Fluorinated Ethylene Propylene (FEP)
FEP is a fluoroplastic (fluorine-based thermoplastic). It has a fairly high density among thermoplastics. In addition, it has a fairly high ductility and a very low tensile strength. The graph bars on the material properties cards below compare FEP to: fluoroplastics (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
Elastic (Young's, Tensile) Modulus
0.43 GPa 0.062 x 106 psi
Elongation at Break
300 %
Flexural Modulus
0.6 GPa 0.087 x 106 psi
Flexural Strength
24 MPa 3.5 x 103 psi
Tensile Strength: Ultimate (UTS)
20 MPa 2.9 x 103 psi
Thermal Properties
Glass Transition Temperature
60 °C 140 °F
Heat Deflection Temperature At 1.82 MPa (264 psi)
50 °C 120 °F
Heat Deflection Temperature At 455 kPa (66 psi)
70 °C 160 °F
Maximum Temperature: Autoignition
630 °C 1170 °F
Maximum Temperature: Mechanical
200 °C 390 °F
Melting Onset (Solidus)
260 °C 500 °F
Specific Heat Capacity
1170 J/kg-K 0.28 BTU/lb-°F
Thermal Conductivity
0.22 W/m-K 0.13 BTU/h-ft-°F
Thermal Expansion
95 µm/m-K
Electrical Properties
Dielectric Constant (Relative Permittivity) At 1 Hz
1.9
Dielectric Constant (Relative Permittivity) At 1 MHz
2.0
Dielectric Strength (Breakdown Potential)
22 kV/mm 0.86 V/mil
Electrical Dissipation At 1 Hz
0.00026
Electrical Dissipation At 1 MHz
0.00065
Electrical Resistivity Order of Magnitude
16 10x Ω-m
Otherwise Unclassified Properties
Density
2.1 g/cm3 130 lb/ft3
Limiting Oxygen Index (LOI)
80 %
Refractive Index
1.4
Water Absorption After 24 Hours
0.010 %
Common Calculations
Stiffness to Weight: Axial
0.11 points
Stiffness to Weight: Bending
12 points
Strength to Weight: Axial
2.6 points
Strength to Weight: Bending
7.6 points
Thermal Diffusivity
0.088 mm2/s
Thermal Shock Resistance
35 points
Followup Questions
Further Reading
ASTM D2116: Standard Specification for FEP-Fluorocarbon Molding and Extrusion Materials
Fluoroplastics: Volume 2 - Melt Processable Fluoropolymers, Sina Ebnesajjad, 2003
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