Nitrile rubber is produced by the emulsion polymerization method using butadiene and acrylonitrile. It is mainly produced using the low-temperature emulsion polymerization method and has excellent oil resistance, high wear resistance, good heat resistance, and strong adhesion. Its disadvantages are poor cold resistance and poor ozone resistance, poor insulation performance, and slightly lower elasticity. Nitrile rubber is mainly used to manufacture oil-resistant rubber products. It is abbreviated as NBR and is a synthetic rubber obtained by copolymerization of butadiene and acrylonitrile. It is a synthetic rubber with good oil resistance (especially aliphatic oil) and aging resistance. Nitrile rubber contains acrylonitrile in percentages ranging from 42 to 46, 36 to 41, 31 to 35, 25 to 30, and 18 to 24. The higher the acrylonitrile content, the better the oil resistance, but the cold resistance decreases accordingly. It can be used for a long time in 120℃ air or 150℃ oil. In addition, it has good water resistance, airtightness, and excellent bonding performance. It is widely used in the manufacture of various oil-resistant rubber products, various oil-resistant gaskets, pads, sleeves, soft packaging, soft rubber hoses, printing rubber rollers, cable rubber materials, etc. It has become an indispensable elastic material in industries such as automobiles, aviation, petroleum, and copying.
NBR has excellent oil resistance. The butadiene-diene monomer can be copolymerized into three different chain structures: cis, trans and 1,2-alkyl. In the typical NBR structure, the trans form accounts for approximately 78%. Due to the presence of cyano groups in the molecular chain structure of NBR, its oil resistance (such as resistance to mineral oil, liquid fuels, animal and vegetable oils, and solvents) is superior to natural rubber, chloroprene rubber and styrene-butadiene rubber. Compared with other rubbers, NBR has a wider range of application temperatures. Its long-term operating temperature is 120°C, and it also has good low-temperature resistance, with a minimum glass transition temperature of -55°C.
NBR has excellent chemical stability and good processing performance. As the content of acrylonitrile in its structure increases, its relative density rises, the vulcanization speed accelerates, the tensile strength improves, but the rebound performance decreases, and the cold resistance deteriorates. Due to the easy electrical polarization of the cyano groups in NBR, its dielectric properties decrease, making it a semiconductor rubber. NBR can be classified into five categories based on the content of ACN: ultra-high, high, medium-high, medium, and low acrylonitrile. The production methods include continuous and batch polymerization methods. The continuous polymerization method is usually used for single-variety and large-scale production, with low consumption. The batch polymerization method is suitable for multi-variety and small-batch production, with a small amount of polymerization catalyst used and high construction consumption. So far, there is no trend of mutual substitution.
Although nitrile rubber has excellent physical and mechanical properties as well as processing performance, its performance is inferior to that of fluorine-based rubber and acrylate rubber when used in acidic gasoline and at high temperatures (150°C). Therefore, German companies, Canadian companies and Japanese companies have developed highly superior hydrogenated nitrile rubber (HNBR). In addition, they have also developed rubber with extremely high cold resistance and high purity nitrile rubber as well as spandex-like nitrile rubber (XNBR).
Advantages:
1. It has excellent resistance to oil, water, solvents and high-pressure oil.
2. It has good compression set, anti-wear and elongation properties.
3. It is used for manufacturing fuel tanks, lubrication tanks, and rubber parts in petroleum-based hydraulic oils, gasoline, water, grease, silicone oil, diester-based lubricants, alcohol-based hydraulic oils, etc., especially sealing parts.
Depending on the material, the static operating pressure is less than 20 MPa. Sometimes it is also used dynamically, with a dynamic operating pressure less than 5 MPa, and semiconductor vacuum sealing.
The available size specifications are: cross-sectional diameter approximately 0.35 - 12 mm, inner diameter can reach 1000 mm or more.
Compared with other sealing elements, O-ring seals have the following many advantages:
- Simple structure, integrated groove design, reducing processing and design costs;
- Compact structure, small part shape;
- Simple installation, reducing risks;
- 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 fluid media.
Characteristics description
Nitrile rubber has superior performance in petroleum-based products. Its operating temperature range can be expanded to -55°C to 125°C (-67°F to 275°F) through special formulation blending, making it the most widely used sealing material.
Nitrile rubber is a copolymer of butadiene and acrylonitrile. The acrylonitrile (ACN) content in the NBR molecule is variable (18% to 50%), which can adjust the oil resistance and low-temperature resistance of the material. The higher the acrylonitrile content, the better the properties for lubricating oil and fuel, but the low-temperature elasticity is worse. Conversely, when the acrylonitrile content is lower, the low-temperature resistance is better, but at the expense of the properties for lubricating oil and fuel. The O-ring specifications of military standards AN and MS require low-acrylonitrile nitrile rubber to ensure its low-temperature performance.
Nitrile rubber has excellent compression set, anti-tear, and wear resistance, but does not have good weather resistance and ozone resistance, and has only medium heat resistance. Advantages
· Excellent compressive permanent deformation resistance
· Excellent tear resistance
· Excellent wear resistance Disadvantages
·Resistant to ozone, sunlight and adverse climates
·Moderate heat resistance
Special applications
·NSF 61 drinking water certified material
·British WRC, German KTW drinking water certified material
·FDA certified white list material
°C -40°~100°C Special formula -55°~125°C °F -40°~212
