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Science Forum Index » Materials Forum » nitrile vs. epdm
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| martin44236 |
 Posted: Tue Oct 14, 2003 7:33 pm |
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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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| Entropyfoe |
| Posted: Tue Oct 14, 2003 10:06 pm |
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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
Quote:
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.)
entr0pyf0e |
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| Guest |
| Posted: Wed Oct 15, 2003 7:08 am |
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Quote: 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
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.)
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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| Uncle Al |
| Posted: Wed Oct 15, 2003 9:32 am |
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martin44236 wrote:
Quote:
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.)
Easy. Nitrile is resistant to non-polar solvents (gasoline,
kerosene). That is why it was invented. Epdm will swell enormously
and even disintegrate. Take a sample of each and soak in a closed
vial. I imagine you will have results within an hour, certainly
overnight. The swelling is reversible if you catch it early - though
you may leach out the antioxidant package.
If you have an IR, only nitrile rubber will have CN stretch. Can't
miss it.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net! |
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