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Polybenzimidazole fiber



PolyBenzImidazole or PBI fiber (1983) is a synthetic fiber with an extremely high melting point that also does not ignite. Because of its exceptional thermal and chemical stability, it is often used by fire departments and space agencies.

Additional recommended knowledge

Contents

PBI's Inventor - “Speed”

PBI fiber was invented by Carl Shipp “Speed” Marvel, (1894.Sept.11-1988.Jan.04).

During World War II, Marvel worked for the National Defense Research Committee to create synthetic rubber, and the efforts of the group that he spear-headed were crowned by success within one year’s time (perhaps so soon because Marvel had so much fun as a chemist and because he was so good at what he did, having earned the reputation of working more than 3 times faster than other synthetic fiber chemists).

In the latter portion of his career, Marvel became interested in the problem of creating high-temperature stable polymers and his investigations carried out under the sponsorship of the U.S.D.A., the U.S.Army, and finally, the U.S.Air Force bore fruit with the synthesis of PolyBenzImidazole that was found to have significant applications to national defense as well as to everyday living. PolyBenzImidazole is as useful to the fabrication of spacesuits as it is to the manufacture of oven mitts. In 1986 (aged 92), Carl Marvel’s many (74) years of faithful and productive service to his profession and to his country were rewarded when President Ronald Reagan presented the National Medal of Science to him in the East Room of the White House. Marvel died on 4 January 1988.

Production

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."

PBI is prepared by step-growth polymerization from tetra-aminobiphenyl and diphenyl isophthalate spun via a dry spinning process using dimethyl acetamide as the solvent.

First U.S. Commercial PBI Fiber Production: 1983, Celanese Corporation

Current U.S. PBI Fiber Producers: Celanese Corporation

Current european PBI powder producer: HOS-Technik [1]

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
  • dyeable to dark shades with basic dyes following caustic pretreatment
  • 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
  • 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
  • abrasion resistant

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
  • 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 (73.4 °F) 0.41 W·m-1·K-1 Low
Upper working temperature 260-400 °C (500-752 °F) High
Thermal Properties Grade
  • continuous temperature: 540 °C (1,000 °F)
  • melting temperature: 760 °C (1,400 °F) under pyrolysis
  • retains fiber integrity and suppleness up to 540 °C (1,000 °F)

Major industrial PBI fiber uses

  • high-performance protective apparel such as:
    • firefighter turnout coats and suits
    • astronaut space suits
    • high temperature protective gloves
    • welders' apparel
    • race car driver suits
  • braided packings
  • aircraft wall fabrics

Future Industrial PBI Fiber Uses

Fuel Cell Electrolyte

Extensive plastics use slashes fuel cell cost (by Stephen Moore @ 2004.Dec.01)

Ticona (Kelsterbach, Germany)(stand 6/A7) has unveiled a prototype plastics-based hydrogen fuel cell that if mass-produced at a level of 20,000 two kW units, would reportedly cost only €790/kW (stack cost). The cost of the prototype itself was €3000/kW, which is also significantly less than existing fuel cells that extensively employ stainless steel components and cost around €10,000/kW.

Fuel cell technology should be available for commercial-scale production by 2010 at the latest and the EU has set a target of reducing stack productions costs to €500/kW by then."With €790/kW, we are already very close to meeting the target," says Ticona president Lyndon Cole.

The heart of the fuel cell comprises bipolar plates made from graphite-filled Vectra liquid crystal polymer (the graphite loading is around 85%) manufactured by SGL Carbon. These can either be stamped from rolls or injection molded. End plates and connection parts are molded from Fortron PPS.

Ticona is working with German start-up PEMEAS, based in Frankfurt, to incorporate the latter's polybenzimidazole (PBI) membrane material in commercial fuel cells. This will enable operation at higher temperatures of approximately 120 °C to 200 °C.

Carsten Henschel, director of communications at PEMEAS, says, "Higher operating temperature enable simpler fuel cell design." For example, low-temperature cells require complex water management systems to humidify membranes, whereas PBI does not require humidification. PBI membranes are more tolerant of CO contaminants in hydrogen reformed from natural gas, so gas purification is also simplified. Stainless steel-based fuel cells cannot operate at such high temperatures due to corrosion issues.

"The first volume commercial applications for fuel cells will most likely be portable devices [such as mobile phones]," says Thomas Hensel, VP of marketing at Ticona. Usage should also spread rapidly to residential power and the automotive sector.

See also

References

Polybenzimidazole (PBI) - Material Information
Summary of Polybenzimidazole

 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Polybenzimidazole_fiber". A list of authors is available in Wikipedia.
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