Carbon fibres – Innovative and Sustainable : Transforming Coal and Waste Plastics into High-Performance Carbon Fibres for Economic Growth and Pollution Reduction 07-11-2025
Carbon fibres – Introduction
Carbon fibres are rapidly gaining attention across sectors for their lightweight, high-strength performance, featuring in aircraft, automobiles and wind turbines. Yet the typical feedstock for producing carbon fibres remains the costly polymer polyacrylonitrile (PAN). Recent research introduces a compelling alternative: using cheap coal combined with waste plastics to create carbon fibres at lower cost and environmental impact. This breakthrough in sustainable materials has the potential to reshape how carbon fibres are manufactured.
The Sustainable Alternative Feedstock
The core strategy involves liquefying coal and using hydrogenolyzed waste plastics as the solvent. Coal, especially low-rank coal, possesses a rich aromatic structure and high carbon content, making it suitable for transformation into carbon fibres. At the same time, plastics such as high-density polyethylene (HDPE) pose a growing environmental threat. By converting HDPE into a solvent via hydrogenolysis, scientists have found that this plastic-derived solvent can replace traditional petroleum-derived or coal-derived oils in coal liquefaction. The result: a coal-plastic liquid mixture that can be processed into carbon fibres. EurekAlert!+2RSC Publishing+2
Process Overview
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HDPE is hydrogenolyzed into a plastic-derived liquid (PDL).
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This PDL is mixed with coal (in one demonstration, a low-bituminous Utah coal) at a 1:1 mass ratio.
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The coal-plastic mixture is subjected to mild solvolysis liquefaction (lower temperature, lower hydrogen pressure than conventional methods) to yield a coal-plastic liquid. RSC Publishing+1
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The liquid is upgraded under thermal conditions to form mesophase coal-plastic liquids (MCPLs), suitable for melt spinning.
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The MCPLs are melt-spun, stabilized, carbonized (for general-purpose carbon fibres) and, in some cases, graphitized (for high-performance carbon fibres). Science
Performance Results
The study demonstrates impressive mechanical properties for fibres derived using this method:
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One bundle of fresh fibres had a diameter of 10.8 µm, Young’s modulus of ~194 GPa and tensile strength of 0.85 GPa. EurekAlert!+1
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After optimized heat treatment, the fibres reached diameters of ~11.7 µm, modulus ~238 GPa and tensile strength ~1.15 GPa, aligning with general-purpose carbon fibres.
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With graphitization at ~2800 °C, the fibres reached diameters ~8.2 µm, modulus ~759 GPa and tensile strength ~4.03 GPa, identifying them as high-performance carbon fibres.
These results indicate that the process not only works but competes with high-end commercial carbon fibre grades.
Environmental and Economic Implications
By using waste plastics as solvent and cheap coal as precursor, the process addresses two major sustainability challenges: plastic waste streams and traditional expensive precursors. The elimination of solvent recycling complexity further reduces cost and environmental burden.
Moreover, broader life-cycle and techno-economic analyses of coal-derived carbon fibre pathways indicate potential cost savings and lower embodied energy compared with PAN-based routes.
Future Outlook
The research team plans to extend the scope by processing real-life waste plastic mixtures (beyond HDPE) and testing a wider variety of coal types. They also aim to explore liquefaction under lower temperatures and hydrogen pressures to enhance sustainability and scalability. RSC Publishing+1
The implications are significant: widespread use of more affordable carbon fibres could enable lightweight components in automotive, aerospace, sporting goods and wind turbines at reduced cost and environmental impact.
Why This Matters
For the manufacturing world, the emergence of a process that takes coal and waste plastics to high-value carbon fibres is a game-changer. It means a shift toward circular economy practices, novel precursor materials, and more sustainable advanced composites. The viability of high-performance carbon fibres from unconventional feedstocks suggests that future material supply chains can be both cost-effective and environmentally conscious.
Conclusion
Turning coal and waste plastics into carbon fibres marks a breakthrough in sustainable materials science. With mechanical properties comparable to commercial high-performance carbon fibres, this pathway offers an economically and environmentally favorable alternative to PAN-based production. As the research progresses toward industrialization, it points toward a future where advanced composites are not just high performing, but also aligned with sustainability goals. Using waste plastic and affordable coal feedstocks could reshape the carbon fibre industry and help drive broader adoption of lightweight, high-strength materials in multiple sectors.
