PEI Machining

A Guide to PEI CNC Machined Parts: Properties, Applications and Design Considerations

What is PEI?

PEI (Polyetherimide) is a high performance amorphous thermoplastic which is typically transparent amber in colour.

PEI is commonly used for structural components requiring high strength and rigidity at elevated temperatures as well as broad chemical resistance.

Please see our PSU (Polysulfone) page for an alternative high performance thermoplastic which has similar characteristics but is cheaper and more readily available.

Main Attributes of PEI:

High mechanical strength
High rigidity
Very good dimensional stability
Relatively high long term service temperature
Flame resistant
Good chemical resistance
Excellent electrical properties
High strength to weight ratio
Glass-filled grade available
Low thermal conductivity
Highest dielectric strength of any thermoplastic
Transparent amber
High tensile strength
Semi transparent
Good UV resistance and weatherability
Most grades suitable for use with food
Can withstand dry heat sterilisation at 180°C, ethylene oxide gas and gamma radiation

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Detailed information about PEI for designers can be found in the tabs below. Please note: this information is provided as a guide only.

PEI Machining Service - PEI Milling & Turning

Penta Precision supplies highly accurate PEI machined parts throughout the UK. Customers turn to us when they have had quality and delivery issues with their existing suppliers and need a reliable precision machining partner.

We communicate well with customers, we take care with the projects placed with us and we are consistent in our service delivery. See our Proven Process page to find out more about our winning formula.

"Penta Precision have supported us and our customers for approximately five years. Their pricing is competitive, with quality levels and delivery performance being consistently excellent. They communicate well and are responsive to the production deadline pressures that every company must overcome from time to time." Phillip - Director

Penta Precision provides the following PEI machining services:

CNC milled parts – prototypes & large batch runs
CNC turned parts – prototypes & large batch runs
Insert installation
Part marking
Manual milling
Manual turning
Machining design advice
Machining drawing service

Reasons to Choose Penta:

ISO 9001:2015 quality assurance
Consistent high quality machined parts
Reliable delivery dates - our track record speaks volumes
Exceptional customer service and communication
Machining design advice
Extensive experience in our field

We are regularly machining high performance thermoplastics for customers all over the UK. Our customers depend on our machining expertise as well as our outstanding delivery performance, to machine the highest quality parts. If you'd like to discuss how we can help you with your PEI machining requirements, here's a list of ways to get in touch with us.

Mechanical Properties	Value	Parameter	Norm	Notes
Modulus of Elasticity (tensile test)	3200 MPa	1mm/min	DIN EN ISO 527-2	For tensile test: specimen type 1b
Tensile Strength	127 MPa	50mm/min	DIN EN ISO 527-2
Tensile Strength at Yield	127 MPa	50mm/min	DIN EN ISO 527-2
Elongation at Yield	7%	50mm/min	DIN EN ISO 527-2
Elongation at Break	35%	50mm/min	DIN EN ISO 527-2
Flexural Strength	164 MPa	2mm/min, 10 N	DIN EN ISO 178	For flexural test: support span 64mm, norm specimen
Modulus of Elasticity (flexural test)	3300 MPa	2mm/min, 10 N	DIN EN ISO 178
Compression Strength	23/41/92 MPa	1% / 2% / 5% 5mm/min, 10 N	EN ISO 604	Specimen 10x10x10mm
Compression Modulus	2800 MPa	5mm/min, 10 N	EN ISO 604	Specimen 10x10x50mm, modulus range between 0.5 and 1% compression.
Impact Strength (Charpy)	113 kJ/m²	max. 7.5J	DIN EN ISO 179-1eU	For Charpy test: support span 64mm, norm specimen
Ball Indentation Hardness	225 MPa		ISO 2039-1	Specimen in 4mm thickness

Mechanical Properties

Value

Parameter

Norm

Notes

Modulus of Elasticity (tensile test)

3200 MPa

1mm/min

DIN EN ISO 527-2

For tensile test: specimen
type 1b

Tensile Strength

127 MPa

50mm/min

DIN EN ISO 527-2

Tensile Strength at Yield

127 MPa

50mm/min

DIN EN ISO 527-2

Elongation at Yield

50mm/min

DIN EN ISO 527-2

Elongation at Break

35%

50mm/min

DIN EN ISO 527-2

Flexural Strength

164 MPa

2mm/min, 10 N

DIN EN ISO 178

For flexural test: support span 64mm, norm specimen

Modulus of Elasticity (flexural test)

