Sustainable, strong performance of a lignin-strengthened adhesive formulation with novel deep eutectic solvents

Abstract

Lignin-strengthened acrylic resin adhesives have been developed in this study, which could lead to enhanced environmental friendliness and adhesive performance. Acidic deep eutectic solvents (DES) and DES-CTAB were used to pretreat Broussonetia papyrifera to obtain a concentrated pretreatment liquor rich in lignin and mono-saccharide-derived compounds (MDES and MDES-CTAB) that were then polymerized with acrylic monomers and APS to obtain adhesives. The comprehensive performance of the adhesive was systematically evaluated by adhesion performance tests, rheological analysis and molecular dynamics simulation. The results showed that the wood bonding strength reached 6.62 and 6.33 MPa under the optimized conditions for MDES and MDES-CTAB adhesive_{without PEGDA}, respectively. The adhesive showed the best adhesion to polar substrates (iron plate) (6.56 and 5.07 MPa) and remained stable within the range of −80 °C to 100 °C, with poor acid/water tolerance. To further improve solvent resistance, PEGDA was added to obtain adhesive_with PEGDA, which showed decreased bonding strength but improved water resistance. Physicochemical analysis found that MDES-CTAB displayed superior initial stability in contrast to MDES. The MDES-CTAB system underwent more thorough polymerization, leading to a higher conversion rate. Molecular simulations confirmed that lignin and polysaccharides significantly enhanced interfacial bonding strength through strengthened hydrogen bonding and van der Waals forces. This study provides a theoretical basis for the development of green high-performance biomass-based adhesives.