Kraft Lignin-Based Polyurethane with GVL: A Sustainable Coating Alternative for Recycled Linerboard

Julia C. Figueiredo; Roberto C. C. Lelis; Rosane N. Castro; Fernando J. B. Gomes; Ericka F. A. Redmond; Biljana Bujanovic

doi:10.3390/polym18010118

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Kraft Lignin-Based Polyurethane with GVL: A Sustainable Coating Alternative for Recycled Linerboard

Formally Refereed

Authors:

Julia C. Figueiredo, Roberto C. C. Lelis, Rosane N. Castro, Fernando J. B. Gomes, Ericka F. A. Redmond, Biljana Bujanovic

Year:

2026

Type:

Scientific Journal

Station:

Forest Products Laboratory

DOI:

https://doi.org/10.3390/polym18010118

Source:

Polymers

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Abstract

Food packaging is the largest segment of the global plastics market, yet its low degradability and limited performance in preserving perishable goods highlight the need for more sustainable alternatives. This study investigates the use of industrial softwood kraft lignin, a renewable polyol, and γ-valerolactone (GVL), an excellent green lignin solvent, to synthesize bio-based polyurethane (PU) coatings for recycled linerboard. PU was synthesized with hexamethylene diisocyanate (HDI), GVL, and 1,4-diazabicyclo[2.2.2]octane (DABCO) as a catalyst and applied to recycled linerboard (166.6 g/m²) at three coating weights: 13.5, 16.5, and 23.5 g/m². The coating enhanced water resistance, as shown by the reduced water vapor transmission rate (WVTR) and Cobb₁₈₀₀ values. Oil resistance was also significantly improved, reaching a Kit rating of 11 at the highest coating weight. Mechanical performance was maintained or enhanced, with increases in ring crush strength (RCT) and tensile index. These findings confirm the effectiveness of lignin-based PU in improving both the barrier and mechanical properties of packaging paper. Additionally, this approach presents an environmentally responsible alternative to petroleum-based coatings, adding value to lignin as a byproduct of the pulp and paper industry and supporting the transition toward more circular and sustainable packaging materials.

Keywords

paper packaging, linerboard, coating, lignin-based polyurethane, green solvents, barrier and mechanical properties, repulpability, biodegradation

Citation

Figueiredo, Julia C.; Lelis, Roberto C. C.; Castro, Rosane N.; Gomes, Fernando J. B.; Redmond, Ericka F. A.; Bujanovic, Biljana M. 2026. Kraft Lignin-Based Polyurethane with GVL: A Sustainable Coating Alternative for Recycled Linerboard. Polymers. 18(1): 118. 20 p. https://doi.org/10.3390/polym18010118.