acrylonitrile-butadiene rubber

Description

Nitrile rubber (NR) is a copolymer of butadiene and acrylonitrile. It is produced in different ratios varying from 25:75 to 75:25. The manufacturer’s designation should identify the percentage of acrylonitrile. Nitrile rubber under the common trade name Buna N is well known for its excellent resistance to oils and solvents owing to its resistance to swelling when immersed in mineral oils. Moreover, its chemical resistance to oils is proportional to the acrylonitrile content. However, it is not resistant to strong oxidizing chemicals such as nitric acid, and it exhibits fair resistance to ozone and to UV irradiation which severely embrittles it at low temperatures. Nitrile rubber is used for gasoline hoses, fuel pumps diaphragm, gaskets, seals and packings (e.g., o-rings) and finally oil-resistant soles for safety work shoes.

Chemical Properties

(Medium acrylonitrile) D (polymer) 0.98, tensile strength (psi) 1000–3000, elongation (%) 100–700, maximum service temperature 121– 148C. Combustible.

Uses

(High acrylonitrile) Oil well parts, fuel-tank liners, fuel hoses, gaskets, packing oil seals, hydraulic equipment. (Medium acrylonitrile) General-purpose oil-resistant applications, shoe soles, kitchen mats, sink topping, and printing rolls. (Low acrylonitrile) Gaskets, grommets, and O-rings (flexible at a very low temperature), adhesives. Fuel binder in solid rocket propellants.

Definition

nitrile rubber: A copolymer ofbuta-1,3-diene and propenonitrile. Nitrilerubbers are commercially important synthetic rubbers because oftheir resistance to oil and many solvents.See also buna rubber.

Definition

A copolymer of butadiene and propenonitrile (acrylonitrile) (CH₂=CHCN). It is an important rubber due to its resistance to oil and solvents.

Definition

(acrylonitrile rubber; acrylonitrilebutadiene rubber; nitrile-butadiene rubber; NBR). A synthetic rubber made by random polymerization of acrylonitrile with butadiene by free radical catalysis. Alternating copolymers using Natta–Ziegler catalyst have been developed. Approximately 20% of the total is used as latex; also available in powder form. Its repeating structure may be represented as –CH2CH=CHCH2CH2 CH(CN)–.

Industrial uses

Nitrile butyl rubber (NBR) has excellent resistance to mineral and vegetable oils, but relatively poor resistance to the swelling action of oxygenated solvents such as acetone, methyl ethyl ketone, and other ketones. It has good resistance to acids and bases except those having strong oxidizing effects. Resistance to heat aging is good, often a key advantage over natural rubber. With compounding, nitrile rubbers can provide a good balance of low creep, good resilience, low permanent set, and good abrasion resistance.
Tear resistance is inferior to that of natural rubber, and electrical insulation is lower. Uses of NBR include carburetor and fuel-pump diaphragms and aircraft hoses and gaskets. In many of these applications, the nitriles compete with polysulfides and neoprenes.
An outstanding feature of nitrile rubber is its compatibility with many different types of resins permitting it to be easily blended with them. In combination with phenolic resins it provides adhesives with especially high strengths. Nitrile rubber phenolic resin solvent solutions are used in shoe sole-attaching adhesives, for structural bonding in aircraft, adhering automotive brake lining to brake shoes, and many other industrial applications. The ratio of butadiene to acrylonitrile in the commercially available rubbers ranges from a low of about 20% to as high as 50% acrylonitrile. The various grades are usually referred to as high, medium-high, medium-low, and low acrylonitrile content.