Soy Properties and Soy Wood Adhesives

Soy flour has been used for many years as a wood adhesive. Rapid development of petroleum-based infrastructure coupled with advancement of synthetic resin technology resulted in waning usage since the early 1960s. Discovery of using polyamidoamine–epichlorohydrin (PAE) resin as a co-reactant has been effective in increasing the wet bond strength of soy adhesives and led to a resurgence in soy-based adhesive consumption. Technology for making wood adhesives from soy is reviewed in this chapter. It is clear from this review that commercial processing technology used to make various soy protein-containing products influences protein adhesive properties. Thermal denaturation of soy flour does not influence the dry or wet bond strength either without or with added PAE. However, in case of soy protein isolate, the hydrothermal process used to provide proteins with more functionality for food applications make these proteins much better wood adhesives, especially in wet bond strength both without and with added PAE.