NBR - Nitrile Rubber
What is Nitrile Rubber
Nitrile, also known as Buna-N or NBR (nitrile-butadiene rubber) is a type of synthetic rubber polymer. It is a copolymer made up of a combination of acrylonitrile and butadiene molecules. There are different grades available with nitrile rubber manufacturers and suppliers. The higher the acrylonitrile (ACN) content in a grade of nitrile rubber, the higher will be the oil resistance but then the low temperature flexibility will get poorer. Nitrile is a highly popular elastomer that is extensively used in the seal industry today. Its applications range from automotive and aeronautical industries to manufacturing fuel and oil handling hoses, grommets, self-sealing fuel tanks, and seals, as it surpasses the capabilities of ordinary rubbers. Nitrile butadiene is also used in the production of various goods, such as footwear, adhesives, sealants, sponges, expanded foams, and floor mats. It is further employed to create disposable non-latex gloves, automotive transmission belts, hoses, O-rings, gaskets, oil seals, V belts, static and dynamic hydraulic seals, synthetic leather, printer’s form rollers, and cable jacketing.
NBR’s robustness also makes it an excellent material for disposable gloves used in laboratories, cleaning, and medical examinations. Compared to natural rubber, nitrile rubber is more resistant to oils and acids and boasts superior strength, although it has relatively less flexibility. This is why nitrile gloves are more durable than natural rubber gloves, especially when natural rubber gloves degrade when exposed to ozone or chemicals. Moreover, nitrile rubber is less likely to trigger an allergic reaction than natural rubber. Unlike polymers intended for consumption, where slight variations in chemical composition or structure can have a significant impact on the body, NBR’s overall properties remain unchanged by minor structural or compositional discrepancies.
Properties of Nitrile Rubber
Nitrile rubber grades can be differentiated based on their acrylonitrile content, which plays a crucial role in determining their properties. Nitrile rubber (NBR) quality with high acrylonitrile content exhibits excellent oil and performance properties, while NBR with low acrylonitrile content shows better temperature and cold resistance. Despite having moderate physical properties, nitrile rubbers display remarkable resistance to abrasion and excellent tolerance to oil and hydrocarbon solvents. High nitrile content grades have lower gas permeability, but poor ozone and modest heat resistance. Carboxylation (XNBR) or hydrogenation is often employed to improve their temperature resistance and physical properties.
By altering the acrylonitrile content in nitrile rubber, various properties can be adjusted. Higher acrylonitrile content leads to better resistance against aromatic hydrocarbons, while lower acrylonitrile content enhances low-temperature flexibility.
High Nitrile: >45% ACN content
Medium Nitrile: 30-45% ACN content
Low Nitrile: <30% ACN content
The higher the ACN content, the higher the resistance to aromatic hydrocarbons.
The lower the ACN content, the better the low temperature flexibility.
The best overall balance for most applications is medium ACN content.
Nitrile Rubber Characteristic
