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Polybenzimidazole fiber: Wikis


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Polybenzimidazole or PBI fiber (1983) is a synthetic fiber with an extremely high melting point that also does not readily ignite, because of its exceptional thermal and chemical stability. The Federal Trade Commission definition for PBI fiber is "A manufactured fiber in which the fiber-forming substance is a long chain aromatic polymer having recurring imidazole groups as an integral part of the polymer chain". Kermel, a polyamidoimide, is a related "high performance polymer."

PBI is used to fabricate high-performance protective apparel such as firefighter turnout coats and suits, astronaut space suits, high temperature protective gloves, welders' apparel, race driver suits, braided packings, and aircraft wall fabrics.[1]



PBI is prepared by step-growth polymerization from 3,3',4,4'-tetraaminobiphenyl and diphenyl isophthalate (an ester of Isophthalic acid). The resulting polymer is processed as a solution in dimethyl acetamide via a dry spinning process.


The first U.S. commercial PBI fiber was produced by Celanese.

PBI fiber characteristics

The chemical formula of Poly[2,2’-(m-phenylen)-5,5’ bibenzimidazol] (PBI) is believed to be: ([NH-C=CH-C=CH-CH=C-N=C-]2-[C=CH-C=CH-CH=CH-])n OR (C20N4H12)n of Molar mass 308.33608 ± 0.01764 g/mol.

Chemical Resistance

Chemical Resistance Grade
Acids - concentrated Poor
Acids - dilute Fair-Poor
Alcohols Good
Alkalis Good-Poor
Aromatic hydrocarbons Good
Greases and Oils Good
Halogenated Hydrocarbons Good
Ketones Good
Chemical Resistance Grade

It is dyeable to dark shades with basic dyes following caustic pretreatment and resistant to most chemicals.

Electrical Properties

Electrical Properties
Dielectric constant @ 1 MHz 3.2
Dielectric strength 21 kV·mm-1
Volume resistivity 8x1014 Ω·cm
Electrical Properties

Features low electrical conductivity and low static electricity buildup.

Mechanical Properties

Mechanical Properties
Coefficient of friction 0.19-0.27
Compressive modulus 6.2 GPa
Compressive strength 400 MPa
Elongation at break 3%
Hardness - Rockwell K115
Izod impact strength 590 J·m-1 unnotched
Poisson's ratio 0.34
Tensile modulus 5.9 GPa
Tensile strength 160 MPa
Mechanical Properties

Features abrasion resistance.

Physical Properties

Physical Properties
Char Yield (under pyrolysis) High
Density 1.3 g/cm³
Flammability Does not burn
Limiting oxygen index 58%
Radiation resistance Good
Water absorption - over 24 hours 0.4%
Physical Properties

Additional features: will not ignite or smolder (burn slowly without flame), mildew- and age-resistant, resistant to sparks and welding spatter.

Thermal Properties

Thermal Properties Grade
Coefficient of thermal expansion 23×10-6·K-1 Low
Heat-deflection temperature - 0.45 MPa 435 °C (815 °F) High
Thermal conductivity @ 23 °C (73 °F) 0.41 W·m-1·K-1 Low
Upper working temperature 260–400 °C (500–752 °F) High
Thermal Properties Grade

Other features: continuous temperature: 540 °C (1,004 °F), melting temperature: 760 °C (1,400 °F) under pyrolysis, retains fiber integrity and suppleness up to 540 °C (1,004 °F).

See also


  1. ^ Hiroshi Mera, Tadahiko Takata "High-Performance Fibers" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.

External links


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