Best Materials for Spring Energized Seals | Advanced EMC Technologies
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Why Spring-Energized PTFE Seals Work in So Many Applications

Spring-energized PTFE seals work incredibly well. Engineers know that when designing equipment for truly hostile operational environments, whether facing cryogenic cold, aggressive media, or extreme pressure cycling, the reliability of the seal is absolutely critical. Traditional seals frequently fail under such harsh conditions, suffering from issues such as chemical attack, thermal degradation, or permanent deformation. The proven industrial solution for conquering these critical limitations lies in the PTFE spring-energized seal.

In this blog post, we discuss exactly why PTFE spring-energized seals work so well, including the use of PTFE and spring-energizers, along with a discussion of where these seals are used.

Where Spring-Energized Seals Conquer Extreme Conditions

Before discussing why these seals work so well, it would be wise to quickly review the many different industries and applications in which they have proven themselves. PTFE spring-energized seals have become indispensable across almost every challenging industrial sector because of their unique performance characteristics. Advanced EMC provides solutions for industries including Oil & Gas/Energy, Medical Devices, Aerospace & Defense, Automotive, and Food, Dairy, and Pharmaceutical.

In Oil & Gas and Energy, seals must handle extremely high pressures, sometimes up to 25 kpsi. They must also maintain integrity when exposed to chemically aggressive media such as sour gas and acid gases. In these applications, the PTFE jacket resists the chemicals while the energized springs help keep the seal in place.

For Aerospace & Defense, especially in cryogenic space applications, seals must survive conditions where temperatures drop below -250°C. Traditional elastomeric seals often shrink and lose sealing force at these cryogenic temperatures. PTFE spring-energized seals compensate for thermal contraction and are suitable for applications such as cryogenic fuel transfer and rocket engines. Virgin PTFE and high-purity filled PTFE variants also exhibit minimal outgassing, meeting NASA/ESA standards for use in a vacuum.

In the Medical Device and Pharmaceutical industries, reliability and purity are paramount. Virgin PTFE is both FDA- and USDA-approved. These seals are crucial in fluid management systems, surgical instruments, and diagnostic equipment. They withstand aggressive sterilization processes, including high-temperature Clean-In-Place (CIP) and Sanitize-In-Place (SIP) procedures, due to PTFE’s high thermal stability and chemical inertness. PTFE is also hydrophobic, repelling water and making it easier to clean complex geometries.

The Material Foundation: Why PTFE?

Polytetrafluoroethylene (PTFE), also know as Teflon®, is a synthetic fluoropolymer of tetrafluoroethylene. This material forms the resilient seal jacket, providing excellent chemical and thermal performance. Pure PTFE is almost completely chemically inert, meaning it resists attack from aggressive media such as acids, solvents, and reactive gases, minimizing the risk of degradation or swelling. It is also hydrophobic and non-wetting.

In addition, PTFE boasts an operating temperature range: it is thermally stable enough for continuous service up to 500°F, and certain specialized compounds can function reliably in cryogenic conditions as low as -450°F. PTFE also has the lowest coefficient of friction of any known solid and is naturally self-lubricating, which means it performs well in dry or non-lubricated applications. All of these are reasons to choose PTFE as the seal jacket in a spring-energized seal.

PTFE Spring-Energized Seals Work So Well

The core principle of a spring-energized seal lies in its architecture: a polymer seal jacket housing an internal metallic spring energizer. The spring’s primary job is to apply a continuous force against the sealing surface. This initial force ensures a consistent seal is maintained, especially at low system pressures.

The energizer’s constant force provides permanent resilience to the seal jacket, compensating for operational issues that would cause conventional seals to fail, including:

  • Jacket wear
  • Hardware misalignment and eccentricity
  • Dimensional changes due to thermal contraction or expansion
  • Misalignment

When system pressure increases, the pressure begins to supplement the spring force. This drives the seal lip against the mating surface, resulting in a tighter, highly efficient barrier. The spring design also ensures that the seal maintains force over time, eliminating the problem of permanent deformation or compression set seen in elastomers.

Engineers can select from various spring types to suit specific needs. The V spring (V ribbon spring energized seal) is an excellent candidate for cryogenic and vacuum applications, where coil springs (spiral pitch springs) work well, where low friction and high pressure are involved, typically in medium-speed applications. The helical flat spring is adapted to a wide range of pressures, from high pressure all the way down to vacuum conditions. An elastomeric O-ring energizer can be used when the use of metal must be avoided, and is adapted well to extreme pressures.

Conclusion

Robust, reliable sealing is absolutely necessary in mission-critical operations, regardless of the industry. Spring-energized PTFE seals provide a superior engineering solution. By combining the chemical inertness, wide temperature range, and low friction of PTFE with the persistent mechanical force of a metallic spring, these seals eliminate issues like compression set and loss of sealing force over time. They flex, adapt, and hold their seal integrity even when conditions shift fast.

