FEP vs. PEI
Both FEP and PEI are thermoplastics. There are 24 material properties with values for both materials. Properties with values for just one material (11, in this case) are not shown.
For each property being compared, the top bar is FEP and the bottom bar is PEI.
Metric UnitsUS Customary Units
Mechanical Properties
| Elastic (Young's, Tensile) Modulus, GPa | 0.43 | |
| 3.4 to 5.6 |
| Elongation at Break, % | 300 | |
| 3.0 to 34 |
| Flexural Modulus, GPa | 0.6 | |
| 3.4 to 5.9 |
| Flexural Strength, MPa | 24 | |
| 140 to 210 |
| Tensile Strength: Ultimate (UTS), MPa | 20 | |
| 110 to 160 |
Thermal Properties
| Glass Transition Temperature, °C | 60 | |
| 210 |
| Heat Deflection Temperature At 1.82 MPa (264 psi), °C | 50 | |
| 200 to 210 |
| Maximum Temperature: Autoignition, °C | 630 | |
| 530 |
| Maximum Temperature: Mechanical, °C | 200 | |
| 170 |
| Specific Heat Capacity, J/kg-K | 1170 | |
| 1050 to 1220 |
| Thermal Conductivity, W/m-K | 0.22 | |
| 0.18 to 0.23 |
| Thermal Expansion, µm/m-K | 95 | |
| 20 to 53 |
Electrical Properties
| Dielectric Constant (Relative Permittivity) At 1 MHz | 2.0 | |
| 3.2 to 3.7 |
| Dielectric Strength (Breakdown Potential), kV/mm | 22 | |
| 30 to 33 |
| Electrical Resistivity Order of Magnitude, 10x Ω-m | 16 | |
| 14 to 15 |
Otherwise Unclassified Properties
| Density, g/cm3 | 2.1 | |
| 1.3 to 1.5 |
| Limiting Oxygen Index (LOI), % | 80 | |
| 47 to 50 |
| Water Absorption After 24 Hours, % | 0.010 | |
| 0.17 to 0.25 |
Common Calculations
| Stiffness to Weight: Axial, points | 0.11 | |
| 1.5 to 2.1 |
| Stiffness to Weight: Bending, points | 12 | |
| 39 |
| Strength to Weight: Axial, points | 2.6 | |
| 24 to 30 |
| Strength to Weight: Bending, points | 7.6 | |
| 40 to 44 |
| Thermal Diffusivity, mm2/s | 0.088 | |
| 0.11 to 0.14 |
| Thermal Shock Resistance, points | 35 | |
| 44 to 100 |