by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Machined and Molded Polymer Bearings: Nylon 66, PEEK, and PPS

Nylon 66, PEEK, and PPS are available in bearing grades, but how should they be manufactured? The choice of manufacturing method can have a significant impact on their tolerances, performance, and cost. 

This blog post focuses on machined and molded polymer bearings, including their benefits and limits, how they compare to metal options, and the best ways of manufacturing bearings made from three very different materials: Nylon 66, PEEK, and PPS. 

Introduction to Polymer Bearings

Polymer bearings are low-friction, lightweight alternatives to traditional bearings. They are corrosion-resistant and offer varying degrees of chemical resistance. Polymer bearings are also known for their ability to run dry or with minimal lubrication, as well as good wear characteristics. They are also electrically insulating and offer quieter operation than their metal counterparts.

However, polymer bearings do have their limits. They are more susceptible to thermal expansion and may have lower load limits and PV than their metal counterparts, but the addition of fillers can mitigate this issue. In some cases, they may be susceptible to moisture uptake. 

The table below summarizes the major differences between metal and polymer bearings.

Metal vs Polymer Bearings

FeatureMetal BearingsPolymer Bearings
FrictionLow only with lubricationLow due to inherent lubricity
LubricationRequiredOften not required
Wear MechanismAbrasive/adhesive fatigueTransfer film formation
CorrosionPossibleNearly immune
Shock/VibrationNo dampingNatural damping
SpeedHighModerate
LoadHigherModerate
Temperature LimitsExcellentVaries by polymer
MaintenanceHigherVery low

Machined vs. Molded Polymer Bearings

Machined bearings are best for small production runs where tight tolerances and complex geometries are involved, and machining is ideal for prototypes, custom components, and specialty rotating equipment. This approach to manufacturing bearings also allows the material to remain homogenous with no molded-in stresses.

Molded bearings are the best option for high-volume production, and they are more cost-effective for simpler geometries. Molding also means reduced part-to-part variation; however, molded-in stress may be present, and there are limits to surface finish.

When choosing between machined and molded polymer bearings, the key factors are:

  • Geometry
  • Tolerances
  • Cost
  • Production volume

Nylon 66, PEEK, and PPS

Among the various options for polymer bearings are Nylon 66, PPS, and PEEK. The table below summarizes the differences between these materials.

Performance Comparison: Nylon 66 vs. PPS vs. PEEK

Property / FactorNylon 66PPSPEEK
Max Continuous Use Temperature~100–120°C~200–220°C~240–260°C
Wear ResistanceGood (improved with lubrication)Very goodExcellent (especially filled grades)
FrictionLowLowVery low
Moisture AbsorptionHigh (can swell, affects tolerances)Very lowVery low
Dimensional StabilityModerate (affected by humidity)HighVery high
Chemical ResistanceModerateExcellentExcellent
Mechanical StrengthGoodHighVery high
Impact ResistanceVery goodModerateGood
Creep ResistanceModerateGoodExcellent
PV CapabilityLow–MediumMedium–HighHigh–Very High
CostLowMediumHigh
Machining SuitabilityExcellentExcellentExcellent (best with filled grades)
MoldabilityExcellentGoodGood
Typical ApplicationsRollers, appliance bearings, automotive interior componentsPumps, compressors, chemical processing, precision housingsAerospace, oil & gas, high-speed bearings, semiconductor tools

Manufacturing Nylon 66, PEEK, and PPS Bearings

There are several different bearing materials available, but of interest in this blog post are Nylon 66, PPS, and PEEK bearings.

Nylon 66

Nylon 66 is very easy to mold because of its low viscosity, forging processing window, and good flow characteristics. However, there is going to be high mold shrinkage, which requires careful part design to keep warpage under control. Nylon also absorbs moisture, which means that drying is important before molding takes place. 

Nylon also machines easily, but its high ductility leads to stringy chips that necessitate the use of chip-breakers. Heat buildup is also an issue with nylon, and moisture absorption can impact the level of precision that can be achieved. It does, however, respond well to secondary machining on already molded parts, but does not work well with tight-tolerance CNC components.

PEEK

Because PEEK high a high melt temperature around 343°C, a very narrow thermal window that requires precision temperature control, and requires a heated mold, it is considered challenging to mold. However, with the right processing parameters and careful design, PPS can be molded and can manufacture parts with excellent thermal and mechanical performance (but is more expensive). 

PEEK is very difficult to machine. Its high modulus and hardness make it especially tough on cutting tools, and reinforced grades can be highly abrasive. It also generates an abundance of heat, thus requiring the use of coolants. However, machining PEEK supports excellent tolerances and surface finishes when the right combination of feed and speed is used. In fact, PEEK is frequently machined for low-volume aerospace and medical components.

PPS

PPS is not as easy to mold as Nylon 66 because its melt temperature is higher, it possesses a narrower processing window, and has high viscosity. However, it does exhibit very low shrinkage and excellent dimensional stability. PPS molding is very predictable and an excellent option once the right processing parameters have been figured out.

PPS is machinable, definitely more so than Nylon, but tends to be more brittle. It produces short chips and there is a risk of edge chipping during more aggressive cuts. On the other hand, it is good for tight tolerances. Note that filled grades of PPS can accelerate tool wear. Machining PPS is ideal for high-precision parts where dimensional stability is important.

Conclusion

Machined and molded Nylon 66, PPS, and PEEK bearings continue to gain traction because of properties such as low friction, wear characteristics, damping, corrosion resistance, and chemical compatibility. If you are in need of polymer bearings, Advanced EMC is here to help. Our team of engineers and bearing experts can help you from initial design to manufacturing to testing. Contact us today to learn more.

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.