O-ring material
Epichlorohydrin O-Rings
Epichlorohydrin O-rings are the ECO seal, a polyether rubber with the oil and fuel resistance of nitrile, lower fuel permeation, and ozone and weather resistance that nitrile lacks. No temperature range for epichlorohydrin is on file here, and the compound sheet governs. Conquest supplies epichlorohydrin O-rings in AS568 and metric sizes as a distributor, quoted in the compound the print names.
- Family
- Epichlorohydrin (ECO)
- Standard range
- No family range on file; the compound sheet governs
- Durometers
- 70 Shore A quoted as standard; other hardnesses by compound
- Standards
- ASTM D1418 CO and ECO; ASTM D2000 CH line callouts on specific compounds
- Product
- O-rings in AS568 and ISO 3601 sizes, quoted in the compound the print names
No family range is on file for this material; the compound datasheet and your application govern the final choice.
Larger and non-standard sizes: an O-ring beyond the molded size lists can be supplied as a spliced and vulcanized O-ring, which the maker joins from cord of the same compound. That page lists, family by family, which makers offer the compound as cord, and what to send for a quote.
What epichlorohydrin is, and where it is chosen
Epichlorohydrin rubber is a polyether, made as a homopolymer (CO) or as a copolymer with ethylene oxide (ECO), with a saturated backbone and chlorine on the chain. It resists petroleum oils and fuels the way nitrile does, passes less fuel vapor, damps vibration, and stays flexible in the cold, and unlike nitrile it shrugs off ozone and weather. That combination puts it in fuel-system seals, diaphragms and hoses, and in outdoor oil service where nitrile cracks. The Parker® handbook lists it in its compatibility table without a text figure, so this page publishes no range; the compound sheet you order from governs.
Where epichlorohydrin fails
Ketones, esters, aromatic solvents and brake fluid swell it, and its heat resistance is modest, so hot oil is HNBR's or polyacrylate's job. Some compounds corrode steel in contact under damp conditions, which the compound maker's sheet will say. Where the medium is fuel at moderate temperature and the seal sits outdoors, epichlorohydrin is the usual fit; where it is only oil, nitrile costs less.
How to specify
Send the AS568 dash number or the inside diameter and cross-section, the durometer, the fuel or oil by name, the temperature and whether the seal is exposed to weather, and any ASTM D2000 line callout. The quote names the compound your print or your engineering specifies and sends its datasheet with the range it carries.
Sizes and forms we supply
All 369 AS568 sizes (349 general-purpose dash sizes plus the 20 boss-seal sizes) and the ISO 3601 metric series, in the durometers listed above; O-ring cord for rings spliced and vulcanized by the maker in odd diameters (static service only), where the compound is made as cord. The AS568 chart and the metric chart carry the dimensions, and the dash number guide explains the numbering.
Sources: No text temperature figure appears in ORD 5700 section 2.2 and no maker sheet is on file, so this page states none; Parker O-Ring Handbook ORD 5700, section 2.2 (read 2026-09-14) (compatibility table, family named only); Apple Rubber, O-ring material selection guide (what the family is and where it is used, qualitative), read 2026-09-14; ASTM D1418; ASTM D2000 (documents named, not reproduced).
Parker is a trademark of Parker Hannifin Corporation. No affiliation or endorsement is implied.
Reviewed by Grant Midstokke, Conquest Seal Corporation. Last updated September 2026. Material ranges are the published references named beside them; the compound datasheet and your application govern the final choice.
Frequently asked
What is epichlorohydrin used for?
Fuel and oil seals that must also resist ozone and weather and pass little fuel vapor, in fuel systems, diaphragms and outdoor oil service.
What temperature range does epichlorohydrin have?
No range is on file here, so this page states none; the compound datasheet governs.
Epichlorohydrin or nitrile?
Both handle oil and fuel. Epichlorohydrin adds ozone resistance and lower permeation and costs more; nitrile is the default where the seal sits indoors.
What is the difference between CO and ECO?
CO is the homopolymer and ECO the copolymer with ethylene oxide; the copolymer is more flexible in the cold and is the usual O-ring compound. The print's ASTM D1418 letters say which.
Which durometer?
70 Shore A is the hardness quoted as standard. The durometer guide covers the choice.
Related guides
Send the part number and the quantity for Epichlorohydrin
The AS568 dash number or the inside diameter and cross-section, the durometer, the quantity, the medium and temperature, and any specification the print names. A Conquest representative replies.
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