What is O-rings?
O-rings are annular sealing devices commonly used in various industries to prevent the passage of liquids, gases, or other contaminants between two surfaces. They are made from a flexible material, usually silicone or a synthetic elastomer such as nitrile, rubber, or Viton. The main function of the O-ring is to compress itself to achieve a tight sealing when the two surfaces are assembled.
Because of their simplicity, low cost, and high efficiency, O-rings are widely used in various applications such as automotive, aerospace, hydraulic systems, and chemical processing. They come in a variety of sizes, materials, and hardness levels to suit different environmental conditions and pressure requirements. Proper selection and installation of O-rings are essential to ensure the desired sealing performance and extend the service life of the component.
Types of Material Used to Construct O-rings
O-rings are used in applications that require resistance to pressure, temperature, and chemical exposure. To cater to these diverse requirements, O-rings are made from various materials. Here are some common materials used to construct O-rings:
Silicone (VMQ)
According to its vulcanization temperature, silicone rubber can be divided into two categories: high-temperature heating vulcanization type (HTV) and room-temperature vulcanization type (RTV). The high-temperature adhesive is mainly used for manufacturing all kinds of silicone rubber products, while room-temperature adhesive is mainly used as an adhesive, pot-sealing material, or mold.
Hot Vulcanized Silicone Rubber (HTV)
Hot vulcanized silicone rubber (HTV) is the most important kind of silicone product, and methyl vinyl silicone rubber (VMQ) is the most important kind of HTV, commonly known as high-temperature rubber. Methyl vinyl silicone rubber (raw rubber) is colorless, odorless, and non-toxic, with no mechanical impurities of the glue, raw rubber according to the demand to participate in the appropriate reinforcing agent, structural section preparation, curing agent and other additives mixed, and then temperature molding or extrusion molding, and then the second stage of vulcanization made of all kinds of products. Its finished products have excellent electrical insulation, arc resistance, corona, spark resistance, waterproof, moisture-proof, impact resistance, shock resistance, psychological inertia, permeability, and other functions.
Mainly used in aviation, instrumentation, electronic appliances, sailing, metallurgy, machinery, automobile, medical and health parts, can do all kinds of shapes of sealing rings, gaskets, tubes, and cables, but also can do human organs, blood vessels, breathable film, and rubber mold, fine forging release agent.
Room Temperature Vulcanized Silicone Rubber (RTV)
Room-temperature vulcanized silicone rubber is generally condensed and formed in two categories. Condensed room-temperature vulcanized silicone rubber is characterized by the condensation reaction between the silicon hydroxyl group and other active substances, which can be cross-linked into an elastomer at room temperature. The product is divided into single-component packaging and two-component packaging. Single component room temperature vulcanized silicone rubber (RTV-1 adhesive for short) is one of the first products of condensed liquid silicone rubber. It is made of foundation polymer, crosslinking agent, catalyst, filler, and additive. The product is packaged in a sealed hose, extruded when used, and can be vulcanized into an elastic body after contact with air, which is very convenient to use. Vulcanized rubber can be used in (-60 ~ +200℃) temperature limit for a long time, with excellent electric cut-off edge function and chemical invariance, water resistance, ozone resistance, weather aging resistance, a variety of metal and non-metal data has superior adhesion. Mainly used for coating all kinds of electronic components and electrical equipment, encapsulation data from insulation, moisture-proof, and shock-proof effect; As the appearance maintenance data of semiconductor devices; It can also be used as sealing interstitial material and elastic adhesive. Silicone O-rings are known for their flexibility and stability at extreme temperatures, both high and low. They also offer excellent resistance to UV light and ozone.
Nitrile Rubber (NBR)
What is nitrile rubber? Nitrile rubber also referred to as NBR, is a synthetic copolymer of acrylonitrile (ACN) and butadiene. This unsaturated copolymer is made up of 2-acrylonitrile and various butadiene monomers, offering a range of physical and chemical properties depending on the composition of nitrile in the polymer.
