Wet spinning of solid polyamic acid fibers

Recent research at the NASA Langley Research Center has involved the production of polyamic acid fibers from resins derived from the reaction of 3,3′,4,4′‐benzophenonetetra‐carboxylic dianhydride and 3,3′‐diaminobenzophenone or 4,4′‐oxydianiline in N,N‐dimethylacetamide. Resins were extruded into aqueous solutions of ethylene glycol, ethanol, or N,N‐dimethylacetamide in order to induce filament formation. These filaments were then washed in water and dried using air or vacuum ovens. Fractured fiber ends were examined using an optical or scanning electron microscope for the presence of macropores, termed voids. Coagulation bath concentration and composition, resin inherent viscosity, resin % solids, and filament diameter were studied to determine their effect on the production of solid core fibers.