Effects of the degree of oxidation of pitch fibers on their stabilization and carbonization behaviors

The stabilization of isotropic pitch (IP)-derived pitch fibers (PFs) and mesophase pitch (MP)-derived PFsin air was performed at different heating rates and with different final stabilization temperatures. The stabilized fibers (SFs) and carbon fibers (CFs) were characterized by elemental analysis, FT-IR, TG-MS and SEM to investigate the influence of the degree of oxidation of the SFs on the microstructures and mechanical properties of the CFs. Results showed that a slow heating rate during stabilization was beneficial to the oxidative cross-linking of PFs, and the corresponding CFs had a higher carbonization yield and tensile strength at the lower heating rate. When both IPF and MPF were stabilized at 270 o C, the two resulting CFs all reached their optimal performance. In addition, the FTIR peak intensity ratio of the C=O band at about 1700 cm –1 to the C=C band at 1600 cm –1 of the SFs had a good relationship to the carbonization yield and tensile strength of the CFs, and thiscan beusedto optimize the degree of oxidation of the SFs. Moreover, insufficiently stabilized fibers released a great deal of H 2 and CH 4 , causing some porosity in the resulting CFs with a low tensile strength, especially forthe insufficiently stabilized IPCF. While over-stabilized fibers released a large amount of CO and CO 2 , causing cracked textures in the corresponding CFs, especially inthe over-stabilizedMPCF. Therefore, this research into the stabilization and carbonization behaviors of pitch fibers has great significance for improving the mechanical properties of pitch-based CFs.