For applications that demand unparalleled performance where failure is not an option, PTFE spring-energized seals work extremely well as they provide the durability, adaptability, and precision required. When specifying a PTFE spring-energized seal, never take for granted the finish of the mating surface. Advanced EMC Technologies offers expert polymer sealing solutions, leveraging more than 100 years of combined experience. Contact Advanced EMC today to learn how spring-energized seals can improve the reliability and lifespan of your system.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Polymer Seals for Electrified Systems: Managing Heat, Voltage, and Friction

Designing Polymer Seals for Electrified Systems: Managing Heat, Voltage, and Friction

The ability do design polymer seals for electrified systems is vital in modern engineering. The current shift toward electrified systems, whether in EV drivetrains, aerospace actuators, or high-voltage power converters, means that engineers must transform how they think about sealing. Traditional seal design focused on pressure and fluid compatibility. Electrified systems however, add three new variables: electrical conductivity, insulation integrity, and heat dissipation.

The wrong choice of polymer can lead to arcing, insulation breakdown, or premature wear, while the right one can enhance reliability and extend component life. This blog post is going to explore how seal designers can manage heat, voltage, and friction for electrified systems.

Polymer Seals for Electrified Systems

Electrified systems subject seals to hybrid stresses: electrical, thermal, and mechanical. Thermal gradients develop near conductive components, especially in high-current zones or power-dense assemblies. Electrostatic fields and stray currents can compromise material integrity, accelerating degradation. Mechanical wear and vibration persist just as they do in traditional systems—but the allowable frictional losses are often much lower.

Different applications bring unique sealing demands. In electric traction motors, for example, shaft seals must prevent the ingress of coolant while also blocking stray currents. DC/DC converters, meanwhile, are in need of seals that double as dielectric barriers.

Balancing Dielectric and Thermal Properties for Polymer Seals for Electrified Systems

Polymers in electrified systems must play a dual role: insulate against high voltage while managing heat generated in compact assemblies. They key properties involved in designing polymer seals for electrified systems include dielectric strength, thermal conductivity, and wear rate, all of which determine seal performance and longevity.

Common polymer choices include:

  • PTFE is chemically inert, possess excellent dielectric strength, and exhibits ultra-low friction, making it ideal for high-speed, low-load applications.
  • PEEK has high mechanical strength and temperature capabilities, meaning it can tolerate heavier loads but at the cost of slightly higher friction.
  • PPS and UHMW-PE are cost-effective options that combine good dielectric resistance with moderate wear performance.
  • Filled compounds (carbon, graphite, glass) are used to enhance wear and sometimes conductivity, though they may reduce dielectric performance.

Creep resistance, thermal aging, and the ability to maintain integrity across temperature extremes all influence selection. In many cases, designers use blended materials or layered seal architectures to balance insulation with heat dissipation.

Managing Heat

Electrified systems are going to generate localized hotspots located near bearings, windings, and current-carrying seals. Without appropriate heat management, polymers can easily soften, creep, or degrade. Effective seal deisgn for electrified system design requires careful consideration of factors such as thermal pathways, geometry, and material stability.

Thin cross-sections, for example, help to minimize thermal buildup ,but must still resist extrusion issues. Conductive fillers or metal housings can help spread heat away from the seal interface. Engineers must also account for the glass transition temperature of materials, their continuous-use temperature, and their oxidation resistance.

Heat cycling has a major influence on seal preload and spring energizers. In EV cooling pumps, for example, repeated swings from –40°C to 150°C demand highly resilient fluoropolymers and careful thermal expansion matching between the seal and shaft.

Managing Voltage

Seals can be damaged by electrical stress over time. Potential issues include dielectric breakdown, corona discharge, and surface tracking can —  all of which lead to performance loss or catastrophic failure.

Engineers can mitigate these issues through material and design strategies such as:

  • Choosing polymers with a high dielectric strength (PTFE, PEEK, PPS)
  • Using conductive fillers to safely dissipate charge buildup.
  • Designing surface contours and creep distances that reduce the risk of arcing 
  • Grounding components to divert stray currents away from sealing interfaces

Managing Friction

Friction directly affects energy efficiency, thermal load, and component life. In electrified systems, even a small amount of frictional increase can have a significant impact on range of performance. 

Designers must strike a careful balance between low friction and effective sealing contact. Surface finish, lubrication strategy, and seal geometry all play a part, and spring-energized PTFE seals are often chosen for their low-leak, low-drag characteristics.

Because many electrified systems operate in dry or low-lubrication conditions, polymers with intrinsic lubricity or dry-film coatings are critical. Comparing dry-film lubricants, filled PTFE blends, and hybrid polymer systems helps determine which approach provides the best combination of sealing and efficiency.

System-Level Integration—The Interplay of Heat, Voltage, and Friction

Heat, voltage, and friction are not independent. Heat increases friction and reduces dielectric strength. High voltage accelerates wear through localized arcing. Frictional heating compounds both mechanical and electrical stress.

System-level analysis is, therefore, essential for engineers designing a successful polymer seal for electrified systems. Finite element analysis (FEA) can be used to model thermal and mechanical stresses, while electrical field modeling predicts voltage gradients across seal interfaces. 

By co-designing seals with their housings and integrating thermal barriers or conductive paths, engineers can significantly improve both the electrical safety and mechanical durability of seals for electrified systems.

Conclusion: Engineering Reliability in the Electrified Era

Electrification means that no longer is seal design just about blocking fluids or retaining pressure. These seals must manage a delicate balance between heat, voltage, and friction.

When properly designed, polymer seals do not just survive these stresses. They enable higher efficiency, longer service life, better range, and greater system reliability. In the electrified era, seal design is an exercise in electrical and mechanical synergy.

At Advanced EMC, our team of experts can help you find the right solution when designing polymer seals for electrified system. Contact us today to learn more.