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Polyetherimide (PEI)

PEI is a thermoplastic, further classified an an imide plastic. It can have a moderately high tensile strength among the thermoplastics in the database.

The properties of PEI include two common variations. This page shows summary ranges across both of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare PEI to: imide plastics (top), all thermoplastics (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Compressive (Crushing) Strength

140 to 180 MPa 20 to 25 x 103 psi

Elastic (Young's, Tensile) Modulus

3.4 to 5.6 GPa 0.49 to 0.81 x 106 psi

Elongation at Break

3.0 to 34 %

Flexural Modulus

3.4 to 5.9 GPa 0.49 to 0.86 x 106 psi

Flexural Strength

140 to 210 MPa 21 to 30 x 103 psi

Impact Strength: Notched Izod

55 to 110 J/m 1.0 to 2.1 ft-lb/in

Rockwell M Hardness

110 to 130

Tensile Strength: Ultimate (UTS)

110 to 160 MPa 16 to 24 x 103 psi

Thermal Properties

Glass Transition Temperature

210 °C 420 °F

Heat Deflection Temperature At 1.82 MPa (264 psi)

200 to 210 °C 390 to 410 °F

Maximum Temperature: Autoignition

530 °C 990 °F

Maximum Temperature: Decomposition

530 °C 980 °F

Maximum Temperature: Mechanical

170 °C 340 °F

Specific Heat Capacity

1050 to 1220 J/kg-K 0.25 to 0.29 BTU/lb-°F

Thermal Conductivity

0.18 to 0.23 W/m-K 0.1 to 0.13 BTU/h-ft-°F

Thermal Expansion

20 to 53 µm/m-K

Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 MHz

3.2 to 3.7

Dielectric Strength (Breakdown Potential)

30 to 33 kV/mm 1.2 to 1.3 V/mil

Electrical Resistivity Order of Magnitude

14 to 15 10x Ω-m

Otherwise Unclassified Properties

Density

1.3 to 1.5 g/cm3 80 to 94 lb/ft3

Limiting Oxygen Index (LOI)

47 to 50 %

Water Absorption After 24 Hours

0.17 to 0.25 %

Water Absorption At Saturation

0.9 to 1.3 %

Common Calculations

Stiffness to Weight: Axial

1.5 to 2.1 points

Stiffness to Weight: Bending

39 points

Strength to Weight: Axial

24 to 30 points

Strength to Weight: Bending

40 to 44 points

Thermal Diffusivity

0.11 to 0.14 m2/s

Thermal Shock Resistance

44 to 100 points

Followup Questions

Further Reading

Reinforced Plastics Durability, Geoffrey Pritchard (editor), 1999

SPI Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., 5th ed., Michael L. Berins (editor), 2000

Modern Plastics Handbook, Charles A. Harper (editor), 1999

Plastics Materials, 7th ed., J. A. Brydson, 1999