EPDM O-RINGS | MATERIALS SIMPLY EXPLAINED
What are EPDM O-rings?
O-rings made of EPDM (ethylene propylene diene rubber) are predestined for use in contact with hot water and steam.
Whether in the sanitary and heating sector or the food industry, EPDM O-rings offer the necessary durability and, if required, industry-specific approvals for these challenging areas of application.
The good media resistance also makes EPDM suitable for use in cooling circuits or pressure systems – not least in the automotive industry. Many practitioners also know EPDM under the trade names of global suppliers such as Keltan®, Vistalon®, Dutral® or Nordel®.
The most important alternatives for EPDM O-rings include the materials NBR and FKM.
Feature | Value |
|---|---|
ISO designation | EPDM |
Trade names | Hypalon |
Chemical name | Ethylene propylene diene rubber |
Media resistance | Good media resistance |
Temperature resistance | -40°C to +150°C |
Standard color | Black |
Standard hardness | 70 Shore A |
Industries | Food, pharmaceuticals, hot water |
Production | Compression molding and injection molding |
Tolerances | DIN ISO 3601 |
Durability | 8 years |
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#1 The 5 most important advantages of EPDM O-rings
1. Good abrasion resistance
2. Very good suitability for hot water and steam
3. UV and ozone resistance
4. Broadly pronounced media resistance
5. Food and drinking water suitability
Mechanical stress, temperatures, media or simply the environment: O-rings are subject to a wide range of stresses.
In some areas, this is not only effective under the operating conditions of the sealing point. For example, ozone in the ambient air can attack O-rings while they are still waiting to be used in the operating fluid store.
Especially NBR O-rings must be handled very carefully in this respect. However, this risk does not exist with O-rings made of EPDM. The material is not susceptible to sunlight or ozone.
This not only makes storage unproblematic, but also enables the sealing elements to be used outdoors.
The high abrasion resistance also allows the use of dynamic seals where the sealing surfaces are in motion.
Similar to NBR, FKM or CR, EPDM O-rings can withstand mechanical stress. A broad media resistance profile and many material approvals for special applications make EPDM O-rings almost universally applicable.
Fields of application include the food and drinking water sectors, which place high demands on the safety of sealing materials.
A comparison of the most important O-ring materials
Material | Temperature resistance | Chemical resistance | Elasticity |
|---|---|---|---|
NBR | -30°C to +120°C | Low | High |
HNBR | -30°C to +150°C | Medium | High |
EPDM | -45°C to +150°C | Medium | High |
SILICONE | -60°C to +200°C | Low | High |
FKM (VITON) | -25°C to +200°C | Medium | High |
FEP coated | -60°C to +200°C | High | Medium |
PTFE | -250°C to +250°C | High | Low |
FFKM | -40°C to +340°C | High | High |
#2 The 3 most common areas of application for EPDM O-rings
Cooling water and heating circuits
Glycol is found in many technical media, as it can lower the freezing point of water to as low as -55 degrees.
Brake fluid or coolant for engines are two examples of applications from the automotive sector. Thanks to their excellent resistance to water and glycol over a wide temperature range, EPDM O-rings are particularly suitable for sealing such systems.
Sealing elements made of EPDM reliably secure the connection points of components such as radiators, pipes, thermostats or pumps. For these safety-critical applications in the automotive sector, EPDM is generally preferred over alternative materials.
Only if contact with mineral oil-based media cannot be ruled out is the more cost-intensive
material FFKM is used.
Food and pharmaceuticals
Food and medical products enter the human organism directly, so that unwanted interactions must be ruled out at all costs.
Those responsible must ensure the flawless quality of the products throughout the entire production chain. O-rings must therefore function reliably in the production facilities in order to prevent contamination.
At the same time, the sealing elements must not affect the products in direct contact. EPDM is tasteless, odorless and inert. Many grades of EPDM O-rings with FDA or USP approvals are completely free of plasticizers.
EPDM O-rings also withstand the aggressive conditions of cleaning and sterilization procedures.
Pressurized fluids
Hydraulic fluids are responsible for power transmission in hydraulic systems. Up to now, mineral oil-based media are used here.
However, their unwanted contact with the environment poses an ecological problem. For this reason, there are growing demands for the use of biodegradable print transfer media.
These changed requirements must of course also be transferred to the other components of the hydraulic systems. EPDM O-rings are not only suitable for conventional media such as DOT 3 and DOT 4 brake fluid, but also for the more environmentally friendly alternative HEPG (polyalkylene glycol) in accordance with DIN ISO 15380.
#3 What is the media resistance of EPDM O-rings?
EPDM O-rings are resistant to hot water and steam.
This also explains the material’s preferred use in sanitary and drinking water technology systems. EPDM O-rings also withstand contact with glycol-based brake fluids at high temperatures.
Many organic and inorganic acids are also part of the resistance profile of the gasket material.
