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.