Chemraz vs Kalrez??

[quizzical1]

Hi All,

been told by a supplier that Chemraz is basically a direct replacement for Kalrez. is this true?

 

[EdStainless]

They have the same base resin chemistry.
No two elastomers are fully interchangeable because fillers and cure agents can vary, even from lot to lot from one producer.

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P.E. Metallurgy, consulting work welcomed

 

[BenjaminM]

Short answer: yes.
Long answer: no.

Keep in mind there are several different flavors of both materials, Kalrez 6375 & 4079 are the only two I've had experience with, there are others. Chemrez has a White, Black, and Special.

All are listed as FFKM.

Compass Publications has an excellent series of books listing chemical compatibility. Both are listed for a variety of materials. Doing a quick survey through the elastomers book, I have not yet spotted anything that is listed as A for one and B or NR for the other. A lot (most) of the Kalrez data is listed at significantly higher temperatures (like up to 500*F) than the Chemraz (mostly 70*F), and there is a lot of the Chemraz that is blank. But I should imagine they have only listed what they have tested.

You should definitely confirm the your chosen materials of construction are compatible with your specific process.

 

[Latexman]

Can you discuss the application? Sounds like there's a lot of experience here to be had.

Good Luck,
Latexman

 

[quizzical1]

Thanks guys,

I have the Compass books as well (per recommendation on another thread I posted) and was looking through it also and getting mixed results.

We mainly use 4079 and 6375 for steam applications. I didn’t see a Chemraz rated as highly as the 6375 unless I missed it.

 

[Latexman]

I didn’t see a Chemraz rated as highly as the 6375

I assume you mean higher application temperature is higher rated. In general, Kalrez® (DuPont) is rated for +5 to +600 [sup]o[/sup]F and Chemraz® (Green Tweed) is rated for -20 to +450 [sup]o[/sup]F.

For higher pressure/temperature steam, Kalrez® is the better choice.

Good Luck,
Latexman

 

[quizzical1]

Thanks Latexman,

that's exactly what I meant about Kalrez being the better choice...

 

[EdStainless]

It is mostly about experience and testing.
At high temps in wet environments the only thing that we used was Aflas, and we only let one person make it.
Simply changing the brand of carbon black or fumed silica will change the long-term behavior of the elastomer.

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P.E. Metallurgy, consulting work welcomed

 

[quizzical1]

EdS,

Boy, do we know that all too well. We were buying non-rated O-rings from McMaster and it was a real crap shoot.

 

[EdStainless]

We even had rules for our Viton and EPDM O-rings, the vendor had to use a fixed process.
Just simple substitutions required re-qualification.
We would typically buy a tow year supply at a time.
And each ring was individually packaged on Mil spec packaging to assure shelf life.
What a pain ....

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P.E. Metallurgy, consulting work welcomed