Connecting soy adhesive properties to product performance
AdhesivesIndustrial UsesWater resistanceWood
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Christopher Hunt, USDA Forest Products Laboratory
Co-Principal Investigators:
Project Code:
Contributing Organization (Checkoff):
Institution Funded:
Brief Project Summary:
Soy adhesives currently dominate the North American market for interior plywood, but is slightly short on performance for European plywood. The market for particleboard adhesives is about 100x larger than for plywood, but is technically more challenging. Despite much literature on soy adhesive formulations and plywood performance tests with new adhesives, there is almost no information about the mechanical and physical properties of cured adhesive films or how common processing variables influence film properties. Auburn University will enhance the program by conducting many analyses in their areas of expertise that are complimentary to FPL, generating efficiency and faster progress. FPL has already funded initial work by Auburn from other sources and we meet every two weeks to ensure an coordinated and effective program.
Information And Results
Project Summary

Project Objectives

Project Deliverables

Progress Of Work

Final Project Results

The goal of our project is to develop useful information about the fundamental properties of soy-based adhesives and share this information as widely as possible. This research is needed because little is understood about the fundamental properties of soy-based adhesives. New understanding: During this year we have two published and one submitted paper in the peer reviewed literature: Hunt, C. G., et.al. (2022). Jet cooking dramatically improves the wet strength of soy adhesives. Journal of the American Oil Chemists' Society. https://doi.org/10.1002/aocs.12664 We published our work discussing the exceptional wet strength generated by jet cooking soy isolate, suggesting, among other ideas, that the jet cooking environment is different from most denaturation processes in that it encourages more protein-protein interactions, as opposed to the typical case where protein molecules interact primarily with themselves. Frihart, C. R., & Gargulak, M. (2022). Dynamic Shear Rheology to Understand Soy Protein Dispersion Properties. Polymers, 14(24), 5490. https://doi.org/10.3390/polym14245490 Use of Dynamic Shear Rheology to Understand Soy Protein Dispersion Properties. Polymers, 14(24), 5490. https://doi.org/10.3390/polym14245490 This paper was very well received by several industry contacts. This paper documents several important aspects of soy rheology, or flow behavior. Flow behavior is very important when trying to apply soy adhesives to wood, especially in particleboard and fiberboard. Effect of Protein Surface Hydrophobicity and Surface Amines on Soy Adhesive Strength The literature is full of conflicting theories explaining why wet strength usually increases with protein denaturation, yet almost no data testing those theories exists. We tested two theories and found protein surface hydrophobicity to be correlated with better wet strength, while exposure of chemically reactive amine groups had no influence on bond strength, even when amine-reactive crosslinking agent PAE was used. Hydrolysis (depolymerization) of protein did not have an obvious impact on strength if done to a small extent, but extensive depolymerization dramatically reduced bond strength. In addition to the peer reviewed papers, we have delivered 12 presentations to technical groups at companies and at conferences. We have also been very active in the soy adhesive discussion group lead by Jeff Caffmeyer and in other discussions with industry and academics in the field. We have also developed new partnerships to accelerate progress in understanding of soy adhesvies: FPL is hosting a student from BOKU university in Vienna, Austria who is conducting experiments at FPL, investigating the role of soy protein denaturation on adhesive performance. Dr. Chris Hunt and Prof. Peresin (Auburn) are organizing a session on bio-based adhesives, with an emphasis on protein adhesives, at the 2024 Forest Products Society International Conference. https://www.fpsconference.org/technical-sessions Dr. Chris Hunt is also on the organizing committee of the international conference on wood adhesives, planned for May 2025 in Vancouver, Canada. https://www.woodadhesives.org/ Findings not yet published: We identified serious flaws in much of the literature with respect to beta sheet content of soy proteins measured by the infrared method. We have determined that commonly used techniques give vastly different answers for the same data. Our approach is to ground truth our infrared data by using x-ray diffraction to calibrate and ground truth the infrared data. A publication is in preparation addressing the proper methodology for using infrared to estimate beta sheet content in soy materials. We plan to then publish the results of using this method on our soy adhesives, and the role of beta sheet in soy proteins on wet bond strength. This work was done in close cooperation with Prof Peresin at Auburn.

Benefit To Soybean Farmers

There are approximately 11 million tons of interior grade adhesive used in wood panels annually. Soy meal currently fills less than 1% of that market, in large part because of the poor wet strength of soy adhesives. Our work is helping soy adhesive makers improve the performance of soy adhesives so that they can capture more of that market, increasing demand for soy meal.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.