Positive Material Identification

[Corgas]

Hello colleagues,

We are trying to sort out sheets that are supposedly made of BUNA N and FKM.

Hardness shore A for both materials are very similar 70 vs 75. Is there another non-destructive method that we can use?
Thanks in advance,
Corgas

 

[Metten]

FKM normally has a higher density: 1.7 to 2.2 kg/L; NBR (Buna N) varies between 1 and 1.4 kg/L. So the weight per sheet should tell you the type.