Elastomer Temperature Range Guide | Seal Operating Limits
Temperature is one of the primary considerations when selecting an O-ring, gasket or seal. Each elastomer has an operating range within which it can maintain the flexibility, strength and sealing force required for reliable service. Exposure outside that range can lead to hardening, excessive softening, permanent deformation or chemical degradation. Temperature must also be considered alongside chemical compatibility. A material that is highly resistant to the process fluid may still perform poorly if the operating temperature exceeds the capabilities of the specific compound.
This guide explains typical continuous-service temperature ranges for commonly used sealing materials, the mechanisms that limit performance at high and low temperatures, and the application factors that can alter the usable range.
How Temperature Affects Seal Performance
Temperature limits should not be treated as a single point at which an elastomer suddenly fails. Material properties change progressively as temperature rises or falls. At elevated temperatures, elastomers can lose mechanical strength, experience increased compression set and undergo accelerated ageing or chemical degradation. Prolonged exposure can permanently reduce the ability of the seal to maintain contact pressure.
At low temperatures, elastomers become progressively stiffer and less able to deform with the sealing surfaces. If the material loses sufficient elasticity, it may no longer respond effectively to movement, pressure changes or surface irregularities.
Published temperature ranges therefore represent a practical operating window within which a particular material or compound is expected to retain useful sealing properties under defined service conditions.
| Temperature Condition | Typical Effect on Seal Performance |
|---|---|
| Low Temperature | Elastomer becomes stiffer and less able to follow movement or surface irregularities |
| Normal Service Range | Material retains its intended elasticity and sealing characteristics |
| Elevated Temperature | Compression set, ageing and loss of mechanical properties generally increase |
| Excessive Temperature | Permanent deformation, hardening, cracking or chemical degradation may occur |
Compression set is particularly important at elevated temperatures. As permanent deformation increases, an elastomer may no longer generate sufficient sealing force after prolonged compression. Chemical exposure can further alter the practical temperature limit, which is why temperature and media compatibility should always be assessed together.
See our Chemical Compatibility Guide for further information on selecting elastomers for different process media.
Continuous Service Temperature Ranges
The table below provides typical continuous-service temperature ranges for commonly used sealing materials. These figures are intended as material-family guidance rather than absolute operating limits.
Actual temperature capability varies according to compound formulation, hardness, cure system, application media and operating conditions. Specialist grades may offer considerably different performance, particularly in low-temperature or high-temperature applications.
| Material | Typical Continuous Service Range |
|---|---|
| NBR | -30°C to +100°C |
| HNBR | -30°C to +140°C |
| EPDM | -45°C to +150°C |
| FKM | -20°C to +200°C |
| Silicone (VMQ) | -60°C to +200°C |
| FFKM | -25°C to +240°C |
| PTFE* | -200°C to +260°C |
*PTFE is a fluoropolymer rather than an elastomer. Figures shown are typical material-family guidance only; the temperature rating of the specific compound should always be confirmed.
Always confirm the temperature rating of the specific compound being specified where the application operates close to either end of the recommended range.
Low Temperature Sealing
Low-temperature sealing performance is governed by an elastomer’s ability to remain flexible and recover after deformation. As temperature falls, molecular movement reduces and the material becomes progressively stiffer. Eventually it may become unable to maintain effective contact with the sealing surface.
Standard NBR and many FKM compounds have more limited low-temperature capability, while silicone and specially formulated low-temperature grades can retain flexibility at considerably lower temperatures.
For demanding cold-service applications, values such as TR10 can provide more useful information than a general published minimum temperature. TR10 indicates the temperature at which a previously stretched elastomer has recovered 10% of its deformation during controlled warming and is commonly used as an indicator of low-temperature elastic recovery.
Brittleness temperature should not be interpreted as the minimum reliable sealing temperature. A compound can remain physically intact while already being too stiff to provide effective sealing performance.
| Material | Typical Lower Limit | Specialist Grade Capability |
|---|---|---|
| Silicone (VMQ) | -60°C | Excellent inherent low-temperature flexibility |
| EPDM | -45°C | Actual capability varies by compound formulation |
| HNBR | -30°C | Selected grades to approximately -40°C |
| NBR | -30°C | Low-temperature formulations to approximately -50°C |
| FKM | -20°C | Specialist low-temperature grades to approximately -45°C |
Where an application operates continuously at low temperature, the properties of the specific compound grade can be more important than the polymer family alone. Selection should therefore be confirmed against the required minimum operating temperature and service conditions.
High Temperature Sealing
At elevated temperatures, the principal limitations for elastomeric seals are typically permanent compression set, loss of mechanical properties and accelerated chemical ageing rather than a sudden thermal failure.
FFKM generally provides the highest temperature capability among commonly specified elastomer families, while FKM and silicone also offer strong elevated-temperature performance. Standard NBR is more restricted and is normally selected for moderate-temperature applications where its other properties are advantageous.
PTFE can operate at high temperatures in many sealing applications, but it is a fluoropolymer rather than an elastomer and behaves differently under load. It should therefore be evaluated separately from elastomeric materials.
| Material | Continuous Upper Limit | Short-Term / Specialist Capability |
|---|---|---|
| NBR | +100°C | Up to approximately +120°C short term |
| HNBR | +140°C | Up to approximately +160°C short term |
| EPDM | +150°C | Up to approximately +175°C short term |
| FKM | +200°C | Up to approximately +230°C short term |
| Silicone (VMQ) | +200°C | Selected grades to approximately +220°C |
| FFKM | +240°C | Specialist grades up to approximately +325°C |
| PTFE* | +260°C | Grade and seal design dependent |
*PTFE is a fluoropolymer rather than an elastomer. Short-term and specialist-grade figures should not be treated as continuous operating limits.
Some specialist compounds have documented short-term or intermittent temperature ratings above their continuous-service limits. These should only be used where the grade-specific technical data confirms that the expected temperature, duration and application conditions are acceptable.
For sustained high-temperature service, selecting a compound with suitable temperature margin rather than operating continuously near its upper limit can improve long-term sealing reliability.
Selecting a Material for Temperature
Temperature and chemical compatibility should always be considered together. Exposure to certain fluids, concentrations or cleaning media can reduce the practical operating range of an otherwise suitable elastomer. As a general starting point, select a material whose continuous-service range comfortably covers both the minimum and maximum operating temperatures of the application. The proposed compound should then be checked against the process media, pressure, exposure duration and any temperature cycling.
Where equipment experiences both very high and very low temperatures, the most demanding condition may not necessarily be the maximum temperature. Low-temperature flexibility, compression set and thermal cycling can all determine whether the seal remains effective throughout the complete operating cycle.
International Seal can assist with compound selection for applications involving demanding temperature or chemical conditions. Provide the seal type and dimensions, minimum and maximum temperature, process media, pressure and whether the application is static or dynamic, and we can help identify an appropriate material and grade.