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Polyetheretherketone (PEEK): A Complete Guide on High-Heat Engineering Plastic

Polyetheretherketone (PEEK) is a high-performance, engineering thermoplastic characterized by an unusual combination of properties. These properties range from high temperature performance to mechanical strength and excellent chemical resistance.

But, what are the key characteristics which make PEEK a high-performance plastic? What it is made up of? Get all the technical information on Polyetheretherketone, explore what are its key properties and benefits in detail! Also, learn about popular application (aerospace, automotive, medical...) and processing conditions for this polymer.

Let’s begin by defining the polymer...

What is PEEK – Polyetheretherketone?


Polyetheretherketone (PEEK) is a semi-crystalline, high-performance engineering thermoplastic. This rigid opaque (grey) material offers a unique combination of mechanical properties, resistance to chemicals, wear, fatigue and creep as well as exceptionally high temperature resistance, up to 260°C (480°F).

The polymer belongs to polyketone family of polymers (PEK, PEEK, PEEKK, PEKK, PEKEKK) and amongst them, PEEK is the most widely used and manufactured in large scale.


Polyetheretherketone (PEEK): A Complete Guide on High-Heat Engineering Plastic

PEEK [CAS: 29658-26-2; Chemical Name: poly(oxy-1,4-phenyene-oxy-1, 4-phenyene)] has:


PEEK can be processed by conventional methods such as injection molding, extrusion, compression molding etc.

Thanks to these properties, PEEK and its composites are widely used in aerospace, automotive, structural, high temperature electrical and biomedical applications.

Despite high price of the polymer, the added value that PEEK materials bring by offering the possibility of manufacturing parts include lightweight, strength or toughness and able to survive longer in harsh environments.

PEEK is fully recyclable plastic. PEEK has been commercially available from ICI since early 1980s. Nowadays, there are many producers of PEEK, such as:

Supplier Brand(s)
Lehmann & Voss LUVOCOM®
RTP Company RTP 2200 Series
Victrex VICTREX®, VICTREX™ PEEK VICOTE™
SABIC LNP™ THERMOCOMP™, LNP™ LUBRICOMP™, LNP™ STAT-KON™
Solvay KetaSpire®, Solviva® Zeniva®, Tribocomp®
Evonik VESTAKEEP®

» View all PEEK commercial grades and more suppliers in Omnexus Plastics Database

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Key Properties of Polyetheretherketone (PEEK)


  1. PEEK exhibits exceptional tensile properties. When reinforced with carbon fibers, tensile strength of 29000psi can be achieved with excellent properties retained at 299°C
  2. The polymer also exhibits excellent creep resistance. When combined with flexural & tensile characteristics, it provides an excellent balance of properties where the material is required to withstand high loadings for long periods at high temperature without permanent deformations
  3. Its flexural modulus at very high temperatures can further be improved with glass- or carbon-reinforcement. (Reinforcement also increases creep and fatigue resistance, thermal conductivity of the polymer as well as heat distortion temperature)


  4. Polymer Matrix Selection for Very High Temperature Composites

  5. The polymer exhibits high volume resistivity and surface resistivity. It can maintain good insulating properties in a broad temperature range and environmental changes
  6. PEEK has V0 flammability rating down to 1.45 mm and an LOI of 35%. Its smoke and toxic gas generation are extremely low
  7. Crystallinity imparts excellent resistance to wide range if liquids and superb fatigue performance
  8. PEEK is insoluble in all common solvents. It does not undergo hydrolysis and can be used for thousands of hours in steam or high-pressure water without significant property degradation
  9. More properties of PEEK include:
    • Low friction
    • Good dimensional stability
    • Exception insulation properties
    • Excellent sterilization resistance at high temperature
    • Biocompatible
    • Long life
    • Inherent purity


Neat PEEK Vs Reinforced Grades and Other Polymers


Below table lists the properties of unfilled, 30% glass fiber-reinforced, 30% carbon fiber-reinforced PEEK grades:

