A New Strategy for the Preparation of High‐Strength Hydrophobic Aldehyde‐Free Starch Adhesive

ABSTRACT Starch adhesives are often used in the plywood sector. They are sustainable, formaldehyde‐free, and biodegradable. However, the problems of poor gluing strength and hydrophobicity need to be overcome. In this study, natural starch was oxidized by sodium persulfate to obtain oxidized starch. Oxidized starch adhesive (SSA‐15%) was crosslinked with PVA. The results show that the dry and wet shear strength of the prepared oxidized starch adhesive (SSA‐15%) can reach 2.95 MPa and 1.31 MPa, which is 163% and 120% higher than that of the natural starch adhesive. Sodium persulfate causes the large number of hydrophilic hydroxyl groups in starch to oxidize directly to carboxyl groups, improving the hydrophobicity of starch. The hydroxyl group present in oxidized starch interacts with the secondary hydroxyl group in PVA to form a hydrogen bond. This interaction enhances the adhesive bonding performance, resulting in improved mechanical properties and increased bonding strength of the final products, while also contributing to the formation of a more robust network structure. The study showed that the oxidized adhesive has good hydrophobicity and storage thermal stability. It is a simple and green biomass wood adhesive, which provides theoretical support for the promotion and application of aldehyde‐free adhesives.