Polybenzazole group

Polybenzazole group of fibers include PBI (Celanese) and polybenzoxazole (Zylon, Toyobo). These are wholly aromatic structures. The applications for PBI include fire-blocking fabrics for aircraft seats, firefighters suits, racing-car driver suit, etc. However, these fibers have poor resistance to both UV and visible light, and so must be protected from intense radiation source. 

Each of these major fibre groups has been described in detail elsewhere"- and so their major features only are presented below. They may be divided into the following the thermosets, the aramids and arimids, the polybenzazoles, and the semicarbons. Not only are the generic chemistries similar within each grouping but their properties and potential application suitabihties are similar. 

Polybenzazole fibre group polybenzimidazole and polybenzoxazole fibres... 

An alternative route to polybenzazoles was devised, by polymerizing dinitro difunctional nucleophilic monomers with terephthaloyl chloride, followed by reduction of the nitro groups and cyclization [35], This approach has the advantage of oxidative stability of the dinitro monomers complete conversion in reduction and cyclization are unlikely to be easily achieved. 

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