Interfacial catalysis and lignin nanoparticles for strong fire- and water-resistant composite adhesives

Wood is increasingly replacing concrete to reduce CO 2 emissions in buildings, but fossil-based adhesives are still being used in wood panels. Epoxidized lignin adhesives could be a potential replacement, but their preparation has so far required low-molecular weight lignin and long reaction times....

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Published inGreen chemistry : an international journal and green chemistry resource : GC Vol. 24; no. 17; pp. 6487 - 65
Main Authors Henn, K. Alexander, Forssell, Susanna, Pietiläinen, Antti, Forsman, Nina, Smal, Ira, Nousiainen, Paula, Bangalore Ashok, Rahul Prasad, Oinas, Pekka, Österberg, Monika
Format Journal Article
LanguageEnglish
Published Cambridge Royal Society of Chemistry 30.08.2022
Subjects
Adhesive strength
Adhesives
Carbon dioxide
Carbon dioxide emissions
Catalysis
Concrete
Emissions
Fire resistance
Green chemistry
Lignin
Molecular weight
Nanoparticles
Phenols
Renewable resources
Resins
Sustainable yield
Thermal stability
Water resistance
Wet strength
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Summary:Wood is increasingly replacing concrete to reduce CO 2 emissions in buildings, but fossil-based adhesives are still being used in wood panels. Epoxidized lignin adhesives could be a potential replacement, but their preparation has so far required low-molecular weight lignin and long reaction times. Here we show a new efficient method to produce epoxidized kraft lignin (EKL) from regular kraft lignin by using interfacial catalysis. We demonstrate that EKL combined with biocolloids in the form of lignin nanoparticles (LNPs) produces a strong adhesive comparable to commercially available ones when cross-linked at 130-160 °C for only 3-5 minutes. The adhesive was free of phenol or formaldehyde, had a lignin content of over 80% and still showed impressive wet strength and incredible thermal stability. The process was shown to be scalable and environmentally more sustainable than resins from fossil-based feedstock or currently available ones from renewable resources. Lignin was epoxidized using interfacial catalysis, which improved the reaction speed and solubility immensely. Epoxidized lignin was cured with lignin particles into thermosets that could be used as a strong adhesive or fire-resistant coating.
Bibliography:Electronic supplementary information (ESI) available: Additional NMR FTIR, and DSC data of EKL and LNPs, dynamic light scattering (DLS) results of LNPs, and additional results from mechanical tests and surface response models (with statistical data) including a discussion of the mode of adhesive failure and images of representative samples. Video of close-ranged ignition test of EKL:LNP-coated adhesive joint and lifting 10 kg with an adhesive sample glued with a spread of 100 g m
2
and respective curing time and temperature of 5 min and 130 °C. See DOI
https://doi.org/10.1039/d2gc01637k
ISSN:1463-9262
1463-9270
DOI:10.1039/d2gc01637k