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Polyketone (POK) is usually described in applied terms: "more wear-resistant than POM," "more chemically resistant than polyamide." But behind these comparisons lies one specific chemical idea — the carbonyl group in the main chain. This is a scientific analysis and research review: where polyketone's properties come from, why it is difficult to synthesize, and what the studies on crystallinity, photochemistry, friction and barrier performance show.

The carbonyl chain: one structural idea, many consequences

An aliphatic polyketone is an alternating copolymer of carbon monoxide (CO) and an olefin. In the simplest case the chain has the form …–CO–CH₂–CH₂–CO–CH₂–CH₂–…, where every second unit derives from a CO molecule. The main chain is built entirely of carbon atoms, and the carbonyl groups (C=O) are embedded in it in a strictly regular manner.

The key to almost all of the properties is the polarity of the carbonyl. Strong dipole-dipole interactions act between adjacent chains, while the chain itself contains neither ester nor ether bonds that are prone to hydrolysis. Hence polyketone's signature triad: chemical resistance to hydrocarbons and fuels, resistance to hydrolysis, and the ability to absorb impact. Below we go through each consequence in turn — and show which research it rests on.

Catalysis: why polyketone is difficult to synthesize in the first place

The central chemical problem is to force CO and the olefin to alternate strictly, rather than form random sequences or plain polyolefin blocks. The CO molecule readily coordinates to a metal, so without the right catalyst the reaction "gets stuck."

The breakthrough came in the late 20th century: it was shown that cationic palladium(II) complexes with cis-coordination and weakly- or non-coordinating anions deliver high activity and clean alternation of units. The review by Drent & Budzelaar in Chemical Reviews (1996) summarized this class of catalysts and effectively opened the way to industrial production of the first olefin/CO copolymers. It was this catalytic chemistry, rather than the monomer itself, that long held polyketone back.

The current research frontier is shifting toward non-alternating polyketone: new palladium catalysts (in particular systems with bridging phosphine ligands, work from 2023–2025) make it possible to insert additional ethylene units between the carbonyls, altering the balance of crystallinity and processability. This is an active topic in the latest reviews on polyketone synthesis.

Crystalline structure and polymorphism: where the stiffness comes from

The regularity of the chain yields high crystallinity — and hence stiffness and chemical resistance. X-ray structural studies reveal two crystalline forms in aliphatic polyketones. The denser α-phase (density around 1.39 g/cm³) is characteristic of perfectly alternating ethylene/CO copolymers and arises from the very efficient dipole-dipole interactions in the lattice. The less dense β-phase (around 1.30 g/cm³) tolerates more defects in the chain and more side groups, and is the stable form at elevated temperatures prior to melting. In both forms two chains adopt an all-trans conformation along the c axis; the difference lies in the packing arrangement.

The role of propylene here is not cosmetic but structural. According to crystallization studies, above approximately 2.9 mol% propylene the polymer crystallizes exclusively in the β-phase, and both the degree of crystallinity and the melting temperature decrease as the propylene content rises. This is why the pure ethylene-CO copolymer melts at around 257°C — too close to the thermal decomposition temperature — while commercial terpolymers are engineered into a 200–220°C processing window by adding a little propylene. This is a classic example of how controlled chain "defectiveness" makes a material processable.

The photodegradation paradox: the very same carbonyl

The carbonyl group that gives polyketone its strength and chemical resistance simultaneously makes the polymer chain sensitive to ultraviolet light. Under UV, carbonyls initiate chain scission via Norrish mechanisms. There is an important detail here, well documented in the literature: in a strictly alternating ethylene-CO copolymer, Norrish type I (radical scission next to the carbonyl) dominates, whereas Norrish type II is practically suppressed — because such a chain has no hydrogen atom in the γ-position to the carbonyl, which that reaction requires.

The rate of photodegradation is proportional to the CO content. In outdoor ageing studies, a film with 1% CO lost its elongation at break after roughly six days of exposure, while a film with 13% CO reached the same state in less than a day. It was on this chemistry that photodegradable plastics were once based — including the ring-shaped can holders that were meant to break down in sunlight so as not to harm animals.

Mechanics, friction and barrier performance: what the research says

Polyketone is often positioned as "more wear-resistant than POM." How well is this supported? In comparative tribological studies (pin-on-disc against a steel counterface), polyketone showed a wear rate several times lower than POM — in individual studies more than fourfold — as well as a higher limiting PV value than polyamide and POM. Base-resin producers cite even higher ratios (up to ~10× versus POM), so for a specific friction pair the figure is worth verifying by testing.

