Overview

About 20 billion pounds of adhesives are used annually in the United States in the production of plywood, particleboard, labeling, packaging, and sizing, among other things. The various forms of wood adhesives represent an extremely large and diverse market, probably the largest in the world today [1]. Soy-based adhesives were first developed in 1923 when a patent was granted for a soy meal-based glue [2]. However, those soy protein adhesives had low gluing strength and little water resistance. Adhesives produced from petroleum-based chemicals have overcome those disadvantages, but many concerns have surfaced about air quality and environmental pollution, and even toxicity during product manufacturing, distribution, and use. Among these adhesives, about 8 billion pounds are formaldehyde-based adhesives annually used by the wood-based product industries. The greatly expanding markets for adhesives, the threat of limited world oil reserves, and increasing concerns over environmental pollution have forced industry to seek new adhesives from bio-based polymers. Protein modification is designed to improve functional properties by altering protein s molecular structure or conformation, through physical, chemical, or enzymatic agents, at the secondary, tertiary, and quaternary levels. Soy protein, as discussed in Chapter 9, has potential uses in the production of adhesives with high gluing strength and improved water resistance [3 5].

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 [6]. Adhesive foam from modified soy proteins through...