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.

Spring Energized PTFE Seal composite bushings
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Bearing-Grade Polymers in Aerospace Mechanisms

Engineers often rely on bearing-grade polymers for critical aerospace applications. Bearing-grade materials, including PEEK, Torlon, and polyimide composites, are able to offer the strength and stability needed to replace metals in aerospace mechanisms. 

This blog post is going to explore the defining properties, performance advantages, and design considerations of bearing-grade polymers in aerospace mechanisms.

The Engineering Challenge: Bearings in Aerospace Systems

Bearings in aerospace mechanisms face extreme operatging conditions. They must operate under high loads and speeds, withstand temperature extremes from cryogenic levels to over 500°F, and perform in vacuum or radiation environments without failure. Traditional metal bearings—though strong—can corrode, seize, or wear rapidly under these conditions. They often require lubrication, which is problematic in vacuum or high-temperature applications. Given these operating conditions, bearing-grade polymers are an attractive alternative to traditional metal bearings.

What is a Bearing-Grade Polymer?

Bearing-grade polymers are engineered plastics formulated specifically for high-performance bearing and bushing applications.  Many of their enhanced properties are the result of additives  such as graphite, PTFE, carbon fiber, glass, or molybdenum disulfide (MoS₂). Key parameters that define their performance include maximum pressure (P), velocity (V), and the combined PV limit, which measures load-speed endurance.

Advanced EMC’s Bearing Material Guide identifies several polymer families optimized for aerospace use, including:

  • Fluorolon 3015 (PEEK BG): it has a high PV capability, good chemical resistance, and good thermal stability.
  • Torlon 4435: known for its excellent high-temperature performance and low friction under high loads.
  • Fluorolon 4031–4033 (Polyimide-based): exhibits outstanding thermal resistance and dry-running capabilities.
  • Fluorocomp 6000/6010 (Polyimide Composites): has superior load-bearing and temperature tolerance with low wear.

Advantages of Bearing-Grade Polymers in Aerospace

Weight Reduction and Fuel Efficiency

Bearing-grade polymers are up to 80% lighter than metal counterparts. This type of weight savings directly contributes to SWaP objectives and offers much better payload and fuel efficiency.

Self-Lubrication and Maintenance-Free Operation

It is possible to obtain aerospace-grade polymers that are either naturally self-lubricating or feature built-in lubricants. This material property effectively eliminates the need for external lubrication, which is ideal for vacuum environments and reduces maintenance requirements.

Dimensional Stability and Low Thermal Expansion

Bearing-grade polymers have excellent dimensional stability and low thermal expansion. Such material properties allow them to maintain consistent clearances across a wide tempreature range. This stability prevents problems with binding or deformation that is common with metal bearings during rapid temperature shifts.

Chemical and Radiation Resistance

Polymer-grade materials include those that exhibit excellent performance even in the presence of chemicals such as hydraulic fluids, de-icing agents, fuels, and radiation without exhibiting degradation. Their chemical and radiation resistance helps ensure a long service life even in highly aggressive environments.

Vibration Damping and Noise Reduction

In addition to mechanical durability, polymers also provide  vibration damping and noise attenuation. Not only can this enhance comfort but it can also reduce wear in sensitive control systems.

Spring Loaded Seal

Common Aerospace Applications

There are a host of aerospace applications that depend on bearing-grade polymer solutions. These include ….

  • Actuation Systems – Bearings in flight control, flap, and slat actuators benefit from low friction and dry-running capability.
  • Landing Gear Components – Lightweight polymer bushings withstand impact loads and resist corrosion in outdoor conditions.
  • Satellite and Spacecraft Mechanisms – Polyimide and PEEK bearings can perform reliably in vacuum and cryogenic environments.
  • Environmental Control Systems (ECS) – Bearings resist thermal cycling in high-speed air-handling systems.
  • Turbomachinery and Pumps – High-PV polymers operate effectively without lubrication in auxiliary pumps and gear mechanisms.

Comparative Overview: Bearing-Grade Polymer Families

The table below offers an overview of the most commonly used bearing-grade polymers.

MaterialTemperature Limit (°F)Max PV (psi·ft/min)AttributesTypical Aerospace Use
Polyimide (Fluorolon 403x)570250,000–300,000Low friction, high temperature, chemical resistanceSpace mechanisms, dry-running bearings
PEEK (Fluorolon 3015)480100,000High PV, chemical resistance, thermally stableAircraft actuators, gearboxes
Torlon 4435500100,000High temp, high strength, low wearLanding gear bushings, structural bearings
PPS (Fluorolon 5065)40025,000Low friction, moderate loadCabin systems, auxiliary components
Composite (Fluorocomp 6000)55080,000Polyimide-carbon composite, high load, high tempDry-running or high-stress joints

Design and Integration Considerations

When designing aerospace compoents from bearing-grade polymer materials, engineers must account for issues such as creep, outgassing, and thermal expansion. Attention must also go into ensuring proper clearance, wall thickness, and housing interference, all of which are crucial to maintaining alignment and preload in the presence of fluctuating temperatures. Surface finish and counterface material also have an impact on wear performance. 

Note that manufacturers such as Advanced EMC are capable of ensureing consistency through precision machining, molding, and post-processing that are in compliance with AS9100 and NASA outgassing standards.

Conclusion

Bearing-grade polymers reduce weight, extend component life, and perform where metals cannot, whether their enviroment is cryogenic vacuum conditions or at the heart of high-speed actuation systems. And as aerospace systems continue to rapidly move toward greater efficiency and autonomy, polymer bearing technology will remain a cornerstone of reliability and innovation.

Advanced EMC provides engineered polymer bearing solutions optimized for aerospace performance. Contact our knowledgeable team today to learn how high-performance materials like PEEK, Torlon, and polyimide composites can enhance your next aerospace design.