Chemraz and Kalrez are both perfluoroelastomer (FFKM) O-ring ranges, Chemraz from Greene Tweed and Kalrez from DuPont (Chemours). Across the 6 grades that cross-reference directly, the two ranges land within a few degrees of each other far more often than the marketing suggests: 2 of the 6 pairs carry an identical maximum continuous temperature rating, Chemraz is rated higher on 2 and Kalrez on 2. The largest gap in the range is 35°C, between Kalrez 6375 and Chemraz 555.
Temperature alone should never decide a substitution. Match the fluid first, then the temperature window, then the hardness.
Chemraz to Kalrez cross-reference table
Every Chemraz grade below is listed by its manufacturers as an equivalent to the Kalrez grade on the same row. Maximum continuous temperature and hardness are taken from the published datasheets linked at the foot of this page.
How each pair differs
Choosing between Chemraz and Kalrez
Both ranges are perfluoroelastomers, so both resist the great majority of process chemistries. The decision usually comes down to three things: which grade your OEM already specifies, what the seal actually sees in service, and what a UK distributor can get to you in time.
The published limitation on each grade is the most useful column here. A compound's weakness, not its headline temperature, is what causes the failure you get called about.
| Grade | Primary service | Published limitation |
|---|
| Kalrez 7075 | Semiconductor wafer fabrication | - |
| Chemraz 526 | Semiconductor processing | - |
| Kalrez 9100 | Oil and gas | - |
| Chemraz 696 | Subsea | - |
| Kalrez 8475 | Oil and gas downhole | - |
| Chemraz 633 | Oil and gas | - |
| Kalrez 4079 | Steam | Not recommended for fully fluorinated solvents; cost |
| Chemraz 615 | Refinery | - |
| Kalrez 6375 | Chemical process | Lower temp ceiling than 4079; not for high-purity semiconductor plasma |
| Chemraz 555 | Pharmaceutical | - |
| Kalrez 0040 | Aerospace fuels | - |
| Chemraz 505 | Aerospace | - |
Substitution rule of thumb: a cross-reference is a starting point for a conversation with your supplier, not a drop-in guarantee. Confirm the fluid, the temperature excursion (not just the steady state), the hardware groove, and whether the application is explosive-decompression rated before you swap a grade.
Related FFKM references
Manufacturer datasheets
Every figure on this page is taken from the manufacturers' own published data:
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