Simriz is Freudenberg's perfluoroelastomer line, using SZ numbering. It is common on European process plant where Freudenberg already supplies the seals. This page lists every Simriz compound covered on MLC -
4 of them - with maximum continuous temperature, low-temperature limit and hardness side by
side, so you can pick a grade without opening each datasheet in turn.
FFKM (perfluoroelastomer, ISO 1629 designation FFKM) is the most chemically resistant elastomer
family in general use. It costs many times what FKM does, so it is specified where a Viton seal will
not survive: aggressive amines, hot steam, strong bases, oxidising plasma, or a mixed-chemistry
process where nobody wants to qualify a different seal for each stage. Grade choice within a brand is
mostly a trade between temperature ceiling, chemical breadth and hardness.
Simriz compounds compared
| Compound | Max continuous | Min temp | Hardness |
Colour | Family |
|---|
| Simriz SZ481 | 230°C | -10°C | 75 Shore A | Black | Chemical-grade FFKM, marketed as Kalrez 6375 equivalent for sub-230C |
| Simriz SZ485 | 280°C | -10°C | 75 Shore A | Off-White | Semi-conductor grade FFKM |
| Simriz SZ487 | 300°C | -10°C | 75 Shore A | Black | Thermal/chemical FFKM marketed as direct Kalrez 4079 alternative |
| Simriz SZ498 | 327°C | 0°C | 90 Shore A | Black | Hardest Simriz, RGD-rated |
Every compound above links to its full specification, size availability and UK supply options.
Manufacturer: Freudenberg-NOK.
Cross-referencing Simriz to another brand
FFKM grades are not interchangeable by number, and no cross-reference is exact - two compounds can
share a hardness and a temperature rating and still behave differently in your specific media. Treat
any equivalent as a starting point for qualification, not a drop-in. These head-to-head pages set out
where each pair actually differs against Kalrez, Chemraz, Perlast:
Choosing a grade
Start with the lowest temperature ceiling that covers your process, not the highest available. The
broad-resistance grades near the top of a range carry a price premium and often a lower
low-temperature limit, so specifying the flagship compound for a 150C duty costs money and can make
cold-start sealing worse. Confirm the low-temperature figure in the table above against the coldest
condition the seal sees, including shutdown and cleaning cycles, rather than the running temperature
alone.