10 - Soy Protein Adhesives

Abstract

The greatly expanding markets for adhesives, the threat of limited world oil reserves, and increasing concerns over environmental pollution have forced the adhesive industry to seek new adhesives from bio-based polymers. Soy protein has potential uses in the production of adhesives with high gluing strength and improved water resistance. This chapter discusses how the complexity of the soy proteins can be harnessed to produce valuable adhesives with desirable performances for wood particleboard, plywood, wood veneer, strawboard, fiberboard packaging, children's glue, color paints, and casting material for the foundry industry. Soy proteins are good resins for binding various fibers, recycled newspapers, wood, and agricultural residue fibers. The composite made from soy proteins and waste newspapers looked like granite but handled like hard wood. Adhesive foam from modified soy proteins through extrusion can be used for plywood applications. Alkali is commonly used in protein adhesive preparations. The binding strength and water resistance of the alkali-modified soy protein adhesives can be enhanced. Alkali increases the degree of unfolding of protein molecules, resulting in an increased contact area and exposure of the hydrophobic bonds. Combination of the alkaline hydrolysis protein fractions with phenol-resorcinol-formaldehyde resin can speed up the curing process of soy protein adhesives.