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 (FeCl3) 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.