Eco-Friendly Biobased Adhesives Prepared from Different Polyester-type Glucose with High Cross-Linked Structure

To resolve the environmental problem caused by formaldehyde-based adhesives, a facile method was proposed to prepare polyester-type glucose-based wood adhesives from polybasic acid (PBA) and glucose (G). This study involved the use of phosphoric acid (PA), maleic acid (MA), and citric acid (CA) to react with glucose to prepare phosphoric acid-glucose adhesive (PG), maleic acid-glucose adhesive (MAG), and citric acid-glucose adhesive (CAG), respectively. The adhesives were characterized by structural analysis, soluble content, thermal properties, and bonding strength. The result indicated that PA, MA, and CA could undergo esterification with G. They could be cured to form cross-linked structures without any agent. When the molar ratio of PA/G was <0.75, PG adhesives possessed higher wet shear strength than MAG and CAG adhesives. Its hot water shear strength (63 ± 3 °C-3 h) and boiling water shear strength (93 ± 3 °C-3 h) were 0.77-0.88 MPa and above 0.74 MPa, respectively. When the molar ratio of MA/G was ≥0.75, the hot water strength of the MAG adhesive satisfied with Chinese national requirement of GB/T 9846-2015 (>0.7 MPa). This work provides new visions and facile methods for the designs and developments of carbohydrate-based adhesives with high water resistance and strong bonding strength. This clean polyester-type wood adhesive can also replace formaldehyde-based adhesives, which is of important significance in protecting human health.