POK polyketone: properties, grades, processing, applications and equivalents
Polyketone POK / PK for friction, chemical contact and stable geometry
Polyketone POK / PK is a high-performance semi-crystalline thermoplastic for parts whose service life is governed by friction, contact with liquids or lubricants, micro-clearance stability, low water absorption and predictable behavior after operating cycles. Exablend® POK is positioned as a material platform for gears, rollers, valves, metering units, pump elements, fuel-contact and chemically loaded components.
What Is Polyketone POK / PK and Why It Is Evaluated at the Assembly Level
Polyketone is a semi-crystalline aliphatic polymer based on carbon monoxide and olefins. Its regular chain structure, polar carbonyl groups and dense morphology produce a combination valuable for moving parts: wear resistance, hydrolytic stability, low moisture dependence, chemical resistance and barrier behavior.
Evaluation starts with the mechanism of function loss
A gear, roller, bushing, metering element or bearing component can lose its function gradually: the clearance changes, noise increases, wear particles appear, smoothness of travel deteriorates, or the surface swells after contact with water or a working fluid.
POK is correctly considered for parts where friction, the operating environment, impact toughness, shrinkage and repeatable geometry form a single engineering problem.
Position among engineering polymers
PA6/PA66 have a broad structural track record, but water often becomes a design factor. POM performs well in many dry gear drives, yet it does not always cover requirements for chemical or fuel contact. PBT is appropriate for housings and electrical components, but it is not always the optimal candidate for assemblies with intensive friction. PPS, PPA and PEEK are justified for higher temperature or chemical regimes, though they may create an over-specified solution.
POK’s strong zone is a moving part in a liquid or chemical environment where stable clearance, controlled wear and predictable geometry matter.
POK should be positioned as a platform for managing assembly function: contact surface service life, fit stability, behavior after moisture or chemical exposure, and repeatability of series-production geometry.
POK vs POM, PA6, PA66, PA12, PBT and PPS: An Honest Engineering Selection Map
Polyketone is not the cheapest engineering plastic and should not be presented as a universal replacement for all materials. Its strong zone is parts where friction, chemical contact, moisture, stable clearance and service life act simultaneously. In this block, POK is compared with its closest engineering alternatives without hiding its weak points: in cost-effectiveness it is inferior to commodity PA, POM and PBT, but it often wins where part failure is driven by wear, moisture, chemical attack or unstable motion.
Polyketone grades for different part operating regimes
After the initial assessment of the assembly, it is important to move from the general logic of POK to a specific grade. Exablend® POK includes glass-filled, mineral-filled and carbon-filled compounds for friction parts, chemical contact, stable geometry, high stiffness and precision molding.
Exablend® POK GF30 G2
Glass-filled POK with 30% GF for technical parts that require a combination of stiffness, wear resistance, chemical resistance and dimensional stability.
Go to product page →50% GF · high rigidityExablend® POK GF50 F4
Highly filled POK with 50% glass fiber for structural parts where stiffness, strength, dimensional stability and performance under load are critical.
Go to product page →50% GF · low shrinkageExablend® POK GF50 S4
POK with 50% GF for high stiffness, low shrinkage, precision molding and series-production parts where repeatable geometry after cooling matters.
Go to product page →25% MF · low warpageExablend® POK MF25 S2
Mineral-filled POK for precise functional parts, housings, pump and valve components that require wear resistance, surface quality and warpage control.
Go to product page →20% CF · dimensional precisionExablend® POK CF20 TRM
Carbon-filled POK with 20% CF for dimensional accuracy, fuel contact, barrier behavior and an electrically conductive surface profile in technical assemblies.
Go to product page →If the technical specification is not yet detailed, selection should not start from the GF or CF percentage alone. First, define the part’s operating regime: the friction pair, environment, temperature, tolerances, shrinkage, surface requirements, electrical profile and geometry stability over cycles.
The advantages of polyketone emerge in the combination of properties
What matters to a technical decision-maker is not a list of characteristics but the risk the material removes from the part: clearance change after moisture, wear in liquid, gear-mesh noise, wall permeability, degradation after media contact or molding instability.
Tribology
In a gear drive, wear means a change of tooth profile, backlash, noise, local heating and a growing amount of wear particles.
Chemical contact
The material is assessed by retention of mass, surface, strength, travel and dimensions after exposure to a specific medium.
Moisture and hydrolysis
Low moisture dependence reduces the risk of fit change, jamming, unstable actuation force and increasing noise.
