How to Select Rubber Gasket Material

The fluid is the primary filter. EPDM swells rapidly in petroleum oils and fuels, so it must never be used in oil service. NBR handles petroleum oils and aliphatic fuels but fails in ozone, strong acids and brake fluid. FKM covers most fuels and chemicals except steam, ketones and hot concentrated alkalis. PTFE is the fallback when no elastomer survives the chemical environment.

If the fluid is a mixture — for example biodiesel, glycol-water or amine-treated hydrocarbons — check each major component. A material compatible with the base fluid may swell or harden in an additive.

Temperature limits are continuous service values, not one-hour peaks. Standard NBR is limited to about +120°C; above that, HNBR or FKM is required. EPDM reaches +150°C and tolerates steam. VMQ silicone spans −60°C to +200°C. FKM reaches +200°C. PTFE extends to +260°C but lacks elastic recovery.

Remember that elevated temperature softens elastomers and increases extrusion tendency. If the joint operates near the material's upper limit, use a harder compound or reduce the extrusion gap.

Full-face gaskets distribute bolt load over a large area and are forgiving of flange warping. Inner-bolt-circle ring gaskets need more uniform bolt preload. Thin gaskets (1/32–1/16 in) require smooth flanges and high bolt load; thick gaskets (1/8–1/4 in) conform better to rough surfaces but need more bolt travel.

Hardness matters: 50–60 Shore A for rough or low-load flanges; 70 Shore A for general industrial; 80–90 Shore A for high pressure or small extrusion gaps.

The chart below summarizes temperature, media compatibility, hardness range and typical cost for the six most common flat gasket materials.

Elastomer gaskets are not the right choice for every joint. Above about +260°C, PTFE or metal gaskets are required. Above 50 bar static with large extrusion gaps, consider PTFE backup rings or metal-reinforced designs. In highly aggressive chemicals that attack FKM, FFKM or PTFE is the next step.

We do not claim to manufacture spiral-wound, ring-type joint or solid metal gaskets. For those requirements we can redirect you to appropriate suppliers or recommend an O-ring, bonded seal or PTFE solution from our catalog.