Investigation of the Influence of Fiber Stretching on N2-Pretreated PAN-Fibers and Development of a Shortened Stabilization Process Meeting the Requirements of the Carbon Fiber Industry

Carbon fibers (CF) are characterized by their excellent mechanical properties and low specific weight. However, due to the high production costs of CF, the application areas of this material are highly limited. A more cost-effective production of CF through the use of N₂-pretreatment can further increase the spread in mass markets. In the research presented, the influence of fiber stretching on the properties of pretreated Polyacrylonitrile (PAN)-fibers as well as the resulting carbon fibers is investigated on continuous scale. The investigations show that the fibers can be stretched much more (> 10%) during N₂-pretreatment than in air atmosphere without impairing the mechanical properties of resulting CF. With increasing stretching ratio, the E-modulus and tensile strength of the pretreated fibers are increasing while the elongation remains on a similar level as the reference carbon fibers. Using this effect, a more efficient stabilization process has been developed in which the first of four stabilizations zones has been skipped. This method ensures high acceptance by the industry, as the process parameters of the other three remaining stabilization zones are untouched. As a result, the thermal conversion time of CF has been reduced by 20% while the mechanical properties of the CF are maintained.