azmater.com Epichlorohydrin rubber offers excellent oil, fuel, and ozone resistance with moderate heat stability, making it ideal for O-rings in automotive and fuel system applications. Ethylene propylene diene rubber (EPDM) provides superior weather, heat, and chemical resistance but lacks compatibility with oils and hydrocarbons, suited for O-rings in water, steam, and brake fluid environments.
Table of Comparison
| Property | Epichlorohydrin Rubber (ECO) | Ethylene Propylene Diene Rubber (EPDM) |
|---|---|---|
| Chemical Resistance | Excellent against oils, fuels, and chemicals | Good resistance to water, steam, and weathering; poor against hydrocarbons |
| Temperature Range | -40degC to 120degC (-40degF to 248degF) | -50degC to 150degC (-58degF to 302degF) |
| Compression Set | Low, maintains seal integrity | Moderate to low, good for long-term sealing |
| Ozone and UV Resistance | Good resistance | Excellent resistance |
| Applications | Automotive fuel systems, oil handling seals | Water systems, HVAC, outdoor seals |
| Cost | Moderate | Low to moderate |
Introduction to O-Ring Materials: ECH vs. EPDM
Epichlorohydrin (ECH) rubber offers excellent resistance to oils, fuels, and ozone, making it ideal for O-rings in automotive and fuel system applications. Ethylene propylene diene monomer (EPDM) rubber provides superior resistance to weathering, heat, steam, and various chemicals, commonly used in water, brake, and HVAC sealing systems. Selecting between ECH and EPDM depends on the specific fluid compatibility, temperature range, and environmental exposure requirements of the O-ring sealing application.
Chemical Structure and Composition Differences
Epichlorohydrin rubber (ECO) features a copolymer of epichlorohydrin and ethylene oxide, characterized by a unique chlorinated oxygen-containing backbone enhancing oil and fuel resistance. Ethylene propylene diene rubber (EPDM) consists of ethylene, propylene, and a diene monomer, providing unsaturation sites for vulcanization while delivering excellent weather, ozone, and heat resistance. The chlorinated structure of ECO imparts superior hydrocarbon resistance, whereas the saturated backbone of EPDM offers superior chemical stability in polar environments.
Mechanical Properties Comparison
Epichlorohydrin rubber offers superior oil resistance and good mechanical properties including tensile strength around 10-15 MPa and elongation exceeding 300%, making it ideal for dynamic O-ring applications in automotive and industrial environments. Ethylene propylene diene monomer (EPDM) rubber exhibits excellent weathering, ozone resistance, and high elongation up to 400%, but has lower tensile strength typically between 7-12 MPa, making it more suitable for static sealing under harsh environmental conditions. The mechanical property differences heavily influence O-ring performance, with Epichlorohydrin favored for enhanced durability against oils and fuels, while EPDM excels in outdoor exposure and temperature extremes.
Temperature Resistance: ECH vs. EPDM
Epichlorohydrin rubber (ECH) offers excellent temperature resistance, maintaining flexibility and sealing performance between -40degC and 125degC, with short-term exposure up to 150degC. Ethylene propylene diene monomer rubber (EPDM) demonstrates superior heat resistance, withstanding continuous temperatures from -50degC to 150degC and peaks up to 170degC, making it ideal for high-temperature applications. Both elastomers resist thermal degradation, but EPDM's enhanced resistance to heat aging and ozone makes it more suitable for prolonged high-temperature environments in O-ring seals.
Chemical Resistance and Compatibility
Epichlorohydrin rubber (ECO) exhibits superior resistance to oils, fuels, and ozone, making it highly compatible with petroleum-based fluids while maintaining excellent impermeability. Ethylene propylene diene rubber (EPDM) provides outstanding compatibility with polar solvents, weathering, acids, alkalis, and steam but shows poor resistance to petroleum oils and solvents. For O-ring applications requiring chemical resistance to oils and hydrocarbons, Epichlorohydrin is favored, whereas EPDM is optimal for exposure to water, acids, and alkalis.
Performance in Automotive and Industrial Applications
Epichlorohydrin rubber (ECO) offers excellent resistance to oils, fuels, and weathering, making it highly suitable for O-rings in automotive fuel systems and industrial hydraulic applications. Ethylene propylene diene monomer (EPDM) rubber excels in heat, ozone, and steam resistance, enabling superior performance in automotive cooling systems and industrial water handling. Both elastomers provide durability and sealing reliability, but ECO is preferred for hydrocarbon exposure while EPDM is ideal for high-temperature and aqueous environments.
Aging, Weather, and Ozone Resistance
Epichlorohydrin rubber (ECO) exhibits superior resistance to oil, ozone, and weathering compared to Ethylene Propylene Diene Monomer (EPDM) rubber, making it highly durable for O-rings exposed to harsh environmental conditions. EPDM rubber offers excellent aging resistance and outstanding performance against ozone and weathering but has limited oil resistance, reducing its effectiveness in oil-exposed applications. For O-ring applications requiring long-term exposure to aggressive chemicals and environmental factors, Epichlorohydrin rubber generally provides better longevity and stability.
Cost Considerations and Availability
Epichlorohydrin rubber (ECO) offers a cost-effective solution for O-rings due to its balanced pricing and moderate production complexity compared to Ethylene Propylene Diene Monomer (EPDM) rubber, which often incurs higher costs linked to enhanced weather and chemical resistance properties. Availability of Epichlorohydrin is generally stable, supported by established manufacturing processes, whereas EPDM supply can fluctuate based on raw material access and demand in automotive and industrial sectors. Choosing between ECO and EPDM for O-rings hinges on budget constraints and the specific performance requirements of the application environment.
Environmental Impact and Regulatory Issues
Epichlorohydrin rubber (ECO) O-rings are known for their excellent resistance to oils and chemicals but pose environmental concerns due to the release of toxic chlorinated compounds during production and disposal, leading to stricter regulatory scrutiny under agencies like the EPA and REACH. Ethylene propylene diene monomer (EPDM) rubber O-rings offer superior environmental profiles with lower emissions of hazardous substances and better recyclability, making them more compliant with global environmental regulations including REACH and RoHS directives. Selection between ECO and EPDM for O-rings often hinges on balancing chemical resistance requirements with compliance to increasingly stringent environmental standards and regulatory mandates.
Key Factors for Selecting O-Ring Material
Epichlorohydrin rubber offers excellent resistance to oils, ozone, and weathering, making it suitable for sealing applications exposed to hydrocarbons and moderate heat up to 135degC. Ethylene propylene diene rubber (EPDM) provides superior resistance to heat, steam, and polar solvents, with a wider temperature range from -50degC to 150degC, ideal for outdoor and automotive O-rings exposed to weather and chemicals. Key factors for selecting O-ring material include chemical compatibility, temperature range, compression set resistance, and environmental exposure, where Epichlorohydrin excels in oil resistance and EPDM in heat and weather resistance.
Infographic: Epichlorohydrin rubber vs Ethylene propylene diene rubber for O-ring