Feb 21 2003
An infusible, Polybenzimidazole (PBI) is a black high performance polymer with a wholly aromatic molecule of high thermal stability. Semi-fabricated items are made, normally by the polymer manufacturer, by powder sintering processes.
Polybenzimidazole (PBI) has excellent high temperature properties - probably on balance the best of any commercially available polymer - and is very expensive. It is strong, stiff, very hard, has a particularly high strength in and recovery from compression and a CTE similar to that of aluminium.
Polybenzimidazole (PBI)has good chemical resistance resisting many harsh chemical environments better than many other high performance polymers, but is attacked by polar aprotic solvents and, at elevated temperatures, by strong aqueous acids and (to a lesser extent) alkalis.
Despite absorbing (slowly) a high percentage of water at saturation, Polybenzimidazole (PBI)is stable to hydrolysis and resists high pressure steam.
Key Properties
The key properties of Polybenzimidazole ( PBI ) are tabulated below.
Table 1. Key properties
| Chemical Resistance |
| Acids - concentrated |
Fair |
| Acids – dilute |
Good |
| Alcohols |
Very Good |
| Alkalis |
Good/Fair |
| Aromatic hydrocarbons |
Very Good |
| Greases and Oils |
Very Good |
| Ketones |
Very Good |
| Electrical Properties |
| Dielectric constant @ 1 MHz |
3.2 |
| Dielectric strength ( kV.mm-1 ) |
21 |
| Volume resistivity ( ohm.cm ) |
8x1014 |
| Mechanical Properties |
| Coefficient of friction |
0.19 - 0.27 |
| Compressive modulus ( GPa ) |
6.2 |
| Compressive strength ( MPa ) |
400 |
| Elongation at break ( % ) |
3 |
| Hardness – Rockwell |
K115 |
| Izod impact strength ( J.m-1 ) |
590 unnotched |
| Poisson’s ratio |
0.34 |
| Tensile modulus ( GPa ) |
5.9 |
| Tensile strength ( MPa ) |
160 |
| Physical Properties |
| Density ( g.cm-3 ) |
1.3 |
| Flammability |
Does not burn |
| Limiting oxygen index ( % ) |
58 |
| Radiation resistance – Alpha |
Good |
| Water absorption - over 24 hours ( % ) |
0.4 |
| Thermal Properties |
| Coefficient of thermal expansion ( x10-6 K-1 ) |
23 |
| Heat-deflection temperature - 0.45 MPa ( °C ) |
435 |
| Thermal conductivity @ 23 °C ( W.m-1.K-1 ) |
0.41 |
| Upper working temperature (°C ) |
260 - 400 |
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