A separate area is barrier properties. Owing to its dense polar packing, polyketone has very low permeability to hydrocarbons and acid gases, which is why it is considered and used as an inner barrier layer in flexible composite pipes and anti-corrosion liners for oil and gas environments. Combined with the absence of hydrolyzable bonds, this makes the material a logical candidate wherever polyamide gradually degrades from contact with fuel or hot glycol.

From Carilon to POKETONE: a brief history and the present day

The history of polyketone is instructive precisely as the history of a technology. Shell brought the first aliphatic polyketone to market under the Carilon brand in 1996 (the Carrington site, United Kingdom), but as early as around 2000 it wound down production owing to the then-weak demand and competition from established engineering plastics; some of the patents were passed on.

The material got a second wind thanks to the South Korean group Hyosung: after years of research and substantial investment, the company announced its development in 2013 and launched industrial production under the POKETONE brand in 2015 (the Ulsan plant). As of the mid-2020s, Hyosung remains the principal industrial producer of polyketone, and the material itself remains a niche but steadily available engineering thermoplastic. In parallel, as mentioned above, academic chemistry is moving toward non-alternating polyketones and new palladium catalysts — meaning the material's story is not yet over.

And what about us: Material Wizard polyketone

Material Wizard supplies and compounds polyketone under its own Exablend® line of solutions. The numerical ranges given in this article are typical of the class and drawn from open sources; for design calculations, verify the parameters against the TDS of the specific grade.

A broader overview of the field is in the product hub polyketone (POK); the applied, design-engineering side of the topic (when to design a part for POK instead of POM/polyamide) is covered in the article when to design a part for POK. To select a grade for a specific application, consult a specialist.

Expert analysis: 5 questions worth asking

• Which grade and filler? Unfilled polyketone and GF-filled compounds behave differently in terms of stiffness, shrinkage and wear — start from the task, not from "just POK."
• Is there a UV load? Because of the carbonyl chemistry, outdoor service requires stabilized grades and verification on the specific color.
• What is the processing window? The working melt temperature is narrow (typically up to ~250–260°C); overheating leads to degradation — control of the barrel and residence time is critical.
• What is the chemical contact? Polyketone is strong against fuels, glycols and hydrocarbons, but compatibility with a specific reagent and temperature should be confirmed by testing.
• Why POK specifically, and not POM/polyamide? Polyketone wins when wear resistance, chemical resistance and impact toughness are needed simultaneously; if only one parameter is critical, a cheaper conventional material is often the better choice.

Frequently asked questions

Is polyketone a type of polyamide?

No. Polyketone is a distinct class: an alternating copolymer of CO and an olefin with carbonyl groups in the chain. Polyamide (nylon) has amide bonds and behaves differently, notably absorbing more moisture.

Why does commercial polyketone melt at around 220°C rather than 257°C?

The pure ethylene-CO copolymer melts at around 257°C — too close to thermal decomposition. Adding a small proportion of propylene lowers the crystallinity and the melting temperature to a working 200–220°C.

Is polyketone really photodegradable?

The carbonyl group makes the chain sensitive to UV (Norrish reactions), and the rate depends on the CO content. But engineering grades are UV-stabilized; the photodegradable materials were special low-CO films, not structural parts.

How much more wear-resistant than POM is polyketone?

In comparative studies the wear of polyketone is several times lower than POM (individual studies — more than 4×), and producers cite even higher figures. For a specific friction pair the value is worth verifying by testing.

Where is polyketone objectively better than polyamide?

Wherever there is contact with fuels, glycols or moisture: polyketone is more resistant to hydrocarbons and does not hydrolyze, whereas polyamide gradually degrades under such conditions and changes dimensions through water absorption.

Sources and scientific literature

• Drent E., Budzelaar P.H.M. Palladium-Catalyzed Alternating Copolymerization of Alkenes and Carbon Monoxide. Chemical Reviews, 1996.
• Recent Advances in Synthesis of Non-Alternating Polyketone Generated by Copolymerization of Carbon Monoxide and Ethylene. Polymers / PMC, 2024.
• Crystalline structure in aliphatic polyketones; On the effect of the nature of the side chain over the crystalline structure. Polymer (ScienceDirect).
• Melting and crystallization behavior of aliphatic polyketones. Journal of Applied Polymer Science.
• Photochemistry of Ketone Polymers. I. Studies of Ethylene-Carbon Monoxide Copolymers. Macromolecules.
• Outdoor ageing of ethylene–carbon monoxide alternating copolymer; Chemical and physical modifications by outdoor exposure. Polymer Degradation and Stability / Polymer.
• Dry sliding wear characteristics of some industrial polymers against steel counterface. Wear (ScienceDirect).
• Hyosung POKETONE technical materials; reference data on the history of Carilon.

Note: the numerical values are given as typical for the class based on open sources; they do not replace the technical data sheet (TDS) of a specific grade.