3300 MPa

2mm/min, 10 N

DIN EN ISO 178

Compression Strength

23/41/92 MPa

1% / 2% / 5% 5mm/min, 10 N

EN ISO 604

Specimen 10x10x10mm

Compression Modulus

2800 MPa

5mm/min, 10 N

EN ISO 604

Specimen 10x10x50mm, modulus range between 0.5 and 1% compression.

Impact Strength (Charpy)

113 kJ/m²

max. 7.5J

DIN EN ISO 179-1eU

For Charpy test: support span 64mm, norm specimen

Ball Indentation Hardness

225 MPa

ISO 2039-1

Specimen in 4mm thickness

Thermal Properties	Value	Parameter	Norm	Notes
Glass Transition Temperature	216°C		DIN EN ISO 11357	Found in public sources
Melting Temperature	N/A		DIN EN ISO 11357
Service Temperature	200°C	short term		Found in public sources. Individual testing regarding application conditions is mandatory
Service Temperature	170°C	long term
Thermal Expansion (CLTE)	5 10^-5 K^-1	23-60°C, long	DIN EN ISO 11359-1;2
Thermal Expansion (CLTE)	5 10^-5 K^-1	23-100°C, long	DIN EN ISO 11359-1;2
Thermal Expansion (CLTE)	6 10^-5 K^-1	100-150°C, long	DIN EN ISO 11359-1;2
Specific Heat	1.2 J/(g*K)		ISO 22007-4:2008
Thermal Conductivity	0.21 W/(K*m)		ISO 22007-4:2008

Thermal Properties

Value

Parameter

Norm

Notes

Glass Transition Temperature

216°C

DIN EN ISO 11357

Found in public sources

Melting Temperature

N/A

DIN EN ISO 11357

Service Temperature

200°C

short term

Found in public sources. Individual testing regarding application conditions is mandatory

Service Temperature

170°C

long term

Thermal Expansion (CLTE)

5 10^-5 K^-1

23-60°C, long

DIN EN ISO 11359-1;2

Thermal Expansion (CLTE)

5 10^-5 K^-1

23-100°C, long

DIN EN ISO 11359-1;2

Thermal Expansion (CLTE)

6 10^-5 K^-1

100-150°C, long

DIN EN ISO 11359-1;2

Specific Heat

1.2 J/(g*K)

ISO 22007-4:2008

Thermal Conductivity

0.21 W/(K*m)

ISO 22007-4:2008

Electrical Properties	Value	Norm
Specific Surface Resistance	10¹⁴ Ω	DIN IEC 60093
Specific Volume Resistance	10¹⁴ Ω*cm	DIN IEC 60093

Electrical Properties

Value

Norm

Specific Surface Resistance

10¹⁴ Ω

DIN IEC 60093

Specific Volume Resistance

10¹⁴ Ω*cm

DIN IEC 60093

Other Properties	Value	Parameter	Norm	Notes
Water Absorption	0.05 / 0.1%	24h / 96h (23°C)	DIN EN ISO 62	Ø ca. 50mm, h=13mm
Resistance to hot water/bases	+			+ good resistance
Resistance to weathering	-			- poor resistance
Flammability (UL94)	V0	Corresponding to	DIN IEC 60695-11-10	Corresponding means no listing at UL (yellow card). The information might be taken from resin, stock shape or estimation. Individual testing regarding application conditions is mandatory.
Density	1.28 g/cm³

Other Properties

Value

Parameter

Norm

Notes

Water Absorption

0.05 / 0.1%

24h / 96h (23°C)

DIN EN ISO 62

Ø ca. 50mm, h=13mm

Resistance to hot water/bases

+ good resistance

Resistance to weathering

- poor resistance

Flammability (UL94)

Corresponding to

DIN IEC 60695-11-10

Corresponding means no listing at UL (yellow card). The information might be taken from resin, stock shape or estimation. Individual testing regarding application conditions is mandatory.

Density

1.28 g/cm³