Carboxylated nitrile rubber vs. epichlorohydrin rubber for fuel hose - What is The Difference?

Carboxylated nitrile rubber (XNBR) offers superior fuel resistance, tensile strength, and abrasion resistance compared to epichlorohydrin rubber (ECO), making it ideal for high-performance fuel hoses. While ECO rubber provides excellent low-temperature flexibility and chemical resistance, XNBR's enhanced durability and oil resistance optimize fuel hose longevity and safety.

Table of Comparison

Introduction to Carboxylated Nitrile and Epichlorohydrin Rubber

Carboxylated nitrile rubber (XNBR) features enhanced oil resistance and improved mechanical strength due to the presence of carboxyl groups, making it ideal for fuel hose applications requiring durability and compatibility with various fuels. Epichlorohydrin rubber (ECO) offers superior ozone, weather, and heat resistance, with excellent flexibility in low temperatures, suited for fuel hoses in demanding environmental conditions. Both elastomers provide strong fuel resistance, but the choice depends on specific performance needs such as abrasion resistance or ambient temperature resilience.

Composition and Chemical Structure Comparison

Carboxylated nitrile rubber (XNBR) contains nitrile groups with added carboxyl functional groups that enhance oil and fuel resistance, while epichlorohydrin rubber (ECO) exhibits a unique copolymer structure of epichlorohydrin and ethylene oxide, offering excellent resistance to fuels and ozone. XNBR's polar carboxyl groups increase intermolecular forces, improving tensile strength and fuel barrier properties, whereas ECO's ether linkages contribute to its flexibility and chemical degradation resistance. The chemical backbone of XNBR is predominantly acrylonitrile butadiene copolymer modified with carboxylation, contrasting with ECO's saturated polymer structure, which impacts fuel hose durability and performance differently under exposure to hydrocarbon fuels.

Fuel Resistance Properties

Carboxylated nitrile rubber (XNBR) exhibits superior fuel resistance compared to epichlorohydrin rubber (ECO) due to its enhanced cross-link density and polar functional groups, which improve swelling resistance and durability in hydrocarbon environments. XNBR maintains mechanical integrity and resists degradation when exposed to gasoline, diesel, and ethanol-blended fuels, making it ideal for demanding fuel hose applications. Epichlorohydrin rubber, while offering excellent resistance to ozone and weathering, typically shows moderate fuel resistance and higher swelling rates in aromatic and oxygenated fuels than carboxylated nitrile rubber.

Temperature Performance Range

Carboxylated nitrile rubber (XNBR) offers a temperature performance range typically from -40degC to 120degC, making it suitable for fuel hoses exposed to a broad spectrum of environmental conditions. Epichlorohydrin rubber (CO) excels in temperature resistance with an operating range of approximately -40degC to 150degC, providing enhanced heat tolerance for fuel hose applications subjected to higher thermal stress. The wider temperature range of epichlorohydrin rubber makes it preferable in high-temperature fuel delivery systems requiring durability and chemical resistance.

Mechanical Strength and Durability

Carboxylated nitrile rubber (XNBR) exhibits superior mechanical strength and enhanced abrasion resistance compared to Epichlorohydrin rubber (ECO), making it ideal for high-stress fuel hose applications. XNBR maintains excellent tensile strength and elasticity under extreme temperatures, contributing to long-lasting durability and resistance to fuel oil permeation. Epichlorohydrin rubber provides good ozone and weather resistance but generally shows lower mechanical robustness and shorter lifespan when exposed to aggressive fuels and continuous flexing.

Flexibility and Bend Radius

Carboxylated nitrile rubber (XNBR) exhibits superior flexibility and a smaller bend radius compared to epichlorohydrin rubber, making it ideal for fuel hoses requiring tight routing and dynamic movement. XNBR's enhanced cross-linking and polar groups improve elasticity and resistance to kinking under flexural stress. In contrast, epichlorohydrin rubber provides moderate flexibility but generally demands a larger bend radius, limiting its application in compact or highly flexible fuel hose assemblies.

Compatibility with Automotive Fuels

Carboxylated nitrile rubber (XNBR) offers excellent resistance to a wide range of automotive fuels, including gasoline, diesel, and ethanol blends, making it ideal for fuel hose applications requiring durability and fuel permeability resistance. Epichlorohydrin rubber (ECO) provides superior compatibility with polar solvents and certain biofuels but generally exhibits lower resistance to aromatic hydrocarbons and some gasoline additives compared to XNBR. Fuel hoses made from XNBR typically demonstrate better long-term performance and chemical stability in conventional and blended fuel environments than those made from Epichlorohydrin rubber.

Aging and Ozone Resistance

Carboxylated nitrile rubber (XNBR) exhibits superior fuel resistance and enhanced ozone resistance due to its polar carboxyl groups, making it more durable under aging conditions in automotive fuel hose applications. Epichlorohydrin rubber (CO) offers excellent resistance to ozone and weathering as well but generally shows better flexibility and low temperature performance at the cost of slightly lower fuel resistance compared to XNBR. For fuel hoses requiring long-term exposure to ozone and oxidative aging, XNBR provides improved mechanical stability and resistance to cracking, while epichlorohydrin rubber balances ozone resistance with enhanced cold flexibility.

Cost Considerations and Economic Impact

Carboxylated nitrile rubber (XNBR) generally offers a lower initial cost compared to epichlorohydrin rubber (ECO), making it a more budget-friendly choice for fuel hose manufacturing. Epichlorohydrin rubber, despite its higher price, provides superior resistance to fuel, oils, and chemicals, reducing long-term maintenance and replacement costs. Evaluating the total cost of ownership reveals that ECO's durability can offset upfront expenses, leading to better economic efficiency in demanding automotive and industrial fuel applications.

Application Suitability for Fuel Hose Manufacturing

Carboxylated nitrile rubber (XNBR) offers superior fuel resistance and enhanced mechanical strength, making it ideal for fuel hose applications requiring high durability and chemical stability. Epichlorohydrin rubber (ECO) provides excellent resistance to oils, ozone, and weathering, ensuring reliable performance in fuel systems exposed to harsh environmental conditions. For fuel hose manufacturing, XNBR is preferred when high abrasion resistance and fuel compatibility are critical, whereas ECO is suited for hoses demanding exceptional resistance to aging and low permeability to combustible fluids.