EPDM elastomer

Identify the polymer and finished compound

Parker's E0740-75 EPDM report gives 6% typical compression set against a 25% maximum, after 22 h at 150°C using ASTM D395 Method B on a plied specimen. Use the compound, cure and test setup when comparing this result with a different seal. Parker MTR128786

EPDM is ethylene-propylene-diene rubber. Parker distinguishes this terpolymer, whose diene provides cross-linking sites, from the ethylene/propylene copolymer EPM. “Ethylene propylene rubber” is therefore not a sufficiently precise description for every procurement or substitution. Parker Material Offering Guide, ORD 5712

A polymer grade is also different from a finished rubber compound. ARLANXEO's Keltan portfolio supplies EPDM grades as the basis for compounds used in seals, hoses, roofing, cables and other products. A named raw polymer does not establish the hardness, cure, extractables or sealing properties of a fabricated gasket. ARLANXEO Keltan

Cure and formulation matter

Trelleborg's O-Rings & Back-up Rings catalog, Edition June 2024, explicitly distinguishes standard sulfur- and peroxide-cured EPDM:

The catalog makes operating limits application-dependent. These entries do not establish universal limits for either cure system. Trelleborg catalog, table 9, page 43

Specify the resulting properties and evidence needed by the application rather than assuming that the cure label alone guarantees them. For purchased seals, cure is a manufacturing variable to control with the supplier, not an instruction to apply a generic shop heat-treatment cycle to finished parts.

Read physical tests with their conditions

Hardness, tensile strength, elongation and compression set answer different questions. Hardness is not a direct tensile modulus, sealing force or pressure rating. A useful comparison preserves test standard, specimen geometry, aging medium, temperature, duration and acceptance basis.

For example, Trelleborg lists compression set <20% after 24 hours at 100°C for E70, versus <30% after 24 hours at 150°C for E75, using the specified ISO 815-1 / ASTM D395 methods and specimens. The hotter test is not directly comparable with the cooler one; these entries do not demonstrate that E75 has worse recovery. Trelleborg table 9

Parker's E0740-75 report MTR128786, dated April 25, 2012, separately shows specification limits and measured typical results: hardness 73 Shore A against 75 ±5, and compression set 6% against a maximum 25%, after 22 hours at 150°C, ASTM D395 Method B, plied specimen. These are report results for that compound and test, not batch acceptance data for an arbitrary EPDM part. Parker E0740-75 report

Illustrative recovery calculation: assume a compression-set test starts at 10.0 mm thickness, compresses the specimen to 7.5 mm and measures 9.5 mm after the specified release/recovery procedure. Set relative to imposed deflection is (10.0 − 9.5)/(10.0 − 7.5) ×100 = 20%. This hypothetical arithmetic is not a test result, a remaining-force percentage or a seal-life estimate. Use the prescribed method and recovery conditions when reporting real measurements.

Fluid compatibility and temperature are coupled

Parker recommends E0740-75 for selected water/steam and polar-fluid applications, but explicitly does not recommend it for mineral-oil products, including oils, greases and fuels. Its general recommended temperature range is −70 to +250°F (approximately −57 to +121°C), while the same sheet separately identifies hot water and steam up to 400°F (approximately 204°C). Preserve that media distinction; it is not a blanket 204°C dry-air or lifetime rating. Parker E0740-75 recommendations

Trelleborg's sheeting overview likewise gives −40 to +120°C as typical for its standard EPDM compounds and describes higher-temperature special formulations. A sheet-family description cannot replace the selected O-ring compound's recommendations. Trelleborg EPDM sheeting

For cyclic hot-water or steam service, agree whether exposure is continuous, intermittent or part of a cleaning cycle, and identify cooling/depressurization conditions. Require suitable compound testing and assembly trials rather than deriving life from a maximum-temperature headline.

Sealing geometry and fabrication

Chemical suitability is only one input to seal selection. Define static or dynamic duty, pressure differential, gap/extrusion risk, squeeze, stretch, groove fill, surface finish and motion. Parker's guide treats material selection and gland design as separate engineering tasks and makes users responsible for application-specific analysis and testing. No single EPDM hardness establishes a universal pressure capacity. Parker ORD 5712

For sheet gaskets, include flange geometry, bolt loading, thickness, compression control and any reinforcement. A tensile-strength coupon does not establish flange sealing stress or resistance to blowout. For profiles or spliced cord, specify joint location and qualification; the material name does not establish that a splice behaves like a continuously molded ring.

EPDM's weathering reputation also does not qualify its bond. Trelleborg describes resistance to UV, ozone and aging while warning that EPDM has poor adhesion characteristics. Bonding to metal, coatings or other polymers therefore needs an appropriate supplier-approved preparation/adhesive process and environmental testing. Trelleborg sheeting guidance

Qualification and release

Where potable-water, food-contact, medical, electrical or fire requirements apply, obtain the current documentation for the exact compound and finished product. A family name, color or another compound's approval does not establish compliance. Keep fluid-contact scope, extraction conditions, cure/post-cure and any permitted processing changes in the record.

Use the supplier's handling information for the actual uncured compound, finished rubber, adhesives and cleaners. Establish storage and traceability requirements with the supplier. A raw-polymer storage recommendation is not automatically a shelf-life limit for a finished seal.

Release against compound identity, dimensions, workmanship and required material/functional tests. Distinguish initial properties, changes after exposure, specification limits and measured lot results. For replacements, investigate both material degradation and assembly causes such as damage, incorrect groove geometry or incompatible lubricant before changing compounds.

Source versions and related reference

Primary sources were reviewed November 1, 2026. Trelleborg's table 9 footer states Edition June 2024; Parker's E0740 report states April 25, 2012, and ORD 5712 prints ©2021. The ARLANXEO and Trelleborg sheeting pages have no visible technical revision date. Older reference reports are identified as such, rather than presented as new qualification data.

Material selection through production