The Reaserch And Application Of Soy-based Wood Adhesive

In this study, the soy protein-based wood adhesive isenvironment-friendly, non-toxic, and has broad market prospects. Inthe cross-linking experiment, hydroxyproline with protecting groupswas choosed to cause the exposure of hydrophobic groups, introducinga large number of hydroxyproline hydroxyl groups, enhancinghydrogen bonding between the adhesive and the wood molecules,further improving the water resistance.After the first phase of alkali modified, urea modified secondstage, the third step and hydroxyproline grafted joint modification, theconclusions have been obtained as follows.The density of soy protein adhesives has little effect on thebonding strength. Viscosity of soy protein will determine theperformance of bonding. After urea modification, the viscosity of thesolution has been reduced，thereby the liquidity could be increased.Phosphorylation of urea can be used to improve the characters of theSPI solution. The impact of pH value is not very obvious.The Hydroxyproline grafting modification method can effectively improve the adhesive properties and water resistance of soy proteinisolate. A total solids content of14%was an optimal viscosity valuefor application and would be adopted in the following experiments.Pressing temperature and time is important factors for the shearstrength of wood. High temperature (>120℃) and the long time (>6min) for curing is very detrimental. Therefore, the best hot pressingcondition is120℃and6min. Adding wheat gluten has a significantimpact on increasing the adhesive strength of Hyp-SPI. The Hyp-SPIadhesive performs better than two kinds of commercially availableadhesives currently.After analyzing in the method of infrared spectroscopy andthermogravimetry, the changes of a variety of modified soy proteinactive groups have been obtained and the mechanism of modificationreactions has been understood. Hydroxyproline grafting can increasehydroxyl content of soy protein isolate surfaces, and thus form morehydrogen bonds with wood molecules. The connection between themolecules in the Hyp-SPI/ASPI residues and residues within thepeptide chain form a solid three-dimensional network structureeventually. The formation of hydrogen bonds happened betweenvarious groups of Hyp-SPI and the wood elements.