December 12, 2019, 04:18:25 AM
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Topic: Which electrode-supporting material?  (Read 376 times)

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Offline Cantacoxinha

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Which electrode-supporting material?
« on: July 09, 2019, 01:26:10 PM »
We are doing some electrochemical measurements in ethyl acetate. One of the electrodes we used was a tiny disc mounted in acrylic (PMMA) cylinder and then polished. However, that polymer cylinder was badly damaged (partially dissolved?) by ethyl acetate when the current was applied.

Which material might be used as electrode support instead of acrylic? Glass is unfortunately excluded. Will PTFE or some other polymer tolerate ethyl acetate? Are such electrodes with PTFE commercially available?

Offline Enthalpy

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Re: Which electrode-supporting material?
« Reply #1 on: July 10, 2019, 02:43:19 PM »
Oi!

From the mechanical engineer point of view (I'm not a chemist), what you need is a "compatibility list" (search keywords) like this one
https://www.fireflysci.com/news/2019/4/4/gb015oa0azy4o7ran22h52ote7yvsh
which tells that "Ptfe" has excellent compatibility with "ethyl acetate". Unless the current does something mysterious to me.

If the desired part isn't available commercially for chemical apparatus, you could let your mechanical lab make the disk or cylinder out of some Ptfe rod. Give them the original Pmma part if the shape can be recognized, don't even make a drawing.

Ptfe is so weak that you can even shape it with a knife.

Offline Cantacoxinha

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Re: Which electrode-supporting material?
« Reply #2 on: July 11, 2019, 07:40:30 AM »
Thanks for answering!

We don't have a lab for making custom electrodes, does somebody know a supplier or producer of such PTFE-supported electrodes or a place where I could order these? I've been ordering compounds many times, but never an electrode.

Offline Grasshopper

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Re: Which electrode-supporting material?
« Reply #3 on: July 17, 2019, 06:21:46 AM »
Am I right in thinking that there are commercial electrodes that are housed in epoxy resin rather than PMMA? Cured epoxy should be resistant to a lot of solvents. If you need a certain size/shape of electrode, though, that could be a trickier problem to solve, and a good starting point might be to contact the manufacturer of your original electrode...?

Offline Enthalpy

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Re: Which electrode-supporting material?
« Reply #4 on: July 17, 2019, 04:29:56 PM »
At least Engineeringtoolbox mentions only a "fair" resistance of epoxy to ethyl acetate
https://www.engineeringtoolbox.com/chemical-resistance-epoxy-d_786.html

How accurate must the plastic part be? With a knife, you can cut Ptfe easily. With a saw or file, the difficulty is to hold the part in a vice, and not file beyond the final size.

Maybe hot-melt adhesive is worth trying, to build the plastic part from glue
https://en.wikipedia.org/wiki/Hot-melt_adhesive
This list tells that the main constituent, poly(ethylene vinyl acetate), is completely insoluble in ethyl acetate
https://www.eastman.com/Literature_Center/R/RES001.pdf
at least the trial is cheap and quick.

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