Property Unfilled 30% carbon fiber 30% glass fiber
Dielectric Constant 3.2 3.2 - 3.4 3.3 - 4.2
Dielectric Strength (kV/mm) 20 18.5 - 19 15 - 24
Volume Resistivity (x 1015 Ohm.cm) 16 - 17 1 - 8 15 - 16
Elongation at Break (%) 30 - 150 1 - 3 2 - 3
Flexibility (Flexural Modulus) (GPa) 3.7 - 4 13 - 19 9 - 10
Young Modulus (GPa) 3.5 - 3.9 13 - 22.3 9 - 11.4
Toughness (Notched Izod Impact at Room Temperature) (J/m) 80 - 94 85 - 120 95 - 130
Density (g/cm3) 1.26 - 1.32 1.4 - 1.44 1.49 - 1.54
Thermal Insulation (Thermal Conductivity) (W/m.K) 0.25 0.9 - 0.95 0.43

  • In comparison to fluoropolymers, PEEK show superior tensile strength, HDT, operating temperature, bonding, processing and toxic gas emission; but they are inferior in terms of chemical resistance, cost, toughness and UV weathering
  • As compared to PPS, PEEK has markedly superior thermal resistance, toughness and flashing
  • PEEK has much higher temperature performance, wear resistance, chemicals resistance and fatigue performance as compared to PES

PEEK is not normally blended with other polymers. However, it forms miscible blends with a range of other polyketones and PEI.

PEEK/PEI blends have higher Tg. And, its blends with PES and PPS are highly compatible..

Limitation of PEEK


  1. Expensive, applicable for highly demanding application
  2. Processing at high temperatures
  3. Attached by some acids, such as conc. Sulphuric, Nitric, Chromic… and is attacked by halogens and sodium
  4. Low resistance to UV light

Popular Application of Polyetheretherketone (PEEK)


It is extensively used in demanding applications such as aerospace, automotive, electrical, medical etc. Because of its robustness, PEEK is used to fabricate items, including bearings, piston parts, pumps, HPLC columns, compressor plate valves, and cable insulation. Let’s discuss some of its applications in detail.

PEEK Offers Weight and Noise Reduction in Automotive Applications Automotive - With the growing trend of miniatured engine compartments, PEEK offers a solution to replace metals and offer weight reduction, noise reduction and functional integration.

The most important performance benefits of Polyetheretherketone are enhanced dry and lubricated surface interaction, outstanding mechanical performance over a wide temperature range, ease of processing and excellent fatigue properties. The main applications include:

  • Under-the-hood piston units
  • Seals
  • Washers
  • Bearings
  • Various active components used in transmission, braking and air-conditioning systems

Aerospace - PEEK polymers and its composites are replacing aluminum and other metals in several aircraft parts. Huge numbers of large volume components with fine tolerances can be cost-effectively formed and used without assembly or modification. In aerospace market, PEEK finds use in:

PEEK and Its Composites Replace Metal in Airplane Parts
  • Critical engine parts as the polymer can withstand high temperatures and the tribological interaction of dry and lubricated material contacts
  • In aircraft exterior parts, PEEK provides excellent resistance to rain erosion
  • In interior components, its inherent flame retardancy and low smoke and toxic gas emission reduce hazard in the event of a fire
  • The polymer is used for manufacture of convoluted tubing to protect wires and fiber optic filaments for aircraft electrical systems

Medical and Healthcare - Polyetheretherketone provides cost-effective, innovative parts with excellent wear, heat, electrical and chemical resistance. Its applications in healthcare mainly consist of dental instruments, endoscopes and dialyzers

  • PEEK is replacing aluminum for the handles on dental syringes and sterile boxes that hold root canal files
  • The polymer can withstand up to 3,000 autoclave sterilization cycles in which temperatures typically reach 134°C
  • It maintains outstanding mechanical strength, excellent stress cracking resistance and hydrolytic stability in the presence of hot water, steam, solvents and chemicals
  • It offers improved biocompatibility of load bearing implants

Electrical / electronic - Polyetheretherketone possesses excellent electrical properties, which makes it an ideal electrical insulator.