Barrier behavior
In fuel, gas and metering systems, permeability, sorption and wall stability can be as critical as strength.
Wear index comparison of POK, PA and POM
Polyketone demonstrates pronounced wear resistance compared with traditional engineering plastics. In the comparative data presented, the wear index of POK is taken as 3 arbitrary units, PA as 8 and POM as 30. The lower the value, the lower the wear under comparable test conditions.
In practical terms, this means POK can outperform POM by roughly a factor of 10 and polyamides by roughly a factor of 3 in wear resistance. For a series-production part, such data must be confirmed on the real friction pair, speed, pressure, temperature and presence of contaminant particles.
low wear index
medium wear index
high wear index
| Test | POK / Exablend® | POM / acetal | PA66 | Engineering interpretation |
|---|---|---|---|---|
| Taber abrasion test1 | ↑↑ very low wear | high wear | failure or severe damage | Simulates surface abrasion typical of friction with dust, sand or microparticles. |
| ASTM D-3702 PV limit2 | highest level | medium | low | A key parameter for dynamic friction assemblies where pressure and speed generate the thermal load. |
| Bevel-gear wear test3 | almost no wear | significant damage | significant damage | Allows assessment of long-term performance under gear-tooth contact conditions. |
| Pin-on-Disk4 | low wear | higher | higher | Shows surface resistance to sliding friction in a controlled contact configuration. |
| Friction noise coefficient5 | −16% vs POM | baseline level | depends on humidity and the friction pair | Characterizes undesirable acoustic effects arising from contact between materials. |
- The Taber abrasion test simulates abrasion with dust, sand and microparticles.
- PV limit describes the limiting combination of pressure and speed in a friction assembly.
- The bevel-gear wear test is useful for assessing wear in gear drives.
- Pin-on-Disk shows sliding friction in a controlled contact configuration.
- Friction noise matters for drives, metering units, household appliances and mechanisms with acoustic requirements.
| Chemical | Duration | Mass change, % | Strength loss, % | Comment |
|---|---|---|---|---|
| Acetic acid 5% | 365 days | +2.8 | −8 | No change in appearance. |
| Acetone 100% | 365 days | +4.7 | −10 | Slight yellowing. |
| Benzene 1%, BTX mixture | 120 days | 0 | −1…−5 | Geometry retained. |
| Ammonium hydroxide 10% | 365 days | −4.0 | −13 | Darkening; structure stable. |
| Ethylene glycol-based antifreeze | 730 days | +0.6 | −7 | Full integrity. |
| Chloroform 100% | 730 days | +25.4 | −25 | Swelling; not recommended without separate validation. |
| Media type | POK resistance | Application comment |
|---|---|---|
| Aliphatic hydrocarbons | ★★★★★ | Hexane, octane, diesel — usually no significant changes after testing. |
| Aromatic hydrocarbons | ★★★★☆ | Toluene, xylene — slight yellowing possible; confirmation at operating temperature is required. |
| Alcohols and glycols | ★★★★★ | Ethanol, antifreeze — a strong zone for liquid contact. |
| Ketones, ethers, esters | ★★★★☆ | Acetone, ethyl acetate — moderate swelling possible. |
| Weak and medium-strength acids | ★★★★☆ | Strength retention depends on concentration, temperature and contact time. |
| Alkalis and salts | ★★★★★ | NaOH, NH₄OH, CaCl₂ — stability under moderate regimes after formulation verification. |
| Water, humidity and aqueous media | ★★★★★ | Low water absorption and better dimensional stability compared with polyamides. Contact with steam or hot aqueous media requires verification for temperature, pressure and cycle duration. |
| Detergents and enzymes | ★★★★☆ | Slight discoloration possible; function is verified in the actual formulation. |
How POK works in an assembly: friction, moisture, chemicals and stable clearance
This block shows the regimes in which POK should be tested first: a moving part, liquid contact, micro-clearance stability, water absorption, wear and geometry repeatability over cycles.
Selection map
POK is not presented as a universal material. It should be included in testing first when the part is moving, contacts a liquid, has a critical clearance or shows PA/POM risks in the real geometry.
Water absorption
In wet assemblies, POK reduces the risk of fit change and travel stability issues compared with polyamides, but actual behavior must be verified on the specific grade and geometry.
Metering systems
For metering units, valves and pump components, what matters is small precision mechanics, chemical contact, repeatable travel, surface cleanliness and micro-clearance stability.
