- Family
- AU / EU (polyurethane)
- Standard range
- -40 C to 82 C (Parker® O-Ring Handbook ORD 5700)
- Durometers
- By compound; the compound datasheet states the hardness
- Standards
- ASTM D1418 AU/EU
- Product
- O-rings in AS568 and ISO 3601 sizes, quoted in the compound the print names
Service temperatures here are the family figures published in Parker O-Ring Handbook ORD 5700A/US §2.2; 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.
Polyurethane O-rings (AU polyester, EU polyether) have among the highest abrasion, extrusion and tensile resistance of the O-ring elastomers (Parker ORD 5700), which makes them a high-pressure hydraulic and dynamic rod seal material. The Parker O-Ring Handbook (ORD 5700) rates the family from -40 C (-40 F) to 82 C (180 F), with one hard limit: hot water and steam hydrolyze it. Conquest supplies polyurethane O-rings in AS568 and metric sizes, usually at 90 Shore A.
Polyurethane O-ring specifications
| Property | Value | Source |
|---|---|---|
| Continuous service temperature | -40 C to 82 C (-40 F to 180 F) | Parker ORD 5700 |
| Material designation | AU (polyester) and EU (polyether) under ASTM D1418 | ASTM naming |
| Strong against | Abrasion, extrusion, tearing; petroleum oils and fuels; ozone | Parker ORD 5700 |
| Weak against | Hot water and steam (hydrolysis), temperatures above about 82 C, ketones, acids | Parker ORD 5700 |
| Typical duty | High-pressure hydraulic cylinders, dynamic rod and piston seals, pneumatic tools | Parker ORD 5700 |
| Gland note | Bridges larger extrusion clearances than the elastomer tables allow, per Trelleborg | Trelleborg gland guidance |
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); and X-rings and backup rings in the same families. The AS568 chart and the metric chart carry the dimensions, and the dash number guide explains the numbering.
Polyurethane against the alternatives
| Factor | Nitrile 90 A | Polyurethane 90 A | Viton® 90 A |
|---|---|---|---|
| Continuous range (Parker ORD 5700) | -34 C to 100 C | -40 C to 82 C | -26 C to 204 C |
| Abrasion and extrusion | Good | Higher | Good |
| Petroleum oils, fuels | Excellent | Good | Excellent |
| Hot water, steam | Not recommended | Destroyed (hydrolysis) | Poor in standard grades |
| Ozone | Poor | Good | Excellent |
| Compression set | Good | Fair | Good |
| Cost | Lowest | Low to middle | Higher |
Typical applications
High-pressure hydraulic cylinder rod and piston seals, mobile-equipment hydraulics with dirty or abrasive fluid, pneumatic tools and cylinders, quick-disconnect couplings, and any dynamic seal where a nitrile ring extrudes or wears out first; also the hard backup material beside a softer O-ring at pressure, per the backup-ring guidance in the durometer guide.
Ranges are the Parker ORD 5700 figures. Polyurethane is the usual fit for high-pressure dynamic seals in oil below 82 C; nitrile where cost and set resistance matter more than abrasion, and Viton for heat. The durometer guide covers extrusion and backup rings.
Sources: AS568; ASTM D1418; ISO 3601; ORD 5700; Parker O-Ring Handbook.
Parker is a trademark of Parker Hannifin Corporation. Viton is a trademark of The Chemours Company; 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
Polyester or polyether polyurethane?
Polyether (EU) resists hydrolysis better; polyester (AU) is stronger in abrasion. State the medium and temperature.
Can polyurethane O-rings take hot water?
No. Hydrolysis above about 82 C or in hot water is the material's one hard limit.
Why 90 A?
The material's advantage is extrusion resistance at high pressure, which the hard grades deliver; softer grades exist for special cases.
Does polyurethane take a set?
Its compression set is fair rather than good, so a polyurethane seal in long static service at temperature is checked against the compression set guide; its home is dynamic service.
Related guides
Send the part number and the quantity for Polyurethane
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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