Polybenzimidazole fibres

Polybenzimidazole fibre forms one of the most fire-resistant textiles (mp 760 °C usable to 540 °C) and, although very expeusive, is used for high-tech applicatious, such as protective clothing for fire fighters, astronauts and motor-racing drivers. 

More recently, polybenzimidazole fibre has become available commercially. The fibre is obtained by spinning from a solution of the polymer in dimethylacetamide. Suggested applications include protective clothing and dust filters for hot flue gases. 

Polybenzazole fibre group polybenzimidazole and polybenzoxazole fibres... 

These fibre-formimg polymers are so-called ladder polymers and possess wholly aromatic polymer chains. The two common examples available commercially are the polybenzimidazole FBI (Intertek, formerly Celanese) with the full chemical name poly (2,2 -(m-phenylene)-5,5 -bibenzimidazole) and the polybenzoxazole Zylon (Toyobo) with the full chemical name polyfpara-phenylene benzobisoxazole) and generic acronym PBO. Their similarity in polymer chain stractures and high degrees of... 

Fibre choices for thermal protective clothing include inherently flame resistant (FR) fibres such as the meta- and para-aramids, polyamide-imide, polybenzimidazole, modacrylic and chemically modified fibres such as viscose and modal, polyester, and nylon, as well as FR treated or finished cotton and wooP"" (see also Chapter 8). The... 

Successful construction of textile fabrics as substrates for the integration of solar cells has to take into account the type and grade of polymer used, the type of fibre extruded from it, and subsequent fabric construction. Fibre selection is very much determined by its ability to withstand successfully the elevated temperatures required for the deposition of the thin layers comprising a solar cell. Where these temperatures are as high as 400 °C or more, as in the deposition of many types of solar cell, selection is restricted to high-performance fibres, such as glass fibres, polyimides, polybenzimidazoles and polybenzoxazoles, but these types of fibre are expensive. However, it has been demonstrated that nanocrystalline silicon films can be successfully laid down at temperatures as low as 200 °C [4, 5], a factor that then broadens fibre choice to include a range of commodity fibres. 

These fibre-forming polymers are so-called ladder polymers and are essentially wholly aromatic polymer chains. The two examples commonly available commercially are the polybenzimidazole PBI (Celanese) with the full... 

The general process used to synthesise aromatic polybenzimidazoles (PBIs) is presented in Section 4.3.3. More detailed information can be found in previously published books [87,88]. During 1960-1970 a number of publications, comparable to those on polyimides, reported the synthesis and properties of all aromatic and aryl-aliphatic polybenzimidazoles. Most of these polymers were prepared by the two-step process illustrated in Fig. 14 with the reaction of 1,3-benzenedicar-boxylic acid diphenyl ester 27 and [l,l -biphenyl]-3,3, 4,4 -tetramine 11 yielding ultimately PBI 29. All the applications - laminates and filament winding resins, adhesives, fibres and foams - used polymer 29, which was produced in semicommercial quantities by the Whittaker Corporation (Narmco Division) under the generic trade mark Imidite . Currently, forty years later, this polymer is manufactured by Hoechst-Celanese and its only commercial success is in the area of heat resistant fibres and fabrics. It is, however, worth noting the adhesive properties of this polymer and the reasons explaining the major obstacles to the development of PBIs as heat-resistant adhesives. 

Moulded polybenzimidazole has the highest compressive strength of any unfilled resin (400 MPa), of 427 "C and HDT of 435 °C. It can withstand temperatures of 700 °C for several minutes. The LOI is 58%. However, it is degraded in hot aqueous acids. Poly benzimidazole can be solution spun into fibre and is extensively nsed in fightfighters clothing and other fire blocking applications. 

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