Investigation of combined N-2- and KMnO4-pretreatment to reduce stabilization time of polyacrylonitrile-based carbon fibers

Lightweight materials are continuously gaining importance due to their potential in the reduction of energy consumption. Carbon fibers and fiber reinforced composites exert impeccable mechanical properties while maintaining a low density. However, carbon fibers and their composites have significantly high production costs, which limit their application areas. Currently they are used in areas such as the aerospace and wind energy sectors where mechanical properties maintain a supremacy above the costs. In order to expand the application opportunities of carbon fibers, it is necessary to reduce the process time during their thermal conversion and thus ultimately reduce production costs. In the present article, an innovative approach is pursued in which the residence time during stabilization is reduced by 20% using a combination of an aqueous KMnO4- and an atmospheric N-2-treatment of the polyacrylonitrile precursor material. After validation on a continuous production scale, the results show that it is possible to accelerate desired stabilization reactions using a combined application of KMnO4 and N-2. Not only can partial stabilization steps be skipped, but the activation temperature of the stabilization reactions can also be reduced, so that stabilization could proceed at lower temperatures, ultimately leading to energy and cost reductions.