Carbon fibers with high performance are critically important materials for various industries, especially pitch-based carbon fibers including isotropic pitch-based and mesophase pitch-based are applied widely in the fields of aerospace, defense, sports, electronics, environmental protection, etc. Therefore, their development and fabrication have been a research focus in recent years. Carbon fiber production is a complicated process including raw material pretreatment, pitch preparation, melt-spinning, stabilization, carbonization, and graphitization. Each step has a significant influence on the properties and performance of the final carbon fiber product, and thus should be controlled effectively for preparing carbon fiber with desirable performance. This review presents a systematic and critical review of the preparation mechanism, influence factors, operational conditions, and various properties of the carbon fiber product, which was clarified along the master line of the step-by-step preparation of pitch-based carbon fibers. Besides, the current issues of carbon fiber production and its potential industrialization, which is the main challenge for the broad application of pitch-based carbon fibers, are also discussed in detail in this review.

In this work, isotropic pitch precursors are synthesized by the bromination-debromination method with ethylene bottom oil (EO) as the raw material and bromine as the initiator for pitch formation and condensation reactions. The aggregation structure, molecular weight distribution, and molecular structure of isotropic pitch precursors are characterized by thermal mechanical analyzer (TMA), MALDI TOF-MS, and ¹³C NMR, respectively, for revealing the mechanism of synthesis of isotropic pitch precursors. The results show that at low bromine concentrations, polycyclic aromatic hydrocarbons (PAHs) were mainly ordered in cross-linked structures by bromination-debromination through substitution reactions of side chains. The condensed reactivity can be improved by the effect of bromine, meaning that condensation reaction was aggravated by the method of bromination-dehydrobromination. In the presence of excess bromine, the cross-linked stereo structure of PAHs changed to the planar structure of condensed PAHs, which was not conducive to the subsequent spinning and preparation of carbon fibers.