NBR rubber material analysis

Date:29-05-2020
Abstract:

Nitrile rubber is made from butadiene and acrylonitrile […]

Nitrile rubber is made from butadiene and acrylonitrile by emulsion polymerization. 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 to manufacture oil resistant rubber products. Referred to as NBR, it is a synthetic rubber made by copolymerization of butadiene and acrylonitrile. It is synthetic rubber with good oil resistance (especially paraffin oil) and good aging resistance. The content (%) of acrylonitrile in nitrile rubber is 42-46, 36-41, 31-35, 25-30, 18-24 and so on. The greater 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 ℃ or in oil at 150 ℃. In addition, it also has good water resistance, air tightness and excellent bonding properties. Widely used in the production of various oil-resistant rubber products, a variety of oil-resistant gaskets, gaskets, sleeves, flexible packaging, flexible hoses, printing and dyeing rubber rollers, cable adhesive materials, etc., becoming indispensable in the automotive, aviation, petroleum, photocopying and other industries Elastic material.

NBR has excellent oil resistance. The succinic monomer can be copolymerized into three different chain structures: cis, trans and 1,2-yenyl. The trans form accounts for about 78% of the typical NBR structure. Because the NBR molecular chain structure contains cyano groups, oil resistance (such as resistance to mineral oil, liquid fuel, animal and vegetable oils and solvents) is superior to natural rubber, neoprene and styrene-butadiene rubber. Compared with other rubbers, NBR has a wider temperature range. Its long-term use temperature is 120oC. At the same time, NBR has good low temperature resistance, and the minimum glass transition temperature can reach -55oC.

NBR has good chemical resistance. The processing performance is good. With the increase of the relative density of propionitrile in its structure, the vulcanization speed is accelerated, the tensile strength performance is improved, but the resilience performance is reduced, and the cold resistance is deteriorated. Because the cyano group in NBR is easy to be polarized by the electric field, the dielectric properties are degraded and it is semiconductor rubber. According to the level of ACN content, NBR can be divided into 5 categories: super high, high, medium high, medium and low acrylic. There are two production methods: continuous and batch polymerization. The continuous polymerization method is usually used for production of small varieties and large production volumes, with low consumption. The batch polymerization method is suitable for multi-variety and small batch production. The number of polymerization tags is small and the construction cost is high. So far, the trend of mutual substitution has not been seen.

Although nitrile rubber has excellent physical mechanical properties and processing performance, it has not been used in acid gasoline and high temperature (150oC) environments for a long time. It is not as good as fluorine rubber and acrylic cool rubber. For this reason, German companies, Canadian companies and Japanese companies Developed hydrogenated nitrile rubber (HNBR) with excellent performance. In addition, it has developed ultra-cold resistance and high-purity nitrile rubber and XNBR and so on.

advantage:
1. Has good resistance to oil, water, solvent and high-pressure oil.
2. With good compression distortion, anti-wear and elongation.
3. Used to make fuel tanks, lubricating oil tanks and oil-based hydraulic oil, gasoline, water, grease, silicone oil, diester-based lubricants, alcohol
It is a rubber part used in fluid medium such as hydraulic oil, especially a sealing part.
Depending on the material, the static operating pressure is less than 20Mpa. Sometimes it is also used for dynamic, the working pressure under dynamic is less than 5Mpa, and semiconductor vacuum sealing.
Available size specifications are: cross-sectional diameter of about 0.35-12mm inner diameter can reach 1000mm and above
Compared with other sealing elements, O-shaped seals have many advantages as follows:
-Simple structure, integrated groove design, reduce processing and design costs;
-Compact structure, small parts appearance;
-Easy installation and reduced risk;
-Can be applied to various sealing problems, such as: static sealing, dynamic sealing, single-acting and double-acting sealing;
-Wide material selection range, suitable for most fluids.
Feature description
Nitrile rubber has superior resistance to petroleum-based products, and its use temperature range can be formulated through special formulations
Expanded to -55 ° C ~ 125 ° C (-67 ° F ~ 275 ° F), it is the most widely used seal material.
Nitrile rubber is a copolymer of butadiene and acrylonitrile. The content of acrylonitrile (ACN) in the NBR molecule is
Variable (18 to 50%), which can be used to adjust the oil resistance and low temperature resistance of the material. The more acrylonitrile content
The higher the resistance to lubricants and fuels, the lower the elasticity at low temperatures. Conversely, when the acrylonitrile content
The lower the temperature resistance, the better, but at the expense of lubricating oil and fuel resistance. Military specifications AN and
The O-ring specifications of MS require low acrylonitrile butadiene rubber to ensure its low temperature resistance.
Nitrile rubber has superior compression permanent deformation, tear resistance, and wear resistance, but does not have good weather resistance and resistance
Ozone function, and heat resistance is only moderate.
advantage
﹒ Superior compression set
﹒ Superior tear resistance
﹒ Good wear resistance
Disadvantages
﹒ Resistance to ozone, sunlight, poor climate
﹒ Moderate heat resistance
Special application
﹒ NSF 61 drinking water certified materials
﹒ British WRC, German KTW drinking water certification materials
﹒ FDA certified whitelist materials
° C -40 ° ~ 100 ° C Special formula -55 ° ~ 125 ° C
° F -40 ° ~ 212