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Exploring the manufacturing potential of biobased materials containing lignin
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Date
2025-12
Abstract
This thesis focuses primarily on the production of carbon fibres from lignin. Carbon fibres (CFs) are a high value product that is currently hampered by its high cost and environmental impact. As a result, it is currently limited to critical applications in aerospace, energy, automotive and luxury sectors. Nevertheless, the CF market is seeing sustained growth, and is forecast to have a compound annual growth rate (CAGR) of 10.9% from 2025 to 2030. Lignin is a highly available byproduct of the paper and pulping industry and is being explored as a green alternative to existing solutions such as polyacrylonitrile (PAN) or pitch. It is normally burned as a low value fuel, but its high carbon content suggests that it could be the most viable option to produce CFs in a sustainable manner. Despite its potential, mechanical properties obtained from lignin so far have not been able to match even the weakest commercial carbon fibres produced.
This thesis investigates the challenges to producing CFs from lignin, and how to make them a viable alternative to their petroleum-based counterparts. A successful blend of Organosolv lignin blended with thermoplastic polyurethane (TPU) was utilised due to their high miscibility. Optimisation to the fibres was carried out at the precursor stage to improve mechanical properties using either toluene diisocyanate (TDI) or ultraviolet (UV) irradiation. These treatments modify the skin regions, resulting in carbon yield and microstructural changes.
Biomass was explored to determine its feasibility for sustainable additive manufacturing. Lignin/cellulose blends were added to TPU to form highly printable filaments, whilst spent coffee grounds (SCGs) blended with TPU were investigated as dual-purpose nitrate absorbent/ controlled release fertiliser system. Nitrate uptake occurred within the first 8 hours, followed by varied release depending on the blend and nitrate concentration.
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Peer-reviewed
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University of Limerick
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Sustainable Development Goals
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Attribution-NonCommercial-ShareAlike 4.0 International