What is PEEK?

PEEK (Polyether Ether Ketone) is a semi-crystalline thermoplastic from the polyaryletherketone (PAEK) family. It’s used when high strength, temperature resistance, and chemical resistance are required beyond what standard engineering plastics can provide. We’ve put together this guide to give you a deeper understanding of this material. Our experts will cover:

PEEK material explained
What is PEEK plastic used for? 
PEEK properties 
Common applications
Advantages and disadvantages of PEEK plastic
Manufacturing processes for PEEK

PEEK material explained

In engineering terms, PEEK occupies the apex of thermoplastic performance, bridging the gap between metals and polymers. Its cost is significantly higher than commodity plastics, but in high-reliability, high-performance contexts, PEEK is often the material of record when, as the saying goes, failure is not an option.

Engineers select PEEK material when design constraints demand a combination of strength, heat tolerance, and chemical inertness that would otherwise require metal alloys. In many industries, it has moved from a specialty option to a baseline material for mission-critical components, supported by decades of proven service in aerospace, energy, and medical systems. This reputation makes PEEK not just a material choice, but an engineering strategy for extending component life, reducing maintenance intervals, and withstanding extreme operating conditions.

You can learn more in our experts’ Ultimate guide to engineered plastics.

What is PEEK plastic used for?

PEEK plastic is specified in environments where conventional engineering plastics cannot meet performance requirements. It maintains strength and dimensional stability under sustained high temperatures, resists degradation in chemically aggressive media, and tolerates heavy mechanical loads. Its combination of low weight and high strength makes it an effective substitute for metal in designs where mass reduction is critical.

PEEK properties

The following data defines PEEK’s performance envelope across mechanical, thermal, electrical, and environmental parameters. Values are based on standardised test methods and represent typical performance for unfilled grades under controlled conditions.
 

 

Mechanical properties	Parameter	Value	Unit	DIN/EN/ISO
Modulus of elasticity (tensile test)	1mm/min	4200	MPa	527-2
Tensile strength	50mm/min	116	MPa	527-2
Tensile strength at yield	50mm/min	116	MPa	527-2
Elongation at Yield	50mm/min	5	%	527-2
Elongation at break	50mm/min	15	%	527-2
Flexural strength	2mm/min 10N	175	MPa	178
Modulus of elasticity (flexural test)	2mm/min 10N	4200	MPa	178
Compression strength	1%/2% 5mm/min 10N	23/43	MPa	604
Compression modulus	5mm/min 10N	3400	MPa	604
Impact strength (Charpy)	Max. 7,5J	N.B.	kJ/m²	179-1eU
Notched impact strength (Charpy)	Max. 7,5J	4	kJ/m²	179-1eU
Ball indentation hardness	–	253	MPa	2039-1

 

Thermal properties	Parameter	Value	Unit	DIN/EN/ISO
Glass transition temperature	–	150	°C	53765
Melting temperature	–	341	°C	53765
Heat distortion temperature	HDT, Method A	162	°C	ISO-R 75 Method A
Service temperature	Short term	300	°C	–
Service temperature	Long term	260	°C	–
Thermal expansion (CLTE)	23-60°C, Long	5	10-5K -1	11359-1;2
Thermal expansion (CLTE)	23-100°C, Long	5	10-5K -1	11359-1;2
Thermal expansion (CLTE)	100-150°C, Long	7	10-5K -1	11359-1;2
Specific heat	–	1.1	J/(g*K)	22007-4:2008
Thermal conductivity	–	0.27	W/(K*m)	22007-4:2008

 

Electrical properties	Parameter	Value	Unit	DIN/IEC
Surface resistance	–	1014	Ω	60093

 

Other properties	Parameter	Value	Unit	DIN/EN/ISO/IEC
Water absorption	24h/96h (23°C)	0.02/0.03	%	62
Resistance to hot water/bases	–	+	–	–
Resistance to weathering	–	–	–	–
Flammability (UL94)	Listed (value @ 1,5mm)	V0	–	60695-11-10
FDA Approved	–	YES	–	–

Common applications

PEEK is used in environments where strength, heat resistance, and chemical stability are critical.

Advantages and disadvantages of PEEK plastics

PEEK's durability and broad temperature range, especially its resistance to high temperatures, make it an effective solution for manufacturers. Demand for this material is increasing among manufacturers as the need increases for higher mechanical properties at lighter weight.

Advantages

●    Excellent high-temperature resistance:
PEEK products can generally withstand temperatures up to 180°C continuous use, ensuring a long life and reliability in harsh environments. PEEK temperature range varies, depending on the grade. Some grades can be used continuously at temperatures up to 250°C. Note, PEEK material temperature range starts at -70°C. PEEK material melting temperature is generally 341°C.
 
●    Mechanical strength and high dimensional stability:
PEEK plastic material exhibits excellent properties in terms of strength, stiffness, creep and fatigue, enabling the manufacture of lightweight parts, and better performance over time. Wear resistance in abrasive or humid environments, a low coefficient of friction and excellent wear resistance can help prolong the life and maintain the integrity of the parts.
 
●    Lightweight:
PEEK material density is approximately 1.30 g/cm³, about one-fifth to one-sixth the density of common metals, which is why it’s often chosen for weight-sensitive designs. 
 
●    Chemical resistance:
A PEEK component has outstanding chemical resistance, even at high temperatures, 
thanks to the material’s ability to withstand many acids, bases, hydrocarbons and 
organic solvents.
 
