Crosslinking of Electrospun Polybenzimidazole Fibers and Mats

Abstract

Polybenzimidazole nanofibers and mats are prepared by electrospinning. The process parameters are optimized including the polymer concentration, additives, spinning voltage, and collector substrates. The prepared fibers have a diameter of less than 200 nm and are in form of porous mats of thicknesses from 10 to 30 µm with an apparent density of 0.2-0.3 g cm-3, corresponding to a porosity of 75-84%. The polymer fibers are crosslinked by thermal curing at temperatures of 390-450 °C under an inert atmosphere. Attempts are also made to introduce crosslinkers in the precursor solution before electrospinning and to activate the covalent crosslinking by heat treatment at 280 °C of the electrospun fibers. Thus obtained fibers exhibit limited solubility (<5%) in hot (80 °C) dimethylacetamide, a typical solvent of the polymer. In hot phosphoric acid (85% at 80 oC) the nanofiber mat exhibits excellent structure stability and swelling resistance, which are essential for reinforcement of the composite membranes for e.g. polymer fuel cell and other applications.

Keywords: Polybenzimidazole fibers, electrospinning, crosslinking