nitrile vs. epdm

I have 2 O-rings. Both are similar in appearance, texture, etc. Due to my supplier's confusion, they may be the same or they may be
different. _IF_ they are different then one is nitrile rubber and the other is epdm. Is there a simple test (destructive is OK) to tell them apart?? (Otherwise I'll spend a couple hundred dollars at a lab to figure it out.)
Thanks.
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Consult one of the common chemical compatibility charts used for o-rings. Find a slovent or acid that each material has different compatability with, ie one fails miserably in say gasoline, whereas the other survives well. Do the test, or better 2 or 3 such tests. -Jay

entr0pyf0e
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yep.. gasoline or toluene/pentane/isooctane (standard testing solvents for O-rings in gas installations) will tell you easily if it is NBR or EPDM. EPDM will double in size, while NBR should be relatively unimpressed (max. about 3% vol increase). If you are sure, those two materials are the only options, life is that simple :-)
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