True Oil-Resistant Buna-N (Nitrile) O-Rings: Engineered for Zero Swell
Stop replacing hardened or swollen seals every three months. Whether your legacy drawing specifies “Buna-N” or “Nitrile (NBR)”, you need the exact same thing: a pure elastomer engineered to survive harsh mineral oils, synthetic lubricants, and aggressive additives. No recycled rubber. No “fake” oil resistance. Just factory-direct precision that slashes your costs.
Defeating the Flaws of Cheap Seals & High Western Overhead
For procurement managers and fluid power engineers, a leaking seal is a catastrophic failure, and bloated western manufacturing costs destroy your margins. RiseUp is a direct-source factory that custom-compounds our oil-resistant Buna-N O-rings to specifically eliminate the biggest risks in your supply chain:
1. Eliminating “Fake Oil Resistance” (Zero Swell): Many generic NBR seals are diluted with cheap recycled rubber. When exposed to oil, they swell by over 30%, causing valves to jam. We guarantee a 100% pure Oil-Resistant Grade Nitrile that strictly maintains its precise dimensional volume under pressure.
2. Mastering Specific Fluid Compatibility: Standard NBR handles basic mineral oil, but what about synthetic gear oils with aggressive additives? Our polymer engineers formulate specific Buna-N compounds to ensure total chemical compatibility, ending your anxiety over complex fluid environments.
3. Extended Service Life (No More 3-Month Failures): Cheap NBR O-rings often harden and crack after a few months in warm oil. By utilizing optimized High-ACN (Acrylonitrile) compounds, we drastically extend your seal’s thermal and chemical stability.
4. The “Buna-N” North American Guarantee: Does your engineering team specifically demand “Buna-N”? Rest assured, Buna-N and NBR are the exact same polymer class. We perfectly match your legacy AS568 dimension specifications with zero tooling fees.
5. The China Supply Chain Advantage (Maximum ROI): While US, European, Japanese, and Korean manufacturers pass their exorbitant overhead costs down to you, our fully integrated China supply chain offers an unbeatable price-to-performance ratio. By partnering directly with our factory, you dramatically reduce your BOM expenses, ultimately empowering your end-products to be vastly more competitive in the global market.
Not All Nitrile is Created Equal: The Secret of ACN Content
A generic “oil-resistant” label on a packing slip is not enough to protect your equipment. The actual resistance of a Buna-N O-ring to swelling, softening, and chemical degradation is entirely dictated by its Acrylonitrile (ACN) to Butadiene ratio.
Cheap manufacturers lower the ACN percentage and add excessive carbon fillers to cut costs. The result? Seals that turn into mush or swell uncontrollably when exposed to complex industrial fluids. As a direct compounding factory, RiseUp controls the polymer matrix at a molecular level, offering three distinct ACN formulations to match your exact failure points:
Tuning the Polymer to Your Specific Environment
High ACN (45% – 50%): The Ultimate Oil Defender. Engineered for direct contact with highly aromatic fuels, modern synthetic lubricants, and aggressive oil additives (like sulfur and phosphorus). It delivers a near-zero volume swell rate.
Medium ACN (30% – 35%): The Industry Gold Standard. The “sweet spot” formulation that perfectly services 80% of general hydraulic and pneumatic applications. It provides excellent resistance to standard petroleum-based oils while maintaining highly reliable flexibility down to -34°C (-30°F).
Low ACN (18% – 24%): The Arctic Specialist. Specifically compounded for heavy mobile machinery operating in freezing outdoor conditions. We push the dynamic sealing capabilities down to an impressive -54°C (-65°F), while still offering moderate oil resistance.
The Fluid Compatibility Matrix: Where Buna-N Thrives (and Fails)
A generic “oil-resistant” claim is dangerous. In critical fluid power systems, you need absolute certainty. Specifying Buna-N in the wrong fluid will result in catastrophic swelling, shrinkage, or complete dissolution.
🟢 Excellent Compatibility (The "Green Light" Zone)
Our Oil-Resistant Buna-N formulations provide long-lasting, zero-swell sealing performance in:
Petroleum-Based Oils & Greases: Standard mineral oils, motor oils, and ISO VG hydraulic fluids.
Synthetic Lubricants (Specific): Most synthetic gear oils and polyalphaolefin (PAO) base oils.
Water-Glycol Fluids (HFC): Fire-resistant hydraulic fluids commonly used in mining and die-casting.
Silicone Greases: Excellent compatibility with standard silicone-based assembly lubricants.
🔴 DO NOT USE (The "Red Light" Danger Zone)
Do NOT specify any Nitrile/Buna-N O-ring for the following environments. They will fail rapidly:
❌ Automotive Brake Fluids (DOT 3 / DOT 4): Glycol-ether brake fluids will cause Buna-N to instantly swell and rupture. The Fix: You must switch to our [EPDM O-Rings].
❌ Polar Solvents (MEK, Acetone): Strong solvents will literally dissolve the Nitrile polymer structure.
❌ Ozone & UV Exposure: Direct sunlight, electric motors, or outdoor weathering will cause deep “ozonolysis” cracking in standard Buna-N.
