O-rings and seals are utilised in a wide variety of industries to let you firmly secure the attachments in pipes, tubes, and other parts of complicated hydraulic and pneumatic systems. Due to a range of uses, a wide variety of O-ring content alternatives are also available. Nitrile (Buna), Neoprene, Ethylene Propylene (EPDM Rubber), Silicone, Fluorocarbon (Viton) as well as PTFE (Teflon) are the most widely used materials for O-rings and seals.

To address several of your queries about O-rings, Flextron has developed an extensive O-ring material collection guide, which will discuss the characteristics and functionality and the thermal stability and hardness of every O-ring material.

Factors to Consider When Picking O-rings

According to a study, for optimal efficiency, an O-ring should be selected based on chemical compatibility, application temperature, sealing pressure, lubrication requirements, durometer, size and cost. 

There are several variables to evaluate when choosing the best O-ring for a particular application. They include but are not restricted to operational conditions, chemical stability, sealing strength, temperature, durometer, complexity and cost. Based on the particular case, you can also consider the properties of abrasion, damage, ozone, electrical tolerance. Also, you should conduct sufficient field checks to ensure that the fluid, temperature, intensity and environmental parameters are consistent with the O-ring of your preference.

O-ring Material Selection Guide

O-rings and seals are made by manufacturers using multiple elastomers with different chemical and physical properties to meet a wide range of uses. Let’s take a discuss a few of them below:

Nitrile Butadiene Rubber (NBR)

Resistant to: water, petroleum & fluids including hydraulic fluids

Not suitable for: phosphorus ester base hydraulic fluids, vehicle braking fluids, ketones, heavy acids, ozone, freons, halogenated hydrocarbons and methanol

Thermal range: -40° to +250°F, but this is the average for lower and upper tolerance levels for the multiple nitrile butadiene rubber (NBR) compounds. 

Hardness: 40 to 90 durometer Shore A

Ethylene-Propylene (EPDM)

EPDM has an impeccable reputation in the sealing field due to its outstanding tolerance to heat, water and steam, ammonium, moderate acidic and oxygenated chemicals, ozone and sunlight (UV). However, experts do not prescribe EPDM substances for diesel, petroleum and oil and hydrocarbon conditions.

Resistant to: intense cold, steam, boiling water, sunlight & UV, dilute acids, ketones, ammonium.

Not suitable for: fat-derived oils and di-ester based solvents

Temperature range: -65° to +450°F

Hardness Range: 40 to 90 durometer Shore A

Neoprene (CR)

Neoprene is a multipurpose elastomer with mild resistance to petroleum oils and weather conditions (ozone, sunlight, UV, and oxygen). Neoprene O-rings have a comparatively low compression set, good toughness, discolouration and flex cracking tolerance.

Resistant to: coolants (freons, ammonia), heavy aniline oils, soft acids and silicate ester solvents

Not suitable for: phosphate ester fluid as well as ketone

Temperature Range: -45° to +250°F

Hardness: 50 to 80 durometer Shore A 

Fluorocarbon (Viton)

While we speak about fluorocarbon O-rings, Viton is a common trade name that might come to your mind. Fluorocarbon (FKM) elements combine high-temperature tolerance with great chemical tolerance. These characteristics make them a common alternative for various applications, such as the aircraft and transportation sectors.

Resistant to: petroleum lubricants and fluids, certain phosphate ester-based fluids, silicone and silicate ester-based lubricants, acids & halogenated hydrocarbons

Temperature range: standards-15°F to +400°F; however, some Parker FKM Viton substances can survive temperatures down to –65F and up to +450F.

Hardness: 50-95 Durometer Shore A

Silicone

Silicone O-rings have several remarkable characteristics, including exceptional durability and fatigue resistance, high ozone and UV tolerance. Despite these features, specialists do not suggest silicone O-rings for complex applications. Low strength and weak abrasion resistance, and high gas permeability make them incompatible with many other petroleum fluids, ketones, water, and steam.

Resistant to: dry heat (air at 400°F) and extreme alkyl point oils

Not suitable for: several petroleum liquids, ketones, water and steam.

Temperature Range: -175F to +450°F

Hardness: 40-80 Durometer Shore A

Polytetrafluoroethylene (PTFE)

Polytetrafluoroethylene (PTFE) O-rings are built for use in extreme conditions with temperatures varying from-450°F to 600°F. PTFE O-rings are compliant with a wide variety of chemicals, like acetone, isopropyl, methyl, etc. They also have poor permeability and low absorption of carbon. Regrettably, due to polytetrafluoroethylene characteristics, pure PTFE O-rings are very stiff and difficult to apply. O-ring manufacturers, like Flextron, then overcome this issue by combining PTFE content with different fillers to allow consumers greater flexibility. PTFE seals are widely used in dairy, medicinal and healthcare industries.

Resistant to: Several chemicals, except alkali metals, fluorine, some fluoro-chemicals like chlorine trifluoride and oxygen difluoride

Not suitable for: Applications that need O-Ring stretch and compression

Temperature Range: -260°F to 300°F

Hardness: 55 to 60 durometer Shore D

Standard vs Custom O-ring Materials From Flextron

As an approved dealer, in addition to the regular O-ring materials listed above, we at Flextron also provide custom seals specifically designed for your particular application. We take good care of any technical criteria, constraints, upgrade of installation, etc. Please contact us to know more or to talk to our o-ring sealing experts.