O-rings perform critical functions in a wide variety of industries and applications, from maintaining seals in car engines to keeping medical devices sterile. This high demand helps make the gaskets and seals market a multi-billion dollar business, valued at $59.61 billion in 2017 and growing, according to Grand View Research data.
To support this wide range of applications, o-rings are made from a variety of specialized materials. Not all o-rings are the same, and different materials have varying physical and chemical properties that make them suitable for specific applications.
Here’s an introductory reference guide to assist you in choosing the right o-ring material for your needs.
Nitrile rubber, also known as NBR or Buna-N, is one of the most popular o-ring materials. First developed between the World Wars as a synthetic alternative to natural rubber, nitrile combines excellent resistance to petroleum products with an operating temperature range of -40 degrees F to 257 degrees F. It can also be modified for operating at temperatures over 300 degrees F with improved resistance to sunlight, weather exposure and ozone. This makes it popular for use in aerospace and automobile engines and other components, as well as in applications involving propane and natural gas.
Fluorocarbon or FKM, commonly known by the brand name Viton, is another extremely popular o-ring material. It combines exceptional resistance to chemicals with even better heat resistance than silicone o-rings, making it nearly ideal as a universal o-ring material.
Viton has a temperature range of -13 to 446 F, with specialized modifications allowing use at temperatures as low as -40 F. It also returns to its shape easily after being compressed, keeps gas from leaking and exhibits a long shelf life. These properties make fluorocarbon useful for aircraft engines, automobile fuel handling systems, chemical processing and vacuum applications. However, fluorocarbon should not be exposed to alkalis, ketones or Skydrol fluids.
Commonly known as EPDM, ethylene-propylene rubber has some properties that make it useful for certain specialized applications. EPDM can handle temperatures from -40 to 275 F. It resists water, steam, mild acids, alkali and oxygenated solvents. However, it does not do well at handling environments with gasoline, petroleum oil and grease, or hydrocarbons. It is especially suitable for use with low torque drive belts.
O-rings made from silicone rubber, also known as VMQ, share the temperature resistance of other popular o-ring materials, but they also possess some chemical properties that make them useful for unique applications. Standard silicone o-rings can handle a temperature range from -85 to 400 F, and can be modified with phenyl to cope with temperatures as low as -148 F. Additionally, silicone rubber exhibits high chemical inertness, making it resistant to corrosion or contamination.
These properties make silicone excellent for medical uses as well as applications in extreme temperature conditions. However, silicone has low resistance to abrasions and friction, so it may not be suitable for some dynamic sealing applications. It is also permeable to gases and should not be exposed to concentrated acids or ketones.
Fluorosilicone, or FVMQ, shares both the chemical resistance of fluorocarbons and the wide temperature stability of silicones. It resists fuels, oils and solvents. It can handle a temperature range from -75 to over 400 F.
These properties make fluorosilicone one of the most popular materials for use in aerospace fuel systems and in automotive fuel emission systems. However, like silicone, its low tear and friction resistance makes it unsuitable for dynamic sealing applications. It should also not be used with ketones, brake fluids or hydrazine.
Neoprene rubber was developed as one of the earliest oil-resistant alternatives to natural rubber, and remains popular for a wide range of o-ring applications. Neoprene can handle a temperature range from -40 to 250 F. It resists the effects of soils, sunlight, oxygen and ozone, as well as ammonia and Freon. It is tough and resilient, resuming its shape after being subjected to pressure.
Its ammonia and Freon resistance make it the preferred material for refrigeration applications, while its other properties make it useful for applications in transportation and uses requiring weather resistance. However, it is vulnerable to oxidizing acids, ketones, esters and hydrocarbons with nitro, chlorinated, aromatic properties.
Find the Right O-Ring for Your Product
O-ring materials come in a wide variety of forms with different ranges of temperature, abrasion and chemical resistance. Some are suitable for automobile and aircraft engines, others are ideal for medical applications, some are perfect for refrigeration and most are adaptable to a wide range of general uses.
Knowing which o-ring is best suited to your application will help ensure the quality, performance and durability of your product. Talk to your supplier for more help choosing the o-ring that’s right for you.