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a polymer containing benzimidazole rings in the main macromolecular chain:

where R = H, C6H5, or an alkyl.

Polybenzimidazoles are produced mainly by solid-phase poly-cyclic condensation of aromatic tetraamines with diphenyl esters of aliphatic or aromatic dicarboxylic acids. Of current practical importance are polybenzimidazoles based on aromatic acids (mainly o,o′-diaminobenzidine and diphenyl isophthalate), called aromatic polybenzimidazoles:

Most polybenzimidazoles are colorless or slightly colored amorphous or crystalline compounds, depending on their structure, with molecular weights up to 40,000. They have high heat resistance: rapid decomposition of aromatic polybenzimidazoles in air begins at 450°-600°C, and of aliphatic polybenzimidazoles, at 300°-400°C. Polybenzimidazoles are also characterized by high chemical stability and, in particular, resistance to hydrolysis—for example, some polybenzimidazoles are unchanged upon boiling in 70-percent H2 SO4 and 25-percent NaOH for 10 hr.

Polybenzimidazoles made from aliphatic polymethylene dicarboxylic acids (for example, sebacic acid) are superior in strength to the aromatic polybenzimidazoles. The latter are soluble, for example, in dimethylacetamide.

Polybenzimidazoles are used to make adhesives, heat-resistant films and fibers, binders for glass-fiber-reinforced plastics used in the construction of airplanes and rockets, antifriction materials, and ablation heat-shielding coatings for spacecraft. Fabrics made from polybenzimidazoles have high resistance to heat and fire and are hydrophilic, comfortable to wear, and resistant to abrasion.

Polybenzimidazoles are produced in the USA. An adhesive produced under the name Imidite 850 and a binder for glass-fiber-reinforced plastics under the name Imidite 1850 are produced from polybenzimidazoles.


References in periodicals archive ?
Her thesis, which was funded by US based Trevi Systems, explored the development of a desalination membrane that utilizes the unique chemical and thermal strength of the material polybenzimidazole (PBI), with the chemical phenomenon known as phase-inversion, whereby removal of the solvent from a liquid-polymer solution produces a porous and solid membrane.
The MEA consists of catalysts, gas diffusion layers, and the Celtec membrane, made with the company's temperature-resistant polymer polybenzimidazole.
They chemically modified polybenzimidazole, a plastic used to make fibers in protective clothing for firefighters and racecar drivers.
The products are pseudo-thermoplastics formed from polybenzimidazole (PBI), a polymer resin that does not burn in air.
The materials covered include high performance Polyethersulfones, Polyetherimides, Polyphthalamides, Polyphenylene Sulfide, Polyaryletherketones, Polyamideimides, Polyimides, Polybenzimidazole, Liquid Crystalline Polyesters and Perfluoropolymers.
Among various types of polymer suitable for high-temperature polymer electrolyte fuel cell (HT-PEFC) application such as, phosphonated perflurosulfonic acid membrane, sulfonated aromatic hydrocarbon polymer membrane, inorganic-organic composite membrane [3], and phosphoric acid doped polybenzimidazole (PBI) are reported as promising candidates due to its high performance, excellent oxidation and thermal stability, low fuel permeability, nearly zero water drag coefficient and high ionic conductivity at temperature up to 200[degrees]C.
Another study on CEX is relevant to removal of CEX from electrolyte solution using polybenzimidazole nanoltration membrane [21, 24] and suggested that the role of ionic form of CEX is significant in membrane separation processes.
VT extended that work by also showing that one could make multiblock copolymers of poly(dimethyl siloxane) and ULTEM or related polyimides and blend them either with PEEK or in some cases with polybenzimidazole (PBI) to produce highly compatible and even miscible systems.
Since it was developed for NASA nearly 50 years ago, polybenzimidazole has built an outstanding reputation for retaining its physical properties at temperatures that wilt other polymers and some metals.
BCC also noted that while perfluorosulfonic acid polymers "and their close relatives" currently dominate the membrane market for PEM fuel cells, other materials may become useful in the near future, including sulfonated hydrocarbons, heterocyclics such as polybenzimidazole (PBI) and "their related polymers and esters modified.
Fibre types employed include aramids, cotton, modacrylic, polyamide, polybenzimidazole (PBI), polypropylene, ultra high molecular weight polyethylene (UHMWPE) and Vectran.
Wang et al [8] separated cephalexin from electrolyte solution using polybenzimidazole (PBI) nanofilteration membrane and analyzed the effect of pH of solution during separation.