Soy Protein Structures and Wood Adhesive Performance Properties

Abstract

Formaldehyde emissions from urea-formaldehyde bonded wood products have led to consumer health concerns and to companies looking for no-added formaldehyde adhesives. Most of soy flour/meal is not consumed by humans and has a reasonable cost leading to research on soy wood adhesives. In the literature there is considerable valuable information about soy modification, but there are also important weaknesses in the understanding of fundamental protein structure. Nature developed non-structural proteins to be compact dispersions (rice-like) for dealing with very crowded cell environments making the common speculation that the hydrophobic proteins can become completely uncoiled (spaghetti-like) in water unreasonable. Changes in the internal protein structure (denaturation) can influence the soy colloidal properties and improve the wood adhesive performance by further hydrophobic/hydrophilic aggregation of proteins, but these changes do not eliminate the ability of the protein to absorb water and lower wet strength for the bonded wood products. Crosslinking of the proteins in soy products by adding other chemicals has been shown to play an important role in improving the wet strength of soy-bonded wood products at commercially viable levels. Thus, the model of tying together the dispersed particles, like sticky rice, has been accepted by food researchers and fits with the results in the adhesive literature.

Citation

Frihart, Charles R. 2026. Soy Protein Structures and Wood Adhesive Performance Properties. In: Netravali, Anil N.; Etzler, Frank M., eds. The Wide World of Adhesion. Beverly, Massachusetts: Scrivener Publishing: 623-641. https://doi.org/10.1002/9781394449538. Chapter 18.