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    Synthesis and Characterizations of Eco-Friendly Organosolv Lignin-Based Polyurethane Coating Films for the Coating Industry

    Year: 2022

    Journal: Polymers, Volume 14, FEB

    Authors: Bergamasco, Sara; Tamantini, Swati; Zikeli, Florian; Vinciguerra, Vittorio; Scarascia Mugnozza, Giuseppe; Romagnoli, Manuela

    Organizations: project PON MISE (Imprese e Competivita) [F/2000 03/01-03/X45]; project BIOEDILCARBON-Gruppi di Ricerca Regione Lazio [A0375-2020-36712]; Departments of Excellence-2018 program (Dipartimenti di Eccellenza) of the Italian Ministry of Education, University and Research for the project Landscape 4.0-Food, well-being and environment of the Department for Innovation in Biological, Agro-Food a

    Keywords: wood coating; wood color; contact angle; SEM; Py-GC; MS; FTIR mapping; beech; bio-circular economy

    Three different formulations of bio-based polyurethane (PU), varying the weight ratio between Organosolv lignin and a commercial isocyanate, were synthesized. The coating formulations were characterized by SEM, pyrolysis-GC/MS, FTIR spectroscopy and FTIR mapping, which confirmed the successful formation of urethane bonds between commercial isocyanate and hydroxyl groups deriving from lignin. The coatings were applied on beech wood samples to measure color and contact angles, and eventually FTIR mapping of the coated wood samples was performed. FTIR mapping is an interesting tool to monitor the distribution of PU chemical bonds on the coating surface and to evaluate the homogeneity of the applied coating films. Increasing the lignin content of the PU coatings results in more red-yellow and darker tones, while the commercial PU coating is transparent. For a higher lignin concentration, the solid content as well as the weight gain of the applied coatings increase. A higher percentage of lignin in the prepared PU formulations leads to superficial cracks and therefore higher coating permeability compared to the commercial PU, but the prepared lignin-based PU coating still makes a raw wood surface significantly more hydrophobic. Apparently, additives such as film-formers with low surface tension to counteract cracks' formation are necessary to improve the performance of lignin-based PU coatings.
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