Preparation of continuous large-diameter mesophase pitch-based carbon fiber with good weavability and potential ultra-high thermal conductivity

Abstract

Large-diameter mesophase pitch-based graphite fibers exhibit superior thermal conductivity but suffer from weaker elongation at break, posing adverse challenges for their continuous production and weaving processability, and consequently hindering large-scale commercialization. To address this issue, this study employs a complete set of engineered production lines to spin 1K-bundle pitch fibers with a diameter of 30 μm, followed by continuous oxidation and 1600 °C heat treatment to prepare continuous large-diameter mesophase pitch-based carbon fibers. The fibers exhibit a tensile strength/modulus of 1.56 GPa/267 GPa, and an elongation at break of 0.58 %, demonstrating good yarn spreading and weaving processability. Ultimately, the process of 3000 °C graphitization indirectly actives their latent thermal conductivity, yielding a mesophase pitch-based graphite fibers with a thermal conductivity of up to 1294 W⋅m⁻¹⋅K⁻¹, which surpasses that of commercial carbon fiber K1100 by 17.7 %. This is because a smaller draw-down ratio leads to smaller shrinkage ratio and the flow rate gradient, causing a smaller flow direction change behavior of the MP liquid-crystal molecules, thereby maintaining high molecular orientation. The “two-step” process used in this study effectively resolves the contradiction between high thermal conductivity and poor weavability of large-diameter fibers, providing a feasible technical route for the development and commercialization of ultra-high thermal conductivity mesophase pitch-based carbon fibers.