Polybenzimidazole (PBI)
PBI is a thermoset plastic. It has the highest mechanical heat stability among thermoset plastics. In addition, it has a moderately low density and a fairly high dielectric strength. The graph bars on the material properties cards below compare PBI to other thermoset plastics (top) 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
350 MPa 50 x 103 psi
Elastic (Young's, Tensile) Modulus
5.9 GPa 0.85 x 106 psi
Elongation at Break
3.0 %
Fatigue Strength
56 MPa 8.1 x 103 psi
Flexural Modulus
6.5 GPa 0.95 x 106 psi
Flexural Strength
220 MPa 32 x 103 psi
Impact Strength: Notched Izod
27 J/m 0.5 ft-lb/in
Tensile Strength: Ultimate (UTS)
160 MPa 23 x 103 psi
Thermal Properties
Glass Transition Temperature
410 °C 770 °F
Heat Deflection Temperature At 1.82 MPa (264 psi)
430 °C 810 °F
Maximum Temperature: Decomposition
590 °C 1090 °F
Maximum Temperature: Mechanical
340 °C 640 °F
Specific Heat Capacity
930 J/kg-K 0.22 BTU/lb-°F
Thermal Conductivity
0.41 W/m-K 0.24 BTU/h-ft-°F
Thermal Expansion
23 µm/m-K
Electrical Properties
Dielectric Constant (Relative Permittivity) At 1 Hz
3.4
Dielectric Constant (Relative Permittivity) At 1 MHz
3.8
Dielectric Strength (Breakdown Potential)
23 kV/mm 0.88 V/mil
Electrical Resistivity Order of Magnitude
13 10x Ω-m
Otherwise Unclassified Properties
Density
1.3 g/cm3 81 lb/ft3
Limiting Oxygen Index (LOI)
58 %
Water Absorption After 24 Hours
0.4 %
Common Calculations
Stiffness to Weight: Axial
2.5 points
Stiffness to Weight: Bending
46 points
Strength to Weight: Axial
34 points
Strength to Weight: Bending
50 points
Thermal Diffusivity
0.34 mm2/s
Thermal Shock Resistance
84 points
Followup Questions
Further Reading
Thermosets: Structure, Properties and Applications, Qipeng Guo (editor), 2012
Modern Plastics Handbook, Charles A. Harper (editor), 1999
Plastics Materials, 7th ed., J. A. Brydson, 1999