Knowledge about nitrile rubber

Introduction to nitrile rubber

Nitrile butadiene rubber (NBR) is a copolymer formed by polymerization of acrylonitrile and butadiene monomer. It is mainly produced by low-temperature emulsion polymerization. It has excellent oil resistance, high wear resistance, good heat resistance and strong adhesion.Its disadvantages are poor low temperature resistance, poor ozone resistance, poor insulation performance, slightly low elasticity.

Nitrile rubber is mainly used in the manufacture of oil resistant rubber products.Acrylonitrile content (%) in nitrile rubber has 42 ~ 46, 36 ~ 41, 31 ~ 35, 25 ~ 30, 18 ~ 24 and other five kinds.The higher the content of acrylonitrile, the better the oil resistance, but the cold resistance decreases accordingly.It can be used for a long time in air at 120 ° C or oil at 150 ° C.In addition, it also has good water resistance, air tightness and excellent bonding properties.Widely used in making all kinds of oil resistant rubber products, a variety of oil resistant gaskets, gaskets, sleeves, flexible packaging, soft rubber hose, printing and dyeing cots, cable rubber materials, etc., in the automotive, aviation, petroleum, copy and other industries become essential elastic materials.

performance

NBR has excellent oil resistance.The reeireulation of butanediene monomers can be copolymerized into cis, trans, 1, 2-reeireulation of three different chain structures.About 78% of typical NBR structures are trans.Because of the cyanide group in the molecular chain structure of NBR, the oil resistance (such as mineral oil, liquid fuel, animal and vegetable oil and solvent) is better than that of natural rubber, neoprene rubber and styrene butadiene rubber.Compared with other rubber, NBR has a wider range of use temperature. Its long-term use temperature is 120oC. At the same time, NBR has good low temperature resistance and the lowest glass transition temperature can reach -55oC.[1]

NBR has good chemical stability and processing performance. With the content of acrylonitrile in its structure, the relative density increases, the curing speed speeds up, the tensile strength performance improves, but the resilience energy decreases, and the cold resistance deteriorates.Because the cyanide group in NBR is easy to be polarized by electric field, its dielectric properties decrease, so it is a semiconductor rubber.According to the content of ACN, NBR can be divided into five categories: ultra high, high, medium high, medium low acrylonitrile.The production mode is divided into two kinds: continuous polymerization and intermittent polymerization.Continuous polymerization is usually used for production of fewer varieties and large yields with low consumption.The batch polymerization method is suitable for many varieties and small batch production, the number of polymerization tags is less, and the construction consumption is high.So far, there is no discernible trend towards substitution.[1]

Although nitrile rubber has excellent physical and mechanical properties and processing performance, but for a long time in the acid gasoline and high temperature (150oC) environment performance is not as good as fluorine rubber and acrylic acid rubber, so German companies, Canadian companies and Japanese companies developed excellent performance of hydrogenated nitrile rubber (HNBR).In addition, also developed with extremely super cold resistance and high purity nitrile rubber test and XNBR.