Reactive hyperbranched core-shell architecture for developing high-performance bio-based adhesive

Abstract

Soybean meal (SM) adhesives offer a promising alternative to formaldehyde-based adhesives; however, their broader application is hindered by suboptimal adhesive properties and inadequate water resistance. In this study, we designed a novel reactive core-shell architecture (DAS@HBPA/EP) composed of dialdehyde starch (DAS) as the core and hyperbranched epoxy (HBPA/EP) as the shell, aimed at developing an SM adhesive with excellent water resistance, high bonding strength, and superior toughness. The reactive shell of DAS@HBPA/EP formed covalent bonds with protein molecules in SM, creating a highly interconnected structure that enhanced both the adhesive properties and water resistance of SM. Additionally, the microphase separation induced by the DAS core and the flexible hyperbranched shell provided the SM adhesive with improved toughness. As a result, plywood bonded with the SM/DAS@HBPA/EP adhesive exhibited exceptional dry shear strength (up to 2.14 MPa) and wet shear strength (1.24 MPa), representing a 589 % improvement over the pure SM adhesive. This performance is comparable to commercial melamine-urea-formaldehyde (MUF) resins (E₀ grade). Furthermore, the SM/DAS@HBPA/EP adhesive showed a high residue rate (82.30 %) and low water absorption rate (0.94 %), along with a uniform and dense microstructure. This simple and cost-effective strategy presents a novel approach to advancing technological innovation in the development of multifunctional composite materials.