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

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), C-13 nuclear magnetic resonance (C-13 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.

Automated summary

A fully biomass-based citric acid-glucose (CAG) adhesive with excellent bonding strength and water resistance was successfully developed in this study. The properties of the adhesive were tuned by adjusting the reaction conditions. The CAG adhesive showed superior performance compared to traditional urea-formaldehyde (UF) resin adhesives in the application of plywood.