NBR Rubber Gaskets (Nitrile / Buna-N)

Oil, fuel and hydraulic flat seals in nitrile rubber. Custom cut, sheet stock and flange gaskets for petroleum service.

Overview

NBR rubber gaskets — also called nitrile gaskets or Buna-N gaskets — are the standard flat-seal choice for petroleum oils, fuels and hydraulic fluids. The acrylonitrile content (typically 18–40%) controls oil resistance and low-temperature flexibility; higher ACN improves oil resistance but stiffens the compound at cold temperatures. For flange service, NBR is most often specified at 70 Shore A for general use, 80 Shore A for higher bolt loads, and 90 Shore A when extrusion resistance is needed. The practical temperature range is approximately −40°C to +120°C continuous. LT-NBR grades extend low-temperature sealing to about −55°C but reduce some oil resistance. NBR flat gaskets are used on hydraulic manifolds, fuel system flanges, gearbox covers, oil pans, and industrial equipment handling mineral oils and diesel. They are not suitable for outdoor ozone exposure, aromatic fuels in high concentrations, or brake fluid. In those cases, FKM, HNBR or EPDM should be considered. We supply NBR gaskets as die-cut parts, waterjet prototypes, sheet stock and CNC flashcut profiles. Send ID, OD, thickness, hardness and drawing for a quote. NBR gaskets are single-use and should be replaced after disassembly.

Types

Die-Cut NBR Gaskets

Steel-rule or punch-die cut gaskets for medium-to-high volume. Best for simple profiles and consistent tolerances.

Best for: Hydraulic flanges, gearbox covers, oil pan gaskets

Waterjet NBR Gaskets

Tooling-free cutting for prototypes and complex shapes. Slightly looser tolerance than die-cut but fast turnaround.

Best for: Prototypes, one-offs, irregular profiles

NBR Sheet Stock

Uncut nitrile sheet for customers who fabricate their own seals. Standard 60–70 Shore A, black.

Best for: MRO shops, field fabrication, large quantity blanket orders

Materials

Material	Properties	Best For
NBR 70 Shore A (Medium ACN)	General oil and fuel resistance; −30°C to +100°C typical	Hydraulic flanges, general industrial oil service
NBR 90 Shore A	High hardness for bolt-load retention and extrusion resistance	High-pressure hydraulic manifolds, confined grooves
LT-NBR	Low-temperature compound; −40°C to −55°C cold flexibility	Cold climate machinery, mobile hydraulics
High-ACN NBR	Superior aromatic fuel and solvent resistance; reduced low-temp flexibility	Fuel systems with aromatic content

Sizing

NBR gaskets are made to customer drawing or matched to common flange dimensions. Tolerances depend on cut method.

Thicknesses

• 1/32"
• 1/16"
• 3/32"
• 1/8"
• 3/16"
• 1/4"
• Custom

Cut methods

• Die-cut
• Waterjet
• Flashcut
• Sheet

Applications

Hydraulics

Manifold flanges, pump covers, valve bodies, adapter plates

Automotive

Fuel sender flanges, oil pan joints, transmission covers

Industrial Machinery

Gearbox inspection covers, oil bath housings, lubrication systems

Oil & Gas

Diesel fuel flanges, lube oil systems, low-pressure hydraulic skids

Frequently Asked Questions

What is the difference between an NBR gasket and a nitrile gasket?

There is no difference. NBR is the ISO/ASTM abbreviation for nitrile butadiene rubber; nitrile gasket and Buna-N gasket are common trade names for the same material.

Is NBR an oil resistant rubber gasket?

Yes. NBR is the most widely used oil resistant rubber gasket material for petroleum oils, hydraulic fluids and aliphatic fuels.

When should I choose 90 Shore A over 70 Shore A?

Use 90 Shore A when bolt preload is high, the flange gap must remain small under pressure, or extrusion into clearance gaps is a concern. 70 Shore A conforms better to rough or warped flanges.

Can NBR gaskets handle biodiesel or ethanol blends?

Standard NBR tolerates low-level biodiesel and ethanol blends. High aromatic or high-oxygenate fuels swell NBR over time; specify high-ACN NBR or FKM for severe fuel service.

Why does my NBR gasket crack outdoors?

NBR has poor ozone and UV resistance. Outdoor exposure causes surface cracking. For ozone or UV environments, switch to EPDM or CR neoprene.

Can NBR gaskets be used for steam?

No. NBR is not recommended for steam or hot water service. Use EPDM or AFLAS for steam, and EPDM for hot water.