killswitch
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Is ethanolamine supposed to make MHN catch fire?
I had quite possibly my most harrowing experience with energetic materials today at 10:14 AM Eastern Time.
I attempted to stabilize a week-old batch of purified mannitol hexanitrate with the addition of one drop of a liquid base.
Diphenylamine is the preferred stabilizer for this purpose, but I had none on hand. I did, however, have ethanolamine on hand and attempted to
stabilize the mannitol hexanitrate with this substance.
It did not go as planned.
The pressed MHN immediately caught fire, and a gout of flame at least three centimeters in length shot out of the drinking straw. Remembering the
hard-earned wisdom of Yamato71, I made no attempt to extinguish it and instead retreated to a safe distance while all 1.5 grams of material burned
down, leaving a charred lump of polycarbonate plastic.
I'm assuming diphenylamine does not produce instantaneous ignition. So what mechanism did ethanolamine promote that diphenylamine would not?
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Dany
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hello Killswitch,
don't forget that nitrate ester are hydrolyzed by bases (e.g., sodium hydroxide). both ethanolamine and diphenylamine are bases but the former is a
much stronger than the latter. also, ethanolamine is an ambident nucleophile, this mean it can attack either by the -OH group or the -NH2 group. I
think that when you mix ethanolamine with MHN the amino group of ethanolamine will displace the nitrate group of the nitrated polyol. Apparently, the
reaction is exothermic and since the heat generated is faster than the heat dissipated to the surrounding the mixture will heat up to reach the
ignition temperature of MHN. what you get is called a thermal runaway. Diphenylamine is a weak nucleophile because the lone pair of the nitrogen is
conjugated with the phenyl group (that form many mesomers), so this lone pair is less available for nuclophile attack. Generally, diphenylamine is
added to nitrocellulose based propellant to capture the nitric oxide released during the decomposition of the nitrocellulose. It is known that the
decomposition of nitrocellulose is autocatalyzed by nitric oxide.
Dany.
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papaya
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Remainded me this: https://www.youtube.com/watch?v=bin_W1xVPfY
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Dany
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this is a nice video Papaya, but here the reaction is a fast oxidation of aniline by N2O4. this is not the case when pouring or mixing ethanolamine
and MHN.
DANY
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papaya
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Yes, but I think it's a bad idea to mix random amine bases to things that can give off NO2. OK, let's discuss what is there specific for diphenylamine
in stabilization of gunpowder and why monophenylamine (aniline in video) behaves differently.
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Dany
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First of all if you mix virtually any amine or even any carbonaceous substance with N2O4, you will get a hypergolic reaction because the organic
substance is reacting not with NO2 but with N2O4 and undergo a rapid decomposition-combustion reaction. N2O4 is on the edge of stability, as you see
in the video, if you warm it it will start to decompose to brownish gas (NO2):
N2O4l=2NO2g
as for diphenylamine that is used as a stabilizer in nitrocellulose formulation, once the NOx is formed the nitrogen of the amine react
with it to form probably a nitroso compound, but don't forget that you shouldn't compare the two situation (in the video and that of nitrocellulose)
because the reaction are different and the concentration of each component is different.
[Edited on 3-8-2013 by Dany]
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papaya
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OK, then teach us what must be used for stabilization and what cannot, but don't forget to provide citations, since post-factum interpretations of
anything doesn't mean one could predict something 
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