This material is widely used in the automotive and aerospace industries for oil and fuel handling hoses, seals, and rings due to its overall resistance to oil, fuels, and chemicals, as well as its ability to handle wide temperature ranges. Compared to natural rubber, NBR is less likely to cause adverse allergic reactions while providing superior strength and acid resistance although it is less pliable. While it is prone to ozone, ketones, esters, and aldehydes attack, it possesses remarkable resistance to aliphatic hydrocarbons. NBR is suitable for general-purpose applications and is known for its low cost and good mechanical properties.
Fluorocarbon (FKM)
Fluoro rubber refers to synthetic polymer elastomers that contain fluorine atoms attached to carbon atoms in the main or side chains. The introduction of fluorine atoms gives rubber excellent heat resistance, oxidation resistance, oil resistance, corrosion resistance, and atmospheric aging resistance.
It has been widely used in aerospace, aviation, automobile, petroleum, and household appliances, and is an irreplaceable key material in the cutting-edge industry of national defense. Fluorine rubber has a high degree of chemical stability and is the best dielectric resistance of all elastomers at present. Fluorine rubber has excellent weather aging resistance and ozone resistance. Fluorine rubber seals, used for engine sealing, can be long-term work at 200℃~250℃, and short-term work at 300℃, its working life can be the same as the engine repair life, up to 1000~5000 flight hours (time 5~10 years). It is commonly used in applications involving aggressive chemicals, fuels, and oils.This material is widely used in the automotive and aerospace industries for oil and fuel handling hoses, seals, and rings due to its overall resistance to oil, fuels, and chemicals, as well as its ability to handle wide temperature ranges. Compared to natural rubber, NBR is less likely to cause adverse allergic reactions while providing superior strength and acid resistance although it is less pliable. While it is prone to ozone, ketones, esters, and aldehydes attack, it possesses remarkable resistance to aliphatic hydrocarbons. NBR is suitable for general-purpose applications and is known for its low cost and good mechanical properties.
Ethylene Propylene Diene Monomer (EPDM)
EPDM is a terpolymer of ethylene, propylene, and unconjugated diolefin, which began commercial production in 1963. Worldwide consumption is 800,000 tons per year. The most important characteristic of EPDM is its excellent oxidation resistance, ozone resistance, and erosion resistance. As EPDM belongs to the polyolefin (PO) family, it has excellent vulcanization characteristics.
EPDM has the lowest specific gravity of all rubbers and can absorb large amounts of fillers and oils with little effect on properties, making it possible to produce rubber compounds at a low cost. Compared with other commonly used general rubber or special rubber, the main performance advantages of EPDM rubber lie in the following aspects: cost-effective, raw rubber density is only 0.86 ~ 0.90g/cm3, is the lightest rubber density commonly used; And can be filled in large quantities to reduce the cost of rubber material. Excellent aging resistance, weather resistance, ozone resistance, sunlight resistance, heat resistance, water resistance, water vapor resistance, ultraviolet resistance, radiation resistance, and other aging properties, when used with other unsaturated diene rubber such as NR, SBR, BR, NBR, CR, etc., EPDM can play the role of high molecular antioxidant or antioxidant. Excellent chemical resistance, acid, alkali, detergent, animal and plant oils, alcohols, ketones, etc. Excellent water resistance, hot water, and steam; Resistance to polar oils. Excellent insulation performance, volume resistivity 1016Q·cm, breakdown voltage 30 ~ 40MV/m, dielectric constant (1kHz, 20℃)2.27. Suitable for a wide range of temperatures, the lowest use temperature is -40 ~ -60℃, can be used for a long time under the condition of 130℃. EPDM O-rings are commonly used in applications involving hot water, steam, and brake fluid systems. However, EPDM is not recommended for use with petroleum-based fluids.
Polyurethane (PU)
Also known as Neoprene, CR O-rings offer good resistance to ozone, UV light, and weathering. They also provide moderate resistance to oils and chemicals. CR is suitable for general-purpose applications where moderate temperature and chemical resistance are required.
Perfluoroelastomer (FFKM)
FFKM O-rings are highly resistant to extreme temperatures and aggressive chemicals. They are often used in semiconductor manufacturing, aerospace, and other demanding applications. FFKM has excellent resistance to almost all chemicals, but it is also one of the most expensive O-ring materials.
