Effects of inorganic filler on performance and cost effectiveness of a soybean‐based adhesive

A modified soybean‐based adhesive with improved bonding properties and technological applicability but reduced cost was developed based on the effects of inorganic fillers on the performance of a defatted soybean meal flour (DSF) adhesive. Investigations with Fourier transform infrared spectroscopy, X‐ray diffraction measurement, thermogravimetric analysis, scanning electron microscopy, rheology tests, zeta potential analysis, and plywood evaluation demonstrated that adding inorganic fillers could improve the technological applicability of the adhesive by alleviating shear thinning and decreasing the viscosity up to 71.2%, reduce the adhesive cost up to 9.5% and result in various effects on bonding properties. Two fillers, montmorillonoid and kaolin, were suitable for plywood for exterior use owing to significantly improved water resistance up to 58.9% resulting from penetration of DSF/crosslinker chains into the interlayers of the silicates via intercalation, stable chemical bonds between the fillers and crosslinker, and excellent compatibility between the filler particles and DSF adhesive.