Last Updated on December 11, 2019
O-rings are critically important for a wide range of applications, from aircraft and automobile components to medical devices and scuba diving equipment.
To serve this diverse range of functions, o-ring manufacturers have developed a number of customized materials with specialized physical and chemical properties suitable for specific uses.
Here’s a guide to help you work with your supplier to select the o-ring material that’s right for your product’s purposes.
Buna-N, also known as nitrile or NBR, was first developed during the buildup to World War II as a synthetic solution to shortages of rubber needed for military applications. It combines a temperature tolerance of -40 degrees F to 257 degrees F with strong resistance to the chemical effects of petroleum.
It can be customized to handle temperatures over 300 degrees F and to resist weather effects, sunlight and ozone. These qualities make it suitable for use in automobile and aircraft engines and components, and for uses that require contact with natural gas and propane.
Neoprene rubber, also known as CR, was initially invented to meet the need for an oil-resistant alternative to natural rubber. It can function in temperatures from -40 degrees F to 250 F. It returns to its original shape after being pressurized.
It resists corruption from soil, oxygen, ozone, sunlight, Freon and ammonia. These properties make neoprene a popular solution for the refrigeration industry. It also serves uses requiring weather resistance, such as transportation applications. It should not be exposed to certain types of hydrocarbons, ketones, esters and oxidizing acids.
Viton, also known as fluorocarbon or FKM can withstand temperatures from -13 degrees F to 446 F, and can be modified to handle -40 F. It also exhibits remarkable resistance to chemicals. Additionally, it resumes its shape after compression, resists gas leakage and lasts a long time in storage.
These qualities make Viton suitable for use with automotive fuel handling systems, aircraft engines, chemical processes and vacuum seal applications. On the other hand, Viton does not mix well with ketones, alkalis or Skydrol fluids.
Silicone rubber, also known as VMQ, shares the temperature tolerance of other common o-ring materials, along with some distinctive chemical qualities.
It can withstand temperatures from -85 degrees F to 400 F, and when modified with phenyl, it can function at -148 F. It remains stable when interacting with a wide range of chemicals, making it difficult to corrode or contaminate. This makes silicone especially suitable for use at very cold or hot temperatures and for sterile medical applications.
It is also used for scuba diving equipment. However, silicone does not handle ketones or concentrated acids well, and is permeable to gases. It also tears easily, making it unsuitable for stressful dynamic sealing uses.
Fluorosilicone, or FVMQ, combines the temperature resistance of silicone rubber with the chemical resistance of Viton. It can endure temperatures between -75 degrees F and 400 F.
It also handles contact with solvents, oil and fuel. This makes fluorosilicone useful for automotive fuel emission components and aircraft fuel systems. But like silicone, it tears easily and does not handle ketones well. It should also not be mixed with brake fluids or hydrazine.
EPDM, also known as ethylene-propylene rubber, possesses unique properties that make it suitable for a number of niche applications. In addition to withstanding temperatures from -40 degrees F to 275 F, it resists the effects of water, steam, oxygenated solvents, alkalis and mild acidic chemicals. It does not perform well with hydrocarbons, grease, gasoline or petroleum. It works particularly well with low torque drive belt applications.
Choose the Right O-Ring Material for Your Product
Which of these o-ring materials is right for you depends on the intended application of your product. A knowledgeable supplier can help you select a material with the right temperature resistance, physical properties and chemical properties for your needs.
For best results, ask your supplier to provide you with a prototype sample that you can test for performance and cost before placing a bulk order. Taking the time to choose the right o-ring material will help maximize your product’s performance and longevity.