Elastomer compatible with methylamines

[ZGZtanker]

Hello,

I am having problems with some valves on tank containers transporting anhydrous methylamines (MMA, DMA and TMA).
These valves have internally some encapsulated o-rings (silicon inside, FEP outside).
After some months seems the methylamines have permeated the FEP envelope reacting with the silicon. In fact they had originally a round section and they have became square with the shape of the available space. This is causing some leaks.

We are now searching for an elastomer compatible with methylamines, but we have found contradictory information about this issue. According to some realiable sources seems EPDM or EPR may be suitable. Can anybody with experience on methylamines confirm whether this is right?.

Thank you in advance for your help

Best regards

 

[Demon3]

There's a nice list of materials compatible with methylamine at Air Liquide's site:

http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=43#MaterialCompatibility

Seems to back up what you said. Fluorocarbons are fine but silicones not. I guess you need a 100% fluorocarbon o-ring or one made of the other compatible elastomers listed.

Chris DeArmitt PhD FRSC CChem

 

[btrueblood]

EPDM is listed as compatible, and the preferred elastomer for MMA, DMA and TMA. My reference of choice for O-rings is the Parker handbook (google Parker O-ring Handbook), they have a pretty comprehensive elastomer compatibility table. FKM will work too, provided you use (as Chris suggested) a 100% fluorocarbon elastomer, not one that is blended with nitrile as some can be. EPDM will be substantially cheaper than FKM.

 

[btrueblood]

Oops, hit send too soon. One thing to look at is your expected operating temperatures. EPDM is generally ok in sealing down to about -40 F. FKM's can vary depending on their formulation, but tend to get stiff even at 32 F (as the Challenger crew found to their chagrin).

Be careful with EPR - this typically suggests that the rubber is blended with other polymers, again typically nitrile rubber, which might not work out so well.

 

[ZGZtanker]

Thank you both for your help.

In fact is from air liquide where I obtained this information. It is very helpful to see that Parker fully agrees with EPDM suitability.

Anyway if anybody has field experience with these methylamines I would highly appreciate to confirm EPDM suitability.

 

[ZGZtanker]

Hi btrueblood,

Your information about Parker handbook has been very useful. We are finally going to EPR as Parker recomends.

Thank you very much.

P.D.: difference between EPDM and EPR

http://www.darcoid.com/images/uploads/pdfs/EPRvsEPDM.doc