations ñ A Review of Recent Advances, DSTO. April 2000.

[2]ISSN 20799780, Review Journal of Chemistry, 2012, Vol. 2, No. 3, pp. 240–262. © Pleiades Publishing, Ltd., 2012.

[3]Sreekumar Pisharath*, How Ghee Ang - Synthesis and thermal decomposition of GAPPoly(BAMO) copolymerMarch 2007

[4]端硝酸酯基叠氮醚聚的合成与性能 (Nitrate terminated GAP, i didnt find the auther, publication date, etc.)

[5]Edgar R. Wilson, Milton B. Frankel.- Azide-terminated azido compound ,US patent 4781861 Nov 1988

[6]Eva Landsem, Tomas L. Jensen, Tor E. Kristensen,*Finn K. Hansen,Tore Benneche, and Erik Unneberg -Isocyanate-Free and Dual Curing of Smokeless Composite Rocket Propellants Propellants Explos. Pyrotech. 2013, 38, 75 – 86

[7]Thomas Keicher*, Werner Kuglstatter, Siegfried Eisele, Tim Wetzel, Horst Krause - Isocyanate-Free Curing of Glycidyl Azide Polymer (GAP) with Bis-Propargyl-Succinate (II) Propellants Explos. Pyrotech. 2009, 34, 210 – 217 2009
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EDIT(woelen): Changed second picture on request of OP.

[Edited on 17-1-14 by woelen]

Quote: Originally posted by Cheddite Cheese

Azides and chlorinated solvents do NOT mix. Explosions result.

Quote: Originally posted by PHILOU Zrealone

There is a problem with your second equation you miss one carbon (CH2) in the first member and in the last...probably your -OH has glided to the right. R-O-CH2-CH(ONO2)(OH) and R-O-CH2-CH(OH)2 or R-O-CH2-CH2-CH(ONO2)(OH) and R-O-CH2-CH2-CH(OH)2 are related to aldehyd hydrate.

I didnt know that azido terminated polymer could be cured alone! Until I saw this.

http://link.springer.com/article/10.1007%2Fs13233-012-0033-2

The paper is said to use a copper catalyst in very small quantities to procede the reaction, however the solubility of the copper catalyst in the polymer they used is really really low, or just insoluble, the polymer they used had almost no polar groups in the polymer something like Glycidyl nitrate polymer might dissolve the catalyst(I have no idea what copper catalyst they used, if someone could help me on this, that'd be great!)

The problem with their experiment was that the copper catalyst did not dissolve although in very low %, so the curing took 1 week at 80 °C or 2 weeks at 60°C. This give challenging problems if energetic plasticizers were to be used, such as BTTN, TMETN, DEGDN, etc.

GNP's cost is significantly lower than GAP, however the extra steps it needs to make it azido or diol terminated makes it not worth it... any ways



Triazole polymer formation/Synthesis of Azido terminated GNP

[1] Byoung-Sun Min, Young-Chul Park, Ji-Chang Yoo - Triazole crosslinked polymer formed by the cycloaddition of azide end-capped polymer with dipolarophile acetylenic curative. Macromolecular Research April 2012, Volume 20, Issue 4, pp 429-432
[2]Edgar R. Wilson, Milton B. Frankel.- Azide-terminated azido compound ,US patent 4781861 Nov 1988
[3] Arthur Provatas - Energetic Polymers and Plasticisers for Explosive Formulations ñ A Review of Recent Advances, DSTO. April 2000.