One of the most important considerations for manufacturing seals, gaskets, and grommets is the choice of material. Pieces made from different specialty rubbers “behave” differently depending on the operating conditions and the nature of the application. Looking at the chemical and mechanical properties of each material as well as their suitability for exposure to stressors like chemicals, oil, or extreme temperatures is the critical first step in determining the best material for the job. Factors like part design and dimensions and price are also part of the equation.
MSP Seals supplies customers in Kentucky, Illinois, Ohio, Michigan, and Tennessee with high-quality industry seals for a variety of applications, and we also work with customers globally. We specialize in creating high-performance seals that are durable and help keep equipment running reliably for longer, while also keeping costs low.
Our selection guide will help you understand the key properties of various rubber materials, and examples of specialty materials for various use cases.
Understanding the Factors: Temperature, Chemical, and Abrasive Stress
It’s useful to start by identifying the mechanical properties and resistance to environmental damage that will be important for your application, such as:
- Temperature extremes. Very high or low temperatures can have a negative effect on the integrity of a seal and the durability of the material. Fluctuating temperatures can also weaken materials.
- Chemical compatibility. Seals must be made from materials that are compatible with any fluids and gases with which they will come into contact during normal operations. These substances can quickly break down, or dissolve seals, or compromise their performance.
- Abrasive environments. Particulates, friction from moving parts, and other abrasive factors require materials that are wear resistant and tough.
- Pressure and stress. High pressures can deform seals or cause them to shift during operations. Choosing a material that can resist damage from pressure, such as those with low compression set, keeps seals from permanently deforming.
- Ozone and UV radiation. Some elastomers break down when exposed to ozone or UV radiation, making them a poor choice for outdoor or aerospace applications.
- Compliance. Depending on the intended application, seal materials must comply with environmental regulations, or industry and safety standards.
Comparing Elastomers: When to Choose NBR vs. EPDM vs. FKM
Once you’ve identified what performance requirements or material characteristics your seal needs to have, compare likely materials to determine the best fit. NBR, EPDM, and FKM are three popular synthetic rubbers (i.e., elastomers) and understanding how they differ is helpful in making the decision.
- Nitrile (NBR), or Buna-N: Excellent resistance to petroleum-based chemicals, relatively low production cost, versatile, and commonly used in general industry, automotives, and hydraulics.
- Ethylene Propylene Diene Monomer (EPDM): Excellent resistance to ozone, water and steam, weather, and chemicals such as ester-based hydraulic fluids and brake fluids.
- Fluoroelastomer (FKM): Extremely resistant to acids, hydrocarbons, and other chemicals, handles high temperature extremes in very demanding applications.
Temperature Ranges
Determine the likely temperature range the seal will experience. NBR can perform well in temperatures from -40°F to 250°F, EPDM in temperatures from -40˜F to 300°F, and FKM from -15°F to 400°F.
Chemical Resistance
EPDM is not compatible with petroleum-based materials. NBR can resist chemical damage from petroleum-based materials, but it breaks down in the presence of brake fluids, ketones, and ozone. FKM is generally resistant to a wide range of chemicals, but not ethers, low-molecular-weight esters, or ketones.
Abrasive Resistance
NBR and EPDM both offer generally good abrasion resistance, with NBR being suited to dynamic abrasive forces. Different formulations of FKM offer different degrees of abrasion resistance.
Hardness and Compression Set
Higher compression set materials are more formable, compressible, and prone to deforming under pressure. Whether these characteristics offer an advantage depends on the details of the application. EPDM has a higher compression set than either NBR or FKM, making it more resilient.
Beyond Elastomers: Specialty Materials for Extreme Conditions
The engineering experts at MSP Seals can work with you to determine the right material and grade for every project. In addition to NBR, EPDM, and FKM, there is a large selection of specialty rubbers available for sealing applications, including:
- Perfluoroelastomer (FFKM): Extreme chemical resistance, even at very high temperatures; commonly used in semiconductor and chemical processing applications.
- Polytetrafluoroethylene (PTFE): Very low coefficient of friction, good chemical resistance, reduced elasticity; suitable for static seals in non-stick or other low-friction applications.
- Polyurethane (PU): Resists abrasion and extrusion better than others; good toughness for high-pressure hydraulics that generate mechanical stress.
- Aflas (TFE/P): Chemical- and temperature-resistant fluorostomer often used in oil processing and applications with strong bases, sour gas (i.e., hydrogen sulfide), and steam.
- Silicone (VMQ): Good flexibility in hot and cold temperatures, incompatible with most chemicals and low abrasion resistance; performs best in static sealing applications.
- Hydrogenated Nitrile Butadiene Rubber (HNBR): Superior abrasion and temperature resistance compared to NBR, compatible with petroleum-based fluids in oil drilling and automotive applications.
- Application-specific compounds: Specialty materials in different grades and formulations for applications with unique challenges.
Seal Material Guidance and Manufacturing From MSP Seals
Material choice is a critical first step to project success, and MSP Seals can provide guidance on a variety of materials for hard-working seals that can resist damage from mechanical stress, chemicals, extreme temperatures, and other hazards. With PPAP capabilities to provide sealing solutions, ISO 9001:2015 and ISO 14001:2015 certifications, we are ready to support your next project and needs. Contact MSP Seals today to learn more about our selection of materials, or request a quote to start your order.
