Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Jan 20;14(3):416.
doi: 10.3390/polym14030416.

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

Sara Bergamasco  1 , Swati Tamantini  1 , Florian Zikeli  1 , Vittorio Vinciguerra  1 , Giuseppe Scarascia Mugnozza  1 , Manuela Romagnoli  1
Affiliations

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

Sara Bergamasco et al. Polymers (Basel). .

Abstract

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.

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

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Overview of the general procedure for the preparation of the Organosolv lignin-based PU coating.
Figure 1
Figure 1
Beech wood samples before (a) and after coating application (b–e). (a) W-R, (b) WPU-R, (c) WPU-3:1, (d) WPU-1:1 and (e) WPU-1:3.
Figure 2
Figure 2
Two examples of CA measurement after drop release. In (a) a WPU-R sample, with a high CA, and in (b) a WPU-1:3 sample, with a low CA. Blue angles indicate how the instrument extrapolates the data from the images.
Figure 3
Figure 3
Pictures of measurement areas: (a) WPU-3:1, (b) WPU-1:1 and (c) WPU-1:3. SEM images of PU-3:1 (d,e).
Figure 4
Figure 4
(a) Absorbance band of free isocyanate groups in the three different prepared PU formulations PU-3:1, PU-1:1 and PU-1:3. (b) FTIR spectra of Desmodur®L75 and Organosolv lignin (OL). The three different prepared PU formulations PU-3:1, PU-1:1 and PU-1:3 after air-drying at room temperature (c) and after oven-drying at 60 °C for 72 h (d).
Figure 5
Figure 5
FTIR mapping images based on the absorbance band at 1720 cm−1 (left) and respective microscope pictures of the measurement areas (right). (a) WPU-R, (b) WPU-3:1, (c) WPU-1:1 and (d) WPU-1:3.
Figure 6
Figure 6
Pyrograms of the Organosolv lignin (OL) used and one of the produced PU sample (PU-3:1).
See this image and copyright information in PMC

References

    1. Tamantini S., Del Lungo A., Romagnoli M., Paletto A., Keller M., Bersier J., Zikeli F. Basic Steps to Promote Biorefinery Value Chains in Forestry in Italy. Sustainability. 2021;13:11731. doi: 10.3390/su132111731. - DOI
    1. Nitzsche R., Gröngröft A., Köchermann J., Meisel K., Etzold H., Verges M., Leschinsky M., Bachmann J., Saake B., Torkler S., et al. Platform and fine chemicals from woody biomass: Demonstration and assessment of a novel biorefinery. Biomass Convers. Biorefin. 2020;11:2369–2385. doi: 10.1007/s13399-020-00769-z. - DOI
    1. De Angelis M., Romagnoli M., Vek V., Poljanšek I., Oven P., Thaler N., Lesar B., Kržišnik D., Humar M. Chemical composition and resistance of Italian stone pine (Pinus pinea L.) wood against fungal decay and wetting. Ind. Crop. Prod. 2018;117:187–196. doi: 10.1016/j.indcrop.2018.03.016. - DOI
    1. Füchtner S., Brock-Nannestad T., Smeds A., Fredriksson M., Pilgård A., Thygesen L.G. Hydrophobic and Hydrophilic Extractives in Norway Spruce and Kurile Larch and Their Role in Brown-Rot Degradation. Front. Plant Sci. 2020;11:1–20. doi: 10.3389/fpls.2020.00855. - DOI - PMC - PubMed
    1. Romagnoli M., Cavalli D., Pernarella R., Zanuttini R., Togni M. Physical and mechanical characteristics of poor-quality wood after heat treatment. iForest-Biogeosci. For. 2015;8:884–891. doi: 10.3832/ifor1229-007. - DOI

LinkOut - more resources