Epichlorohydrin O-Rings

What epichlorohydrin is, and where it is chosen

Epichlorohydrin rubber carries oxygen in its main chain, the Parker® handbook's O-group, and is made as a homopolymer (CO), a copolymer (ECO) or a terpolymer (GECO). It resists petroleum oils and fuels the way nitrile does, passes less fuel vapor and gas, and holds its properties from cold to heat, and unlike nitrile it shrugs off ozone and weather. That combination puts it in fuel-system and air-conditioning seals, and in outdoor oil service where nitrile cracks. The Parker handbook rates it in its comparison of elastomer properties (Table 2-2) but prints no temperature figure for it. The range on this page, -40 C to 135 C, is Apple Rubber's printed standard-compound range of -40 F to 275 F in Celsius, one maker's figure; the compound sheet you order from governs.

Where epichlorohydrin fails

Ketones, esters, aldehydes, chlorinated solvents and brake fluid attack it, and it takes a set more readily near the top of its temperature range, so hot oil is often HNBR's or polyacrylate's job. 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 AS568 sizes in millimeters carry the dimensions, and the dash number guide explains the numbering.

Sources: Apple Rubber, Seal Design Guide, Epichlorohydrin page (standard-compound range), read 2026-09-27; Parker O-Ring Handbook ORD 5700, Table 2-2 (comparison of elastomer properties, page 2-9) and the nomenclature table (CO, ECO), read 2026-09-27; AS568 size count, 369 sizes (349 general-purpose plus 20 boss): Parker O-Ring Handbook ORD 5700, section IX size tables (Series 2-XXX and the 3-9XX boss table), read 2026-09-27; ASTM D1418; ASTM D2000 (documents named, not reproduced); Parker O-Ring Handbook ORD 5700, page 2-10 (hardness guidance), read 2026-09-25.

Parker is a trademark of Parker Hannifin Corporation. Apple Rubber is a trademark of its owner; no affiliation or endorsement is implied.