Effects of Pressure from High‐Pressure Homogenization on the Performance of Soybean Flour Based‐Adhesive

A green and sustainable soybean flour (SF) adhesive is considered as a potential alternative to toxic formaldehyde‐based resins. Nevertheless, poor bond stability and low bonding strength is caused by the uneven size distribution and low reactivity of SF. Herein, SF adhesives with excellent and stable performance are synthesized via the synergistic action of high‐pressure homogenization (HPH) treatment by incorporating a green crosslinker. Specifically, an even distribution of the SF particles is obtained after the HPH treatment, from which large soy protein molecules are broken to several small and even single protein molecules. In this way, the adhesion stability is improved. Additionally, more active groups buried in proteins are exposed after the HPH treatment due to the unfolding of the protein molecules. Therefore, a more reactive SF is obtained and thus forms a denser crosslinking structure of resultant the adhesive, providing an increase in bonding strength. Particularly, the effects of homogenizing pressure on the adhesive performance are investigated. The results show that a 215.6% increase of wet bonding strength (1.01 MPa) is obtained after the HPH treatment with a homogenizing pressure of 20 MPa, meeting the standards (GB/T 9846‐2015) for interior applications. Soy flour (SF) is used to replace toxic formaldehyde‐based adhesives. For the poor strength and adhesion stability of SF adhesive, a clean and simple high pressure homogenization technology is employed to pretreat SF for the preparation of bio‐based adhesive with high bonding strength and adhesion stability. Moreover, the effect of homogenizing pressure is studied to optimize the adhesive performance.