Objective The influence mechanism of different soybean meal additions on the water-resistant bond strength and viscosity of modified cottonseed meal-based adhesive was clarified, which provided basis for industrial production and application of protein-based adhesive.

Method High-temperature dephenolized cottonseed meal, low-temperature defatted soybean meal and triglycidylamine were raw materials. The cottonseed meal adhesive modified by soybean meal was synthesized by controlling the addition amount of soybean meal and the ratio of raw materials. Then, poplar plywoods were prepared. The viscosity of the adhesive was measured by rotary rheometer. The structure and morphology of the adhesive were characterized by Fourier transform infrared spectrometer, X-ray crystal diffractometer and scanning electron microscope. Thermogravimetric analyzer and universal mechanical tensile tester were used to analyze the thermal stability and bond mechanical properties of the adhesive. Finally, the mechanism of bond enhancement of the modified adhesive was comprehensively analyzed.

Result With the increase of soybean meal content, the amount of lysine in the system increased, providing more active sites for cross-linking reaction, forming a mechanical interlocking effect of multiple crosslinking network structure, and improving the water-resistant bond performance and viscosity of the adhesive. When the addition of soybean meal was 10%, the dry strength and water-resistant bond strength of adhesive TCM/SM10 were 1.24 and 0.79 MPa, respectively. Compared with TCM, when the addition of soybean meal increased to 30%, the dry bond strength and water-resistant bond strength of the adhesive increased by 60.4% and 27.8%, reaching 1.54 and 0.92 MPa, respectively, and the viscosity of the adhesive increased to 20.689 Pa·s. The thermal stability and toughness were improved.

Conclusion The use of low-temperature soybean meal as a partial substitute for cottonseed meal crosslinking modification to prepare cottonseed meal adhesive effectively improves the coating performance and water resistance of the adhesive, providing new ideas for the production of low-cost and high-performance protein based adhesives. It provides a new idea for producing modified cottonseed meal adhesive with low cost and high performance, and is helpful to promote the large-scale industrial application of protein-based adhesive.