O-Ring Chemical Compatibility Guide

Chemical compatibility is the first question in O-ring material selection and the one most often answered from memory. This guide gives a first-pass screen for the five common O-ring materials against the everyday media families, explains how to read a compatibility rating and what changes it (temperature, concentration, static or dynamic service), and lists eight compatibility traps covered in the Parker® O-Ring Handbook (ORD 5700). Ratings here are general guidance for the material family at moderate temperature; specific compounds, concentrations and temperatures change the answer, so confirm against the compound datasheet before finalizing a seal.

First-pass screen by media family

Use this table to narrow the material choice, never to finalize it.

A = excellent · B = good · C = conditional, verify grade · X = not recommended

Material detail pages: Buna-N, Viton, EPDM, silicone, FFKM.

How do you read a compatibility rating?

A rating summarizes how much an elastomer swells, softens, hardens or loses strength after immersion in a medium, usually at one temperature and one concentration, measured by a fluid-immersion test such as ASTM D471. The letters mean different things in different manufacturers' charts, so read the legend, and read the conditions. A compound's ASTM D2000 line callout encodes the same idea in shorthand: the class letter states the maximum volume swell in reference oil, and the EA, EF and EO suffixes name the aqueous, fuel and oil immersion tests the compound passed. The Parker O-Ring Handbook sets out how much change a seal can tolerate.

The eight compatibility traps

Eight common mistakes, each covered in the Parker O-Ring Handbook (ORD 5700).

Which material owns which media family?

The Parker handbook memory aid covers the three workhorses: nitrile resists oil but not weather, EPDM resists weather but not oil, FKM handles both but costs more. Extended to the other families:

Temperature ceilings above are the Parker handbook standard ranges; the temperature range guide lists every material with its special-compound extents, and the comparisons (EPDM vs FKM, nitrile vs FKM, FFKM vs FKM, FKM vs silicone) walk the pairwise decisions.

These are published manufacturer guidelines, not Conquest Seal recommendations; Conquest quotes the material your print names.

What to send with a compatibility question

The medium by name and concentration (a trade name alone is not enough), the continuous and peak temperature, whether the seal is static or dynamic, the pressure, any secondary media (cleaning chemistry, flushing fluid, lubricant), and the AS568 size or the measured dimensions. With those, the compound your print names can be cross-referenced and quoted against its datasheet. Send them with a quote request.

Viton is a trademark of The Chemours Company; Aflas is a trademark of AGC Inc.; Parker is a trademark of Parker Hannifin Corporation. No affiliation or endorsement is implied.

Sources

1. Parker O-Ring Handbook ORD 5700A/US, sections 2 and 10 (compound selection, compatibility and failure analysis), read 2026-08-12
2. Parker O-Ring Handbook ORD 5700, section 2.2 (elastomer heat and cold figures), read 2026-09-14
3. Parker compound E3609-70 datasheet (FDA), read 2026-08-13
4. ASTM D2000 / SAE J200 line callout letters and suffixes, from published manufacturer guides, read 2026-09-06
5. ASTM D471 (fluid immersion test), named as the test method

Reviewed by Grant Midstokke, Conquest Seal Corporation. Last updated September 2026. Spec values in this guide are drawn from the sources listed above; the compound datasheet and your application conditions govern the final choice.