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Author: Subject: Spontaneous Polymerization of Styrene
JJay
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[*] posted on 13-7-2018 at 14:47
Spontaneous Polymerization of Styrene


I have been running into an increasing number of uses for styrene (although preparation of trinitrostyrene polymers probably won't be one of them), so I've been giving some serious thought to preparing styrene by pyrolysis of polystyrene followed by fractional distillation.

Chemists on YouTube stress that unstabilized styrene can go through an exothermic spontaneous polymerization reaction that is potentially dangerous. They also state that styrene has a strong and offensive odor:

https://www.youtube.com/watch?v=6tEs7P6UUVQ
https://www.youtube.com/watch?v=8dJjsYyyQ2Q

I melted a few styrofoam cups in the campfire as a child, so I think I know what styrene smells like (a kind of sweet smell that is a cross between burning plastic and Lysol). Obviously, I don't want to bother my neighbors with that kind of odor. Is there a serious risk of stinking up the neighborhood if I distill a small amount of styrene?

Of more concern is the risk of spontaneous polymerization. I am not extremely worried about it, but I do recognize that there are some serious risks, and they should be addressed. Can spontaneous polymerization generate enough heat to ignite unstabilized styrene if it is stored at room temperature? I have some hydroquinone and a vacuum pump. Can styrene be safely distilled without a vacuum if it is stabilized with hydroquinone?




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Metacelsus
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[*] posted on 13-7-2018 at 16:19


The hydroquinone won't distill with the styrene into the fractionation column, so you could potentially get polymerization in the column (which would be really annoying to clean). Given that you have a vacuum pump, I would suggest using it.



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JJay
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[*] posted on 13-7-2018 at 16:48


Good point. I think gasoline dissolves polystyrene pretty easily, but the less mess the better.

[Edited on 14-7-2018 by JJay]




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MJ101
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[*] posted on 14-7-2018 at 06:40


@JJay: I can attest to that. I've seen unsavory types add crushed styrofoam cups to molotov coctails to thicken the incendiary.

Are there any additives in the gasoline that would hinder the reaction at later stages?

If so, I guess you could fractionally distill the gas, although that sounds dangerous. :)

Just a beginner's thoughts...
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JJay
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[*] posted on 14-7-2018 at 07:12


I have read about people making napalm that way, but I've never tried it. I can tell you that pouring gasoline into a Styrofoam cup doesn't work out well.

I've never done it, but I think fractionally distilling gasoline would be a good source of large volumes of cheap nonpolar solvents when you don't particularly care about exactly what the solvent is. It's more dangerous than distilling acetone but less dangerous than distilling ether.

I'm not sure exactly what the additives in gasoline would do to styrene, but I definitely don't want any gasoline in my styrene since I don't know exactly what is in the gasoline. If it contains xylenes, they could be hard to remove.

Oh and as far as additives in gasoline inhibiting the reaction go, I have in mind 3-4 particular reactions for styrene: hydrohalogenation (Markinokov and anti-Markinokov), chlorohydrination, and Heck arylation. I might try expoxidation, nitration, hydroboration, and polymerization also.

Trinitrostyrene is an explosive. Unlike styrene, it doesn't polymerize easily.

[Edited on 14-7-2018 by JJay]




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wildfyr
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[*] posted on 17-7-2018 at 13:28


Styrene does have a strong distinctive odor. Its one that I would identify immediately as "terminal alkene" odor. Neighbors will identify it as "weird chemical smell."

Usually dangerous autopolymerization is a matter of scale. If you have 10 grams, then even if it all spontaneously polymerizes, not much heat can build up. If you have 200kg then there is that much more "potential" energy. There certainly have been serious industrial accidents from runaway polymerization of pure monomers.

I personally wouldn't be worried about storing up to about 1 kg, but I would personally put it in the fridge, and add inhibitor. At least half of the reason is that storing it at RT without inhibitor will cause it to oligomerize (slowly) and you will end up with crap that needs to be distilled again.

I've distilled styrene (50-100 g?) in a formal lab setting without a problem. It won't polymerize in the distillation head. Why not do it under vacuum to make it easier though?

[Edited on 17-7-2018 by wildfyr]
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[*] posted on 17-7-2018 at 13:34


Trinitrostyrene would probably make an excellent anionic polymerization monomer, but such reactions require very air/water free conditions and clean materials.

Its unparalleled for living polymerizations.
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