Need some help with Nitrile. 2

[fecormack]

It would be fair to say that rubber is not my field of expertise. I have recently been part of completing a project for a client that requires mineral oil and rubber. I was made aware that natural rubber, as well as many other synthetic materials were not compatible with mineral oil. Having researched it I purchased some nitrile rubber to use as a sealant, under the impression that it would not react. After a few days I noticed that the oil near the rubber was turning a yellow colour. Thinking it might have just been a chemical used to treat the rubber I drained the oil and topped it up with a fresh batch. Once again it turned yellow. Would anyone be able to shed some light as to what is causing the discolouration and if there's anything I can do to prevent it from happening any further?

TLDR: Is it normal for nitrile to leak yellow into mineral oil and can it be prevented?

 

[tom1953]

It's likely that one of the ingredients in the nitrile rubber is leaching into the mineral oil. It could be a plasticizer (e.g., a yellow/darker oil-like material) or maybe an antioxidant or antiozonant (to protect the rubber from oxidation and ozone). It might even be a curatives, but I think that's less likely. It's tough to say what it might be without knowing the composition of the rubber.

 

[fecormack]

Thanks for the info, do you reckon it'll subside after a matter of time?

 

[tom1953]

Sooner or later the discoloring ingredient will be diminished in the NBR (nitrile rubber) and there will be less and less ingredient to discolor the mineral oil. Depending on what the bad actor is and how much is in the formula, it may take a while (or not . . .).
I assume you just bought some NBR off the shelf. If you contacted a rubber part manufacturer, and described your problem, perhaps they could get you some NBR that wouldn't have the tendency to discolor the oil.

 

[GrahamBennett]

Good posts Tom.

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