Soybean meal-based wood adhesive enhanced by ethylene glycol diglycidyl ether and diethylenetriamine

The objective of this study was to improve performance of the soybean meal-based adhesive by an ethylene glycol diglycidyl ether (EGDE) and diethylenetriamine (DETA). Three-ply plywood was fabricated to measure wet shear strength. The functional groups, cross section, crystallinity, thermal behavior, and physical properties of the resultant adhesives were characterized in detail. Results show that DETA reacted with EGDE to form a long chain structure with epoxy groups, which cross-linked the soy protein molecules to form a denser cured adhesive layer to improve the water resistance of the resultant adhesive. In addition, the long chain structure formed an interpenetrating network with the soy protein molecules, which further improved the water resistance of the adhesive. Incorporating EGDE/DETA, the wet shear strength of the plywood bonded by the resultant adhesive was improved by 30.7% to 1.15 MPa, which met the interior use plywood requirement. Additionally, compared with the soybean meal-based control adhesives, the viscosity of the cured adhesive decreased by 39.4-50.3%, that made the resultant adhesive practical for plywood industrial application. (C) 2015 Elsevier B.V. All rights reserved.