Texture and Properties of Acrylonitrile–Ammonium Itaconate Copolymer Precursor Fibers and Carbon Fibers

Acrylonitrile–ammonium itaconate copolymer {PAN-co-(NH₄)₂IA]} was fabricated by free-radical solution copolymerization of acrylonitrile (AN) and ammonium itaconate (NH₄)₂IA]. The copolymer was confected into a spinning solution (dope) and spun into precursor fibers. Then the precursor fibers were converted to carbon fibers by stabilization and carbonization processes. Another copolymer of acrylonitrile–itaconic acid P(AN-co-IA)] and its resultant fibers were studied in contrast. Due to preferable hydrophilicity and facilitating cyclization reaction in stabilization process, PAN-co-(NH₄)₂IA] fibers could increase the draw-ratio in the spinning process and in the stabilization process to attenuate some property-limiting facts in precursor fibers and carbon fibers. It has been found PAN-co-(NH₄)₂IA] precursor fibers gave a 30% improvement in tenacity over P(AN-co-IA) precursor fibers. Results for PAN-co-(NH₄)₂IA] precursor fibers carbonized at 1400°C ultimately showed a 26.7% increase in carbon fiber tensile strength over P(AN-co-IA) based carbon fibers. Characterization analysis using scanning electron microscope (SEM), transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM) manifested that these improvements are due to fewer surface defects, better interior morphology, higher degree of orientation and graphitization.