Radiation-induced structural tailoring of polyacrylonitrile fibers prior to thermal-oxidation stabilization: Proton outperforms electron beam

Irradiation modification technology has proven effective in addressing the issues of prolonged processing time, low efficiency, and excessive exothermic reactions during the heat treatment of polyacrylonitrile (PAN) fibers, emerging as a research focus for optimizing the pre-oxidation process. To investigate the modification effects and mechanisms of different energetic particles, this study conducted proton and electron beam irradiation experiments on PAN fibers. By comparing the effects of two types of ray on fiber structure and thermal properties , we analyze the advantages of proton irradiation as a means of modification and propose a possible mechanism of action of proton irradiation , while further exploring the synergistic pre-oxidation effects of irradiation and heat treatment. The results showed that both proton and electron beams induced the dehydrogenation of the PAN main chain to form free radicals and triggered intermolecular cross-linking to accelerate the pre-oxidation process. However, at the same absorbed dose of 100 kGy, proton irradiation disrupts the crystalline structure of PAN fibers more and increases the crystal spacing. At the same time, the proton irradiation treatment has a stronger effect on the amorphous zone of the fibers, which promotes the diffusion of oxygen into the fibers, resulting in the fusion of the fiber micropores in the longitudinal direction . And it has a better synergistic effect with heat treatment, relieving the exothermic heat and forming more graphitized structure, which is more conducive to the preparation of high-performance carbon fibers. The above results indicate that proton irradiation is superior to electron beam irradiation for structural modulation of PAN fibers and coupling with heat treatment. • Investigating the effect of proton and electron beam irradiation on the structure of PAN fibers. • Proton irradiation has been shown to promote pre-oxidation and improve thermal properties of PAN fibers. • Synergistic pre-oxidation by proton irradiation and heat treatment is considered to be more prospective.