The insensitivity of EPDM to ozone and weather influences should also be emphasized. The suitability for weathered outdoor use and long possible storage times without special precautions make handling EPDM O-rings particularly uncomplicated in practice.
These qualities contribute significantly to the suitability of EPDM for automotive construction.
However, the most significant gap in the resistance list of EPDM O-rings is represented by products based on mineral oil. Lubricants or oils cause the swell the material.
This results in a considerable reduction in hardness and chipping with rounded edges. This weakening of the material causes EPDM O-rings to lose their sealing effect.
EPDM is therefore not suitable in combustion engines for areas that carry coolant but also come into contact with mineral oil-based lubricants.
#4 What is the temperature resistance of EPDM O-rings?
1. EPDM cross-linked with sulphur: -45°C to +120°C
2. EPDM cross-linked with peroxide: -45°C to + 150°C
This applies in principle, and of course also to the media resistance of EPDM O-rings:
The effect of media on the gasket material must always be considered in conjunction with the operating temperature. With EPDM, the use of hot water and steam is particularly important.
Normal qualities reach maximum continuous temperatures of 150 degrees on these media. Special materials designed for this purpose can be used up to 180 degrees. Above this, permanent thermal deformation of EPDM begins and with it the loss of the elastic sealing properties.
In comparison VMQ and FKM have a significantly higher suitability for high temperatures.
Low temperatures cause O-rings to lose their elastic properties. Hardness and embrittlement increase to such an extent that the material can break when subjected to impact stress.
This is basically a reversible process. EPDM O-rings are sufficiently robust down to -50 degrees. This makes the behavior of EDPM similar to materials such as CR or TPU.
In contrast, VMQ achieves significantly lower temperatures.
#5 What are the mechanical properties of EPDM O-rings?
1. High elasticity
2. Very good abrasion resistance
3. Pronounced elongation at break
EPDM is a synthetic rubber produced by the polymerization of three monomers.
The chemical and mechanical properties of the products can be adjusted according to requirements by adjusting the proportions of monomers and other additives. Basically, EPDM has a very high elasticity, which is largely responsible for the reliable sealing effect.
Even after prolonged pressure loads, EPDM O-rings return almost completely to their original shape. This elasticity can be further increased in EPDM O-rings by peroxide cross-linking instead of the standard sulphur cross-linking.
In terms of abrasion resistance, EPDM, together with NBR, CR and FKM, is clearly ahead of silicone-based sealing materials. This makes the dynamic use where the moving sealing surfaces cause increased friction.
In addition, the high mechanical strength and elongation at break are important mechanical properties.
EPDM O-rings can be used during the assembly process during assembly without causing permanent damage. This makes the installation of an externally sealing O-ring particularly unproblematic.
#6 What do I have to consider when designing the groove of an EPDM O-ring?
1. Groove design according to DIN 3771 Part 5
2. Ensure minimum compression of the cross-section of 6% in the static case
3. Always select lower compression for dynamic sealing
4. Allow for up to 6% expansion over the inside diameter of the groove in the event of external pressure
5. Allow for 1 to 3% compression on the outer diameter of the groove if pressure is applied from the inside
The temperature-related shrinkage and expansion behavior of EDPM is low.
Therefore, when designing the groove, no
special precautions for expansion. For many
A compression of 25% is recommended for standard applications.
What should I bear in mind when fitting EPDM O-rings?
1. Provide for entry slopes between 15 and 20 degrees
2. Deburr drill holes
3. Plan sharp edges with a minimum radius of 0.1 to 0.3
4. Use suitable assembly aids (silicone oil)
5. Avoid twisting the O-ring
Important: Due to the lack of resistance, never use mineral oil-based oils or greases to facilitate assembly!
#7 Further important information on EPDM O-rings
Finally, we would like to answer a few questions that we are frequently asked in everyday life.
#7.1 What does EPDM mean for O-rings?
EPDM is an elastomer and is one of the standard materials for O-rings. The abbreviation “EPDM” stands for the chemical term “ethylene propylene diene rubber”.
EPDM O-rings are characterized by their good media resistance and are frequently used in the food and pharmaceutical industries in particular.
#7.2 Where can I find the EPDM data sheet?
You can easily view the data sheet for our EPDM O-rings directly on our website and download it if you wish.
#7.3 How heat-resistant is EPDM?
A distinction must be made between a sulphur and a peroxide cross-linked EPDM:
EPDM O-rings cross-linked with sulphur: -45°C to +120°C
EPDM O-rings cross-linked with peroxide: -45°C to +150°C
#7.4 What does EPDM 70 mean?
The “70” indicates the hardness of the EPDM O-ring material.
The hardness of elastomers (rubber) is specified in the unit “Shore”. Accordingly, “EPDM 70” refers to an EPDM with a hardness of 70 Shore A.
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Lord of the O-rings
Author of the sealing academy
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