Defence of doctoral thesis: Alessio Truncali – Lignin towards thermoset applications

The global shift towards sustainable development requires the replacement of fossil-based materials with renewable alternatives. Lignin, a complex aromatic biopolymer derived from lignocellulosic biomass, represents one of the most abundant sources of renewable carbon. Retrieved as a byproduct from the pulp and paper industry, lignin has thus far been underutilized despite its potential. Its unique chemical structure, characterized by phenolic units linked through various interunit linkages, makes it a strong candidate for creating durable resistant materials. However, lignin’s complex and heterogeneous structure, as well as its limited reactivity, present challenges for its use. In this work, lignin has been investigated for thermosetting applications through different methodologies, including extraction, fractionation, chemical modification, and direct utilization of unmodified lignin. This present research demonstrates different ways to develop materials with enhanced mechanical, thermal, and chemical properties, suitable for industrial applications. To achieve this, various methodologies and lignin sources were employed. Lignin was extracted through a mild extraction from wheat straw in order to valorize agricultural products. Microwave-assisted fractionation was employedin order to isolate lignin fractions with more tunable properties and increased reactivity. Chemical modifications, including epoxidation and allylation, were performed to enhance the reactivity of lignin and improve its compatibility in thermosetting formulations. These modified lignins were incorporated into epoxy-based coatings and thiol-ene systems, demonstrating their potential in producing durable and high-performance materials. In addition to modified lignin, unmodified lignin was directly utilized in coating formulations. This thesis demonstrates that both modified and unmodified lignin can be successfully integrated into thermosetting systems, furnishing materials that meet or exceed the performance of conventional fossil-based counterparts. The work emphasizes the advantages and limitations of each method, highlighting the importance of optimizing processing efficiency, material performance, and environmental sustainability.

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