As a supplier of NBR Cord, I am often asked about its chemical composition. Nitrile rubber (NBR), also known as acrylonitrile - butadiene rubber, is a synthetic rubber copolymer. In this blog, I will delve into what exactly makes up NBR Cord and how these components contribute to its properties.
The Basic Monomers of NBR
NBR is mainly composed of two monomers: butadiene and acrylonitrile. Let's take a look at each of them in detail.
1. Butadiene
Butadiene (C₄H₆) is a conjugated diene hydrocarbon. Its chemical structure contains two carbon - carbon double bonds. The presence of these double bonds gives butadiene its high reactivity and flexibility. When polymerized, the butadiene units form long chains that are crucial for the rubber's elastic properties. Butadiene provides the NBR with good resilience, low - temperature flexibility, and high abrasion resistance. In the NBR Cord, the butadiene segments allow the cord to stretch and return to its original shape without significant deformation, making it suitable for applications where repeated movement or vibration is present.
2. Acrylonitrile
Acrylonitrile (C₃H₃N) is an unsaturated organic compound with a nitrile group (- C≡N). The nitrile group in acrylonitrile is the key factor that differentiates NBR from other types of rubber. The amount of acrylonitrile in the NBR can vary significantly, typically ranging from 18% to 50% by weight. A higher acrylonitrile content in the NBR Cord increases its resistance to oils, fuels, and other chemicals. This is because the polar nitrile groups interact strongly with polar molecules in oils and fuels, preventing them from penetrating the rubber matrix. As a result, NBR Cord with a high acrylonitrile content is commonly used in automotive fuel systems, hydraulic systems, and industrial applications where contact with oils and chemicals is frequent.
Other Additives
In addition to the butadiene and acrylonitrile monomers, several additives are incorporated into the NBR during the manufacturing process of the NBR Cord to enhance its performance and processing characteristics.
1. Reinforcing Agents
Carbon black is one of the most commonly used reinforcing agents in NBR Cord. Carbon black particles are very fine and have a large surface area. When added to the NBR, they form a network within the rubber matrix, which significantly improves the tensile strength, tear resistance, and abrasion resistance of the cord. The type and amount of carbon black used can be adjusted according to the specific requirements of the application. For example, in heavy - duty industrial applications where the cord will be subjected to high stress and wear, a higher loading of carbon black may be used.
2. Cross - Linking Agents
To give the NBR Cord its three - dimensional network structure and improve its mechanical properties, cross - linking agents are used in the vulcanization process. Sulfur is the traditional cross - linking agent for NBR. During vulcanization, sulfur atoms form bridges between the polymer chains of NBR, creating a more rigid and stable structure. This cross - linking process enhances the cord's resistance to heat, chemicals, and mechanical stress. In addition to sulfur, other cross - linking agents such as peroxides can also be used, especially when a higher degree of heat resistance is required.
3. Plasticizers
Plasticizers are added to improve the flexibility and processability of the NBR Cord. They work by reducing the intermolecular forces between the polymer chains, allowing them to move more freely. This results in a lower glass - transition temperature (Tg) of the rubber, which means the cord can remain flexible at lower temperatures. Common plasticizers used in NBR include phthalates and adipates. However, due to environmental and health concerns, there is a growing trend towards using more environmentally friendly plasticizers.
4. Antioxidants and Antiozonants
Antioxidants and antiozonants are added to protect the NBR Cord from degradation caused by oxygen and ozone. Oxygen can react with the double bonds in the butadiene segments of the NBR, leading to chain scission and a decrease in mechanical properties. Ozone, on the other hand, can cause cracking on the surface of the rubber. Antioxidants such as phenolic and amine - based compounds react with oxygen radicals, preventing them from attacking the rubber chains. Antiozonants, such as para - phenylenediamines, form a protective layer on the surface of the rubber to prevent ozone from reacting with it.
How the Chemical Composition Affects the Applications
The unique chemical composition of NBR Cord gives it a wide range of applications.
1. Automotive Industry
In the automotive industry, NBR Cord is widely used in fuel systems, such as fuel hoses and gaskets. The high acrylonitrile content in the NBR provides excellent resistance to gasoline, diesel, and other automotive fuels. The good mechanical properties, including high tensile strength and abrasion resistance, ensure that the cord can withstand the harsh conditions in the engine compartment, such as high temperatures and vibrations.
2. Industrial Sealing Applications
NBR Cord is also commonly used in industrial sealing applications. For example, it can be used as O - rings in hydraulic systems and pneumatic systems. The combination of good chemical resistance and elasticity allows the NBR O - rings to effectively seal the connections and prevent leakage of fluids or gases. You can find Black NBR O - Ring Cord on our website, which is a great option for such applications.
3. Other Applications
Other applications of NBR Cord include consumer goods, such as footwear soles, where its abrasion resistance and flexibility are highly valued. In addition, it can be used in some electrical applications as insulation materials due to its good electrical insulating properties.
Comparison with Other O - Ring Cord Materials
To better understand the properties of NBR Cord, it is useful to compare it with other types of O - ring cord materials.
1. FKM O - Ring Cord
Fluorocarbon rubber (FKM) is known for its outstanding chemical resistance, especially to high - temperature chemicals and solvents. Our Brown FKM O - Ring Cord has excellent resistance to fuels, oils, and many aggressive chemicals. However, FKM is generally more expensive than NBR, and its low - temperature flexibility is not as good as NBR. NBR Cord is a more cost - effective option for applications where the temperature and chemical resistance requirements are not extremely high.
2. Silicone O - Ring Cord
Silicone rubber has excellent high - and low - temperature stability and good electrical insulation properties. Our Clear Silicone O - Ring Cord is often used in applications where resistance to extreme temperatures is required, such as in the food and beverage industry and medical applications. However, silicone rubber has relatively poor resistance to oils and fuels compared to NBR. So, if the application involves contact with oils and fuels, NBR Cord is a more appropriate choice.
Why Choose Our NBR Cord
As a professional NBR Cord supplier, we have strict quality control measures in place. We carefully select the raw materials, including the butadiene, acrylonitrile, and various additives, to ensure the consistent quality of our NBR Cord. Our manufacturing process is optimized to produce NBR Cord with excellent mechanical properties, chemical resistance, and performance. Whether you need NBR Cord for automotive, industrial, or other applications, we can provide you with the right product.
If you are interested in our NBR Cord or any other rubber extrusion products, please feel free to contact us for detailed product information and to discuss your purchasing needs. We are committed to providing high - quality products and excellent customer service.
References
- Morton, M. (1995). Rubber Technology. Kluwer Academic Publishers.
- Rodgers, S. M. (2006). Engineering with Rubber: How to Design Rubber Components. CRC Press.
- Gates Rubber Company. (1987). Rubber Handbook.