Preparation of strong and mildew-resistant soybean meal adhesives with self-assembled core-shell structured nanospheres.

Preparation of soybean meal adhesives offering good water resistance, prepressing adhesion as well as antimildew properties through a green and simple strategy remains challenging. In the present study, a self-assembled nanostructure-based filling enhancement strategy was proposed. Tannic acid (TA) is grafted onto the chitosan framework through free radical grafting, followed by ultrasound induced self-assembly into nanospheres. Chitosan based nanospheres (CS@TA) and ferric chloride (FeCl 3) complexing with nanospheres are combined to modify soybean meal (SM) based wood adhesives synergistically. CS@TA enables interaction with protein chains through hydrogen bonding and Schiff base reactions, which in combination with its nanostructure allows for a more homogeneous dispersion in the SM system. At the same time the Fe (III) ions chelate with the catechol, forming ionic bonds and obtaining a denser structure. The results showed that the dry and wet shear strength (DWSS) of SM/1,2,3-propanetriol triglycidyl ether (GTE) /5%CS@TA/Fe increased by 79% and 693% to 2.28 MPa and 1.27 MPa. At the same time, the residual rate (RD) increased by 9.3–72.5% and prepressing adhesion now reaches 0.71 MPa compared with SM adhesives. And CS@TA nanospheres as well as Fe (III) ions act on the cell membrane of bacteria to provide stronger antibacterial effect, the anti- mildew time has been extended from the initial 2 d to more than 15 d. The construction of multi-network reinforcement strategies through self-assembled nanostructures improves the application potential of SM adhesives and provides ideas for the reinforcement of other engineering materials. [Display omitted] • Self-assembled nanospheres chitosan-based prepared using free radical grafting combined with ultrasonic induction. • Preparation of environmentally friendly adhesives from processing residues soybean meal and biomass materials. • The adhesive has high bond strength, good water resistance and prepressing adhesion. • The anti-mildew of soy protein adhesive was enhanced and extends the storage life. [ABSTRACT FROM AUTHOR]