Preparation of Hollow Fibers from Solutions of AB-poly(benzimidazole) in Phosphoric Acid

Continuous hollow fibers have been obtained for the first time from solutions of poly(2,5(6)-benzimidazole) in phosphoric acid. The rheological behavior of the solutions has been studied, and the kinetics of precipitation of the dope solution with water and 40% NaOH solution has been investigated. It has been shown that water is a soft precipitant, whereas the concentrated alkali leads to hard coagulation and the formation of vacuole defects. The operating parameters of the fiber spinning, such as the ratio between the volumetric flow rate of the internal precipitant to the flow rate of the polymer solution and the nature of the internal precipitant have a decisive influence on the morphology of the resulting fibers. As a result, a laboratory technology for spinning of hollow fibers of poly(2,5(6)-benzimidazole) with a monolithic and asymmetric structure has been elaborated, their thermal properties have been investigated, the residual solvent content in the fiber has been estimated, and the value of the limiting oxygen index has been determined. It has been shown that the hollow fibers of poly(2,5(6)-benzimidazole) have a great potential for use in high-temperature membrane separation.