Polymer Data File:

Polyether ether ketone
- PEEK

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Introduction

Advantages and Limitations

Typical Applications

Processing

Physical and Mechanical Properties

Finishing

Thermal, Electrical and Optical Properties

Health and Safety

Chemical Resistance Properties

Other Information


Introduction

PEEK was one of the first of the 'new generation' of engineering thermoplastics introduced and was developed by ICI in 1977 and first marketed in 1978. The material is one of the polyaryletherketone family - a group of partially crystalline polymers that are suitable for use at high temperatures. The polyether ether ketones have repeating monomers of two ether and ketone groups and PEEK is one of the highest rated thermoplastic materials in terms of heat resistance. The useful properties of the material are retained at temperatures as high as 315oC.

The materials have excellent chemical resistance, high strength and good resistance to burning but equally the high cost of these materials makes applications limited to those where the properties are very necessary.

Typical Applications

Automotive: Piston components, bearing linings.

Electrical engineering: Wire insulation for extremely high temperature applications, cable couplings and connectors.

Appliances: Handles, cooking equipment. 

Medicine: Prosthetics, instruments.

Others: Aircraft parts and wire insulation, pump casings and impellers, monofilament for production of woven products for filters, belting and meshes.

Physical and Mechanical Properties

General physical properties

PEEK is has greater strength and rigidity than many of the engineering thermoplastics and is tough and impact resistant over a wide range of temperatures.

Mechanical properties

PEEK has good mechanical properties and these are retained over a wide temperature range. The co-efficient of friction and wear rate are low over a wide temperature range.

Property

Approximate Value

Tensile strength (@23oC)

97 MN/m2

Tensile Modulus ( @ 1% strain @ 23oC)

3.5 GN/m2

Elongation at Break (@23oC)

Up to 60 %

Flexural Strength (@23oC)

170 MN/m2

Notched Impact Strength (@23oC)

7.5 kJ/m2

Specific Heat (Melt)

2.16 kJ/kgoC

Glass Transition Temperature

143 oC

Heat Distortion Temperature

152 oC

Coefficient of Thermal Expansion

< Tg 4.7 x 10-5 / oC

> Tg 10.8 x 10-5 / oC

Long Term Service Temperature

Up to 260 oC

Specific Gravity

1.32

Mould Shrinkage

0.01 - 0.02 m/m

Water Absorption

Up to 0.5 % (50% rh)

Transparency

Opaque

Thermal, Electrical and Optical Properties

Thermal properties

The thermal oxidative stability of PEEK is excellent and the material has a UL rated continuous operating temperature of around 250oC

Fire behaviour

PEEK has excellent resistance to burning and very low flame spread being rated as UL 94 V-0 for thicknesses down to 2 mm. The LIO (Limiting Oxygen Index) is 35%) and even when burning the material has very low smoke generation. 

Electrical properties

Good dielectric properties with high volume and surface resistivities and good dielectric strength. These properties are retained at temperatures as high as 200oC.

Optical properties

N/A

Natural colour

Grey/brown

 

Chemical Resistance Properties

General

PEEK has excellent chemical resistance and is extremely resistant to many organic and inorganic chemicals. It is dissolved or decomposed only by concentrated anhydrous or strong oxidizing agents.

The material has exceptionally good resistance to hydrolysis in hot water and remains unaffected after several thousand hours at more than 250oC in pressurised water.

Weathering resistance

PEEK is not greatly resistant to UV radiation but has good resistance to beta, gamma and X-rays.

PEEK Chemical Resistance Chart

Advantages and Limitations

Advantages

Limitations

1. Excellent high temperature performance for all mechanical properties

1. Extremely high cost (even for engineering polymers) but the properties can sometimes justify this when it becomes almost the only polymer capable of being used.

2. Excellent electrical performance at high temperatures.

2. Limited supplier base.

3. High rigidity at high temperatures.

 

4. Excellent gamma radiation resistance.

 

5. Excellent hydrolysis resistance.

 

Processing

PEEK can be processed on standard processing equipment and the only concern is that the processing temperatures required are quite high.

Material should be pre-dried at 150oC for 3 hours before processing.

Injection moulding

Injection moulding is best screws with an L/D ratio of 18 to 22. Melt temperatures should be in the range 370 to 400oC. Mould temperatures should be in the range 160 to 215oC.

Injection pressure is 1500 bar, decreasing to 1000 bar for the second stage. Injection speed can be high because the material does not suffer from degradation due to shearing. Screw speed can also be high.

 Mouldings do not require any thermal post-treatment.

Extrusion

Extrusion is best with 3 section screws and an L/D ratio of 22 to 30. Melt temperatures in the range 400 to 430oC and feed temperatures of at least 425oC are recommended.

Can be reprocessed at up to 30%.

Processing Method

Applicable

Injection Moulding

Yes.

Extrusion

Yes

Extrusion Blow Moulding

Yes

Rotational Moulding

Yes

Thermoforming

Yes

Casting

Yes

Bending and joining

Yes

Finishing

Machining

PEEK can be machined easily and accurately.

Surface treatment

PEEK can be printed, hot-foiled or treated with most common methods.

Welding

PEEK can be welded by most common thermoplastic welding techniques.

Bonding

PEEK can be bonded using epoxies, cyanoacrylates, polyurethanes or silicones

Health and Safety

Health and Safety

PEEK has no significant Health and Safety implications.

Other Information

Identification

  • Material has a hard, stiff feel and cannot be cut easily. The high density (1.2 - 1.4) means it sinks in water. Natural colour is grey/brown and colours are sometimes dulled by this base colour.

  • Flame is slightly orange with yellow edges. Low smell and small amounts of smoke.

Last edited: 11/03/2010

Tangram Technology Ltd. 2001

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