Study on the Formation of Skin-Core Type of Heterogeneous Structure in the Cross-section of Precursor of Poly(acrylonitrile) Carbon Fiber

摘要

Production of poly(acrylonitrile) (PAN) carbon fiber is carried out by two steps: (1) stabilization in an oxidative atmosphere (~210°C) followed by (2) carbonization at high temperature (~1,000°C) under N2 atmosphere. In the cross-section of PAN carbon fiber, skin-core type of heterogeneous structure is generally observed (Fig.1). The formation mechanism of this structure is discussed in detail. Highly isotactic PAN sample (~80%) was prepared and used in the form of wet-spun PAN fiber and the solvent cast film. Under mild oxidative conditions (~205°C), the CN intensity in FT-IR spectra was traced as a function of heating time (Fig. 2). Even in a highly isotactic sample, no accelerating effect on the ring formation was observed. A large amount of CN groups were retained in the film, the extent of this residual CN groups was almost the same as that of atactic PAN. No preferential effect of isotactic configuration on the reaction of PAN casts a deep doubt on the well known intra-molecular type of ring formation mechanism [1], An alternative reaction mechanism is presented.