PTFE (Polytetrafluoroethylene)
PTFE O-rings, also known as Teflon, have outstanding chemical resistance and can withstand a wide range of temperatures. They are often used in applications involving aggressive chemicals and high temperatures. However, PTFE is a rigid material and may not provide the best sealing performance in some applications.
How to Choose the Best Material for Your O-rings?
Choosing an O-ring with suitable material is extremely important for the overall performance and reliability of your application. The material plays a significant role in determining the O-ring’s resistance to various factors, such as temperature, chemicals, and pressure. Selecting the proper material can prevent leaks, extend the service life of the O-ring, and maintain the integrity of your system.
Here are some key factors to consider when choosing the best material for your O-ring:
(1) Working environment
Consider the temperature range, pressure, chemical exposure, or other environmental factors that the O-ring will be subjected to. Different materials have different tolerances to high temperatures, low temperatures, high pressures, and chemicals.
(2) Chemical compatibility
Make sure the O-ring material is compatible with the fluids, gases, or chemicals it comes into contact with. Incompatible materials can cause the O-ring to expand, degrade, or fail.
(3) Mechanical properties
Evaluate the tensile strength, elongation, and hardness of the material to determine whether it can withstand the stresses and forces it will be subjected to.
(4) Wear resistance
For dynamic applications, O-rings will experience frequent movement, choose materials with high wear resistance to prevent wear over time.
(5) Compression formability
Good compression formability indicates that the material can maintain its shape and seal effect under continuous pressure.
(6) Regulatory requirements
Depending on your industry, there may be specific regulations or standards governing what materials can be used in your application.
How to Manufacture O-ring?
The manufacture of o ring includes several steps such as material selection, preparation, molding, and post-processing. Here’s an overview of the process:
• Selection of materials
According to the intended use of the o-ring, operating environment, and chemical compatibility choose the appropriate materials. The most common material is silicone rubber, nitrile rubber (NBR), fluorine carbon (Viton), ethylene propylene monomer (EPDM), and polyurethane (PU).
• Raw material preparation: The raw material is mixed with a filler, plasticizer, hardener, colorant, and other additives to obtain the desired properties. The mixture is then ground into a uniform compound.
• Performing
The composite material is cut into small pieces or strips and performed into O-rings. This can be done by extrusion or by casting the material into a continuous cylindrical shape using a performing machine.
• Molding
There are three main methods for forming O-rings: compression molding, transfer molding, and injection molding.
Compression molding: The preformed material is placed into a heated mold cavity, then the mold cavity is closed and compressed. Heat and pressure cause the material to flow, filling the cavity and forming an O-ring.
Transfer molding: Similar to compression molding, the material is first placed in a separate chamber and then transferred to the mold chamber by a plunger or slider. This method is suitable for more complex geometries and higher efficiency.
Injection molding: The material is heated and injected into a high-pressure mold cavity. This method offers the highest productivity and dimensional accuracy but requires more sophisticated equipment and tools.
• Hardening
Molded O-rings undergo a hardening process, also known as vulcanization, to cross-link polymer chains and achieve the desired mechanical properties. This is usually done in an oven or autoclave at a specific temperature and time, depending on the material.
• Post-treatment
After hardening, the O-ring is removed from the mold and subjected to various post-treatment steps such as grinding off excess material, checking for defects, cleaning and quality control, and precision testing.
• Packaging and storage: The finished O-ring is properly packed and stored before being shipped to the customer to avoid damage or contamination.
Please keep in mind that the specific process may vary based on specific materials, equipment, and production requirements.
Silicone Manufacturer for Silicone O-ring Manufacturing
NEWTOP Custom Silicone is a silicone manufacturer based in China with more than 15 years. Our business expands from gaskets, and o-rings to bellows, bushings, tubes, etc. We own advanced manufacturing equipment, a quality control system, and professional techniques to make sure your o-ring can meet tough environments and working standards.
Hi, there, I’m Gary.
I’m the author of this article. I have been in this field for more than one decade. If you are looking for custom-made silicone rubber products or parts, feel free to ask me any questions.
