A study on the preparation of high-strength starch-based adhesives with multiple cross-linked structures based on epoxy modification.

Starch-based adhesives are highly favored for their unique development potential, owing to their abundant raw material sources, formaldehyde-free nature, and sustainability. However, issues such as poor water resistance, low bonding strength, and inadequate mold resistance significantly limit their large-scale production and application. This study addressed these limitations by utilizing diacetyl starch (DS) as the raw material. Polyethyleneimine (PEI) solution was introduced to react with diacetyl starch, generating Schiff base reactions and hydrogen bond cross-linking. Subsequently, epichlorohydrin (ECH) was introduced for substitution cross-linking, resulting in a starch-based adhesive (OSPE) featuring a multi-crosslinked network structure. The dry shear strength and wet shear strength of this starch adhesive bonded plywood reached 2.26 MPa and 1.30 MPa, respectively. Compared to pure DS adhesive, the OSPE adhesive demonstrated significant improvements of 10.24 % and 348.28 % in dry and wet shear strength, exceeding the strength requirements of GB/T 9846-2015 (≥0.7 MPa). The adhesive film also exhibited hydrophobicity, achieving a contact angle of 94°. Furthermore, the OSPE adhesive demonstrated excellent mold resistance during 14 days of storage. This study provides a viable approach for preparing high-performance, mold-resistant starch-based adhesives.