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

Preparing a biobased wood adhesive to solve the formaldehyde pollution problem is crucial. In this study, a xylitol-maleic anhydride hyperbranched polyester resin (XMA) was prepared from two biomass raw materials, xylitol (X) and maleic anhydride (MA). Hyperbranched polyol (HP) and hyperbranched polyacid (HPA) were synthesized via a nucleophilic addition reaction by regulating the molar ratio of X to MA. Then XMA was prepared by melt polycondensation of HP with HPA. The chemical structure of XMA was characterized using Fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance (13C NMR), liquid chromatography–mass spectrometry (LC-MS), and gel permeation chromatography (GPC). This double hyperbranched synthesis strategy increases the internal cross-link density of the resin and imparts excellent mechanical properties. Mechanical tests showed that the dry shear strength of the plywood reached 2.37 MPa, and the strengths were 1.72 and 1.75 MPa after immersion in hot and boiling water for 3 h. The green and simple synthesis strategy of XMA is expected to be applied in the wood industry.