Controllable synthesis of isotropic pitch precursor for general purpose carbon fiber using waste ethylene tar via bromination–dehydrobromination

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Nowadays, the substantial amount of waste ethylene tar (ET) lacks a clean and efficient route for utilization. In this work, a feasible approach was developed to fabricate general purpose carbon fiber (GPCF) using ET as a raw material. The method of bromination–dehydrobromination was used to synthesize controllably isotropic pitch precursor for GPCF. The results show that bromination–dehydrobromination reaction promotes the cyclization and aromatization of small molecules and relatively low molecular weight components and also prevents excess condensation during thermal treatment. The molecular structure of pitch precursor generated from bromination–dehydrobromination reaction has more linear and cross-linked structures as more naphthenic groups and the side chain of aromatic rings. The spinnability of pitch precursors and the mechanical performance of GPCFs are optimized when 10 wt% of bromine is introduced in synthetic reaction. The tensile strength, Young’s modulus, and elongation property of the final GPCF are 1072 ± 66 MPa, 47 ± 7 GPa, and 2.3%, respectively, with the diameter of 10.3 ± 0.5 μm.