Key Takeaways & Executive Findings
- •• Increasing spinning temperature from 309 to 320 °C enhances thermal conductivity of MPCFs from 704 to 1078 W·m−1·K−1. • Tensile strength of MPCFs improves from 2.16 to 3.23 GPa with higher spinning temperature. • Higher spinning temperature promotes a transition from fine-and-folded to large-and-flat graphite layer morphology. • Improved molecular orientation due to lower viscosity and reduced die-swell effect at higher temperatures is key to property enhancement.
Abstract
Mesophase-pitch-based carbon fibers (MPCFs) were prepared using industrial equipment with a constant extrusion rate of pitch while controlling the spinning temperature. The influence of spinning temperature on their microstructures, mechanical properties and thermal conductivities was investigated. SEM images of the fractured surface of MPCFs show that the graphite layers have a radiating structure at all spinning temperatures, but change from the fine-and-folded to the large-and-flat morphology when increasing the spinning temperature from 309 to 320 °C. At the same time the thermal conductivity and tensile strength of the MPCFs respectively increase from 704 W·m−1·K−1 and 2.16 GPa at 309 °C to 1 078 W·m−1·K−1 and 3.23 GPa at 320 °C. The lower viscosity and the weaker die-swell effect of mesophase pitch at the outlets of the spinnerets at the higher spinning temperature contribute to the improved orientation of mesophase pitch molecules in the pitch fibers, which improves the crystallite size and orientation of the MPCFs.
1. Introduction
Mesophase-pitch-based carbon fibers (MPCFs) have been widely used in the fields of aerospace, electronic products, nuclear industry and industrial robots[1–5] owing to their high thermal conductivity and high modulus. These excellent properties are ascribed to their highly oriented large-size graphite microcrystal structure which was derived from the orientated structure of the discoid nematic liquid crystal molecules formed in spinneret channels from the mesophase pitch. It is generally believed that the mesophase pitch molecular arrangement formed in the melt-spinning process plays a decisive role in the structures and properties of the resultant MPCFs. In comparison, the subsequent oxidative stabilization, carbonization and graphitization provide just a further modification and improvement[6]. Therefore, it is necessary to investigate systematically the effect of the spinning conditions on the microstructures and properties of the MPCFs.
Tailoring microstructures and properties of MPCFs are immensely complicated by numerous influencing factors such as raw material, spinning temperature, pressure, winding speed, mesh structure and spinneret shape[7–12]. At present, researchers have investigated the effect of melt-spinning temperature on the microstructures and properties of MPCFs, but these studies are mainly based on the melt-spinning process of the "pneumatic single-hole spinning equipment". For example, Yamada et al.[13] found that the cross section structure of MPCFs changed from "onion-skin" shape to "random" shape and then to "radial" shape with the decreasing of the spinning temperature, eventually reaching a "radial" shape.
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YE Gao-ming, SHI Kui, WU Huang, HUANG Dong, YE Chong, OUYANG Ting, ZHU Shi-peng, FAN Zhen, LIU Hong-bo, LIU Jin-shui (2025). Improving the mechanical properties and thermal conductivity of mesophase-pitch-based carbon fibers by controlling the temperature in industrial spinning equipment. SinoTechIntel Verified Research. https://doi.org/10.1016/S1872-5805(NCM2024-39-02-11)
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
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Frequently Asked Questions
What is the effect of spinning temperature on the thermal conductivity of mesophase-pitch-based carbon fibers?
Increasing the spinning temperature from 309 °C to 320 °C significantly enhances the thermal conductivity of MPCFs from 704 W·m−1·K−1 to 1078 W·m−1·K−1, due to improved molecular orientation and larger crystallite size.
How does spinning temperature affect the tensile strength of MPCFs?
The tensile strength of MPCFs increases from 2.16 GPa at 309 °C to 3.23 GPa at 320 °C, attributed to better alignment of mesophase pitch molecules and a more favorable microstructure.
What microstructural changes occur in MPCFs with increasing spinning temperature?
SEM images show that the graphite layers transition from a fine-and-folded morphology to a large-and-flat morphology as the spinning temperature rises from 309 °C to 320 °C, indicating improved crystallite orientation and size.
Why does higher spinning temperature improve the properties of MPCFs?
Higher spinning temperature reduces the viscosity of mesophase pitch and weakens the die-swell effect at spinneret outlets, leading to better molecular orientation in the pitch fibers, which translates to enhanced crystallite size and orientation in the final carbon fibers.
What is the significance of using industrial spinning equipment in this study?
This study utilizes industrial spinning equipment with a constant extrusion rate, providing practical insights for large-scale production of high-performance MPCFs, as opposed to laboratory-scale pneumatic single-hole spinning equipment.
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