Our reporting showed that extractable material from the adhesive bond-line is a significant factor relating to the poor moisture resistance of soy-based adhesives crosslinked with polyamideamine-epichlorohydrin (PAE). We previously reported Fourier Transform Infrared Spectroscopy (FTIR) and Solid and Solution Nuclear Magnetic Resonance spectroscopy (NMR) data showing the changes occurring when adhesive films and adhesives from plywood samples were subjected to water soaking. In this final report we have shown that a reaction product of water-soluble protein and cross-linking chemical (PAE) is extracted from the soy adhesive and contributes to the poor moisture resistance of these adhesives used in wood composites.

Soy-based adhesives prepared with soy flour, for use in wood composite adhesives, is an area of continued interest for wood composite manufacturers. Since the patenting of these soy-based adhesives for wood composites in 2007, the technology has changed very little and the growth of these adhesives, in the wood composites arena, as well as in other areas of application, has not occurred. A major reason for the lack of growth of these soy-based adhesives in this and other applications is that these adhesives have poor water resistance. Understanding the mechanism of how water affects the chemistry, soy protein structure and resulting strength of the soy adhesive is necessary for finding solutions and solving this poor moisture resistance problem. By studying and benchmarking the physical and chemical properties of the current soy adhesive technology we can then propose possible chemical and physical solutions to the problem of poor moisture resistance of soy adhesives and grow their use in wood composites and other adhesive applications.