Preparation of water-resistant soybean meal-based adhesives with waste paper cellulose via NaOH/urea pretreatment and oxidation.

Fiber agglomeration and poor interfacial combination with the matrix restrict the performance of composites. Herein, soybean meal-based adhesives were fabricated via the addition of dialdehyde cellulose (DAC) obtained from waste paper dissolved in an alkali–urea system and oxidized with sodium periodate. Due to the dissolution by the alkali–urea system, DAC dispersed well in the solution and did not aggregate in the adhesive matrix. Because of the oxidation treatment, DAC was crosslinked with the adhesive matrix via a Schiff base reaction. Meanwhile, hydrogen bonds were formed at the interface between the DAC and the adhesive matrix. Plywood with the SM/DAC/PTGE adhesive reached its highest wet bonding strength of 1.27 MPa (4 wt% DAC addition), a 95% increase compared to that with the unmodified SM/PTGE adhesive. Fine DAC-to-SM interfacial bonding and a dense crosslinking network were constructed in the SM/DAC/PTGE adhesive systems. The cycle of reuse for the alkali–urea system in the experiments demonstrated that the preparation method of the cellulose solution was scalable and sustainable. [ABSTRACT FROM AUTHOR]