Kepstan

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Kepstan® PEKK high-performance polymer

Kepstan® PEKK from Arkema is an ultra-high-performance thermoplastic polymer developed for demanding applications where conventional engineering plastics may not provide the required combination of heat resistance, mechanical strength, chemical resistance and long-term performance.

As part of the poly aryl ether ketone, or PAEK, family, Kepstan® PEKK offers a high-performance material platform for technical components exposed to elevated temperatures, harsh environments, mechanical loads or demanding processing requirements.

Resinex supplies Kepstan® PEKK across Europe and supports customers in exploring suitable grades for injection moulding, extrusion, thermoforming, composites, powder coating and additive manufacturing applications.

What is Kepstan® PEKK?

PEKK stands for polyetherketoneketone. It is a high-performance polymer within the PAEK family, the same broader polymer family as PEEK. Kepstan® PEKK is designed for technical applications where the material must perform under demanding thermal, mechanical and chemical conditions.

A key feature of Kepstan® PEKK is its copolymer structure. The polymer contains both terephthalic and isophthalic units, often described through the T/I ratio. By adjusting this ratio, different Kepstan® PEKK series can deliver different crystallisation behaviour, thermal characteristics and processing profiles. This flexibility allows engineers to select grades that are better aligned with specific performance requirements, manufacturing processes and end-use applications.

Depending on the selected grade and processing method, Kepstan® PEKK can be used in either amorphous or semi-crystalline states, with post-crystallisation also possible in selected applications.

This combination of thermal performance, mechanical strength, chemical resistance, flame resistance and processing flexibility makes Kepstan® PEKK suitable for a wide range of technically demanding applications.

Key benefits of Kepstan® PEKK

Kepstan® PEKK combines several high-performance properties in one material family. This makes it suitable for demanding thermoplastic applications where one property alone is not enough.

• High temperature resistance: Glass transition temperatures are typically around 160°C to 165°C depending on the selected series, with melting temperatures from approximately 305°C to 358°C. The different Kepstan® PEKK series allow the balance between thermal performance, crystallisation behaviour and processing requirements to be adapted to specific application requirements.

• High strength and stiffness: PEKK provides tensile strength and stiffness for demanding structural and technical components. Glass fibre and carbon fibre reinforced grades are available for higher mechanical performance.

• Chemical resistance: Kepstan® PEKK offers high chemical resistance and can be considered for applications exposed to demanding chemical environments and harsh operating conditions.

• Flame resistance and low smoke: Kepstan® PEKK offers inherent flame resistance together with low smoke generation and low toxicity characteristics. These properties can be relevant in applications where flame resistance, smoke performance or FST requirements are important material selection criteria.

• Tunable crystallinity: The crystallisation behaviour of PEKK can be adjusted through the selected polymer series. This provides flexibility when selecting processing conditions and defining the required final material state. Depending on the application and processing technology, PEKK can be processed in either an amorphous or semi-crystalline state, while amorphous parts can also be crystallised in a subsequent process.

• Tribological performance: Selected grades provide low and controlled friction and wear behaviour, including at elevated temperatures. This can make Kepstan® PEKK suitable for selected components where wear and friction performance are important material requirements.

• Barrier and electrical properties: PEKK can provide improved barrier performance compared with PEEK and also offers electrical insulation performance.

Thermal performance and material stability

Thermal performance is one of the main reasons engineers consider Kepstan® PEKK. The material is designed to retain useful mechanical performance at elevated temperatures, making it relevant for components exposed to heat during operation or processing.

The different Kepstan® PEKK series allow the balance between glass transition temperature, melting temperature, crystallisation behaviour and processing requirements to be adapted to the application. This flexibility is important where both part performance and manufacturing route influence the final material choice.

Kepstan® PEKK series overview

Kepstan® 6000 series

T/I ratio: 60/40

Glass transition temperature (Tg): approximately 160°C

Melting temperature: approximately 305°C

Crystallisation speed: Slow

Typical processing fit: Additive manufacturing, thermoforming, film and sheet extrusion, and powder coating

Kepstan® 7000 series

T/I ratio: 70/30

Glass transition temperature (Tg): approximately 162°C

Melting temperature: approximately 336°C

Crystallisation speed: Medium

Typical processing fit: Composites, film extrusion, fabric coating, prepreg production and unidirectional tapes

Kepstan® 8000 series

T/I ratio: 80/20

Glass transition temperature (Tg): approximately 165°C

Melting temperature: approximately 358°C

Crystallisation speed: Fast

Typical processing fit: Injection moulding, extrusion, powder coating and high-performance components

Note: Values are indicative and grade dependent. Final material selection should be based on the relevant datasheet, application requirements and processing conditions.

