Fully Biobased Adhesive from Glucose and Citric Acid for Plywood with High Performance

Abstract

Biomass-based adhesives have attracted much attention due to their eco-friendly, sustainable characteristics compared to formaldehyde-based adhesives; however, their low bonding strength and water resistance restrict their application. Thus, developing a high-performance biomass-based adhesive with excellent bonding strength and water resistance is necessary. In this work, a fully biomass-based citric acid-glucose (CAG) adhesive was produced by the esterification reaction of glucose and citric acid, which was validated by Fourier transform infrared (FT-IR), 13 C nuclear magnetic resonance ( 13 C NMR), and liquid chromatography−mass spectrometry (LC−MS). Furthermore, the properties of the CAG adhesive were tuned considering the effects of reaction time and molar ratio of citric acid/glucose (CA/G). It was revealed that increasing the molar ratio of CA/G is more advantageous to improve the shear strength and water resistance of plywood than the reaction time. The dry and wet strengths of plywood bonded by the CAG adhesive can reach the standard requirement (≥0.7 MPa) when the molar ratios of CA/G were more than 0.6 and the reaction time was 1 h. These results were better than those bonded by the urea-formaldehyde (UF) resin. Therefore, this green adhesive shows great potential to replace the existing industrial UF resin adhesives.

LignoSwitch: A Robust Yet Reversible Bioaromatic Superglue for Enhanced Materials Circularity and Ecodesign

“…Finally, reassembling the same wooden bars (without the need to add extra amount of glue), followed by reheating and subsequent cooling resulted in a robust assembly with similar holding power. The tensile strength of the glued wooden bars at room temperature was measured via a lap shear test and showed an average yield strength of 2.8 MPa (Figure 9a), which is comparable to other reported wood adhesives, either biobased, reversible, or both biobased and reversible, 14,15,39,40 but lower compared to commercial wood adhesives. In that case, failure of the assembly occurred from the wood itself (i.e., via substrate failure, as shown in Figure 9b,c), indicating that the cohesive strength of the LignoSwitch itself is even higher.…”

“…In this context, the sustainable adhesives of the future will have to demonstrate an enhanced sustainability profile, such as being derived from renewable and nontoxic resources, and facilitating the circularity of materials, for instance by providing the possibility to be debonded “on-demand” at the end of life. The development of biobased adhesives − and debondable adhesives − have independently made significant progress in recent years. However, practical adhesive compositions combining the two aspects (renewability of raw materials and reversibility of the glued assembly) remain very rare, and their applicability toward the design of recyclable products has often not been demonstrated.…”

Chemically decomposable imine‐based thermoset using oxidized sugar

“…When exposed to an acidic solution, the imine bond was decomposed, resulting in the appearance of an aldehyde peak at 1715 cm −1 . In the recycling solution, it further decomposed into citric acid, which exhibited a COC peak, representing the carbonyl group of the citric acid structure, at 1180 cm −1 51 . In addition, an imine bond of 1620 cm −1 appeared in the recycled polymer resin, confirming that recycling was successful after decomposition.…”

Synthesis of Fully Biomass High-Performance Wood Adhesives from Xylitol and Maleic Anhydride

“…Ester adhesives are also used in wood composites. Li et al prepared biomass-based citric acid-glucose (CAG) adhesives by esterification of glucose and citric acid . The prepared plywood could reach the standard dry and wet strength (≥0.7 MPa).…”

“…Li et al prepared biomass-based citric acid-glucose (CAG) adhesives by esterification of glucose and citric acid. 23 The prepared plywood could reach the standard dry and wet strength (≥0.7 MPa). Kusumah et al investigated natural adhesives with sweet sorghum bagasse and citric acid for particleboard production.…”