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PEEK vs. PEI

Both PEEK and PEI are thermoplastics. There are 26 material properties with values for both materials. Properties with values for just one material (6, in this case) are not shown.

For each property being compared, the top bar is PEEK and the bottom bar is PEI.

Metric UnitsUS Customary Units

Mechanical Properties

Compressive (Crushing) Strength, MPa 120 to 300
140 to 180
Elastic (Young's, Tensile) Modulus, GPa 4.0 to 24
3.4 to 5.6
Elongation at Break, % 1.6 to 43
3.0 to 34
Flexural Modulus, GPa 3.8 to 19
3.4 to 5.9
Flexural Strength, MPa 150 to 330
140 to 210
Impact Strength: Notched Izod, J/m 78 to 120
55 to 110
Tensile Strength: Ultimate (UTS), MPa 97 to 200
110 to 160

Thermal Properties

Glass Transition Temperature, °C 240
210
Heat Deflection Temperature At 1.82 MPa (264 psi), °C 160 to 300
200 to 210
Maximum Temperature: Autoignition, °C 600
530
Maximum Temperature: Decomposition, °C 570
530
Maximum Temperature: Mechanical, °C 330
170
Specific Heat Capacity, J/kg-K 1390 to 1700
1050 to 1220
Thermal Conductivity, W/m-K 0.25 to 0.93
0.18 to 0.23
Thermal Expansion, µm/m-K 15 to 52
20 to 53

Electrical Properties

Electrical Resistivity Order of Magnitude, 10x Ω-m 3.0 to 14
14 to 15

Otherwise Unclassified Properties

Density, g/cm3 1.3 to 1.5
1.3 to 1.5
Limiting Oxygen Index (LOI), % 38
47 to 50
Water Absorption After 24 Hours, % 0.060 to 0.3
0.17 to 0.25
Water Absorption At Saturation, % 0.22 to 0.5
0.9 to 1.3

Common Calculations

Stiffness to Weight: Axial, points 1.5 to 10
1.5 to 2.1
Stiffness to Weight: Bending, points 36 to 73
39
Strength to Weight: Axial, points 20 to 41
24 to 30
Strength to Weight: Bending, points 36 to 55
40 to 44
Thermal Diffusivity, m2/s 0.1 to 0.51
0.11 to 0.14
Thermal Shock Resistance, points 34 to 57
44 to 100