An elastomer is a primary raw material used for most o rings. They are typically manufactured as gum rubber or manufactured synthetically, and surprisingly today, there are approximately over 32 different synthetic rubbers now available.
Elastomer compounds will typically include a base polymer (around 50-60%) with compounds consisting of various fillers, vulcanising agents, and chemical additives that will help modify and improve the physical properties of the base polymer.
Elastomers are used in o rings and seal applications due to their ability to provide a robust, reliable, and leak-free solution. However, it’s important to note that the material of choice must match its intended application.
Ultimately, an elastomer provides a quick recovery when faced with a compressive force, or when it is extended, i.e., an elastomer will not break when stretched, as after stretching has occurred, the elastomer will retract to within 10% of its original length.
Types of elastomers
Also known as NBR or Buna-N, Nitrile is one of the most common material choices for o rings. Nitrile also offers good mechanical properties and high wear resistance to provide users with excellent resistance to varying temperatures and chemicals.
Depending on the individual compound, it has cold flexibility between -30 degrees Fahrenheit and -70 and heat resistance up to 212 degrees Fahrenheit.
Nitrile is also resistant to weathering and ozone.
Hydrogenated Nitrile (highly saturated Nitrile)
This is often formulated explicitly for specific compounds to provide superior mechanical properties while maintaining high chemical resistance.
Carboxylate Nitrile can provide extensive tear and abrasion resistance, making it a great choice for more dynamic applications.
Overall, Nitrile offers good chemical and temperature resistance and is economically priced.
It is also widely used across fuel and hydraulic applications.
Neoprene resists ozone, chemicals, and aging and can provide robust mechanical properties over a varying temperature range (from -40 degrees Fahrenheit to 250 degrees Fahrenheit).
It is also resistant to paraffin-based mineral oils, silicone grease and oil, carbon dioxide, water and water solvents, and ammonia.
Neoprene is typically used within refrigerant and environmental sealing applications.
FKM (Fluorocarbon, Viton)
As this elastomer is most commonly known, Viton provides excellent resistance to synthetic hydraulic fluids, high temperatures, fuels, various chemicals, and a range of organic solvents. It can also offer a heat-resistant element up to 400 degrees Fahrenheit and has a strong chemical resistance to mineral grease and oil, non-flammable hydraulic fluids, and silicone grease and oil.
This is the elastomer that offers the best chemical compatibility and the highest operating temperature range.
With heat resistance up to 620 degrees Fahrenheit, FFKM also has cold flexibility down to -15 degrees Fahrenheit.
Resistant to a range of chemicals such as aromatic hydrocarbons, chlorinated hydrocarbons, water and steam, high vacuum applications, and much more, FFKM is suitable for turbine engines and chemical processing equipment.
It is also found in aerospace and oil and gas industries.
It’s important to note that this elastomer does not perform well at low temperatures.
Aflas offers excellent chemical resistance and has heat resistance up to 450 degrees Fahrenheit and cold flexibility at -15.
Aflas is also compatible with amines, phosphate esters, engine oils, hot water, and steam.
Ultimately, Aflas is suitable to handle all base chemicals and is primarily found in steam applications.
Note: Aflas is not compatible with aromatic fuels.
EPDM is a great seal for brake systems that use a glycol base found in the automotive industry.
With heat resistance up to 400 degrees in water and steam, EPDM also offers a cold flex down to -70.
Suitable for glycol-based brake fluids, inorganic and organic acids, silicone-based brake fluids, cleaning agents, and silicone grease and oil.
It’s important to note EPDM should not be used in applications using hydrocarbons as the material will swell, causing extrusion.
EPDM is also not compatible with mineral oils.
Silicone resists ozone and weather and provides good insulating neutral properties. Mainly used across static applications as silicone is prone to tearing. However, it offers heat resistance up to 400 degrees Fahrenheit and a cold flex down to -65.
Silicone is also chemically resistant to animal and vegetable greases and oil, flame-resistant insulators, it is a coolant for transformers, resistant to ozone, weather, aging, and offers moderate water resistance.
However, silicone does have a poor resistance to wear and a low tensile strength. It also has poor mechanical properties, so it is not suitable for dynamic applications.
Primarily used across life science applications.
Polyacrylate offers excellent resistance to ozone, oxygen, and mineral oil. Used within the automotive industry, polyacrylate has heat resistance up to 350 degrees Fahrenheit and cold flexibility down to -5.
With a similar composition to that of NBR, it’s also important to note that polyacrylate is not compatible with glycol-based brake fluids, acids, hot water, steam, and aromatic fuels.
To help you choose the best o ring material and elastomer for your application, finding a professional o ring supplier in the UK is key.
A professional o ring supplier in Leeds like Specialist Sealing Products.