Sciencemadness Discussion Board

Super easy way to make your own diaphragm?

MeshPL - 12-6-2015 at 07:58

Hello everybody!
If everybody knows this obvious fact, I'm sorry for wasting your time.

But I've just read, you can make a diaphragm for electrochemical cell with nothing else than some PE, salt and water.

How? Just by mixing finely powdered salt with molten PE, shaping it and washing salt out with water. It has sense, after all, but seems too easy to be possible :o.

Any thoughts?

Source:
https://www.google.pl/url?sa=t&source=web&rct=j&...

Edit: Typos removed. PE stands for PolyEthylene.


[Edited on 12-6-2015 by MeshPL]

Loptr - 12-6-2015 at 08:03

Is PE an abbreviation for polyethylene plastics?

MeshPL - 12-6-2015 at 10:25

Yup. PE stands for polyethylene. Preferably low density, due to lower melting point. (Just above boiling point of water) Not sure about differences in chemical resistance of different polyethylene types though. PCV, rubber and cellulose acetate are supposedly also usable, but polyethylene is commonly available in form of plastic bottles. Also, the source mentions starch as salt eplacement, but removing it from plastic matrix requires use of sulphuric acid.

S.C. Wack - 12-6-2015 at 15:37

Perhaps an alternate route to polyethylene bags for electrochemical cells would be recycling those within a deceased car battery.

byko3y - 12-6-2015 at 15:52

Salt is supposed to be insoluble in a used solvent, because otherwise it all will go into solution and the diaphragm will be left with holes in it. And salt has low adhertion to the plastic, so nothing except friction would hold those salt particles.
What you say sound more like a membrane. I made one using LDPE and cationite, but the membrane should have a specific shape and thickness, and also you need to hold it between two sections of cell without any leaks, so I've abandonned the idea because for now I see/have no suitable tools.

WGTR - 12-6-2015 at 16:23

There is a very curious usage of the word "brain" in this publication. Can anyone shed some light on this?

For non-demanding applications (fairly neutral pH) I've used cellophane. That is, real cellophane, not "Cello", "Cello-Wrap", "Super Cello", or whatever the heck people call non-cellophane, cellophane substitutes. I was surprised at how hard it was to find locally, I finally had to order it online from Paper Mart.

Reminds me of

franklyn - 12-6-2015 at 19:04

the mother of a young woman finds the diaphram her daughter uses and asks her " what's this for " , she answers , err ummm oh it's a shower cap for my cat. :D

.

MeshPL - 12-6-2015 at 22:44

So, will this "PE with tiny holes left from salt being washed out" work?:( You guys don't sound like it would.
Quote:

byko3y said:

Salt is supposed to be insoluble in a used solvent, because otherwise it all will go into solution and the diaphragm will be left with holes in it. And salt has low adhertion to the plastic, so nothing except friction would hold those salt particles.


You're talking about ion-selective barrier?

violet sin - 13-6-2015 at 21:25

you could try some tyvek, available in tons of forms. mail envelopes, painters jump suits, house wrapping vapor barrier material, CD/DVD protective sleeve's and much more. I have a coouple jump suits for sanding and have received many ebay parcels in the envelopes.

https://en.wikipedia.org/wiki/Tyvek
" Tyvek /taɪˈvɛk/ is a brand of flashspun high-density polyethylene fibers "
" Water vapor can pass through Tyvek, but liquid water cannot. All of these properties make Tyvek useful in a variety of applications. "

http://www.faqs.org/patents/app/20140134498
" Patent application title: SEPARATOR MEDIA FOR ELECTROCHEMICAL CELLS "
" Battery separators used in alkaline batteries at present are commonly formed of a polyolefin, preferably polypropylene, polyamide or nylon non-woven sheet. "
" Comparative Example A was Tyvek® 1056D (available from DuPont of Wilmington, Del.), a commercial flash spun nonwoven sheet "

-------------

seems like you may be able to just cut a shape and use as is with relative suces depending on the source/form of tyvek you have access to. I know the envelopes are hard rolled ( so it would seem) as they are super glossy with no apparent breath-ability. the jumpsuits are much more fibery and seem to only have been rolled with a textured roller to bond every so often in a regular pattern. the house wrap material seems to be more like the envelopes in texture than the jump suits. but you may have seen the CD/DVD case backing material, it is much more fiber like with even less roller bonding than the suit material.

but the people using it in the linked patent sulfonated it using U.S. Pat. No. 3,684,554 = SO3 treatement,.. eww.
https://www.google.com/patents/US3684554
I just honestly didn't look too long for something to link, grabbed one of the first that showed up google searching "tyvek diaphram for electrochemical cells"

give it a try, practically free material.

macckone - 14-6-2015 at 14:35

My favorite is polyethylene HEPA vacuum bags.
Some are paper and some are polyethylene with a certain pore size.
The polyethylene are the ones you want.
These are also useful for some vacuum filtrations.

This is a diaphram cell not a membrane cell.

A membrane cell uses an ion selective and that only allows certain
kinds of ions through. They are usually made from special polymers
and are often unidirectional. Meaning they are only ion selective in
one direction.

MeshPL - 15-6-2015 at 04:13

Quote:

macckone said:
This is a diaphram cell not a membrane cell.


Emm... the only one talking about membranes was byko3y.

I'm sorry, if anyone misunderstood me, but what I was describing was nothing else than porous, non-ionoselective diaphragm. Seems like there are some alternatives to it, though. HEPA vacuum bags are a nice idea, Tyvek is also interesting.

GrayGhost - 15-6-2015 at 16:26

Quote: Originally posted by macckone  
My favorite is polyethylene HEPA vacuum bags.
Some are paper and some are polyethylene with a certain pore size.
The polyethylene are the ones you want.
These are also useful for some vacuum filtrations.

This is a diaphram cell not a membrane cell.

A membrane cell uses an ion selective and that only allows certain
kinds of ions through. They are usually made from special polymers
and are often unidirectional. Meaning they are only ion selective in
one direction.


For sodium hydroxide synthesis im used clay pot is not very good, for membrane I read the Naflon is used but is expensive and my city there is not.

macckone - 15-6-2015 at 20:46

Nafion can be mail ordered from the Nafion store. I haven't had any luck getting the better varieties designed for electrolytic cells. If someone knows of a good source we would all appreciate it.

GrayGhost - 16-6-2015 at 09:09

Someone test cellophane?