Frequently Asked Questions — NBR O-Rings
What is NBR (Nitrile) rubber?
NBR (Nitrile Butadiene Rubber), also called Buna-N or nitrile rubber, is the most widely used o-ring elastomer in general industrial applications. Its acrylonitrile (ACN) content can be adjusted between 18 % and 50 % to balance oil resistance against low-temperature flexibility. Higher ACN means better oil resistance; lower ACN means better cold performance.
What temperature range can NBR o-rings handle?
Standard NBR o-rings operate from −40 °C to +120 °C. High-ACN grades (better oil resistance) have a minimum operating temperature of around −25 °C, while low-ACN grades remain flexible to −50 °C. Continuous operation above 100 °C will gradually harden the compound over time.
What chemicals is NBR resistant to?
NBR has good resistance to mineral oils, hydraulic fluids, petroleum-based fuels (petrol, diesel), greases and fats, water, and many salt solutions. It is not suitable for aromatic hydrocarbons, chlorinated solvents, ketones, ozone or UV exposure without protective measures, or phosphate-ester hydraulic fluids.
What are typical applications for NBR o-rings?
NBR is the standard sealing material for hydraulic cylinders and pneumatic actuators, automotive fuel systems and carburettors, industrial compressors and pumps, gearboxes, and any general engineering application involving petroleum-based fluids at moderate temperatures. Its combination of availability, cost, and performance makes it the default starting point for o-ring selection.