Kalrez is DuPont's perfluoroelastomer brand, now sold by Chemours. It is the oldest FFKM line and the one most often written into a drawing by name. This page lists every Kalrez compound covered on MLC -
6 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.
Kalrez compounds compared
| Compound | Max continuous | Min temp | Hardness |
Colour | Family |
|---|
| Kalrez 0040 | 250°C | -25°C | 70 Shore A | Black | Low-temp-capable FFKM |
| Kalrez 4079 | 316°C | 0°C | 75 Shore A | Black | Broad-spectrum FFKM with perfluorinated ether backbone |
| Kalrez 6375 | 275°C | -7°C | 75 Shore A | Black | Spectrum series broad-resistance FFKM |
| Kalrez 7075 | 327°C | 0°C | 75 Shore A | White-Cream | Semiconductor-grade clean FFKM, low metal extractables |
| Kalrez 8475 | 325°C | 0°C | 90 Shore A | Black | Hard FFKM for high-pressure sealing |
| Kalrez 9100 | 327°C | 0°C | 90 Shore A | Black | High-strength FFKM for high-pressure / RGD |
Every compound above links to its full specification, size availability and UK supply options.
Manufacturer: DuPont (Chemours).
Cross-referencing Kalrez 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 Chemraz, Simriz, 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.