Product Code Database
Nitrile rubber, also known as nitrile butadiene rubber, NBR, Buna-N, and acrylonitrile butadiene rubber, is a synthetic rubber derived from acrylonitrile (ACN) and butadiene. Trade names include Perbunan, Nipol, Krynac and Europrene. This rubber is unusual in being resistant to oil, fuel, and other chemicals.
NBR is used in the automotive and aeronautical industry to make fuel and oil handling , seals, grommets, and self-sealing fuel tanks. It is also used in the food service, medical, and nuclear industries to make protective gloves. NBR's stability at temperatures from makes it an ideal material for aeronautical applications. Nitrile butadiene is also used to produce moulded goods, footwear, adhesives, sealants, sponges, expanded foams, and floor mats.
Its resilience makes NBR a useful material for disposable lab, cleaning, and examination gloves. Nitrile rubber is more resistant than natural rubber to and , and has superior strength, but inferior flexibility.
Monomers are usually permitted to react for 5 to 12 hours. Polymerization is allowed to proceed to ~70% conversion before a “shortstop” agent (such as dimethyldithiocarbamate and diethylhydroxylamine) is added to react with (destroy) the remaining free radicals and initiators. Once the resultant latex has “shortstopped”, the unreacted monomers are removed through steam in a slurry stripper. Recovery of unreacted monomers is close to 100%. After monomer recovery, latex is sent through a series of filters to remove unwanted solids and then sent to the blending tanks where it is stabilized with an antioxidant. The yielded polymer latex is coagulated using calcium nitrate, aluminium sulfate, and other coagulating agents in an aluminium tank. The coagulated substance is then washed and dried into crumb rubber.
The process for the production of cold NBR is very similar to that of hot NBR. Polymerization tanks are cooled to 5–15 °C instead of heating up to 30–40 °C close to ambient temperature (ATC). Under lower temperature conditions, less branching will form on polymers (the amount of branching distinguishes cold NBR from hot NBR).
An important factor in the properties of NBR is the ratio of acrylonitrile groups to butadiene groups, referred to as the ACN content. The lower the ACN content, the lower the glass transition temperature; however, the higher the ACN content, the better resistance the polymer will have to nonpolar solvents as mentioned above. Most applications requiring both solvent resistance and low-temperature flexibility require an ACN content of 33%.
| Appearance | |
| Hardness, Shore A | 30–90 |
| Tensile failure stress, ultimate | 500-2500 PSI |
| Elongation after fracture in % | 600% maximum |
| Density | Can be compounded around 1.00 g/cm3 |
Unlike polymers meant for ingestion, where small inconsistencies in chemical composition/structure can have a pronounced effect on the body, the general properties of NBR are insensitive to composition. The production process itself is not overly complex; the polymerization, monomer recovery, and coagulation processes require some additives and equipment, but they are typical of the production of most rubbers. The necessary apparatus is simple and easy to obtain.
In January 2008, the European Commission imposed fines totaling Euro34,230,000 on the Bayer and Zeon groups for fixing prices for nitrile butadiene rubber, in violation of the EU ban on and restrictive business practices (Article 81 of the EC Treaty and Article 53 of the EEA Agreement).
Also known as highly saturated nitrile (HSN), HNBR is widely known for its physical strength and retention of properties after long-term exposure to heat, oil, and chemicals. Trade names include Zhanber (Lianda Corporation), Therban (Arlanxeo ), and Zetpol (Zeon Chemical). It is commonly used to manufacture O-rings for automotive air-conditioning systems. Other applications include timing belts, dampers, servo hoses, membranes, and seals.
Depending on filler selection and loading, HNBR compounds typically have tensile strengths of 20–31 MPa at 23 °C. Compounding techniques allow for HNBR to be used over a broad temperature range, −40 °C to 165 °C, with minimal degradation over long periods. For low-temperature performance, low ACN grades should be used; high-temperature performance can be obtained by using highly saturated HNBR grades with white fillers. As a group, HNBR elastomers have excellent resistance to common automotive fluids (e.g., engine oil, coolant, fuel, etc.).
The unique properties and higher temperature rating attributed to HNBR when compared to NBR have resulted in the wide adoption of HNBR in automotive, industrial, and assorted, performance-demanding applications. On a volume basis, the automotive market is the largest consumer, using HNBR for a host of dynamic and static seals, hoses, and belts. HNBR has also been widely employed in industrial sealing for oil field exploration and processing, as well as rolls for steel and paper mills.
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