The aromatization degree of coal liquefaction pitch is closely related to its molecular structure evolution and the properties of derived carbon fibers. Using refined coal direct liquefaction pitch (RCLP) as raw material, pitches with different aromatization degrees were prepared by the self-pressurization/N₂ blowing two-stage thermal condensation method. Carbon fibers were then produced through melt spinning, oxidative stabilization, and carbonization. As the aromatization degree advanced, the C/H atomic ratio rose from 1.55 to 2.01, with the mesophase content nearing 100%. During RCLP thermal polymerization, large toluene-insoluble molecules were readily generated, yet the enrichment of the mesophase was comparatively sluggish. The spinnable pitch from RCLP had a relatively high aliphatic hydrogen content (33.40% ~ 13.69%) and a lower aromaticity (91.62% ~ 96.90%). Increasing aromatization made the carbon fiber cross-section’s radial transverse texture more distinct and ordered. The carbon layers stacked closely and parallelly, leading to a continuously rising tensile modulus. Due to the inhomogeneity from isotropic and anisotropic component changes, the carbon fiber tensile strength first decreased and then increased. When the spinnable pitch C/H ratio was 1.84, the mesophase pitch-based carbon fiber had an average diameter of 14.78 μm, a tensile strength of 1140 MPa, and a tensile modulus of 209 GPa.

Effect of aromatization degree of coal liquefaction pitch on the mechanical properties of pitch-based carbon fibers
    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Raw materials
        2.2 Liquid-phase carbonization of RCLP
        2.3 Preparation of pitch-based carbon fibers
        2.4 Characterization and testing of material properties
    3 Results and discussion
        3.1 Analysis of composition and properties of pitch
        3.2 Molecular structure analysis of pitch
        3.3 Morphology and molecular structure analysis of carbon fibers
        3.4 Mechanical properties analysis of carbon fibers
    4 Conclusion
    Acknowledgements 
    References

• Wenshuai Xi(Inner Mongolia Research Institute and School of Chemical & Environmental Engineering, China University of Mining and Technology (Beijing), Haidian District, D11 Xueyuan Road, Beijing 100083, People’s Republic of China)
• Xiongchao Lin(Inner Mongolia Research Institute and School of Chemical & Environmental Engineering, China University of Mining and Technology (Beijing), Haidian District, D11 Xueyuan Road, Beijing 100083, People’s Republic of China)
• Caihong Wang(Inner Mongolia Research Institute and School of Chemical & Environmental Engineering, China University of Mining and Technology (Beijing), Haidian District, D11 Xueyuan Road, Beijing 100083, People’s Republic of China)
• Yonggang Wang(Inner Mongolia Research Institute and School of Chemical & Environmental Engineering, China University of Mining and Technology (Beijing), Haidian District, D11 Xueyuan Road, Beijing 100083, People’s Republic of China)
• Jingdong Yang(Inner Mongolia Research Institute and School of Chemical & Environmental Engineering, China University of Mining and Technology (Beijing), Haidian District, D11 Xueyuan Road, Beijing 100083, People’s Republic of China, National Institute of Clean and Low Carbon Energy, Beijing 102211, China)