Sciencemadness Discussion Board

very viscous styrene

mackolol - 26-3-2022 at 14:31

Recently I have purchased some styrene. It smells just like I would imagine: styrofoam after heating, it reacts with chlorine and bromine foming solid...

What boggles me though is its enormously high viscosity. I expected mobile liquid (I'm even pretty sure styrene is a mobile liquid) and instead got super thicc, syrupy liquid.

I would compare it to anhydrous glycerol!

Also, it's completely colorless, even after a month of storage after being opened.

Can it be polymerisation? Rather unlikely, because it's still completely colorless. Maybe it's stabilised with something that makes it this way?

Can anyone give me some hint?

numos - 26-3-2022 at 18:41

This sounds like polymerization to me.

Styrene doesn't keep long, a few years at -20 C, less than a year at room temperature if not stabilized. Polymerization to polystyrene wouldn't impart any color so the fact that it's colorless might not mean much. Styrene is one of those chemicals that you kind of need to distill directly before use anyways, so I suggest to distill a small amount and see if you can get anything less viscous out of it.

Just to note, pure styrene is viscous too, not like glycerol, but still viscous. Stabilizers are most likely small amounts of radical traps and would not affect viscosity.

UC235 - 26-3-2022 at 19:15

Pure styrene is actually less viscous than water. Fortunately, styrene can be partly recovered by distillation. Very polymerized material could be destructively distilled followed by fractionation of the initial distillate which contains a fair amount of oligomeric material. The same process can be used to make styrene from solid polystyrene plastic

mackolol - 27-3-2022 at 00:29

That's what I wanted to avoid :/ . There's going to be a lot of crap, carcinogenic and hard to remove...

unionised - 27-3-2022 at 01:58

Styrene is carcinogenic (though not strongly so).
Most of the material should distil . What will be left is essentially polystyrene (which is practically non- toxic) and a bit of "charred" stuff.
There are plenty of solvents that will remove the polymer- I guess ethyl acetate is probably the least toxic.

You will probably end up scrubbing the char out mechanically unless you are prepared to use something like hot sulphuric acid.

Keras - 27-3-2022 at 02:14

You can stabilise styrene using hydroquinone or BHT

karlos³ - 2-4-2022 at 21:47

Stabilised monostyrene keeps quite well, bought mine 4-5 years ago and its still waterlike from the viscosity.
The key for me(at least thats what I want to believe :D) is, directly after receiving the stuff in a can, to bottle it up and to put it in several bottles, a small one for "regular" use, and larger ones for storage.... I actually have opened the large bottles only 5 times over all the years since I bottled it up.

What speaks for the still surpreme quality, the styrene could be as it is, undistilled even directly from the bottle, be turned via bromohydrin(NBS), base to the epoxide, followed by ammonolysis with 2-amino-2-methylpropanol/isobutanolamine, be turned into crude base with 49,xx% and after oxalate salt formation, still after some losses, over 41,xx% yield, and that is based on the raw, undistilled alkene!

When I tried the same with methylamine, it did not work that well(in yield) or clean(unlike the same product made from acetophenone) yet, and the ethylamine trial I still need to work up.

The styrene is still quite good though, after all these years, water like from its viscousity.

Although I did notice some needle like crystals when pouring some styrene into a beaker, and adding solvent to wash it out, at that point suddenly some large needles will become visible(and audible, making *pling* sounds due to the size :D).
Seems like they had a few years to grow in there :P
Its not much though, but it is noticeable, I haven't weighed them, but it was like ~500mg's at most the last time I measured 24g of styrene out.

unionised - 3-4-2022 at 03:10

"Although I did notice some needle like crystals "
Any idea what they were?

mackolol - 3-4-2022 at 04:34

They were probably polymerised stuff. I notice similar behavior in my styrene. Especially when I chlorinate it. Then on addition of acetone or methanol, there comes out white plasticky goo that sticks to everything and reminds me of nylon from NileRed's videos...

Anyways, what I have done was distillation of my styrene and as you all might expect that was enough. I was left with transparent goo in my flask, which was removed by refluxing few times with toluene (resulting in similar solution I started with, but this time instead of styrene, toluene was the solvent).

Didn't bother to destructively distill that using burner, only tried to with my 500C cheap hotplate and although I've read that polystyrene decomposes at 350C with base catalyst, the decomposition rate with potassium carbonate was negligible in that temp (the stuff got slightly brown).

Well that's interesting what you tell me Karlos , I must have gotten some really old or unproperly handled shit...

unionised - 3-4-2022 at 05:17

Polystyrene dissolves in styrene, so it can't be the crystals.

mackolol - 3-4-2022 at 06:10

Quote: Originally posted by karlos³  

Although I did notice some needle like crystals when pouring some styrene into a beaker, and adding solvent to wash it out, at that point suddenly some large needles will become visible(and audible, making *pling* sounds due to the size :D).

Probably some polar one for example the ones I have mentioned.

karlos³ - 3-4-2022 at 13:36

Quote: Originally posted by unionised  
Polystyrene dissolves in styrene, so it can't be the crystals.

Does DMSO dissolve polystyrene too, though? :P
Because they only precipitated on addition of DMSO from the styrene.

Or was it after I washed the beaker with water?
I'll pay attention next time.
E: oh! My notes do say it was DMSO containing around ~10% of H2O which I used to rinse the beaker!
Because that was alsoo the reaction solvent used there.
That would explain the precipitated crystals much more than plain DMSO would have.

@mackolol soon going to check back in home... course of the next week at last, I have so, so many interesting things to report about :)

[Edited on 3-4-2022 by karlos³]

unionised - 4-4-2022 at 04:40

I have never seen crystalline polystyrene, so I'm still puzzled.

Triflic Acid - 8-4-2022 at 19:48

Polymerized styrene can form hard clear chunks that might look like crystals, sending photos would help tell the difference.