●     Electrical performance:
Is PEEK electrically conductive? No. PEEK electrical properties are excellent over a wide range of temperatures and frequencies. With exceptional insulation characteristics, PEEK is outstanding for electrical engineering and electronics, especially when you factor in PEEK’s heat resistance.
 
●    Thermal insulation:
The thermal properties of PEEK material give it a low coefficient of thermal conductivity. Hence, PEEK offers excellent insulation. PEEK mechanical properties and high-temperature resistance make it an ideal choice for thermal stability.
 
●    Hydrolysis resistance:
PEEK products have been used successfully to improve the reliability of components. With low moisture absorption, PEEK does not hydrolyse in the presence of water (freshwater, salt water or steam), even at high temperatures.
 
●    Recyclable:
The properties of Peek plastics make it completely recyclable and halogen-free. The polymer PEEK also complies with the European RoHS directive and REACH.

Disadvantages

●    Cost
With a melting point of approximately 341°C, PEEK is significantly more expensive 
than common engineering thermoplastics. For large-volume or cost-sensitive 
production, material expense alone can be prohibitive unless its performance 
benefits are essential to the design.

●    Processing requirements
PEEK requires moulding or extrusion equipment that can operate at high temperatures. While injection moulding is widely used, it needs tight temperature control and tooling capable of managing the material’s high viscosity, which increases manufacturing complexity and cost.

●    Availability
PEEK material is produced in smaller quantities than common plastics such as polypropylene or polyethylene. Supply can be limited in some areas, which may result in longer lead times and higher costs. We recommend that you check material availability early in the project to avoid delays.

●    UV Resistance
Without stabilisers, PEEK material will deteriorate under prolonged UV exposure, making it unsuitable for unprotected outdoor use. Adding UV stabilisers can improve its durability in sunlight-exposed applications.

Manufacturing processes for PEEK

PEEK’s melting point of about 341°C demands processing equipment built for high-temperature operation. As it's semi-crystalline, the melt and cooling phases must be tightly controlled to set the right level of crystallinity, which governs its mechanical strength, heat tolerance, and chemical resistance.

1. Injection Moulding
Injection moulding is widely used for PEEK but relies on tight temperature control.

●    Barrel temperature: 370–420°C to fully melt the polymer without degradation.

●    Maintain between 160–200°C to achieve proper crystallisation and prevent amorphous regions that reduce part strength.

●    Key considerations: Allow for shrinkage of up to 2.5% in the mould design, position gates to minimise shear heating, and use wear-resistant screw and barrel materials to handle PEEK’s high viscosity and abrasive fillers.

To learn more, we recommend you dive into our guide, In-depth: the injection moulding process.

2. Extrusion
PEEK extrusion produces continuous stock forms such as rod, sheet, tube, and coated wire.
●    Temperature profile: Similar to injection moulding, with zones carefully graduated to prevent unmelted pellets or thermal degradation.

●    Cooling control: Crystallinity can be influenced by cooling rate—rapid cooling yields lower crystallinity for ductility, while slower cooling increases stiffness and chemical resistance.

●    Equipment requirements: Extruders must be corrosion- and wear-resistant, especially when processing filled grades containing glass or carbon fibers.

3. Compression moulding
Compression moulding involves packing PEEK powder or granules into a heated mould cavity, applying high pressure, and holding until the polymer fully consolidates.

●    Processing temperature: Around 370–400°C for unfilled grades; slightly higher for filled compounds.

●    Pressure: Sufficient to eliminate voids and ensure full consolidation, often 1–2 MPa during melt flow, followed by higher holding pressure during cooling.

●    Advantages: Well-suited for thick sections or large components where injection moulding is impractical. Cooling must be controlled to avoid internal stresses.

4. CNC machining

Machining is typically performed on extruded or compression-moulded stock shapes.
●    Tooling: Sharp carbide or diamond tools are preferred to reduce heat generation and maintain dimensional accuracy.

●    Cutting Speeds: Lower than those for metals; excessive surface speeds can cause softening and gumming due to localised heating.

●    Workholding: Because PEEK has a relatively low modulus compared to metals, clamping pressure should be sufficient for stability but not excessive to avoid deformation.

●    Dimensional stability: Machined parts may require annealing to relieve residual stresses before final finishing.

5. Additive manufacturing (3D printing)

PEEK is increasingly processed via high-temperature Fused Filament Fabrication (FFF) and Selective Laser Sintering (SLS).
●    FFF requirements: Nozzle temperatures of 400–450°C, heated build chambers >120°C, and heated beds around 120–160°C.

●    Crystallinity control: Post-print annealing may be used to increase crystallinity and enhance mechanical properties.

●    SLS considerations: Requires precise control of powder bed temperature (just below melt point) to prevent warping and achieve consistent layer bonding.

●    Challenges: Maintaining consistent interlayer adhesion and minimising warpage due to PEEK’s high shrinkage rate.

Our experts have put together a helpful guide to help you learn more: How 3D printing complements injection moulding.

Download free CADs and try before you buy

Free CADs are available for most solutions, which you can download. You can also request free samples to make sure you’ve chosen exactly what you need. If you’re not quite sure which PEEK fastener will work best for your application, our experts are always happy to advise you.

Whatever your requirements, you can depend on fast dispatch. 

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Questions?

Email us at sales@essentracomponents.co.uk or speak to one of our experts for further information on the ideal solution for your application 0345 528 0474.