A facile strategy for fabricating high-temperature soybean meal–based adhesive with reduced viscosity, prolonged open time, and improved water resistance

Abstract

Soybean-based adhesives fabricated from high-temperature soybean meal (HTSM) have a lower cost but significantly shorter open time and much higher viscosity than the commercial adhesives using low-temperature soybean meal (LTSM). This still limits their wide commercial applications. In this study, fresh soybean meal (FSM) was partially substituted for HTSM, effectively prolonging open time and reducing the viscosity of HTSM-based adhesive without compromising bonding performance. This improvement was mainly attributed to the synergistic interactions between undenatured soybean proteins and hydrophobic soybean oil (SO) present in FSM. Due to less water loss and fewer cross-linkages caused by heat-induced denaturation, the undenatured proteins can obviously reduce viscosity and prolong open time in HTSM-based adhesives. Additionally, the hydrophobic SO with its small molecular weight can inhibit water absorption by HTSM and act as a lubricant, thereby prolonging open time and reducing viscosity to some extent. The optimized HTSM-based adhesive, with 34.3 % FSM addition, exhibited a 91 % reduction in viscosity, an 89 % increase in open time, and a 17.6 % improvement in soaked wet strength (1.27 MPa). Therefore, adding FSM provides a facile strategy for effectively prolonging open time and reducing the viscosity of HTSM-based adhesives, making their performance comparable to commercial LTSM-based adhesives.