Epichlorohydrin (ECO)

Epichlorohydrin rubber(ECO) is a synthetic elastomer known for its excellent resistance to fuels, oils, ozone, and gases. There are two main types of epichlorohydrin rubber: homopolymers (containing only epichlorohydrin units) and copolymers, where epichlorohydrin is combined with other monomers such as ethylene oxide or allyl glycidyl ether. These variations allow formulators to tailor the material’s properties, adjusting flexibility, temperature resistance, and processability to meet specific application requirements.

One of the key advantages of Epichlorohydrin rubber is its low gas permeability. It provides an effective barrier against vapours and gases, making it ideal for use in fuel systems, rubber seals, and gaskets. It also offers good resistance to ozone, weathering, and heat, with typical service temperatures ranging from around -40°C to 135°C. ECO maintains good dimensional stability and compression set resistance, which helps ensure tight seals and long service life in dynamic and static applications. Its reliable mechanical properties, including strength, elasticity, and resistance to deformation, make it a dependable choice for demanding moulded components.

Because of these characteristics, Epichlorohydrin is commonly used in the automotive and industrial sectors for components such as fuel hoses, diaphragms, gaskets, and vibration dampening parts. It is especially useful in situations that require a balance of fuel resistance, thermal stability, and durability.

Epichlorohydrin (ECO) rubber sits somewhere between nitrile rubber (NBR), ethylene propylene diene monomer (EPDM), and fluoroelastomers (FKM) in terms of performance and cost, making it a useful option when a balance of properties is needed.

Compared to NBR, ECO offers better resistance to ozone, weathering, and fuel permeability. While NBR performs well in oil and fuel environments, it can degrade more quickly when exposed to outdoor conditions or elevated temperatures. ECO, on the other hand, maintains greater stability in these settings, while still offering excellent resistance to fuels and oils. It also outperforms chloroprene rubber in fuel and oil resistance, though chloroprene may offer better flame retardancy and flexibility in some general-purpose applications.

In contrast to EPDM rubber, which is known for outstanding weather and ozone resistance but poor oil and fuel resistance, ECO provides similar environmental durability while also withstanding exposure to hydrocarbons. This makes ECO a more versatile choice for sealing applications where contact with fuels or lubricants is expected.

When compared to FKM (such as Viton®), ECO falls short in terms of high-temperature and chemical resistance. FKM is the premium option for demanding environments, but it also comes at a significantly higher cost. ECO offers a more economical alternative for applications that don’t require the extreme performance of FKM but still demand good fuel resistance and long-term durability.

Yes, ECO rubber can be used in dynamic sealing applications, provided that the operating conditions are within its performance limits. Thanks to its excellent resistance to fuels, oils, and ozone, as well as its low gas permeability and good dimensional stability, ECO is well-suited for seals that need to perform reliably over time in challenging environments.

In dynamic applications, where the seal must accommodate movement, pressure fluctuations, or repeated contact, ECO performs particularly well in systems involving rotary or reciprocating motion. It maintains its elasticity and shape under moderate stress, and its compression set resistance helps it maintain an effective seal even after extended use.

It’s important to note that while ECO offers good performance in many dynamic settings, it is not as flexible or abrasion-resistant as some softer elastomers like silicone rubber or certain grades of NBR. For high-speed or highly abrasive environments, materials specifically formulated for extreme dynamic motion may be more suitable.

Overall, ECO is a strong choice for dynamic sealing when resistance to fuels, oils, and gases is a key requirement, especially in automotive applications and industrial applications involving fuel systems, hydraulic components, and engine parts.

While Epichlorohydrin (ECO) rubber offers a strong balance of fuel resistance, low gas permeability, and environmental stability, it does come with certain limitations that may affect its suitability in specific applications.

One of the primary drawbacks of ECO is its limited flexibility at low temperatures. Although it can function in sub-zero conditions, its elasticity becomes reduced below -40°C, which can lead to cracking or seal failure in extremely cold environments. For applications that require better low-temperature performance, other elastomers like silicone or certain grades of NBR may be more appropriate.

ECO’s poor resistance to strong acids, bases, and polar solvents. While it performs well against oils and fuels, it is not suitable for exposure to aggressive chemicals such as ketones, esters, or concentrated alkalis. In chemically harsh environments, more chemically resistant materials like FKM or EPDM are often a better choice.

ECO rubber is also more expensive than standard rubbers like NBR, which can make it less attractive for cost-sensitive applications where its unique properties aren’t essential. Additionally, its processing can be more complex, requiring specific curing systems and careful control over compounding and moulding conditions.

Lastly, ECO is not typically suitable for food or medical applications, as it lacks the regulatory approvals required for contact with consumables or sensitive biological materials.

At Kea-Flex, we understand that selecting the right material is critical to the performance and longevity of your product. Our team works closely with you to assess your technical requirements, environmental conditions, and cost considerations, ensuring you get the most suitable material for your application, whether that’s ECO or an alternative elastomer. We help take the guesswork out of material selection by combining expert advice with decades of moulding experience.

No, Epichlorohydrin (ECO) rubber is not typically approved for use in food-grade or medical applications. Its chemical composition and the curing agents used in its processing do not meet the strict regulatory standards required for materials that come into direct contact with food, beverages, pharmaceuticals, or human tissue.

ECO is formulated primarily for industrial and automotive environments. The very additives and properties that make ECO effective in these applications, such as its resistance to hydrocarbons and low permeability, also mean it may release substances that are not suitable for ingestion or medical use.

For applications where hygiene, biocompatibility, or food safety is critical, materials like silicone rubber, EPDM (in FDA-approved grades), or fluoroelastomers (FKM) with food-grade certification are typically used instead. These alternatives can be specifically formulated to comply with standards set by regulatory bodies such as the FDA, EU 1935/2004, or USP Class VI.

Yes, all Epichlorohydrin (ECO) rubber must be cured, also known as vulcanised, before it can be used in practical applications. In its raw form, ECO is soft, tacky, and lacks the mechanical strength and elasticity required for performance parts. Curing transforms it into a durable elastomer by creating crosslinks between the polymer chains, giving it the flexibility, strength, and chemical resistance needed for real-world use.

ECO rubber is typically cured during the moulding process using either amine-based or peroxide-based curing systems. The choice of curing method depends on the performance requirements of the final product, such as resistance to heat, fuels, and pressure.

Amine curing is the traditional method and provides good low-temperature flexibility, excellent oil and fuel resistance, and strong adhesion to metals. However, it may lead to a higher compression set and offers slightly lower heat resistance compared to peroxide systems. It’s commonly used in automotive and industrial seals, diaphragms, and fuel system components.

Peroxide curing offers enhanced resistance to heat, chemicals, and ageing, along with lower compression set and cleaner processing. It produces more stable long-term properties but may result in a slightly stiffer finished product and usually requires higher processing temperatures and tighter control during moulding.

The curing process itself takes place during compression, injection, or transfer moulding, common techniques used in epichlorohydrin rubber moulding, where heat and pressure are applied to the ECO compound inside a mould. This activates the curing agents and completes the crosslinking process, locking the rubber into its final shape with the desired mechanical and chemical properties.