Built for Pressure: Superior Abrasion & Extrusion Resistance
Chemical oil resistance alone will not stop a leak if your O-ring gets physically shredded by hydraulic pressure. In dynamic cylinders or high-pressure static flanges, the Buna-N seal is subjected to extreme mechanical stress.
Generic trading companies sell soft, poorly-cured rubber that easily succumbs to “nibbling” and extrusion damage. RiseUp compounds our Oil-Resistant Nitrile with premium carbon black reinforcement, ensuring your seals survive both the fluid and the friction:
Precise Hardness Control (70 & 90 Shore A): For standard applications, our 70 Shore A provides the perfect balance of compression and sealing force. For high-pressure hydraulics exceeding 1,500 PSI, we custom-mold rock-solid 90 Shore A Buna-N O-rings to prevent the rubber from being forced into hardware clearance gaps.
Maximum Extrusion Resistance: “O-ring extrusion” is the #1 cause of catastrophic high-pressure leaks. Our densely cross-linked polymer matrix boasts exceptional tensile strength, effectively resisting the shear forces that cause cheaper seals to chip, nibble, and blow out.
Dynamic Abrasion & Tear Strength: Operating a reciprocating piston or rotary shaft? Our reinforced Nitrile compounds drastically lower the coefficient of friction when lubricated, offering supreme wear resistance against continuous metal-on-rubber scraping.
Source Smart: Buna-N Engineering Knowledge Base
Yes, absolutely. “Buna-N” is simply the legacy North American trade name for the synthetic rubber officially known as Nitrile Butadiene Rubber (NBR). When your older CAD drawings call for Buna-N, you can seamlessly plug in our Oil-Resistant NBR O-rings with 100% material compliance.
Shrinkage is often more dangerous than swelling. Generic manufacturers use excessive liquid plasticizers to make cheap rubber feel soft. When exposed to certain aromatic oils or volatile fuels, these fluids act as solvents and “wash out” (extract) the plasticizers. Once the fluid evaporates, the O-ring shrinks below its original dimension, leading to an immediate and total loss of sealing force. Our pure, high-quality compounding prevents plasticizer extraction.
Unlike plastics that melt, Buna-N rubber reacts to extreme heat in oil by
further cross-linking. The polymer bonds become tighter, causing the O-ring to undergo “heat hardening.” It will eventually turn into a rigid, brittle plastic-like ring and shatter under pressure. For continuous hot oil applications above 120°C, you must upgrade to our [FKM / Viton® O-Rings].
HNBR (Hydrogenated Nitrile) is a highly engineered upgrade. By adding hydrogen atoms to the polymer backbone, HNBR eliminates vulnerable “double bonds.” This grants HNBR exceptional heat resistance (up to 150°C), vastly superior abrasion resistance in dynamic oil applications, and total immunity to ozone. If your standard NBR is failing due to high heat or mechanical wear, HNBR is the ultimate solution.
In dynamic reciprocating applications (like hydraulic cylinders), the mating metal surface must be ground to a roughness of
Ra 0.2 to 0.4 µm (8 to 16 µin). If the metal is too rough, it will shred the Nitrile. Ironically, if it is too smooth (Ra < 0.1 µm), it cannot retain a microscopic lubricating oil film, leading to severe stick-slip friction and premature seal failure.
Caution is required. While Buna-N is excellent for standard petroleum, high concentrations of ethanol (like E85) or modern biodiesel can aggressively attack standard Nitrile. For modern biofuels, you must explicitly specify our High-ACN formulation, or upgrade to FKM for absolute chemical immunity.
Absolutely. While standard industrial Buna-N is black due to carbon black reinforcement, we frequently manufacture oil-resistant NBR in custom colors—like Green, Blue, or Red—for OEM assembly lines. This color-coding is critical to prevent workers from accidentally mixing up NBR with EPDM or FKM during high-speed manufacturing.
Standard black industrial Buna-N is
NOT suitable for food contact. However, we custom-manufacture FDA-Compliant White Nitrile using non-toxic, food-grade white fillers, which are extensively used in food processing equipment and dairy pumps to seal food-grade oils.
It depends entirely on your system pressure and hardware clearance gap. Generally, a standard 70 Shore A Buna-N O-ring is safe up to 1,500 PSI. If your system pressure exceeds 1,500 PSI, or if your metal components have large extrusion gaps, you must either upgrade to our
90 Shore A Buna-N or design your groove to accommodate PTFE backup rings to prevent extrusion damage.
According to strict
ISO 2230 guidelines, Buna-N O-rings boast a shelf life of 15 years from the date of cure. To achieve this, they must be stored in airtight, UV-blocking black bags in a cool environment (below 25°C / 77°F) and kept strictly away from ozone-generating equipment like electric motors.
MOQ 500 pcs, Accept Customization for Small Order. Design Products as Your Idea.
Package Method
"Take The Efficient 2026 Booster For Your Business Now "
Alan Chen
Product Sales Manager & Rubber Specialist at RISEUP
