Effects of thermal treatment on the properties of defatted soybean flour and its adhesion to plywood

With an attempt to economically and efficiently improve the water resistance of defatted soybean flour (DSF)-based wood adhesives, DSF was subjected to thermal treatment at various temperatures (65, 80, 95, 110, and 125 °C) for 30 minutes. The effects of thermal treatment temperature onto the chemical structure, crystalline degree, water-insoluble content, and acetaldehyde value of the thermally-treated DSF (T-DSF) was investigated. The thermal stabilities and bonding properties of soybean adhesives prepared from T-DSF and crosslinker epichlorohydrin-modified polyamide (EMPA) were also investigated. Test results indicated that both the water insoluble content and acetaldehyde value of T-DSF increased after thermal treatment, reaching the highest values of 27.28% and 26.81 mmol/g, respectively. All plywood bonded with the T-DSF-based adhesive withstood a 28 h boiling–dry–boiling accelerated aging treatment, while plywood bonded with the DSF-based adhesive delaminated after 4 h of water b...