EPDM: Material for Water and Steam

What Is EPDM? Basics and Properties

EPDM stands for ethylene propylene diene monomer, a synthetic rubber known for its exceptional resistance to weathering, heat, ozone and acids. These properties make the material an ideal choice for a wide range of applications where resistance to environmental influences is critical.

Chemically, it is a terpolymer of ethylene, propylene and a diene monomer. The diene enables cross-linking during vulcanization. This results in high elasticity, good ageing resistance and pronounced heat resistance. EPDM remains flexible across a temperature range of −50 to +150 °C.

Compared with other standard elastomers, the typical profile emerges: against NBR, EPDM is clearly superior in weathering and ozone resistance, while NBR is better suited to oils and fuels. Against SBR, EPDM offers better heat and ageing resistance. The material was first produced in the 1960s. The maximum storage time in accordance with DIN 7716 is 7 years.

Advantages and Limits of EPDM

The limits of EPDM lie clearly with non-polar media. The material is not resistant to mineral oil, greases, fuels and most petroleum products. If an O-ring swells in such media, it loses its sealing effect. For these cases, FKM O-rings or nitrile-based materials are the right choice.

Another point is the acquisition cost. EPDM products can involve a higher initial investment than some alternatives. Over the long service life, however, this difference often evens out. Our media resistance list shows which material suits your medium.

EPDM for Water, Steam and Hot Water

The greatest strength of EPDM is contact with water in all its forms. Where other elastomers become brittle or swell in hot water or steam, EPDM stays tight and elastic over long service lives. This makes the material the first choice in water treatment, in sanitary and heating technology, and in steam technology.

Typical fields of use are seals and membranes in water treatment plants, O-rings in pumps, filters and valves, as well as seals in HVAC systems for heating, ventilation and air conditioning. Here EPDM copes with constant thermal cycling without losing its elasticity.

Specially treated and appropriately approved EPDM is also suitable for drinking water applications, as it releases no harmful substances and is resistant to microorganisms. For hot water in continuous contact, you will find suitable solutions among our hot water O-rings.

Brake Fluid and Polar Media

A classic field of application for EPDM is contact with glycol-based brake fluid. Such polar media attack many other elastomers, whereas EPDM remains resistant. That is why the material is found in brake fluid reservoirs and in hydraulic systems that use brake fluid.

As a general rule: EPDM is well resistant to polar media such as water, many acids, alkalis and, of course, brake fluid. Against non-polar media such as mineral oil, however, it is not resistant. This rule of thumb helps with quick preliminary selection. The specific suitability should always be checked for the particular medium and temperature.

Weathering, Ozone and Outdoor Use

For permanent outdoor use, EPDM is one of the most robust elastomer materials of all. Solar radiation, UV light and ozone take a heavy toll on many rubber materials over time; they crack and become brittle. EPDM withstands these influences over long periods.

This property makes the material ideal for outdoor applications. In the construction industry, EPDM is used as a roofing membrane that provides protection against moisture and UV radiation for many years. Window and facade seals also benefit from the weathering resistance and contribute to the energy efficiency of buildings.

In gardening and landscaping, EPDM liners are used for ponds and artificial watercourses. They combine durability with good compatibility for the surrounding water. For sealing elements outdoors, this means: an EPDM O-ring ages significantly more slowly than comparable standard elastomers.

The Clear Limit: Mineral Oil and Fuels

As versatile as EPDM is with water-based and polar media, its limit with non-polar media is just as clear. EPDM is not resistant to mineral oils, greases, lubricants, petrol, diesel and most petroleum products. In these media the material swells strongly and loses its sealing function.

This limit is not a shortcoming but a property of the material chemistry. Anyone looking for an O-ring for oil or fuel therefore deliberately chooses a different material. FKM O-rings cover high temperatures and mineral oil; NBR is the economical choice for oils and greases in the medium temperature range. Which material suits which medium can be looked up in the media resistance list.

EPDM O-rings and Their Applications

EPDM O-rings are a proven component of many industrial applications where durable seals and resistance to environmental influences are required. They combine weathering and ozone resistance with a broad range of use in water and polar media.

When selecting, the correct size and fit matter, along with the specific chemical, thermal and mechanical requirements of the application, as well as suitable quality standards. EPDM O-rings are known for their longevity, yet regular inspection for wear remains advisable. Store the rings protected from direct sunlight and under controlled temperature to make the most of their service life.

Frequently Asked Questions