A novel approach towards lignin-based non-isocyanate polyurethanes for self-healing anticorrosive coatings

Use of renewable lignocellulosic biomass is a key aspect in the transition to a sustainable bio-economy. Biorefineries, unraveling the lignocellulose in its components (cellulose, hemicellulose and lignin) and converting them into chemicals and materials are central. Most biorefineries have a carbohydrate-only focus with little interest for high-value utilization of the lignin stream. Recently, reductive catalytic fractionation (RCF), pioneered at KULeuven among few others, was introduced and has emerged as a prominent lignocellulose fractionation technology and lignin valorization strategy. RCF, a combination of organosolv and catalysis, is able to produce a stable lignin oil, besides a purified carbohydrate pulp. With the use of proper catalysis and lignocellulosic feedstock, short and highly soluble lignin-derived phenolic oligomers with multiple primary alcohol groups can be isolated and delivered in high yield. This project proposes to study the amination of the lignin oligomers to form pluri-amine building blocks, as well as the synthesis of oligo carbonates from the lignin oligomer precursors as prior feedstock for isocyanate-free polyurethane. Solvent-free polymerization is attempted by reactive extrusion to maximize conversion rate and minimize energy input. The high water resistance of the aromatic lignin structure, the expected anti-oxidant property of the polyphenolic lignin structure, and the dynamic bond breaking/formation property of carbamates suggest for these biobased poly-hydroxy urethanes excellent anti-corrosive and self-healing properties, useful in various metal protection applications.