Chemical Forums
Specialty Chemistry Forums => Citizen Chemist => Topic started by: alodg on June 28, 2014, 08:59:30 PM
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I was looking for a rubber seal for the wooden canister that I have for a battery in order to stop any leaking.
I chose wood so that any leaking of the battery couldn't create a circuit with the case of the canister and potentially blow up! I felt though that I might need a rubber seal to try and prevent any leaking from the canister.
In contact with a UK company called Polymax I was given a sample of EPDM rubber, but was advised that perhaps Viton/FKM would be suitable for what I needed.
ref: http://www.polymax.co.uk/2-2x1-6-nitrile-rubber-70
I am looking to store both AA and AAA batteries from the Eneloop brand, I don't know what they would leak, perhaps Alkaline?, but would like further advice on what kind of rubber like material I would be best going with in order to seal in any leaks as these batteries are going into deep storage.
Many thanks in advance.
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Hi alodg, welcome here!
Ys, alkaline batteries leak a strong alkali. Though, I would be confident with Epdm and several more rubbers, first because it has a significant chemical resistance, and simply because the leaked amount won't eat its way through the diameter of a seal ring.
You could look for a "compatibility table" or "compatibility list", googled together with EPDM and alternatives, and check "strong alkali". Or you could just try: take some sodium hydroxide used to unblock washbasin flows, put a few seal materials in the concentrated aqueous solution for a month, observe - please be careful with the alkali.
To my opinion, the accurate fitting hence the thickness of the seal is more important than the material. Most plastics resist alkalis, and I'd trust a plastic box with a flat cap fitting better than a wooden one. Maybe you find some, for electronics, that have already a seal ring - and even, you may find leaktight battery canisters.
There maybe http://www.conrad.com/ce/
http://www.conrad.com/ce/en/Search.html;ASTPCEN28?search=battery+box
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Hi, thanks for your reply. As for the choice of wooden canister I based this on the fact that I will be storing them in a faraday cage and didn't want the alkali to rupture the coating any way. You can also imagine if it created a circuit also!
The rubber thickness I need is not what they can provide, but I could buy a set to cut my own.. not sure if I'm going to do that. The dimensions I think that I need come in two sizes:
2mm (thickness)
internal diameters:
1.6cm (small)
2.3cm (large)
As for the compatibility lists I don't think that "Alkali" will be listed, typically it's not, I think that the charts are looking for an element or chemical that *is* a strong Alkali, rather than the generic term, but I wouldn't like to expect what that might be e.g. Lithium, Sodium, Potassium, Rubidium, Cesium..
ref: http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/s-Block_Elements/Group__1%3A_The_Alkali_Metals
Anyway, I found this table which did recommend EPDM: http://www.bimba.com/Global/Library/Technical-Tips/Wash-down_Material_Compatibility_Chart.pdf
Living here in the UK I have some Domestos Bleach available to try it, but it doesn't appear to contain Sodium Hydroxide:
http://www.tesco.com/groceries/Product/Details/?id=255771180
Thanks
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Just a random idea: have you thought about putting batteries just in a polyethylene bag - all you need to worry about then is sealing the cables. And as long as the device is not intended to be moved into random positions, gravity is on your side, so could be you don't need the seal.
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The Alkaline could melt through the plastic. that's why I chose wood.
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The Alkaline could melt through the plastic. that's why I chose wood.
Then you are choosing wrongly IMHO. Polyethelene is resistant enough for a heavy duty industrial alkaline storage, it is also used for bottles in which NaOH pellets are sold (both for labs and for general public). Plus, it won't bend when wet, and you can't be sure it won't happen with wood.
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I too would clearly prefer polypropylene or polyethylene over wood. Wood can split, wooden box are often glued and the glue will be chemically weak, and so on.
If the list says that EPDM is good at sodium hydroxide, don't worry more. Such lists are meant for 24/7 flow at chemical industries, a small occasional leak is easier. Strong mineral alkalis (NaOH, KOH...) act essentially all the same.
Bleach is not sodium hydroxide - provided the commercial description uses the words properly. Elsewhere in Europe, sodium hydroxide is easy to find as a washbasin unlocker; at the store, the package carries a "corrosive" warning picture and contains a powder, then you can check the composition for sodium hydroxide.
I have no doubts about Epdm, but trying on the wooden box may be interesting.
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I would assume over a period of time the wood would deteriorate to Alkaline. Of course the duration might be sufficient for the users purposes. (Just an opinion not born in exhaustive research)
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Try TRP. Their universal chemical resistance O-Rings are made from Perfluoroelastomer which offers possibly the broadest chemical resistance of any elastomeric sealing material. Definitely recommended for resistance to Alkaline: https://trp.co.uk/ffkm/universal-chemical-resistance/