Highly inert liquid polymer?

[tabletop]

Hello,

I require a liquid to use as a barrier over some very reactive metal elements to avoid oxidization. I would now like to try polymers. Any suggestions for a highly inert liquid polymer (at room temp)? Halocarbon oil sounds like a start......

 

[patprimmer]

I thought engine oil or white grease.

Regards

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Demon3]

Potassium metal is very reactive and stored in paraffin oil. I would not use any chlorinated materials because they can react with aluminium and explode. Such an explosion destroyed a whole lab at my university.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[btrueblood]

Silicone oils might work too, and are less reactive than pure paraffins.

 

[Compositepro]

The above suggestions are very good. Why are you asking for a "polymer". Technically anything liquid at room temperature is not high in molecular weight and should not be called a polymer. The suggested materials are usually refered to as "oils".

 

[tabletop]

Thanks for the input. I will give some of those a try. Mineral based oils have failed so far. Anyone know much about polyphenyl ether other than that it's expensive and hard to get. It sounds ideal.

 

[Compositepro]

How have they failed? Mineral oils are hydrocarbons and prone to oxidation. Silicone oils are more oxidation resistant. You might look at heat transfer oils which are designed to be as inert as possible at elevated temperatures.

 

[Demon3]

Addition of antioxidants such as vitamin E or other hindered phenols would greatly improve oxidative stability of the organic material.

Some metals catalyse degradation of organics. Transition metals such as copper, iron, chromium and vanadium are particularly bad. These can be deactivated by addition of complexing agents.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[patprimmer]

I thought we were trying to avoid oxidation of the metal, not oxidation of the polymer. Rather than inert, a mild reducing agent might help by being sacraficial re oxidation.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[btrueblood]

Ditto what Pat wrote. Tabletop, could you tell us what metal you are talking about, and what you are trying to protect (maybe also what you've tried so far). Are you the guy that sells the displays of all the elements of the periodic table, mounted in an actual table?

 

[tabletop]

No Im not selling elements, though I have bought off him and he uses argon as a shield. I require a liquid as a shield.

The metals are copper, tin, iron, nickle, gallium. The trouble element is gallium. A liquid abouve 29 degrees C it forms an instant skin of oxide when exposed to everything I've tried. I've tried silicone, mineral and hydrocarbon oils and some work well for all but gallium.

Like to work my way through some of these advanced oils

http://www.vacuumoil.com/vacuumpumpoil.htm

 

[patprimmer]

What happens to gallium if you treat it with silver dip. I think it is a sodium thiosulphate or sodium hydrosulphite solution in water.

If that works, you need to find a similar reactive material that will dissolve in your chosen oil.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Demon3]

I have some gallium, interesting stuff. No liquid is likely to help because all liquids are highly permeable to oxygen, so are all rubbers by definition as both have lots of free volume.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[btrueblood]

Could you use another material, e.g. aluminum, in the same tube to act as an oxygen getter?

You may need to de-aerate whatever grease or oil you are using before pouring it into the tube; try cylcing the oil under alternating vacuum and inert gas (note that nitrogen is not necessarily inert for gallium). Would agree with demon3 you need to look at whatever the tube's seal is made from to limit diffusion of oxygen.

 

[tom1953]

FWIW, Lion Copolymer produces liquid EPDM and EPM polymers (

http://www.lioncopolymer.com/products-chart.htm?e=ProductFamily&id=7)

that might be of use. The used to (and may still) be used as encapsulants for cable splicing applications.


Tom Jablonowski, TSE Industries, Inc.

http://www.tse-industries.com

 

[tabletop]

Gallium attacks aluminum. I will have to look into the concept of "oxygen getters". I guess iron should work too?

The container is acetal and sealed with epoxy. The idea of the liquid is so I can work with the metals before placing in the container without them oxidizing. How long do you think I could leave the de-aerated liquid exposed before it becomes significantly oxygenated?

 

[Demon3]

You could keep your getter separate from the gallium so that no reaction occurs between the two metals. An inert atmosphere could be easier, just pack under nitrogen or if that's not inert enough try argon.

P.S. here's a place to get some gallium

http://www.scitoyscatalog.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=GALLIUM&Category_Code=

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell