Ultra high density carbon fiber derived from isotactic polypropylene fiber without skin‐core structure

Abstract Polypropylene (PP)‐based carbon fibers were prepared by sulfonation process of isotactic PP fibers with concentrated sulfuric acid, followed by stress‐less carbonization under nitrogen atmosphere. The stabilization behaviors of PP fiber under different sulfonation temperatures and time were discussed. The carbonization behavior of the stabilized PP fibers under different carbonization temperatures, as well as the mechanical performance of the obtained carbon fibers were investigated. The results indicated that linear PP molecule were effectively converted into thermally stable structure at higher temperature (≥130°C) in short time (2 h) through sulfonation‐desulfonation reaction, among which ordered graphite structure has been formed prior to the carbonization process. Meanwhile, the carbon fibers were considerably densified by increasing the sulfonation temperature and carbonization temperature, and a bulk density of 1.96 g/cm 3 was achieved. Moreover, the temperature and time of the sulfonation process as well as the temperature of the carbonization process were regulated, and carbon fibers with tensile strength of 262.3 MPa was obtained, which was superior to that of 208.1 MPa for the linear low density polyethylene‐based carbon fibers reported previously. Isotactic PP was proved to be a promising candidate to develop carbon fibers with tunable graphite structure and mechanical performance.