Polyetheretherketone Possesses Excellent Electrical Properties
  • PEEK provides parts with long-term operating reliability over widely fluctuating ranges of temperature, pressure and frequency
  • Its inherent purity, combined with excellent mechanical and chemical stability, minimize contamination and maximize safety during the handling of silicon wafers
  • Outstanding thermal properties enable PEEK polymer parts to withstand the elevated temperatures associated with soldering processes

Some interesting examples of current applications include coaxial connector jacks used in hands-free telephone kits, surface-mounted trimming potentiometers, which are electro-mechanical devices, known as SMDs, designed to correct voltage or resistance errors in printed circuit boards, and as insulators for connector pins on under-sea environment control equipment.

Other key markets:

  • PEEK polymers outperform metals and other materials in many components used in the industrial, chemical and processing industries.
  • PEEK polymers are now finding use in food contact applications, following approval from the US Food and Drug Administration 

  • PEEK in Industrial Applications PEEK in Food Applications

  • PEEK is replacing stainless steel in impeller wheels for regenerative pumps. It provides a significant reduction in wear, reduced noise levels and more consistent running properties. 
  • Polyetheretherketone also offers increased application potential in pipe and hose couplings in modern connector technology. They can withstand exposure to pressures as high as 25,000 psi and to temperatures upto 260° C.


How PEEK is manufactured?


PEEK polymers are obtained by step-growth polymerization by the dialkylation of bisphenolate salts. It involves reaction of 4,4’-difluorobenzophenone or 1,4-bis(4-fluorobenzoyl) benzene with hydroquinone in the presence of alkali carbonates. The polymer is then isolated by removal of alkali metal fluoride and the polymerization solvent.

Molecular Structure of PEEK
Molecular Structure of PEEK

Because of its relatively stiff aromatic polymer backbone, the polymer exhibits some of the highest thermal transitions among several other commercial polymers and hence can be used at temperatures as high as 240°C.

Processing Conditions for PEEK Polymers


PEEK can be processed by conventional methods such as injection molding, extrusion, compression molding etc. However, the processing conditions used to mold PEEK can influence the crystallinity, and hence the mechanical properties.

As a linear thermoplastic, Polyetheretherketone can be melt processed in the temperature range of 370 to 420°C. While processing Polyetheretherketone, no corrosive gases are evolved.




Before processing Polyetheretherketone, drying is recommended for 3 hours at 150°C or 2 hours at 180°C. This is done to avoid any molding defects.

Polyetheretherketone can be processed by injection molding and extrusion. These processes with their processing guidelines are described below:

Injection Molding


  • A mold temperature of 160-190°C is recommended to obtain good crystallization and minimize warping.
  • Post crystallization at 200°C is possible but it is not recommended for applications requiring high dimensional stability.
  • PEEK is suitable for injection of very small parts with tight dimensional tolerances.
  • Injection pressure: 70-140 Mpa
  • Mold shrinkage: Unfilled – 1.2-2.4%, Filled – 0.1-1.1%

Extrusion


  • Cooling temperature have a strong influence on crystallinity and then on performances.
  • For film and sheet extrusion, cooling cylinders at 50°C lead to transparent amorphous material.
  • Cooling cylinders at 170°C lead to opaque and highly crystalline material.
  • It is also possible to produce oriented or bioriented films by the process of extrusion.

3D printing


Thanks to its unique properties, 3D printing of PEEK allows construction of almost any complex design geometry, which cannot be manufactured using other technologies. Fused deposition modeling – FDM (or fused filament fabrication – FFF) methods are used for 3D Printing with PEEK filaments.
  • Nozzle temperature: 360-400 degrees Celsius
  • Heated bed: 120 degrees Celsius

It is an excellent candidate for FFF due to its low moisture absorption as opposed to other common FFF materials, such as Acrylonitrile Butadiene Styrene (ABS).

» Find Suitable PEEK Grade for your Next 3D Printing Development



Commercially Available PEEK Compounds





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