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Polyacrylonitrile (PAN) fibers were stabilized continuously through a series of temperature zones, and the stabilized PAN fibers (SFs) taken out from different zones were irradiated with γ-ray, finally, some of the irradiated SFs were carbonized continuously. Structure changes of the SFs and mechanical properties of the derived carbon fibers were investigated. It is found that γ-ray not only could destroy the nitrile crosslinking bonds and form nitrile groups again in slight SFs, but could make more crosslinked structure including ether crosslinking and carbon-carbon crosslinking in slight and deep SFs, which improved thermal stability of the SFs and tensile strength of the carbon fibers. The irradiation also induced cyclization in short sequence in slight SFs, however, such a cyclization structure didn't significantly improve thermal stability. [ABSTRACT FROM AUTHOR]

Abstract: The influence of gamma-irradiation on the structure and mechanical properties of polyacrylonitrile-based carbon fibers was studied. It was observed that the Young’s modulus of the fibers irradiated increased with irradiation dose, increasing to 267GPa at 300kGy, a 16.1% improvement compared to that of as-received carbon fiber. However, the tensile strength increased to 5.4GPa at 30kGy, i.e., a 17.4% increase, and then dropped to 4.65GPa at 300kGy, which is almost the same as for the untreated fiber. Uniform stress model analysis and Raman spectroscopy show that the degree of covalent cross-linking between the graphene planes increased to a maximum at 30kGy and then remained almost constant with further irradiation. The SEM images show that the degree of surface roughness increased with the increasing irradiation dose. It is believed that when the dose is less than 30kGy, the increased cross-linking is the dominant effect, and thus improves the tensile strength. On the other hand, further irradiation generates surface flaws, which neutralizes the increase and results in a decrease of tensile strength. [Copyright &y& Elsevier]