Selecting the Right O-Ring Material
There are a variety of different O-ring materials, each offering their own unique benefits and suitability for certain applications. O-ring material selection depends on factors such as temperature, chemical or abrasion resistance, and even environmental conditions.
Silicone o rings are particularly resistant to extreme temperatures and environments, making them ideal for use in dynamic or static applications. They also offer excellent ozone, UV radiation and electrical insulation properties.
Temperature Resistant
Silicone o rings can be used in static applications that require resistance to a wide range of temperatures. They can be lubricated to help them stay in place, but they won’t quickly degrade when exposed to extreme heat like that found in some industries such as jewelry, metalworking and automotive manufacturing.
These seals also resist animal and vegetable oil, grease, ozone, oxidative environments and can be used outdoors. They can also withstand dry heat, though they need to be relubricated frequently when exposed to movement to prevent degradation.
This material is non-toxic, which makes it safe for medical and food applications. It is also odorless and does not grow mold. It is highly flexible and insulating, making it an ideal choice for low-closing force sealing. It can be molded or sliced, and it is available in many colors including black rubber for a classic look or clear silicone for a more discreet seal. This is a good alternative to PTFE o rings, which are more rigid and not flexible. They also can’t be compressed to the same degree as a silicone o ring.
Resistance to Chemicals
Chemical resistance is another factor to consider when selecting an O-ring for a specific application. O-rings can be specially formulated to provide better resistance to chemicals depending on the application and environment in which they’re being used.
Viton O-rings, made from a specialized fluoroelastomer that combines carbon and fluorine atoms to create a unique molecular structure, offer excellent chemical resistance and performance. They’re also capable of sustaining high temperatures and harsh outdoor environments without degrading or losing their sealing capabilities.
Silicone (VMQ) o rings are a popular choice for medical and food applications because they’re hypoallergenic. They’re resistant to ozone, UV light and many common industrial chemicals including engine and transmission oil, animal Silicone o rings and vegetable oils and greases, diluted salt solutions and non-petroleum based brake fluids. They can also withstand exposure to most solvents, acids and low temperature applications.
However, silicone does have some limitations and should be avoided in dynamic applications because of its weak tensile strength and abrasion resistance. Other common O-ring materials like nitrile (HNBR) or polychloroprene (CRP) have better abrasion and tear resistance but not as good a chemical and ozone resistance.
Resistance to Heat
Known for their hypoallergenic properties, silicone o rings are ideal for many medical and food industries. Silicone o rings They also withstand a wide range of temperatures, resist UV damage and corrosion, and are resistant to oil and water.
Silicone (VMQ) o rings are also highly resistant to oxidation, ozone and weathering. They also demonstrate good resistance to mineral and vegetable oils, animal and transmission oil, brake fluids, fire-resistant hydraulic fluid, and diluted salt solutions. However, they are not recommended for dynamic applications due to low strength, abrasion and wear resistance, high gas permeability, and low tensile fatigue life.
Despite their impressive range of resistances, it’s essential to keep in mind that silicone does not perform well in dynamic applications. This is because it has a low tensile and compression set. As a result, it is not recommended for use with petroleum fluids or ketones. It is also not compatible with steam above 250°F. Regardless of their remarkable characteristics, all o rings require regular inspection and prompt replacement to avoid significant damage and failure. For this reason, they must be lubricated at all times to prevent abrasion, pinching and deformation.
Resistance to Oils and Grease
Silicone is an ideal material for O-rings in a wide variety of outdoor applications. It offers ozone and UV resistance as well as high resistance to oils, greases, and chemicals. It also acts as a good electrical insulator. Additionally, it is hypoallergenic and does not promote fungus growth.
Fluorosilicone o rings, sometimes referred to as FKM or Viton, offer excellent chemical and oil resistance. They are compatible with a large range of temperatures and are capable of handling petroleum oils and fuels as well as engine, transmission and brake fluids (non petroleum based). They have very good flexibility and compression set resistance. However, they cannot be used in amines, aromatic hydrocarbons, ketones or chlorinated paraffin.
Neoprene O rings are made with a sulfur cure and feature moderate resistance to petroleum oils, ozone, oxygen, weathering, and flame. They have excellent resilience and abrasion resistance but lower tensile strength.
Resistance to Water
Silicone o rings have excellent resistance to water, making them suitable for a wide variety of applications. They also have good ozone resistance, meaning that they can be used in environments exposed to oxygen. Additionally, they are resistant to animal and vegetable oils, diluted salt solutions, engine and transmission oil and brake fluids.
In addition, silicone o rings are non-toxic and medical compliant. They are also able to withstand extreme temperatures, making them ideal for medical devices and food handling equipment. They have a low tensile strength, which makes them unsuitable for dynamic sealing operations.
Other common materials for o-rings include Aflas, polyurethane and Viton. Aflas offers excellent chemical resistance and has a wide temperature range, but it doesn’t offer the same level of ozone or acid resistance as Viton. Viton is a specialized fluoroelastomer that combines fluorine, carbon and hydrogen atoms to form a strong and durable material. It has exceptional resilience and durability, which is why it is such a popular choice for use in o-rings. It can resist chemicals, ozone, fuels and oils, and has a high degree of abrasion resistance.