Carboxylated Nitrile (XNBR)
Carboxylated Nitrile Rubber (XNBR) is a modified copolymer of acrylonitrile, butadiene, and a small percentage of carboxylic acid groups, designed to combine oil and fuel resistance of standard NBR with enhanced tensile strength, modulus, and abrasion resistance.
The carboxyl functional groups introduce intermolecular crosslinks and improved filler–polymer bonding, resulting in superior wear resistance, tear strength, and dynamic durability compared to conventional NBR.
At Eutsler Technical Products, our XNBR formulations are optimized for abrasive, oil-laden, and high-pressure environments where mechanical fatigue, fluid resistance, and adhesion are critical. Typical applications include hydraulic seals, diaphragms, packer elements, gaskets, and dynamic isolators exposed to oils, fuels, and amine-based lubricants.
Performance Advantages
- Exceptional abrasion and wear resistance ideal for dynamic seals, bushings, and packer elements under sliding or reciprocating motion.
- High tensile and tear strength up to 30–50% higher than standard NBR due to enhanced polymer–filler bonding.
- Superior oil, fuel, and grease resistance with excellent performance in petroleum oils, synthetic lubricants, and fuels.
- Enhanced adhesion to metals and fabrics due to carboxyl groups increasing polarity and reactivity for rubber-to-metal bonding.
- Improved modulus and load-bearing capacity that resists deformation under pressure, shear, and mechanical load.
- Excellent compression set resistance which maintains sealing force under prolonged compression and thermal cycling.
- Good resistance to water, mild acids, and glycol-based fluids that are stable in hydraulic and automotive fluids containing amines or additives.
Applications
Eutsler’s XNBR compounds are designed for high-performance environments requiring durable oil and abrasion resistance under dynamic stress:
- Hydraulic and pneumatic seals
- Oilfield packer elements
- Wear pads, bushings, and couplings
- Diaphragms and bellows in oil service
- Automotive and industrial gaskets
- Roller coverings and pump sleeves
- Bonded rubber-to-metal isolators
XNBR is the material of choice when mechanical abrasion and fluid exposure coexist, offering a balance of resilience, oil compatibility, and physical strength unmatched by most hydrocarbon rubbers.
Superior Material Performance
Eutsler’s custom-engineered XNBR compounds provide:
| Property | Typical Range / Description |
|---|---|
| Tensile Strength (psi) | 1,800 – 4,000 |
| Elongation at Break (%) | 200 – 500 |
| Modulus (100% elongation, psi) | 400 – 1,200 |
| Hardness (Shore A) | 40 – 95 |
| Compression Set (70h @ 100°C) | Good – Excellent |
| Resilience / Rebound | Moderate – Good |
| Abrasion Resistance | Excellent (improved vs. NBR and HNBR) |
| Tear Resistance | Excellent |
| Oil Resistance | Excellent (hydrocarbons, lubricants, fuels) |
| Solvent Resistance | Good (hydrocarbons, esters, glycols) |
| Low Temperature Usage | –25 °F (–32 °C) |
| High Temperature Usage | +300 °F (150 °C) continuous |
| Weather / Ozone Resistance | Moderate (improved with additives) |
| Adhesion to Metals | Excellent |
| Water Resistance | Good (may swell slightly) |
Chemical and Environmental Resistance
| Medium | Resistance Level | Notes |
|---|---|---|
| Mineral Oils & Fuels | Excellent | Resistant to aromatic, paraffinic, and naphthenic oils |
| Hydraulic Fluids (HFA, HFB, HFD) | Excellent | Stable in glycol- and ester-based systems |
| Water & Steam (<100°C) | Good | Extended exposure may cause moderate swelling |
| Amines & Detergent Additives | Good | Performs better than NBR under mild amine exposure |
| Acids & Alkalis (mild) | Good | Short-term exposure acceptable |
| Ozone, Weather, UV | Fair – Good | Add stabilizers for long-term outdoor use |
| Brake Fluids (glycol-based) | Limited | Not recommended for prolonged exposure |
Processing & Manufacturing
Eutsler’s production processes ensure uniform filler dispersion, controlled cure kinetics, and reproducible rheology for XNBR compounds:
Mixing
- Two-roll mil
- Reinforcing fillers (carbon black, silica) optimized for modulus and tear strength.
- Controlled addition of curatives to prevent premature scorch.
Curing Systems
- Sulfur-cured: Balanced elasticity and fatigue life.
- Peroxide-cured: Higher thermal and oil stability.
- Metal-oxide co-curing: Enhanced modulus and compression set resistance for high-load parts.
Molding & Fabrication
- Compression, transfer, or injection molded components.
- Rubber-to-metal bonding via carboxyl reactivity with primers or direct adhesion systems.
- Compatible with extrusion, calendaring, and mandrel wrapping for hose or sleeve applications.
Design and Performance Notes
- Dynamic service: XNBR provides 2–3× abrasion life vs. NBR in reciprocating or rotating applications.
- Bonded components: The polar carboxyl groups significantly improve adhesion to metallic substrates.
- Thermal aging: Peroxide-cured XNBR resists oxidative degradation up to 300°F (150°C)
- Low-temperature flexibility: Enhanced with plasticizers or hybrid blends (XNBR/CR, XNBR/EPDM).
- Reinforcement: Carbon black grades (N220, N330) yield excellent balance of modulus and rebound.
Get in Touch with Our Experts Today!
Work with Eutsler for Custom XNBR Compounds
With over six decades of elastomer compounding expertise, Eutsler Technical Products develops and molds custom XNBR materials tailored for your specific environment — balancing modulus, oil resistance, tear strength, and fatigue life.
Our lab verifies every batch with ASTM D412, D624, D395, D573, D471, and D5289 testing, ensuring data-driven reliability and repeatable performance.
Request a quote or consultation today to discuss your application and get an XNBR compound engineered to your exact mechanical and chemical requirements.
Summary
XNBR elastomers from Eutsler Technical Products deliver reliable oil compatibility, outstanding abrasion life, and high tear strength, making them ideal for dynamic sealing and mechanical wear environments where durability and fluid resistance are critical.
- Chemical Family: Carboxylated Acrylonitrile-Butadiene Copolymer (XNBR)
- Service Temperature Range: –25 °F to +300 °F (–32 °C to +150 °C)
- Distinguishing Features:
- Enhanced mechanical and wear performance over NBR
- Excellent oil and fuel resistance
- Superior adhesion and tear strength
- Excellent balance between dynamic fatigue and compression set
- Typical Uses: Hydraulic seals, diaphragms, oilfield components, dynamic isolators, packers, and bushings.
- Limitations: Moderate ozone and weather resistance; low-temperature flexibility not as good as EPDM or VMQ.
Why Choose Eutsler Technical Products?
R&D
Experienced staff develop high performance and long life parts
Material Selection
Over 300 compounds or custom elastomeric compounds available
Mold Design
Custom molds are designed ensuring tolerances are met
Manufacturing
Molding, extrusion and die cutting services to build your part
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