Physico-Chemical Properties of Soybean Meal-Based Adhesives Reinforced by Ethylene Glycol Diglycidyl Ether and Modified Nanocrystalline Cellulose

An eco-friendly soybean meal-based adhesive (SM adhesive) was developed by incorporating ethylene glycol diglycidyl ether (EGDE) and nanocrystalline cellulose (NCC). In order to introduce epoxy groups, NCC was modified by KH560 (denoted as MNCC). The functional groups, thermal stability, and cross section of the resultant adhesive were characterized. Three-ply plywood was fabricated to measure the dry and wet shear strength of the adhesive. The experimental results showed that the epoxy groups on MNCC reacted with the carboxyl group of SM protein molecules, forming a crosslinking network and a ductile adhesive layer. As a result, compared with the SM adhesive modified by EGDE, the thermal stability of the adhesive with MNCC was improved and the wet shear strength was increased to 1.08 MPa.