What to verify in GF/CF POK grades
Reinforcement increases stiffness and dimensional stability under load. For a series-production part, it is important to verify the behavior of the specific geometry in the melt flow and after cooling.
fiber orientation relative to mating surfaces
strength and appearance at flow weld locations
shrinkage along and across the flow direction
actual geometry after cycle stabilization
fit, clearance, noise and actuation force in the real assembly
When POK is technically excessive or carries a high risk of mismatch
Honest positioning of a premium material separates the tasks where POK removes risk from products where another polymer is more rational or a higher temperature class is required.
How to make the decision
The question should be: which risk in the assembly costs more than the difference in material price? If mechanism stoppage, noise, wear in liquid, unstable clearance or permeability are critical, POK should be included in the test matrix.
If the primary requirement is the lowest price, sustained high temperature or extreme chemistry, material selection should start from a different polymer group.
POK is not a universal answer for every part. Its strong role emerges where a standard polymer gradually loses function, while a high-temperature material creates an over-specified solution.
Polyketone processing is part of the material solution
The properties of POK in a part depend on drying, barrel cleanliness, melt residence time, temperature profile, mold temperature, pressure, injection speed, flow direction, weld lines and the actual shrinkage in a specific mold.
GF30 / GF50 S4 / MF25
Typical molding profile: 220 → 245°C, mold temperature around 80°C, pressure 80–130 MPa, medium to high injection speed. For glass-filled grades, controlling fiber orientation and differential shrinkage is critical.
MW-010GP / CF20 TRM / GF50 F4
The unfilled grade offers a wider processing window for injection molding and extrusion. CF20 TRM requires careful control of fiber, surface quality and electrical profile. GF50 F4 can run at higher temperatures in the final zones but requires residence time control.
Drying
GF30: 4–6 h at 90–110°C down to 0.02%. GF50 S4/MF25: 2–3 h at 90–110°C down to 0.02%. MW-010GP: 4–6 h at 80–90°C down to below 0.1%.
Melt residence time
Excessive temperature and prolonged residence in the barrel or hot runner can cause dark specks, viscosity changes, surface degradation and an unstable production run.
Equipment purging
Purging with polyolefins is advisable before and after POK. Particular attention is required after POM, PA and unknown colorants or additives.
Material Wizard as the technical center for material decision-making
The company's role is to match the part's failure mechanism to a material family, select an Exablend® POK grade, assess processing, run application testing and bring the solution to a stable production run.
1. Assembly diagnostics
Friction pair, environment, temperature, cycle life, noise, tolerances, expected economics of failure.
2. Material family selection
POK is compared with PA, POM, PBT, PPA, PPS and PEEK by the risk of functional failure.
3. Exablend® formulation
Unfilled, glass-filled, carbon-filled, mineral-filled, conductive or specially modified formulations.
4. Processing validation
Drying, temperature profile, pressure, weld lines, residence time, purging and actual mold stability.
5. In-part testing
Friction, noise, fit, chemicals, moisture, thermal cycling, service life, repeatability, comparison with the current material.
6. Series stabilization
Batch control, processing recommendations, formulation adjustments, support during launch and scale-up.
The POK landing page should demonstrate engineering confidence: Material Wizard understands the environment, loads, processing, alternatives and the economics of a series-production part.
FAQ about polyketone POK / PK
Brief answers for initial material screening before a technical consultation and testing in a specific part.
What is polyketone POK / PK?
POK / PK is a high-performance semi-crystalline thermoplastic with a strong position in friction assemblies, chemical contact, moisture, fuel and metering environments.
How does POK differ from POM?
POM is often strong in dry mechanisms. POK is worth testing when friction is combined with chemicals, water, fuel, micro-clearance stability, noise or barrier behavior.
When is POK better than PA66?
POK has a practical advantage where the water absorption of PA66 can affect fit, clearance, noise, actuation force or dimensional stability after conditioning.
Is POK suitable for friction parts?
Yes, but the decision is made after verifying the actual friction pair, speed, pressure, lubricant, contact temperature, wear particles and noise after cycling.
When should POK not be used?
POK may be excessive for simple static housings, dry assemblies already running reliably on POM, or parts exposed to sustained high temperatures of the PPS/PPA/PEEK class.
Select the grade PDF file
Select the TDS for the required Exablend® POK grade. If the grade is not obvious, send a technical inquiry describing the part, environment, temperature, friction pair, tolerances and current material.
Send an inquiry about Exablend® POK
Describe the part, contact environment, temperature, friction pair, tolerances, current material and expected volume. This helps us select a POK grade faster or propose an alternative polymer family.