Mechanical performance

Kepstan® PEKK offers a combination of tensile strength, compression strength and stiffness that can be advantageous in demanding mechanical applications. Compared with neat PEEK, selected Kepstan® PEKK grades may offer:

• Approximately 10% higher tensile strength

• Approximately 20% higher compression strength

• Higher yield stress across the temperature range

• High modulus retention up to 165°C

Actual performance depends on the selected grade, reinforcement, processing conditions and test method. These comparisons should therefore be viewed as an indication of material potential rather than a universal performance ranking across all PEKK and PEEK grades.

Chemical resistance, barrier performance and wear behaviour

Kepstan® PEKK offers high chemical resistance and can be considered for applications exposed to demanding chemical environments and harsh operating conditions.

Compared with PEEK, Kepstan® PEKK can provide approximately 2.5 times higher barrier performance. This characteristic can be relevant for applications where limiting gas permeation is an important design requirement, particularly in demanding operating environments.

In addition, Kepstan® PEKK offers electrical insulation performance for applications where both barrier and electrical properties are important.

Kepstan® PEKK can also offer specific advantages in demanding tribological applications, including low and controlled wear rates and coefficient of friction (CoF) behaviour, even at temperatures above the material's glass transition temperature.

This behaviour can be beneficial for components where friction and wear performance must remain controlled during operation at elevated temperatures.

PEKK vs PEEK: what is the difference?

PEKK and PEEK are both high-performance PAEK polymers used when standard engineering thermoplastics cannot meet the required combination of thermal, mechanical and chemical performance. However, they should not be treated as direct substitutes without technical evaluation.

PEEK is a homopolymer, while Kepstan® PEKK is a copolymer containing both terephthalic and isophthalic units. The ratio between these units influences crystallisation kinetics, melting temperature and processing behaviour. This tunable molecular structure is one of the key differences between PEKK and PEEK and allows the Kepstan® PEKK portfolio to offer different combinations of thermal performance and processing behaviour. As a result, engineers can select grades that are more closely aligned with specific application and manufacturing requirements.

Comparison of Kepstan® PEKK and PEEK

Polymer structure

Kepstan® PEKK: Copolymer containing terephthalic and isophthalic units.

PEEK: Homopolymer.

Crystallisation behaviour

Kepstan® PEKK: Can be adjusted through the selected PEKK series.

PEEK: Generally faster and less adjustable.

Thermal profile

Kepstan® PEKK: Higher Tg range in the Kepstan® PEKK series, approximately 160°C to 165°C.

PEEK: Typical Tg around 143°C.

Processing flexibility

Kepstan® PEKK: Relevant for technologies such as thermoforming, additive manufacturing, composites, injection moulding and extrusion.

PEEK: Well established in injection moulding and extrusion.

When to consider

Kepstan® PEKK: When higher Tg, crystallinity control, barrier performance, wear behaviour or processing flexibility are important.

PEEK: When existing PEEK grades and production routes already meet the application requirements.

More flexibility in processing

One of the most significant differences between PEKK and PEEK is crystallisation behaviour. PEEK crystallises relatively quickly, while the crystallisation rate of Kepstan® PEKK can be adjusted through the selection of the 6000, 7000 or 8000 series.

This provides a broader processing window and enables Kepstan® PEKK to be considered for technologies beyond conventional injection moulding and extrusion.

Depending on the selected grade and application requirements, Kepstan® PEKK can be processed using:

• Injection moulding

• Extrusion

• Thermoforming

• Compression moulding

• FDM / FFF additive manufacturing

• SLS additive manufacturing

• Composite manufacturing

• Powder coating

• Laser welding

The slower crystallisation behaviour of the 6000 series, intermediate behaviour of the 7000 series and faster crystallisation behaviour of the 8000 series allow the material to be matched more closely to the selected processing technology and application requirements.

When should you consider PEKK?

PEKK may be particularly interesting when:

• A higher glass transition temperature is required

• Improved barrier performance is important

• Controlled crystallisation behaviour is beneficial

• Thermoforming or additive manufacturing is being considered

• Friction and wear performance at elevated temperatures are important

• Processing flexibility is a key part of the material selection process

PEEK may remain the preferred choice when:

• Existing production processes are already optimised for PEEK

• The established PEEK grade portfolio meets the application requirements

• The required combination of thermal, mechanical and chemical properties is already achieved with PEEK

The final material selection should always be based on the specific application, processing technology and performance requirements. Both PEKK and PEEK offer high-performance PAEK solutions, but their differences can make one material more suitable than the other depending on the intended application.

Kepstan® PEKK product range

The Kepstan® PEKK portfolio is structured around three polymer series. Each series has a different T/I ratio, influencing crystallisation behaviour, melting temperature and processing suitability. This allows engineers to select grades that are more closely aligned with specific processing requirements and end-use applications.

