HNBR vs Peroxide Cured Nitrile

[Kindra]

I am having a hard time finding a clear comparison of HNBR vs Peroxide Cured Nitrile. My thought is that they are the same material as there is hydrogen in peroxide however I cannot find anything in righting to prove this. My issue is the NBR is not compatible with the Carbonic Acid however HNBR is. And I cannot find Peroxide Cured Nitrile in any chemical compatibility charts. Your help is greatly appreciated.

 

[Metten]

They are not the same. HNBR (hydrogenated) is treated NBR. You can vulcanize NBR and HNBR by peroxides.
HNBR is more resistant to (ozone) aging on paper. In my opinion all other properties depend on the formulation, ACN content etc.

 

[btrueblood]

I'm not sure either nitrile is compatible with carbonic acid; can you not switch to a more compatible elastomer (EPDM would be one).

 

[Kindra]

Per the efunda chemical compatibility chart HNBR is compatible. Unfortunately for this vendor EPDM is not an option. Thank you for your input.

 

[GrahamBennett]

Correct me if I am wrong but isn't carbonic acid just carbon dioxide dissolved in water? If true then this is just a very weak inorganic acid and most polymers would be suitable unless there are other overriding factors (such as service temperature) that preclude the use of lower cost alternatives to HNBR.

 

[btrueblood]

Per the Parker O-ring handbook, nitrile and HNBR are listed as a "2" = "ok for static seals only" for carbonic acid.

 

[tom1953]

The R.L. Hudson Fluid Compatibility Guide (

http://rlhudson.com/Chemicals/ChemicalGuide.aspx)

shows HNBR as "Best" with NBR as "Good" (no indication as to the curing system of either).
tom

 

[RubberDog]

The NBR still have a lot of insaturation (double bonds), on the main polymer chain.
So still passive of being attacked by the oxygen present on the carbonic acid, or any other oxidant.
Peroxide cured NBR only increases the temperature limit, as the bond C-C have much more energy than C-S or S-S, when you have vulcanization (by the way, Vulcanization must have sulphur... It is a patented, expired of course, but was the process name. Peroxyde is cure...).
NBR can be vulcanized by sulphur or cured by peroxyde,
HNBR will depend of the residual insaturation. Smaller residual insaturation, less double bond on the main chain, and better resistance to oxidation, ozone, etc.
HNBR with certain residual insaturation still possible to vulcanize. Reducing even further, there is no residual insaturation to have the sulphur linking, and you will have to cure wih peroxyde.
It will give you the best resistance to temperature, oxidation and ozone.