Effects of γ-ray irradiation on the radial structure heterogeneity in polyacrylonitrile fibers during thermal stabilization

Abstract

The radial structural heterogeneity of thermally-stabilized polyacrylonitrile (PAN) fiber is considered to be a limiting factor affecting the mechanical properties of the resulting carbon fibers. In this study, we demonstrate that a low-dose (60 kGy) γ -ray irradiation pretreatment can effectively mitigate the radial structural heterogeneity of PAN fibers after thermal stabilization. The characterization results indicate that low-dose γ -ray irradiation only affects the physical structure of PAN through decreasing its crystalline size and crystallinity, rather than inducing chemical cross-linking and/or intramolecular cyclization. It is proposed that an increased amorphous region in PAN fibers prompted by low-dose γ -ray irradiation can facilitate oxygen diffusion from skin to core during stabilization, which results in the increased structural homogeneity of stabilized PAN fibers.