I want to make some STF by mixing polyethylene glycol and fumed silica. To my dismay, I found the original sample I ordered (Lucas DOT-3 synthetic
brake fluid) is not true polyethylene glycol, but rather some similar stuff. I found an OTC source, MiraLax, but this appears to be a white powder at
room temperature.
So my question to you is, is there a way to make this MiraLax permanently a liquid and still have it remain pure polyethylene glycol? If not, is there
an appropriate substitute to make a decent shear thickening fluid?battoussai114 - 4-9-2015 at 19:08
GREAT! JUST LOST A BIG PIECE OF TEXT
What I meant was, I don't know of any established techniques of reducing PEG molecular weight (higher molecular weight PEG is solid and, as it
decreases it becomes liquid). Maybe heat treatment will do, can't say for sure.
Try getting ethylene glycol from anti-freeze and use basic catalysis to get it to polymerize. If you look around it seems the amount of catalyst, and
its type, dictates how high the molecular weight will be. This way you can have some control over the PEG rheology which, I guess, will be important
to get nice results.elementcollector1 - 5-9-2015 at 06:45
I would assume that I want the molecular weight to be as high as possible without becoming solid, to which a cursory glance suggests a MW of about
700.
Of course, I have no idea about basic catalysis. I'm also at a college, with almost no access to equipment. battoussai114 - 5-9-2015 at 07:13
But basic catalysis should be easy (I guess), Potassium or Sodium Hydroxide is readily available as drain cleaner and I think its soluble in Ethylene
Glycol, in this case you'd have an homogeneous catalytic process and wouldn't have to worry about dispersion and all that stuff that makes
heterogeneous processes a pain. Just get the drain cleaner, calculate how much will be needed, add to the EG and mix throughly. I'm currently out of
the campus and don't have access to scientific papers, but there is probably some study somewhere about how reaction conditions influence the
molecular weight of the PEG when you use a basic catalyst.
I'm also at a college, with almost no access to equipment.
elementcollector1 - 5-9-2015 at 08:33
Sounds good. How would I tell the reaction had completed, if it went from a clear liquid to a clear liquid?elementcollector1 - 6-9-2015 at 17:09
On second thought, I've decided to use Oobleck instead. Much simpler to make. But now I have a bunch of brake fluid and fumed silica on hand - any
idea what to do with these?battoussai114 - 6-9-2015 at 21:23
But oobleck can't stop bullets... although silica stf alone can't either, I think they treat high resistance fibers with it.
Fumed silica makes decent sorption column packing depending on its shape. Is it powdered or pellets?
No ideas for the break fluid so far.elementcollector1 - 7-9-2015 at 06:54
Powdered.
I never needed it for bullet resistance, I'd just use UHMWPE for that.MrHomeScientist - 8-9-2015 at 07:33
Try it in a silicon thermite! Extremely finely powdered and pure, it should yield some nice Si.
I was going to suggest Oobleck until I saw you found it yourself. It's some crazy stuff. We built a nice little demonstration piece where you can put
it on a large speaker and play different tones through it - one of the weirdest things I've seen!careysub - 8-9-2015 at 10:50
[Edited on 8-9-2015 by careysub]battoussai114 - 8-9-2015 at 14:07
Powdered won't do for absorption columns. About the brake fluid, toss it in a pyrolysis chamber and make some syngas? Really can't think of anything
interesting.
