Understanding O-Ring Materials and Compounds

Keeping o-rings on hand so you have them when you need them is a great idea. However, before you buy you should be certain that you understand some basic information about o-rings such as the materials, the shore hardness, the shelf life, and standard color options. Understanding this information will not only help guide you on which o-rings to use for specific applications but will also help you determine what to buy and how long you can keep them on hand.

Nitrile (Buna-N): This is the most commonly used o-ring material with a 40 to 90 durometer shore hardness. Providing excellent resistance to petroleum products. It also offers an excellent compression set, tear, and abrasion resistance. It does not offer good resistance to ozone, sunlight, or weather unless it is specifically compounded to do so. Temperature range: -40° to +250°F. Shelf life of 15 years. Available in black and white.

Fluoroelastomer: This material offers excellent mechanical and physical properties with good resistance to petroleum products, low compression set, and high-temperature resistance. Offers a shore hardness of 60 to 90 durometer. Ideal for vacuum service and low gas permeability. Temperature range: -15° to +400°F. Shelf life of 5 to 10 years. Available in white, brown, and black.

Chloroprene: This elastomer is moderately resistant to petroleum and offers good ozone and weather resistance and good compression set with a shore hardness of 25-90 durometer. Excellent for sealing refrigeration fluids such as Freon®. Temperature range -65°- +250°F. Shelf life of 15 years. Available in black

Silicone: This elastomer is ideal for weather and ozone resistance and offers a shore hardness range of 30 to 90 durometer. It offers limited oil resistance and is not recommended for dynamic sealing applications due to poor tensile and tear strength and low abrasion resistance. Temperature range -80° - +450°F. Unlimited shelf life. Available in white.

Highly Saturated Nitrile: This material offers better resistance to high temperature, superior physical properties, and improved chemical resistance over traditional nitrile compounds. It has shore hardness offerings of 70-90 durometer. This material has improved resistance to ozone and sunlight and excellent resistance to compression set. Temperature range -40°- +325°F. Shelf life of 15 years. Available in green, black, and blue.

Ethylene Propylene (EPM, EPDM) (EPR): Excellent resistance to Skydrol® fluids used in commercial aircraft hydraulic systems, offering a shore hardness ranging from 70 to 90 durometer. Recommended for hot water, steam, and phosphate ester-type hydraulic fluids. Resistance to some acids, alkalies, and ozone. Not recommended for petroleum fluids or diester lubricants. Temperature range: 65° - +300°F. Available in black. Unlimited shelf life.

PTFE: This is a white thermoplastic fluoroethylene resin that offers heat resistance, low friction, dielectric strength, weatherability, toughness, no water absorption, and flexibility. Temperature range: -65°- +500°F. Unlimited shelf life. Available in black and white.

Aflas: This material offers high temperature, chemical, and electrical resistance properties and shore hardness of 70 to 90 durometer. Recommended for use with oils, lubricants, hydraulic fluids, transmission, and power steering fluids, sour oil and gas, ozone, steam, acids, bases, alcohols, and other chemicals. Temperature range: +25° - +450°F. Unlimited shelf life. Available in black.

Need Orings? APG Has You Covered!

Now that you know the different capabilities of each of the o-ring materials you are ready to buy! You can shop orings now! Not sure what you need for your specific application or need a size that you don’t see available? Give us a call today at 1-800-888-5223 and one of our o-ring experts would be happy to assist you with your product selection. We look forward to exceeding your expectations!