Improving Pre-oxidation Activity of Coal-Tar-Based Isotropic Pitch Fibers and Properties of Their Carbon Fibers via a Feedstock Modification by 2,3-Dimethyl-2,3-diphenylbutane

This study aimed to address the issue of the low oxidation activity of coal-tar-derived isotropic pitch (IP) fibers stemming from the high aromaticity of coal tar pitch (CTP). Thus, 2,3-dimethyl-2,3-diphenylbutane (DMDPB) was proposed to modify CTP. Then, spinnable IPs were prepared by an air oxidation process, followed by melt spinning, stabilization, and carbonization, to produce general-purpose isotropic pitch-based carbon fibers (IPCFs). The influences of varying dosages of DMDPB on the molecular structure of IPs and oxidation performance of as-spun fibers were investigated as well as the mechanical properties of their IPCFs. The results suggest that some methyl side chains were introduced onto the aromatic molecules of CTP through radical grafting reactions so as to inhibit the polycondensation among CTP molecules. Since the methyl side chain content increased with the rising dosage of DMDPB, the pre-oxidation activity and the stabilization efficiency of the as-spun fibers were significantly enhanced. Additionally, an appropriate amount of introduced aliphatic side chains led to the formation of more cross-linked oxygen-containing functional groups during stabilization, thus reinforcing the mechanical properties of the resultant IPCFs. When the DMDPB dosage was increased to 8%, the average tensile strength of the prepared IPCFs reached 1013 MPa, representing an increase of 69%. This study enlightens the preparation of cost-effective, high-performance IPCFs through the optimization of precursor molecular structures.