Structural evolution of the polyimide/polyacrylonitrile fibers during carbonization

• 1、College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029

Abstract：In this paper, polyimide/polyacrylonitrile (PI/PAN) fibers were prepared by wet-spinning method, following by carbonization at temperature ranging from 500 to 1500 ℃ to obtain PI/PAN-based carbon fibers. The effects of carbonization temperature on the structures and properties of PI/PNA-based carbon fibers were investigated by EA, XRD, Raman and TG-IR analyses. The results indicated that the graphite structure was formed and gradually became ordered by increasing carbonization temperature, finally resulting in carbon fibers with carbon content of 96%, compact structure and excellent electrical properties. During carbonization, the decomposition of the polymer chain of PI/PAN fibers occured in the temperature range of 500-700 ℃, and the CO and CO2 are predominant gaseous by-products at the initial stage. Whereafter, the turbostraticgraphitic structure were formed by the recombination of molecular chain. The growth of graphite-like crystal were accelerated by denitrification reaction at temperatures higher than 900 ℃. The aromatic layer increased gradually after 1100 ℃. Moreover, the mechanism of structural evolution of PI/PAN-based carbon fibers were proposed.

Keywords： fiber polyimide polyacrylonitrile carbonization