ABSTRACT
Soy protein (SP) which exists in soy flour, soybean meal, soy protein concentrate, and soy protein isolate is one of the vegetable proteins. It represents a very practical and inexpensive material for bio-based adhesives. The positive public perception of SP makes it very competitive as a wood adhesive. While SP is weak in adhesion strength and water resistance compared to the traditional formaldehyde-based resins, the performance of the SP adhesive bonded composites would be significantly improved if a strong chemical bonding between the SP adhesive with the cellulosic materials can be achieved. In order to enhance the bonding performance, this chapter presents the current modification methods of soy- based adhesives, which describes: (1) Chemical modifications including alkali denaturation, surfactant denaturation, organic solvent denaturation, enzymatic treatment, epoxy groups crosslinking, formaldehyde compounds crosslinking, acylation and silanation; (2) Physical modification including compression, high temperature treatment, ultrasound treatment and blending with hydrophobic additives; (3) Nanoparticle modification using cellulosic nanofibers, inorganic nanoparticles and nano-clays. In addition, it also illustrates the use of the soy adhesive as a substitute for other adhesives in this chapter.
