What are the properties of nitrile rubber?

Nitrile rubber is prepared by emulsion polymerization of butadiene and acrylonitrile. The nitrile rubber is mainly produced by low temperature emulsion polymerization. It has excellent oil resistance, high wear resistance, good heat resistance and strong adhesion. The disadvantages are poor low temperature resistance, poor ozone resistance, poor insulation performance and slightly lower elasticity. Nitrile rubber is mainly used in the manufacture of oil-resistant rubber products, abbreviated as NBR, a synthetic rubber obtained by copolymerization of butadiene and acrylonitrile. It is an oil resistant (especially alkane oil) and a synthetic rubber with good aging resistance.

The acrylonitrile content (%) in the nitrile rubber has five kinds, such as 42 to 46, 36 to 41, 31 to 35, 25 to 30, and 18 to 24. The more acrylonitrile content, the better the oil resistance, but the cold resistance is correspondingly reduced. It can be used for a long time in air at 120 ° C or in oil at 150 ° C. In addition, it has good water resistance, air tightness and excellent bonding properties. Widely used in the manufacture of various oil-resistant rubber products, a variety of oil-resistant gaskets, gaskets, casings, flexible packaging, soft rubber hoses, printing and dyeing rubber rollers, cable rubber materials, etc., in the automotive, aviation, petroleum, copying and other industries become essential Elastic material.

NBR has excellent oil resistance. The dibutyl monomer can be copolymerized into three different chain structures: cis, trans and 1,2-indenyl. The trans form in a typical NBR structure accounts for about 78%. Due to the cyano group in the molecular chain structure of NBR, oil resistance (such as mineral oil, liquid fuel, animal and vegetable oil and solvent) is superior to natural rubber, neoprene and styrene butadiene rubber. Compared with other rubbers, NBR has a wider use temperature. Its long-term use temperature is 120 °C, while NBR has good low temperature resistance and the minimum glass transition temperature can reach -55 °C.

 NBR has good chemical resistance and good processing performance. With the increase of the relative density of the acrylonitrile content in the structure, the vulcanization rate is accelerated, the tensile strength performance is improved, but the resilience performance is decreased, and the cold resistance is deteriorated. Since the cyano group in the NBR is easily polarized by electric field, the dielectric properties are lowered, and it is a semiconductor rubber. NBR can be classified into super high, high, medium high, medium and low acrylonitrile according to the ACN content. The production method is divided into two types: continuous and batch polymerization. Continuous polymerization is generally used for low-yield and high-volume production with low consumption. The batch polymerization method is suitable for multi-variety and small-volume production, the number of polymerization labels is small, and the construction cost is high. So far, there is no tendency to replace each other.

Although nitrile rubber has excellent physical and mechanical properties and processing properties, it has been used for a long time in acid gasoline and high temperature (150 ° C) environments, such as fluorine-like rubber and acrylate rubber. For this reason, German companies, Canadian companies and Japan The company has developed hydrogenated nitrile rubber (HNBR) with excellent performance. In addition, it has also developed ultra-cold-resistant and high-purity nitrile rubber and shuttle-based nitrile rubber (XNBR).