N-bromosuccinimide (NBS) has notable selectivity for brominating aromatic compounds with alkyl side chains. This study employs NBS in lieu of liquid bromine to prepare spinnable isotropic pitch derived from ethylene tar pitch (ETP) using a selective photobromination-debromination approach. The prepared isotropic pitches were then utilized to fabricate isotropic pitch-based carbon fibers (IPCFs) through a process involving melt spinning, oxidative stabilization, and subsequent carbonization. As the amount of NBS added increases in the photobromination stage, the softening point, pitch yield, average molecular weight, and degree of polymerization of the resulting isotropic pitch gradually increase, whereas its spinnability first improves but then decreases. Compared with the isotropic pitch manufactured through thermal polymerization alone, the isotropic pitch that undergo photobromination–debromination exhibits a more linear molecular structure formed by methylene/ethylidene-bridged aromatic units. This molecular structure enhances its spinnability, significantly improving the mechanical performance of the resulting IPCFs. The isotropic pitch produced with 15 wt% NBS during photobromination demonstrates exceptional spinnability, yielding carbon fibers with excellent mechanical characteristics. These fibers exhibit a tensile strength of 1333 MPa, Young’s modulus of 64 GPa, and an elongation property of 2.4%. This work provides a new method for the high value-added utilization of ET by controlling the molecular structure of the pitch precursor.

中文翻译：

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一种选择性光溴化-脱溴法从低成本乙烯焦油沥青中可控制备具有高拉伸强度的碳纤维可纺各向同性沥青


N-溴琥珀酰亚胺 （NBS） 对具有烷基侧链的溴化芳香族化合物具有显著的选择性。本研究采用 NBS 代替液态溴，使用选择性光溴化-脱溴方法制备由乙烯焦油沥青 （ETP） 衍生的可纺各向同性沥青。然后利用制备的各向同性沥青，通过熔融纺丝、氧化稳定和随后碳化的过程制造各向同性沥青基碳纤维 （IPCF）。随着光溴化阶段 NBS 添加量的增加，所得各向同性沥青的软化点、沥青产率、平均分子量和聚合度逐渐增加，而其可纺性首先提高，然后降低。与单独通过热聚合制备的各向同性沥青相比，经过光溴化-脱溴化的各向同性沥青表现出由亚甲基/亚乙基桥芳烃单元形成的更线性的分子结构。这种分子结构增强了其可纺性，从而显著提高了所得 IPCF 的机械性能。在光溴化过程中，用 15 wt% NBS 产生的各向同性沥青表现出优异的可纺性，从而产生具有优异机械特性的碳纤维。这些纤维具有 1333 MPa 的拉伸强度、64 GPa 的杨氏模量和 2.4% 的伸长率。本工作通过控制沥青前驱体的分子结构，为ET的高附加值利用提供了一种新方法。