Kepstan® 6000 series

The 6000 series has the slowest crystallisation rate within the Kepstan® PEKK portfolio. It is particularly suited to applications where controlled crystallisation and processing flexibility are important, including:

• Additive manufacturing

• Thermoforming

• Film and sheet extrusion

• Powder coating

Kepstan® 7000 series

The 7000 series offers an intermediate crystallisation rate, providing a balance between processing behaviour and high-performance material properties. Potential applications include:

• Structural composites

• Film extrusion

• Fabric coating

• Prepreg production

• Unidirectional tapes

Kepstan® 8000 series

The 8000 series provides the highest melting temperature and fastest crystallisation rate within the Kepstan® PEKK portfolio. It is designed for applications requiring high thermo-mechanical performance and can be used for:

• Injection moulding

• Extrusion

• Powder coating

• High-performance components

The commercial Kepstan® PEKK portfolio comprises three series with up to four viscosity levels per series, providing a broad range of grade options. Depending on the grade, materials are available in forms including flakes, pellets and powders.

Compounds and reinforced grades

Kepstan® PEKK is available in different material configurations to support specific application requirements. The portfolio includes glass fibre reinforced grades, carbon fibre reinforced grades and wear grades for applications where friction and wear performance are important.

The combination of polymer series, viscosity levels, material forms and reinforcement options allows Kepstan® PEKK to be tailored to a broad range of component designs, performance requirements and processing technologies.

Processing technologies

Kepstan® PEKK offers a broad processing window compared with many high-performance polymers. The material's tunable crystallisation behaviour allows different grades to be matched to specific manufacturing technologies and processing requirements.

Depending on the selected grade, the material can be processed using technologies including:

• Injection moulding

• Extrusion

• Compression moulding

• Thermoforming

• FDM / FFF additive manufacturing

• SLS additive manufacturing

• Composite manufacturing

• Powder coating

• Laser welding

The choice of Kepstan® PEKK series and viscosity level depends on the selected processing technology, component design and required final properties.

Kepstan® PEKK for additive manufacturing

Kepstan® PEKK is particularly relevant for demanding additive manufacturing applications. Its controlled crystallisation behaviour supports processing flexibility and allows manufacturers to tailor final part performance. Depending on the application and processing conditions, parts can be produced in either an amorphous or semi-crystalline state, with post-crystallisation possible where required.

In FDM / FFF processing, selected Kepstan® PEKK grades may offer advantages compared with PEEK, including:

• Improved interlayer adhesion

• Lower printing temperatures

• Improved dimensional stability

• Reduced warpage

• Greater control over crystallinity

• Potential for producing larger components

Actual performance depends on the selected grade, printing equipment, processing conditions, component geometry and post-processing method.

Application areas for Kepstan® PEKK

The combination of thermal performance, mechanical strength, chemical resistance, flame resistance and processing flexibility makes Kepstan® PEKK suitable for a wide range of demanding applications.

Aerospace and defence

Kepstan® PEKK can be considered for lightweight, high-performance components where thermal resistance, mechanical strength and flame resistance are important.

Automotive and transportation

The combination of mechanical performance, temperature resistance and tribological properties can make Kepstan® PEKK suitable for selected demanding automotive and transportation applications.

Oil and gas

Kepstan® PEKK's combination of chemical resistance, high-temperature capability and barrier properties can be relevant for selected applications in demanding oil and gas environments.

Industrial applications

Kepstan® PEKK can be used for high-performance components, structural parts and wear-resistant applications exposed to demanding operating conditions.

Composite applications

Different Kepstan® PEKK grades and processing options enable the material to be used in advanced composite solutions, including prepregs and unidirectional tapes.

Additive manufacturing

Kepstan® PEKK is an option for high-performance 3D printed components where a combination of thermal, mechanical, chemical and flame-resistance properties is required.

Selecting the right Kepstan® PEKK grade

The correct Kepstan® PEKK grade depends on the requirements of the specific application and the intended manufacturing process. Early material selection support can help reduce development risk and ensure the selected grade matches both processing and performance needs.

• Operating temperature

• Required degree of crystallinity

• Mechanical performance

• Chemical exposure

• Friction and wear requirements

• Flame resistance requirements

• Processing technology

• Required viscosity

• Reinforcement requirements

• Component geometry

Kepstan® PEKK from Resinex

Resinex supplies ultra-high-performance polymer solutions for demanding applications and can support customers in exploring suitable Kepstan® PEKK grades. Whether the requirement is for an injection-moulded component, advanced composite, thermoformed part, high-performance film or 3D printed component, Kepstan® PEKK offers a versatile material platform for applications where conventional thermoplastics may not provide the required performance.

Contact Resinex to discuss your application requirements and explore a suitable Kepstan® PEKK solution.

Frequently Asked Questions About Kepstan® PEKK

Kepstan Products

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