POLYBENZIMIDAZOLE AND POLYSULFONE BLENDS

Polybenzimidazole (PBI) and polysulfone (PS) do not form miscible blends; however, the tensile modulus and strength of their blend fibers are comparable to, or better than, that of PBI fibers, depending on process conditions. Fibers spun from an 80/20 PBI/PS solution blend have PBI-like LOI (limiting oxygen indices) and flame shrinkage behavior. Sulfonation and stabilization of this fiber improve its thermal properties. The process window for these blend fibers has been determined. There was no aging phenomenon on as-spun PBI/PS blend fibers, while as-spun fibers made from PBI/polyarylate (PA) and PBI/high modulus aramides (HMA) exhibited remarkable aging effects on fiber properties. This difference probably arises from the fact that 1) the former is not a miscible blend, while the latter are; and 2) the former does not have hydrolysis groups, such as ester and amide groups, as that in the PA and HMA systems.