Chemical modification of soybean flour‐based adhesives using acetylated cellulose nanocrystals

In this study, two types of new bioadhesives formulated from abundant and renewable soybean flour (SF), acetylated soybean flour based adhesive (ASF), and soybean flour‐based adhesive, were modified with acetylated cellulose nanocrystal (ACNC). The apparent viscosity and morphology of the adhesive formulations were characterized. The chemical composition of the formulations was evaluated by FT‐IR spectroscopy and the effect of polyethilenimine (PEI) on the formulations was investigated using the proton nuclear magnetic resonance (1H NMR) spectra. Moreover, water resistance of produced plywood composites bonded with the bioadhesives was measured. The results of FT‐IR and 1H NMR confirmed that chemical modifications of the SF occurred. The scanning electron microscopy (SEM) images showed less holes and cracks on the cross section of the ASF/PEI/NaOH and SF/PEI/NaOH/ACNC formulations. The results showed that the plywood specimens bonded with formulations of the ASF/PEI/NaOH (with a dry weight ratio of ASF/PEI: 5/1 and 6/1), and SF/PEI/NaOH/ACNC had good resistance to water. POLYM. COMPOS., 39:3618–3625, 2018. © 2017 Society of Plastics Engineers